Background: The International Agency for Research on Cancer (IARC) identified formaldehyde as a carcinogen in 2004, yet formaldehyde is widely used in health care settings and various industries. In recent years, photocatalytic oxidation has been developed as a potential technique for removing pollutants arising from organic chemical agents and consequently promoting the health indices. This study investigated the effect of operational factors in optimizing formaldehyde removal from the air using Ag3 PO4 /TiO2 photocatalyst. Methods: An experimental study was designed to investigate the effect of operational factors on the efficiency of formaldehyde degradation. The variables investigated in this study include pollutant retention time, initial pollutant concentration and relative humidity. Sol-gel method was used to synthesize the nano-composite photocatalyst. An ideal experimental design was carried out based on Box-Behnken design (BBD) with response surface methodology (RSM). The sample size in this study includes all the glasses coated with Ag3 PO4 /TiO2 photocatalyst. Results: The maximum formaldehyde degradation of 32% was obtained at the initial concentration of 2 ppm, 20% relative humidity, and 90 minutes of retention time. Based on the statistical results, the correlation coefficient of the present study for the impact of operational factors on formaldehyde degradation was 0.9635, which means that there is only 3.65% probability of error in the model. Conclusion: The operational factors examined in this study  were significantly influential in the degradation efficiency of formaldehyde by the photocatalyst. Due to the high exposure of employees and clients of health and treatment centers to formaldehyde as a carcinogenic substance, the results of this study can be used in ventilation systems to remove environmental pollutants in health care centers and other occupational settings. They are considered as a large group of contaminants with a low boiling point. Benzene, formaldehyde, toluene, styrene, xylene, acetaldehyde, naphthalene, and hexanal are among the most important VOCs in indoor environments.2 The rapid population development and industrialization have increased chemical contaminants.4 Also, it is a raw chemical that is frequently employed as a disinfectant and preservative in various industries.5 Additionally, it is one of the primary components of many building materials such as wallpaper, wood, and paint, and it may even be produced in activities such as cooking and using electrical appliances.6 Pathologists, research and medical laboratory staffs are constantly exposed to gaseous formaldehyde because they use it as a tissue stabilizer, disinfectant, and preservative.8 Formaldehyde is one of the most well-known VOCs due to its highly toxic nature and widespread indoor distribution. Due to its high solubility in water, it is rapidly absorbed through the gastrointestinal and respiratory tracts. Formaldehyde was recognized as a human carcinogen by the IARC in 2004.9 Therefore, controlling and reducing occupational exposure to this pollutant in health care centers and industrial sectors is necessary. According to the study of Soltanpour et al, in both industrial and health care center settings, concentrations of gaseous formaldehyde were higher than the 8-hour threshold limit value - time-weighted average (8-hr TLV-TWA) recommended by the American Conference of Governmental Industrial Hygienists (ACGIH).12 Photocatalytic degradation, known as one of the advanced oxidation processes, consists of three components: light, semiconductor photocatalyst, and oxygen, which is used to produce free radicals. The photocatalytic process begins with the absorption of light by the photocatalyst. It continues with a series of redox reactions that degrade pollutants, but the photocatalyst remains unchanged in these reactions.13 In recent years, photocatalytic oxidation using semiconductors that are activated in visible light has been proposed as a potential technique for removing pollutants arising from organic chemical agents.3PO4 photocatalyst is one of the most extensively utilized photocatalysts in visible light. However, due to the recombination of the hole and excited electron, this photocatalyst cannot be used in practice.14 Heterostructure photocatalysts can overcome the limitations of single-component photocatalysts, such as electron and hole recombination. In this way, the electrons produced in the conduction band and the holes created in the valence band of one photocatalyst are transferred to the conduction band or valence band of the other photocatalyst. Under these conditions, the produced electrons and holes are spatially separated, and the possibility of recombination is reduced.18 Previous studies have shown that combining Ag3PO4 with TiO2 can increase the performance of Ag3PO4 up to 12 times.19 With a 2.58 eV bandgap, the Ag23 The studies conducted in this field have investigated the effect of one factor on degradation efficiency, as a result, the mutual effect of operating factors on degradation efficiency has not been determined. Therefore, with a better understanding of the impact of operational factors on degradation efficiency, this study aimed to evaluate and optimize the impact of these operating factors on degradation efficiency of photocatalyst. Operating factors  can affect the photocatalyst degradation efficiency.Titanium tetraisopropoxide , silver nitrate , sodium dihydrogen phosphate , nitric acid 65% , ethanol 99.5%, acetylacetone , paraformaldehyde ((CH2O)n, Merck ) and acetone  were used as purchased without further purifications. A commercial Pyrex glass with a diameter of 8 cm was used to coat the photocatalyst.3PO4, 1.53 g silver nitrate and 0.995 g sodium dihydrogen phosphate were separately dissolved in 25 mL distilled water. The prepared sodium dihydrogen phosphate solution was added dropwise to the silver nitrate solution and stirred at room temperature for 4 hours. The resulting Ag3PO4 was filtered off, washed with equal volumes of ethanol and water, and dried in an oven at 60°C for 24 hours. To prepare Ag2 particles were prepared by sol-gel method. The initial sol was prepared by mixing titanium isopropoxide (TTIP), acetylacetone (AcAc), and ethanol (EtOH). Finally, nitric acid was added dropwise to obtain a clear solution (The molar ratio of TTIP: AcAc: EtOH: HNO3 was 1:1:40:0.1). After two hours of mixing, which is known as aging time, the prepared Ag3PO4 was added to the solution. Before coating the films on the glass slides, they were first immersed in an ultrasonic bath containing equal volumes of ethanol and acetone for 20 minutes, followed by being immersed in 1% hydrochloric acid solution for 20 minutes. Finally, they were washed with distilled water and placed in an oven at 60°C to dry. In each coating process, the glass substrate was immersed in the prepared sol at a speed of 5 mm/s, and after 10 seconds, it was withdrawn from the solution at the same. Then it was placed in a furnace for 2 h, and at 550 °C for calcination step. TiO The scanning electron microscopy (SEM) images and energy dispersive X-ray analysis spectroscopy were measured by a MIRA3 FEG-SEM field emission scanning electron microscope with an acceleration voltage of 30.0 kV. The UV–Vis diffuse reflectance spectra of the samples were recorded on a Analytik Jena, Specord 250 UV–Vis spectrophotometer in the wavelength range of 300–850 nm.24 The formaldehyde degradation efficiency was calculated according to the following formula: A 3-L photoreactor made of stainless steel was used to test the degradation efficiency of the synthesized photocatalyst. After placing the photocatalyst-coated glass in the photoreactor, in each experiment, first, the desired relative humidity was created by evaporating distilled water and transferring it to the photoreactor. Then the desired formaldehyde concentration was generated by sublimation of paraformaldehyde from the photoreactor’s paraformaldehyde tank. The irradiation of the photocatalyst by light was then started and lasted for 30, 60, or 90 minutes through the quartz window of the photoreactor. A 150-W xenon lamp with a cut-off filter of 420 nm was used as the light source, which was placed on top of the photoreactor, 10 cm away from the photocatalyst. Measurement of formaldehyde concentration inside the photoreactor was performed using the acetylacetone method.C0 is referred to the initial concentration of formaldehyde, and Ct is the concentration of formaldehyde at the time t. where  Parameters that investigated for photocatalytical degradation of formaldehyde were analyzed by standard response surface methodology (RSM) Box-Behnken design (BBD). In this method, each variable is evaluated at 3 levels. The levels of study variables are given in  The morphological properties of the produced photocatalyst were evaluated using SEM images, shown in  The energy-dispersive X-ray spectroscopy (EDS) of this SEM image confirms the presence of Ti, O, Ag, and P elements. Additionally, element mapping demonstrates that all elements  are dispersed uniformly.3PO4/TiO2 composite is shown in 3PO4/TiO2 composite was a combination of the absorption spectra of these two components (TiO2 and Ag3PO4).25 The absorption spectra of the Ag The composite’s bandgap was measured using the Tauc plot, as seen in  Experiments designed by the BBD method and their results are presented in 2 (0.9551) and Predicted R2 (0.9317) for linear model the software has selected the linear model to model operational factors’ effect on the photocatalytic degradation of formaldehyde. According to Adjusted RP value less than 0.05 for each term indicates that this term has a significant effect on the response, all the main parameters of the model have a substantial effect on the formaldehyde photocatalytic degradation efficiency.26 But the terms related to the interaction between the parameters were not effective in the degradation efficiency due to having P value greater than 0.1. These terms were excluded from the study to improve the model. Analysis of variance (ANOVA) of regression parameters of the predicted response surface quadratic model for formaldehyde photocatalytic degradation efficiency is shown in 27 The correlation coefficient of the present study for the impact of operational factors on formaldehyde degradation was 0.9635, which means that there is only a 3.65% probability of error in the model. The final regression model constructed from the coded factors will be according to the following equation: Adequate precision greater than 4 suggests a desirable signal-to-noise ratio, which is 36.5034 for the proposed model in this study. Examination of whether the selected model provides a good approximation of the results of actual experiments was performed using diagnostic charts such as predicted versus actual value plot and normal probability plot of the studentized residuals, and in this way, the adequacy of the model could be judged. The perturbation graphic illustrates the independent influence of each variable on formaldehyde degradation efficiency. As shown in  The contour plots and 3D surface response of the model were utilized to assess the interactive relationships between independent variables and the response. By holding one variable constant and varying the other two in the test range, these graphs study the influence of those two metrics on the intended result. Using Design-Expert software version 12, operational parameters were optimized to achieve maximum degradation efficiency. According to the optimization steps in the software, to optimize the studied operational parameters, the amplitude of change in operational parameters for the software was defined within the test range. The target for formaldehyde degradation was defined as the maximum, and the degree of importance for this response was defined as 5. Also, the target for initial concentration, retention time, and relative humidity was defined as the maximum, minimum, and in range, respectively. The program generated ten operating conditions based on these characteristics, which are listed in the 3PO4/TiO2 are in the nanoparticle range.28 The absorption spectrum of the Ag3PO4/TiO2 composite was a combination of the absorption spectra of these two components (TiO2 and Ag3PO4). This form of composite absorption spectrum indicates that there has been no chemical interaction between the two components, and the synthesized composite consists of two components TiO2 and Ag3PO4 which is consistent with previous studies in this field.19 Also given that the low Eg value indicates better absorption ability in visible light or natural sunlight, it can be concluded that the synthesized Ag3PO4/TiO2 composite in visible light has a better performance than any of its components.29 According to the definitions in the field of nanoparticles, they range in size between 10 and 500 nm, so according to the average size of the synthesized particles and the particle size distribution, synthesized Ag20 Although water molecules in the air are an essential source for producing hydroxyl radicals, which are then used to degrade formaldehyde molecules, relative humidity of 20% seems to be sufficient for this purpose, and higher values reduce the degradation efficiency. A linear trend was observed in decreasing the amount of degradation with increasing relative humidity. One of the reasons for the decrease in formaldehyde removal efficiency by increasing the relative humidity can be the competition between formaldehyde molecules and water molecules for being adsorbed on the active sites of the photocatalyst.20 With increasing retention time, the degradation efficiency has increased. The reason for this increment could be the increased probability of formaldehyde molecules coming into contact with the photocatalyst and free radicals produced by the photocatalyst during longer residence time.30 With increasing initial formaldehyde concentration, the degradation efficiency decreases due to the limited active sites of the photocatalyst, which is occupied by a limited number of contaminant molecules. *OH radicals, which are produced by the reaction of water molecules and photocatalyst active sites, play a very important role in the photocatalytic degradation process of formaldehyde because this substance oxidizes formaldehyde to carbon dioxide and water. As the concentration of formaldehyde increases, more pollutants cover the active sites of the photocatalyst. If the light intensity and irradiation time are constant, fewer photons reach the catalyst surface. As a result, less OH radicals are formed and subsequently the relative number of *OH radicals that attack formaldehyde also decreases. Therefore, an inhibitory effect is created in the photocatalytic degradation.max), the degradation efficiency remains unchanged due to the lack of completion of the active sites of the catalyst by the contaminant. In this study, it seems that Mmax is at concentrations below 2 ppm due to the high volume of the photoreactor. Typically, by increasing the initial concentration of the contaminant from zero to a certain concentration  on the photocatalytic degradation efficiency of gaseous formaldehyde and the optimization of this process were investigated. The correlation coefficient of the model was 0.9635, which shows that the actual data are well consistent with the predicted data. According to the study, the photocatalytic degradation of pollutants from the air can be improved by optimizing the operational parameters effective in the degradation efficiency. The results of this study can be used in ventilation systems to remove pollutants in health care centers and industrial environments. In order to improve the performance of photocatalysts by optimizing the operating factors, it is suggested to study the effect of other operating factors such as light intensity. The authors have declared that there are no financial or nonfinancial competing interests. The code of ethics was received from the ethics committee of Tabriz University of Medical Sciences with the specific ID IR.TBZMED.REC.1397.081. This research study was funded by the Faculty of Health, Tabriz University of Medical Sciences.


Homogeneous step-by-step glycolysis under the successive action of the oligo trimer, bis(2-hydroxyethyl) terephthalate, and ethylene glycol at temperatures of 250, 220, and 190 °C, respectively, was also studied. The composition of products was confirmed using FTIR spectroscopy. Molecular weight characteristics were determined using gel permeation chromatography (GPC), the content of bis(2-hydroxyethyl) terephthalate was determined via extraction with water at 60 °C. The developed kinetic model was found to be in agreement with the experimental data and it could be used further to predict the optimal conditions for homogeneous PET glycolysis and to obtain polymer-based composite materials with desired properties.Polymer composites with various recycled poly-based (PET-based) polyester matrices , copolyesters, and unsaturated polyester resins), similar in properties to the primary ones, can be obtained based on PET glycolysis products after purification. PET glycolysis allows one to obtain bis(2-hydroxyethyl) terephthalate and oligo with various molecular weights. A kinetic model of poly homogeneous glycolysis under the combined or separate action of oligo, bis(2-hydroxyethyl) terephthalate, and ethylene glycol is proposed. The model takes into account the interaction of bound, terminal, and free ethylene glycol molecules in the PET feedstock and the glycolysis agent. Experimental data were obtained on the molecular weight distribution of poly glycolysis products and the content of bis(2-hydroxyethyl) terephthalate monomer in them to verify the model. Homogeneous glycolysis of PET was carried out at atmospheric pressure in dimethyl sulfoxide (DMSO) and N-methyl-2-pyrrolidone (NMP) solvents with catalyst based on antimony trioxide (Sb Polyethylene terephthalate (PET) is one of the most widely used polymers in the world. The share of PET waste is about 25% of the total amount of plastic waste and is about 12% of the total amount of solid waste ,4. There2), nanotubes , and layered silicates (mostly montmorillonite) [There are various routes to use PET waste disposal . Polyethllonite) ,8.There are two key problems regarding the use of recycled polyethylene terephthalate as a matrix for nanocomposites. Firstly, although the addition of nanomaterials can significantly improve the properties of rPET , the proA promising way to obtain monomers for the synthesis of PET, which could be similar in properties to the vPET, is chemical recycling ,14. CurrBoth heterogeneous and homogeneous catalysts are used , with psGlycolysis is classified depending on the phase composition of the reaction mixture as heterogeneous ,37,38 anThe advantage of homogeneous glycolysis over heterogeneous is its high reaction rate. This makes homogeneous glycolysis a more energy efficient process. In addition, the high rate of reaching the equilibrium of the main reaction reduces the amount of impurities formed due to the irreversible side reactions. An important task for further study of homogeneous glycolysis both in solution and in melt is the development of its kinetic model, which takes into account the conditions of the process. The currently existing models take into account only the reactions of ester groups of PET and the resulting products of glycolysis with ethylene glycol, as well as reverse reactions ,41. ThisModels describing a reversible polycondensation reaction in the production of vPET ,43,44,45Poly was used in the form of clear PET flakes, which were obtained from postconsumer PET bottles . Ethylene glycol, zinc acetate and antimony trioxide, dimethyl sulfoxide (DMSO), and N-methyl-2-pyrrolidone (NMP) were purchased from Sigma Aldrich  and were used without further purification.Glycolytic agents were obtained in accordance with the procedures given in the article .Bis(2-hydroxyethyl) terephthalate (BHET-1 sample) was obtained via heterogeneous glycolysis of PET flakes under the action of ethylene glycol with zinc acetate as a homogeneous catalyst in a mass ratio of 100:250:3, respectively. The process was carried out at a temperature of 190 °C and stirring at 200 rpm. The product was purified via recrystallization in water at 60 °C and dried.Oligoethylene terephthalate with terminal hydroxyl groups and with a polycondensation degree equal to 3 (OET-1 sample) was obtained via heterogeneous glycolysis of PET flakes under the action of the obtained BHET-1 agent in a mass ratio of 100:250:3, respectively. The process was carried out under the same conditions as the preparation of BHET-1. The water-soluble components, namely ethylene glycol and zinc acetate, were extracted using water at 20 °C to avoid the simultaneous extraction of bis(2-hydroxyethyl) terephthalate.Homogeneous glycolysis in DMSO was carried out in accordance with the procedure described by Bo Liu et al. . A solutHomogeneous glycolysis in NMP was carried out in accordance with the procedure described by Moncada et al. . SimilarHomogeneous glycolysis under the action of BHET was carried out in a reactor with reflux at a temperature of 250 °C and stirring at 100 rpm for 1.5 h. Antimony trioxide was mixed with ethylene glycol in a mass ratio of 1:1 to obtain a homogeneous transesterification catalyst. PET was preliminarily mixed with BHET-1 at 270 °C. PET, BHET-1 and antimony trioxide solution were used in mass ratios 100:130:2.3 (molar ratio PET:BHET = 1:1) and 100:390:4.9 (molar ratio PET:BHET = 1:3), respectively. The product was isolated similarly to the preparation of OET-1 see .2O3 solution in ethylene glycol 100:110:2.1 (molar ratio PET:OET = 1:1) and 100:330:4.3 (molar ratio PET:OET = 1:3), respectively, at 250 °C and at 50 rpm for 1.5 h. The product was isolated similarly to the preparation of OET-1 .Gel permeation chromatography  with Agilent MIXED-E column , tetrahydrofuran as the mobile phase, and refractive index detector was used to determine the molecular weights of the component present in the analyzed samples. Measurements were made at the temperature of 25 °C and the flow rate of 1.0 mL/min. Narrowly dispersed polystyrene standards with Mp (peak molecular weight) 580; 1280; 2940; 10,110; and 28,770 g/mol and a polydispersity index of no more than 1.12 were used for calibration .To determine the content of bis(2-hydroxyethyl) terephthalate monomer, the product, previously purified from water-soluble components at a temperature of 20 °C, was weighed and the masses of PET and/or OET-1, BHET-1 (tion (1) :(1)YBHET–1 , 1243 cm–1 , and 1176 and 1116 cm–1  [The composition of PET flakes was confirmed by the presence of absorption bands in the range of PET characteristic frequencies: 1715 cm–1) and carbonyl groups in the chain (1720 cm–1) of the FTIR spectrum and it was additionally confirmed by the number average molecular weights of the samples measured using GPC. The degrees of polycondensation of samples OET-1 and BHET-1 were 3.1 and 1.1, respectively, that corresponds to the data obtained previously [The obtained degree of polycondensation of glycolytic agents was determined by the ratio of bands corresponding to terminal hydroxyl groups 3350 cm350 cm–1 A large number of reactions occur during high-temperature polycondensation of PET or glycolysis under the action of ethylene glycol, bis(2-hydroxyethyl) terephthalate, and oligoethylene terephthalates with terminal hydroxyl groups. The main ones include esterification and transesterification reactions, the formation of diethylene glycol or acetaldehyde side reactions, and thermal or thermo-oxidative degradation. A functional group model was used to simulate the process kinetics. The rate constants in the model are defined for the reactions between the functional end groups involved in each reaction, namely bonded, terminal ethylene glycol groups, and free ethylene glycol molecules. The abbreviations used in the kinetic model are given in 1.Polyesters within the same source (feedstock or agent) are in equilibrium. Therefore, the reactions occurring in them do not lead to a change in the molecular weight distribution. Under this assumption, the polydispersity index of polyester from a single source corresponds to the polyester obtained via ideal step-growth polymerization (Flory-Schulz distribution). Thus, the following reactions are not taken into account in the model:A number of assumptions were made to simplify the model:2.The concentration of the catalyst onstants ,43 in Eq3.All reactions under the action of terminal hydroxyethyl groups  [a—activation energy, 18,500 cal/mol [The effective polycondensation rate constant can be determined from Equation (2):l2·min1) ,43; Ea—a cal/mol ,43; R isThe effective alcoholysis rate constant can be determined from Equation (3):ant, 0.5 ,43.4.The volume of the reaction mixture is assumed to be constant, since densities of polyethylene terephthalate, oligoethylene terephthalates, and bis(2-hydroxyethyl) terephthalate are close in magnitude;5.Mass transfer processes, including the presence of ethylene glycol in the gas phase, are not taken into account. This assumption can be made since the reactors in which PET glycolysis is carried out are usually equipped with reflux condensers, which return ethylene glycol back to the reaction mixture. However, violation of this assumption can lead to an underestimation of the conversion by the model relative to one in the real process, since the reactions involving ethylene glycol are at equilibrium;6.The concentration of terminal acid groups is taken equal to 0 for all samples. The calculation was made for polyesters and oligoethers with solely hydroxyl end groups;7.Ester exchange reactions are not taken into account, since their occurrence at the temperatures used makes a significantly smaller contribution than the occurrence of reactions under the action of hydroxyl groups ;8.Reactions for the formation of ethers (DEG units), degradation reactions  are not taken into account.Thus, the model takes into account the reactions during homogeneous PET glycolysis under the action of oligoethylene terephthalates with terminal hydroxyl groups, bis(2-hydroxyethyl) terephthalate, and/or ethylene glycol, which are shown in The plug flow reactor (PFR) model was chosen for homogeneous glycolysis of polyethylene terephthalate . The masThe resulting system of differential equations can be solved using numerical methods.Verification of kinetic models during their development is carried out by comparing the simulation results with experimental data on the concentration of the components of the reaction mixture or functional groups ,45. SincPET is the molar mass of the PET unit (192 g/mol); and MEG is the molar mass of ethylene glycol (62 g/mol).The mass concentration of ethylene terephthalates (excluding EG molecules) in the reaction mixture at the initial moment was determined according to Equation (10):1 and c2 over time t.4 and c5 over time t.The average degrees of polycondensation can be determined from the ratio of terminal and bonded ethylene glycol groups in polyester according to Equations (11)–(14):The calculations using Equation (13) and the following ones do not take into account the difference in the average degree of polycondensation and molecular weight characteristics between the feedstock polyester and the glycolytic agent. This approach can be preferably used for the glycolysis agent consisting solely of ethylene glycol.Next, it is necessary to evaluate the molecular weight distribution of polyesters in accordance with the Flory–Schulz equation (Equations (14) and (15)):To calculate the content of BHET or other fractions of the product, it is necessary to determine the number fraction of ethylene glycol units according to Equations (16) and (17).S > PDIO). A comparison of summary and overall molecular weight distribution is shown in the The calculations using Equation (17) and the following ones take into account the average degree of polycondensation and the molecular weight characteristics of the feedstock polyester and glycolytic agent separately and then summarize them. The molecular weight distribution in this approach is wider than in the calculation of the overall characteristics (PDIEquation (18) allows one to obtain data similar to the result of the Flory–Schulz equation for calculating summary characteristics:Similarly, weight fractions can be estimated using the Flory–Schulz equation (Equation (19)) or summing its results for feedstock and agent polyesters (Equation (20)):Further, it is possible to evaluate molecular weight characteristics, number average, weight average molecular weight of polyester, and polydispersity index, using Equations (21)–(24):The yield was determined through the number fractions of ethylene glycol units according to Equations (25) and (26):In addition, the yield can be similarly defined in terms of weight fractions. In this case, the obtained values should differ within the margin of error.BHET calculated for summary and overall polyesters via number or weight fractions.Thus, the main output data of the model, which can be compared with the experimental ones, are the number average and weight average molecular weights; the polydispersity index for summary; overall, feedstock, or agent polyesters; and the yield of bis(2-hydroxyethyl) terephthalate Y2O3 was set equal to 0.048 mol/L, which corresponds to 1 wt.% of the reaction mixture. The initial concentrations used in the calculation are shown in A step of 0.1 min was used for the numerical solution of the system of differential equations of the material balance. The temperature conditions were set equal to the experimental ones according to BHET was calculated for summary and overall polyesters via number (n) or weight (w) fractions.The experimental results are compared with the simulation ones in It can be noted that the simulation results for the summary and overall BHET yield calculations differ significantly at the initial stages, while they practically coincide at subsequent stages. In addition, the model fits the experimental data at the initial stages worse than at subsequent ones, which can be explained by errors in sampling for such a fast reaction or insufficiently rapid achievement of the desired reaction temperature after the introduction of the catalyst solution in ethylene glycol. Another possible reason for the deviation of the calculation results from the experimental data may be a violation of the assumptions made earlier. In particular, the presence of a part of ethylene glycol in the gas phase (assumption 5) with EG being the main agent of glycolysis in this case can lead to a decrease in the conversion and, consequently, a decrease in the BHET yield.The temperature conditions and the total reaction time were set equal to the experimental ones according to The simulated number and weight average molecular weights are in agreement with ones obtained experimentally. The calculated polydispersity indices are lower than those obtained experimentally, which may be due to the limitations of using the Flory–Schulz distribution (assumption 1). A potential solution to this discrepancy would be to replace the ideal Flory–Huggins distribution for step-growth polymerization. However, we are not aware of a more suitable molecular weight distribution model. The model also underestimates the concentration of bis(2-hydroxyethyl) terephthalate in the final product. Apparently, this may be due to an overestimation of the reaction rate of two terminal hydroxyl groups with the formation of ethylene glycol. A total of 0.49 and 1.23 g/mol of ethylene glycol are present in the final product according to the simulation at a PET:BHET molar ratio of 1:1 and 1:3, respectively.The temperature conditions and reaction time were set in accordance with the experimental ones  to simulThe number average and weight average molecular weights and the polydispersity index for PET:OET-1 with a molar ratio equal to 1:1 are significantly higher than calculated ones. This may be due to both the model assumptions and the higher degree of polycondensation of the glycolysis agent OET-1 relative to the theoretical one. BHET yields for glycolysis under the action of oligoesters are small and differ insignificantly, which corresponds to theoretical expectations.Temperature conditions and reaction times for each stage were set equal to the experimental ones . The conAll results are in good agreement with experimental data, including previously published data  despite Thus, the kinetics model of homogeneous poly glycolysis has been proposed, which takes into account the reactions of terminal and bound groups of ethylene glycol in polyesters, as well as free ethylene glycol molecules. A method for calculating the number average and weight average molecular weights, the polydispersity index, and the content of bis(2-hydroxyethyl) terephthalate monomer was proposed for the model.A homogeneous glycolysis in solution under the action of ethylene glycol in DMSO and NMP, homogeneous glycolysis in the melt under the action of bis(2-hydroxyethyl) terephthalate, and homogeneous glycolysis under the action of oligoethylene terephthalate with terminal hydroxyl groups and with a degree of polycondensation equal to 3 were considered. Moreover, step-by-step glycolysis was also considered, where PET interacts with oligoethylene terephthalates, as well as oligoethylene terephthalates with bis(2-hydroxyethyl) terephthalate and ethylene glycol. The model was found to be in good agreement with the experimental data obtained based on the procedures described in the existing literature regarding homogeneous glycolysis.The deviations in the simulation results do not have a systematic term, with the exception of the polydispersity indices, which were lower than those determined experimentally in all cases. Deviations may be due to the assumptions underlying the model, or errors in the experimental measurements.In general, the model can be used for further study and optimization of the parameters of homogeneous glycolysis of polyethylene terephthalate under the action of ethylene glycol, bis(2-hydroxyethyl) terephthalate, and hydroxyl-terminated oligoethylene terephthalates. The optimal conditions for homogeneous glycolysis can be determined by comparing the output data of the model (molecular weight characteristics and BHET yield) at various concentrations of the catalyst and reagents, temperature, and reaction time. BHET and OET purified via recrystallization could be polymerized in a similar way to the production of virgin PET or copolyesters. Glycolysis products can be used both separately and in a mixture with BHET based on dimethyl terephthalate or terephthalic acid, with the process being carried out on known equipment for the polyethylene terehpthalate synthesis. A deeper understanding of this process will make it possible to produce recycled polymers with desired properties, as well as to control the properties of polymer-based composites on their basis.


Ⅵ-O octahedron was destroyed, and kaolinite was transformed into spatially disordered metakaolinite with very high activity.In this study, the research aim is to enhance the activity index of activated coal gangue and study its activation mechanism. The activation process of coal gangue was optimized through orthogonal tests, and the Back-Propagation (BP) neural network model was improved using a genetic algorithm. With the effects of grinding duration, calcination temperature, and calcination duration, the morphological changes and phase transformation processes of coal gangue were studied at the micro and meso levels to clarify the activation mechanism. The results indicated that the effect of calcination temperature on the strength activity index of coal gangue was most significant, followed by grinding duration and calcination duration. The potential activity of coal gangue can be effectively stimulated through mechanical and thermal activation, and the content of potential active minerals in coal gangue powders was also increased. The activation process of coal gangue for the optimal scheme was obtained as grinding at 76 min first and thermal treatment at 54 min at 749 °C. As the thermal activation under 950 °C, some unstable external hydroxyls, and internal hydroxyls in kaolinite from coal gangue were removed, the Al In recent years, coal consumption has accounted for over 50% of the one-time energy consumption in China . Coal gaironment ,7. In adironment ,9,10.Faced with the present situation of the severe global resources environment situation, the demand for low-carbon and sustainable development, and the current shortage in construction and building materials, researchers have made many explorations into the efficient utilization of coal gangue as a substitute for the construction materials, such as backfilling in mining areas ,12,13,14The focus of current studies is to optimize the ratio of activated coal gangue powder and other types of industrial solid waste mixtures to improve their utilization rate . With anThermal activation also positively disrupts the stable structure of coal gangue and stimulates its activity. Li et al.  and ZhanIt should be noted that, subject to the material cost and test cycle, sometimes we need to use mathematical research methods to process these test data and optimize the process parameters by establishing predictive models. Chiya et al.  used the2 of the BP model was 0.9226, while MLR was only 0.7456, indicating that the BP neural network had better prediction accuracy. Tanja et al. [2 of the model could reach 0.9008. Ehsani et al. [2 of the model could reach 0.976. Among many improved neural network algorithms, the BP neural network based on Genetic Algorithm (GA) doesn’t need an objective function to be continuous or differentiable and can search multiple objects at the same time, reducing the possibility of being trapped in local optimization [However, there are many factors affecting the performance of building materials, and the relationship between various process parameters and material properties is not strictly linear, so it is difficult to predict the performance of building materials by using a simple MLR model . BP neura et al.  adopted a et al.  predictei et al.  predictemization . Becausemization , it is wmization ,40,41. TThis study uses grinding and calcination to activate coal gangue and uses orthogonal experiments combined with the GA-BP model to optimize the activation process of coal gangue and improve its activity index. Finally, the morphological changes and phase transitions of coal gangue under different activation conditions were characterized from a micro and meso perspective, and the activation mechanism of coal gangue was revealed through experiments such as laser particle size analyzer, X-ray fluorescence spectrometer, and scanning electron microscope. The results of this study aim to improve the activity of coal gangue as a supplementary cementitious material, therefore reducing cement consumption and carbon emissions. At the same time, it can effectively solve the accumulation of coal gangue waste and achieve waste resource utilization.2 and Al2O3, accounting for 86.09% of the total mass of coal gangue, while the content of CaO was only 4.58% and much smaller than that of cement in 59.12%. In addition, the loss on ignition of the coal gangue was 5.9 times that of the cement, indicating much more organic matter and residual carbon inside the coal gangue. The mineral composition of the coal gangue is shown in The 42.5 Ordinary Portland cement supplied by Zhucheng Yangchun Cement company limited , the coal gangue in the mining area supplied by Pingmei Shenma Group , and ISO standard sand supplied by Xiamen Aisiou Standard Sand company limited  were used in this test. The chemical compositions of the cement and coal gangue are listed in The mechanical activation of coal gangue in this study was carried out using a ball mill, and the mass ratio of steel balls to coal gangue was 5:1. After ball milling, the coal gangue powder passing through the 0.212 mm square hole sieve was thermally activated using a muffle furnace. After the activation, the coal gangue was naturally cooled in the furnace. The entire activation process of coal gangue was performed by controlling the grinding duration, calcination temperature, and calcination duration. The effects of three factors  of the activation method on the activity of coal gangue were studied in this paper. The morphological changes, phase transitions of activated coal gangue under different conditions, and the activation mechanism were studied through the microscopic and mesoscopic tests, as listed in H28, %) was determined by Equation (1), according to China Standard GB/T 1596-2017 [R and R0 are the 28-day compressive strength of the cement mortar using activated coal gangue and the reference group, respectively.The activity of the coal gangue was evaluated by measuring the compressive strength of the mortar. The design and compressive strength test of the cement mortar were based on China Standard GB/T 17671-2021 . The sig596-2017 .(1)H28=The 28-day compressive strength measured and activity index calculated with Equation (1) of the specimens in different factors and levels were shown in 0.20 = 9.00, indicating that the calcination duration has little effect on the activity of coal gangue, which was consistent with the range analysis results.According to the test results, the calculated range of strength activity index to each factor in these three levels was listed in The significant impact of each activation process on the activity of coal gangue can be clarified through the orthogonal tests, but the related optimizations are based on combinations of established levels, which cannot be optimized in continuous intervals. In addition, only the optimization conditions can be determined through the orthogonal design, and the specific responses cannot be provided, which makes it difficult to evaluate the actual effects of the optimized activation process of coal gangue. Hereto, a neural network model was used to further optimize the activation process of coal gangue. Considering the possibility of interaction between calcination temperature and calcination duration, calcination duration was still used as an input variable in the modeling process. In order to reflect the impact of changes in process parameters on the strength of the specimens more intuitively, the 28-day compressive strength was selected as the response value. To avoid obtaining local optimal values through iterative calculation of neural networks due to limited sample size data in orthogonal tests, the following measures were adopted. First, two genetic algorithm modules were embedded in the main program of the neural network to form a GA-BP neural network, which iterated within randomly generated intervals to avoid falling into the local optima of a single interval. Then, two new sample points as the test set through tests were added to ensure the accuracy of the model. Though it was few in number of orthogonal data, directly using them as both the training and testing sets still led to data leakage during the training process of the neural network, greatly reducing the model’s anti-generalization ability. Therefore, the addition of these two new sample points above was very necessary. The activation process parameters of the two newly added sample points are listed in The GA-BP model was established and operated as shown in (1)Normalization of dataxk, x′k, xmin, and xmax are data before normalization, data after normalization, and the minimum and maximum values in these data sequences for each activation process, respectively.The physical meanings and numerical differences of grinding duration, calcination temperature, and calcination duration are significant. To avoid the difficulties in model convergence and the significant errors of network prediction, Equation (2) was used to normalize these data into the values in 0~1.(2)The operating parameters and hidden layer nodes of the neural networks−7.l, n, and m are the node numbers of hidden layers, input layers, and output layers, and a is a constant between 1 and 10.In the neural network, activation parameters were used as the input parameters. A single hidden layer structure was used. Output nodes were for 28-day compressive strength prediction output. The maximum number of iterations was 1000. The learning rate was 0.1. The activation function was a sigmoid function. The reasonable range of values (2~12) for the number of hidden layer nodes was determined using Equations (3)–(5) , and the(3)The code, selection, crossover, and mutation methods of genetic algorithmsip is the probability that the i-th individual will be selected, iQ is the fitness value, and S is the total number of the selected population.The total number of individuals within the operation matrix was 21 when GA-A was used to optimize the weight threshold. The GA-B encoding length was three, representing the values of three activation parameters. The roulette wheel method was used as the selection operation, shown in Equation (6). The fitness function determined by GA-A was the prediction error of the neural network; the smaller, the better. The roulette wheel rule defaulted to the individual with the highest calculation value as the optimal individual, so it was necessary to take the reciprocal of the fitness function of GA-A. The method used for crossover operation was real number crossover, and the mutation method was single point mutation .(6)pi=Q(4)Determination of the genetic algorithm parametersThe population, crossover probability, and mutation probability of the two genetic algorithm modules were 50, 0.3, and 0.1, respectively. Considering the speed of model operation and the reliability of the results, the number of iterations for GA-A and GA-B were set to 30 and 100, respectively. The convergence of fitness values is shown in 2/kg, and the predicted and measured 28-day compressive strengths were 44.29 MPa and 46.72 MPa, respectively, with an error of 5.20%, weight was w [The prediction results of the GA-BP model improved by the genetic algorithm and the traditional BP model were listed in ht was w  = [1.568Keeping the initial feeding mass at 3 kg, the changes in the passing mass of 0.212 mm square hole sieves and the specific surface area of the coal gangue powders with grinding duration are shown in −1 when the grinding duration was 76 min. The small shoulder peak of Si-O-AlVI bending vibration also slightly declined at 425.94 cm−1. This may be caused by the bond fracture of the Si-O-Si in part of the polysilicon phengite and the destruction of part of the kaolinite phase when it was ground for 76 min, as shown in The XRD analysis results and phase content of coal gangue powder are shown in Overall, effective mechanical grinding was a feasible method to increase the content of potentially active minerals, amorphous active substances, and the number of active sites on the particle surface in the coal gangue powder and enhance the activity of coal gangue.The thermal activation mechanism of coal gangue was studied that withstood the same grinding duration of 76 min and heat treatments at different calcination temperatures for 54 min; the obtained analysis results of XRD and phase content of coal gangue powder as shown in −1 at 749 °C. This was the weak characteristic peak of some hydroxyl groups in the polysilicon phengite that was difficult to separate, and it disappeared completely at 950 °C. In addition, the obtained changes in other phases and the analyses were consistent with the results in The FT-IR curve of coal gangue powders after thermal activations is shown in 2 are shown in 2 atmosphere. The coal gangue powder was in an endothermic state from 30 °C to 322 °C. At 262~322 °C, a weak peak was observed on the TGA curve with increased coal gangue powder mass, resulting in a clear exothermic peak near 330 °C on the DSC curve. During this process, the coal gangue powder adsorbs oxygen, accumulating sufficient oxygen for the subsequent combustion of residual carbon [2 atmosphere, and the dehydroxylation endothermic peak of the kaolinite phase in DSC in the air was covered. According to the studies above, during the treatment of thermal activation, the hydroxyl removal of the kaolinite phase and the combustion of residual carbon and organic matter were important reasons for the significant improvement of the activity of coal gangue. At 618–750 °C, a small endothermic peak was observed on the DSC curve. The calcite decomposed to form CaO, which was converted into Ca(OH)2 during the hydration of cementitious material, thus further activating the activity of activated coal gangue. At 750–1000 °C, the weight loss during this stage was less than 1%. The stage is mainly the dehydroxylation reaction of the polysilicon phengite and the formation of a few mullite and spinel crystal phases; the endothermic and exothermic reactions occurred alternately so that no obvious endothermic and exothermic peaks were observed on the DSC curve.The TGA and DSC test results of activated coal gangue powders under air and Nl carbon . At 322~Ⅵ-O octahedron, and the coordination number of Al3+ became five. As the temperature continued to rise, the remaining externals and internal hydroxyls were removed, and the coordination number of Al3+ became four. The AlⅥ-O octahedron was destroyed, and the kaolinite was transformed into spatially disordered metakaolinite. The Al3+ with a coordination number of four in metakaolinite was unstable, so the coal gangue after the thermal activation at 322~618 °C exhibited very high activity. However, as the temperature continued to rise, the metakaolinite recrystallized into spinel and mullite, and its activity decreased significantly.The thermal activation of coal gangue transformed the kaolinite phase into the amorphous metakaolinite phase. The influence level order of the factors on the strength activity index from strong to weak was the calcination temperature, grinding duration, and calcination duration. The strength activity index increased with an increase in the activation temperature at 0~750 °C but decreased significantly when it exceeded 750 °C. The strength activity index increased in a significant decay rate with an increase in grinding duration.The prediction accuracy of the prediction results of the GA-BP model was higher than that of the BP model. The activation process parameters of coal gangue for the optimal scheme obtained from the GA-BP model were 76 min, 749 °C, and 54 min for the grinding duration, calcination temperature, and calcination duration, respectively, with a high strength activity index of 98.31%.The specific surface area of coal gangue powders was increased significantly by mechanical grinding. At the same time, the content of the amorphous phase and the number of active sites on the surface of coal gangue powder, as well as the content of active substances in coal gangue, were increased. Thus, the activity of the coal gangue was enhanced.3+ with a coordination number of six was converted into active Al3+ with a coordination number of four. Thus, the activity of coal gangue has a significant improvement. At 618–750 °C, the calcite decomposed to form CaO and was converted into Ca(OH)2 during the hydration of cementitious material, which activated the coal gangue.The optimal temperature of the thermal activation was 750 °C. The thermal activation of coal gangue destroys the structure of the kaolinite phase and transforms it into an amorphous metakaolinite phase, in which the AlHowever, in the GA-BP model, the number of hidden layers and the learning rate value need to be determined using continuous attempts. In future research studies, more advanced algorithms can be used to further optimize some hyperparameter values to improve the performance of the model.


What are the main findings?Mechanical properties of steel fiber-reinforced coal gangue concrete (SCGC) are tested, proving the effectiveness of strength enhancement of SCGC and helping to expand the application range of SCGC.The damage evolution model of SCGC under freeze–thaw cycles (FTCs) is established by introducing damage variables of coal gangue and SCGC.What is the implication of the main finding?This study provides key experimental data and a theoretical basis for a wider range of proper uti-lization of coal gangue in cold regions.In order to improve the utilization rate of coal gangue and expand the application range of coal gangue concrete (CGC), a certain proportion of steel fiber was added to the concrete, and the freeze–thaw cycles (FTCs) and flexural tests were used to explore the effects of different mass replacement rates of coal gangue  and different proportions of the volumetric blending of the steel fiber  on the frost resistance of steel fiber-reinforced CGC (SCGC). The governing laws of mass loss rate, relative dynamic elastic modulus and load–midspan deflection curve were obtained on the base of the analysis of testing results. The damage mechanisms of the SCGC under the FTCs were analyzed using the results of scanning electron microscopy (SEM). Based on the Lemaitre’s strain equivalence principle and Krajcinovic’s vector damage theory, a damage evolution model of the SCGC under the FTCs was established by introducing the damage variable of the SCGC satisfying Weibull distribution. The results show an increasing mass loss rate of the SCGC and a decreasing relative dynamic elastic modulus with an increasing mass replacement rate of coal gangue. The proper content of the steel fiber can reduce the mass loss rate of concrete by 10~40% and the relative loss rate of dynamic elastic modulus of concrete by 2~8%, thus significantly improving the ductility and toughness of the concrete. The established damage evolution model is well validated by the experimental results, which further help to improve the modelling accuracy. This study provides key experimental data and a theoretical basis for a wider range of proper utilization of coal gangue in cold regions. Therefore, it is urgent to improve the utilization rate of coal gangue [Coal gangue is an associated product of coal. For every ten tons of coal yield, one ton of coal gangue is produced. As a major and largest coal producer in the world, China had an annual total output of 4.56 billion tons of coal in 2022, accounting for 51.8% of the total output of coal in the world, with an increase of 10.5% in comparison with that in 2021 . So far,l gangue ,8,9,10. At present, many studies have been conducted on coal gangue concrete (CGC). It is found that, due to the need for secondary crushing of coal gangue for coarse aggregates, many internal microcracks are unavoidable. Compared with natural gravel, coal gangue has some particular properties, such as low bearing strength, high brittleness, and rough surfaces. Replacing natural gravel with coal gangue to prepare concrete will reduce the working performance, strength, and durability of concrete ,12. TherIt was found that, in the service process of concrete, compared with the loading test, the durability test was a greater challenge. In China, coal mines are mainly distributed in the northern regions, including Northeast, Northwest, and North China. From the perspective of local materials, one of the major concerns of the application of CGC in the northern regions is whether the frost resistance durability meets the application requirements ,23,24,25The existing research has mainly focused on the frost resistance durability and damage evolution of CGC, and most of the results are consistent with each other or among themselves. However, there are few studies on the influences of fiber incorporation on the frost resistance durability of CGC, mechanistical analysis, and damage constitutive model. This situation has greatly limited the practical application of steel fiber-reinforced coal gangue concrete (SCGC). Therefore, on the basis of existing studies, in this paper, we explored the influences of coal gangue mass substitution rate and steel fiber volumetric fraction on the frost resistance of the SCGC. The influence mechanisms of various factors on the mechanical properties of concrete are analyzed from the microscopic view using a scanning electron microscope (SEM). Based on the damage theory and Krajcinovic’s vector damage theory, the damage variable of the SCGC satisfying the Weibull distribution is introduced to derive the damage constitutive model of the SCGC. This study can help to provide a theoretical basis for promoting the resource utilization of coal gangue and expanding the scope of use of CGC.per se  [According to the 81-2019) , the SCGNational Standard of China for Test Methods of Long-Term Performance and Durability of Ordinary Concrete (GB/T 50082-2009) [fn and mass Wn were measured. When at least one of the following conditions occurred, the test was terminated: (1) 300 FTCs; (2) reduction in the relative dynamic elastic modulus to 60% of the original value, and; (3) a 5% mass loss rate.Referring to the specifications of the 82-2009) , the mol(1)The arithmetic average of the test results of the three parallel specimens was regarded as the deflective strength of this group of the specimens.(2)If the difference between either the minimum or maximum and mean values of the test results of three parallel specimens was greater than 15% of the mean value, the two values (minimum and maximum) should be discarded, and the mean value should be regarded as the test value for this group of the concrete specimens. If the difference between the maximum and mean values and that between the minimum and mean values were all greater than 15% of the mean value, the test results were considered invalid, and the group test had to be repeated.Every time, after 25 FTCs, a group of concrete with each ratio needed to be taken for flexural test. The test was carried out according to the flexural strength test method of concrete as specified in the GB/T 50081-2019 . The loa3 in volume, in order to ensure the smoothness of the observed position. During the test, the specimens were completely dried and strictly sealed for gold spray observation. The SEM instrument used during the experiment was the Czech TESCAN MIRA LMS produced by Tesken Co., Ltd. in Brno, Czech Republic.After the bending resistance test, the SCGC was crushed to prepare concrete samples smaller than 1 cm(1)The test piece mass loss rate is calculated as follows:M is the mass loss rate, in %, to an accuracy of ±0.01; m0 is the mass of the specimen before the FTCs, in kg; and nm is the mass of the specimen after n FTCs, in kg.(2)The relative dynamic modulus of elasticity of the specimen is calculated as follows:EA is the relative dynamic elastic modulus, in %, to an accuracy of ±0.1, and f0 and nf are the transverse fundamental frequencies of the specimen before and after n FTCs, in Hz. The test instrument is a DT-W18 dynamic elastic modulus tester produced by Beijing Digital Yilong Instrument Co., Ltd. in Beijing China , 0.8% (MG2508), 1.0% (MG2510), and 1.2% (MG2512), the mass loss rate is 3.12%, 1.98% (reduced by 36.54%), 2.77% (reduced by 11.22%), and 3.54% (increased by 13.46%) respectively; the relative dynamic elastic modulus is 0.83, 0.90 (increased by 8.43%), 0.88 (increased by 6.02%), and 0.78 (reduced by 6.02%). When the mass replacement rate of the coal gangue reaches 50%, the SCGC with 0.8% and 1.0% of the steel fiber can still withstand 125 FTCs, and the frost resistance index of the SCGC with a 0.8% steel fiber volumetric fraction increases the greatest. The reason for this phenomenon is that the addition of the appropriate amount of steel fiber (0.8%) can enhance the connections in the SCGC structure due to the bridging effect, which slows the development of initial cracks in the SCGC, thus fundamentally reducing the internal damage of the material. However, the excessive addition of steel fiber  will lead to its accumulation and agglomeration in the concrete structure, resulting in that the cement mortar cannot be closely connected with the internal structure of the concrete and thus in an increase in the initial microcracks of the CGC. Thus, the damage is aggravated, leading to the conditions favorable for the emergence and development of cracks. Therefore, if the service life of the SCGC in cold regions is expected to be longer, the volumetric fraction of the steel fiber should be set to 0.8%.In summary, in order to produce SCGC with the best frost resistance, the optimal coal gangue mass replacement rate should be 25%, while the optimal steel fiber volumetric fraction should be 0.8%.When the coal gangue completely replaced the natural gravel, the SCGC with 1.2% steel fiber failed after 75 freeze–thaw cycles. Therefore, in order to ensure the accuracy of the test results, only those for 0, 25, 50 and 75 FTCs were analyzed. The specific results are shown in It can be seen from When the volumetric fraction of the steel fiber was set at 0.8%, 1.0%, or 1.2%, the load–deflection curves of the concrete specimens showed a rapid upward trend before the peak load, but the midspan deflection of the peak load position of the CGC fell within 0.2~0.3 mm, while that of the SCGC increased to 0.5~1 mm. Evidently, the concrete specimen with a steel fiber volumetric fraction of 0.8% had the most obvious improvement. After the peak load, the load–midspan deflection curve of the SCGC was smoother than that of the natural gravel concrete or CGC, and the curve showed a fluctuating downward trend. When the mass replacement rate of the coal gangue was no higher than 50%, and the number of FTCs was no more than 75 times, the load–midspan deflection curve continued to have the second, lower, peak after the first, main, peak, and after the second peak, it showed a fluctuating downward trend. However, compared to the natural gravel concrete and CGC, the SCGC had an obvious improvement in ductility and toughness: the maximum midspan deflection of the natural gravel concrete and CGC was 0.3 and 0.4 mm, respectively. After the incorporation of the steel fiber, the maximum midspan deflection of the SCGC became greater than 5 mm. The ductility and toughness of the concrete were improved the most at a volumetric fraction of the steel fiber at 0.8%. The reason for such an improvement was that during the bending process of the SCGC, the steel fiber possibly played a key role in connecting the concrete on both sides of the crack and hindered the continuous development of the crack upon the failure of the concrete specimen, when the energy required for destroying the SCGC was greater, thereby improving its toughness. When the volumetric fraction of the steel fiber was excessively large, the steel fiber would be unevenly distributed in the concrete mortar. A part of the steel fiber agglomerated, instead of being tightly wrapped, in the cement mortar. Macroscopically, the ductility and toughness of the concrete declined due to the presence of an excessively high volumetric fraction of the steel fiber.In summary, in order to improve the ductility and toughness of SCGC, the coal gangue mass substitution rate should be set to 25%, and the volumetric fraction of the steel fiber to 0.8%. These conclusions are consistent with the analysis results of the SCGC frost resistance described in (a)Microstructure of concrete after curingThe SEM was used for observing and analyzing the microstructure for the specimens of the natural gravel concrete and the CGC with the optimal mix ratio after curing .It can be clearly seen from (b)Microstructure of concrete after FTCsSEM results are often used to explain the change process in the natural gravel concrete, CGC, and SCGC with the number of FTCs from the microscopic point of view. In this study, the influences of the FTCs, coal gangue aggregate, and steel fiber incorporation on concrete are qualitatively analyzed, as shown in It can be seen from From It can be seen from (1)Continual damage of the SCGC under bending;(2)All coarse aggregates are evenly distributed in the SCGC;(3)During bending, the SCGC structure is connected by interface microelements, which constitute the corresponding interface transition zone, and there is congenital damage.There were two kinds of coarse aggregates  used in the SCGC. The coal gangue aggregate is characterized by low strength, some internal micro-damage, and a complex internal structure of the SCGC. Therefore, in order to more easily simulate the damage evolution of MG2508  under the FTCs, the following assumptions were made to build the damage model:σ is the effective stress; ε is the effective strain; E is the elastic modulus, and; D, the damage variable.According to the Lemaitre’s strain equivalence principle :(3)σ=Eε1D of the SCGC includes two parts. The first part is the internal damage of the SCGC after the FTCs. Previous studies have found that the dynamic elastic modulus can more accurately describe the internal concrete damage after the FTCs [Df was determined according to the damage mechanics as follows:Ed0 is the dynamic elastic modulus of the SCGC without an FTC, and; End is the dynamic elastic modulus of the SCGC after n FTCs.Under the FTCs, damage variable the FTCs ,35. TherDp of the SCGC under load. In the statistical damage model, the SCGC is usually considered as a series of defective microunits to satisfy the mandates of the Weibull distribution. Therefore, under the loading conditions, damage Dp of the material can be expressed as the ratio of the number of damaged microunits (fN) to the number of microunits of the material (N) [The second part is damage rial (N) :(5)Dp=NfNf:When the load on the SCGC increases to its yield strength, the microelement damage inside the concrete reaches Dp can be further expressed as follows:Then, damage f(x) in Equation (7) is the probability density function corresponding to the Weibull distribution function satisfied by the damage caused by the load in the SCGC [α and β are the scale and shape parameters, and ε is the effective strain.The microscopic heterogeneity of deformation characteristics and mechanical properties of brittle materials, such as concrete and rock, obeys the law of the Weibull distribution . That isthe SCGC :(8)fε=βαEquation (9) can be obtained by substituting Equation (8) into Equation (7):By combining Equations (5) and (9), the formula of the damage variable of the SCGC under the FTCs is obtained:By bringing Equation (10) into Equation (3), the damage constitutive model of the SCGC before peak load under the FTCs can be obtained as followsijσ is the stress tensor ν is the Poisson ratio; and C1 and C2 are the material constants. For the SCGC, ν = 0.2, C1 = 3.5, and C2 = 0.4; ijε is the strain tensor.The stress–strain curve of the SCGC can be divided into the stages of non-destructive and damaged evolution. The former can be fitted by Equation (11). In order to establish the model of the damage evolution stage, it is assumed that when the concrete is subjected to deformation, the deformation of the fiber and the concrete is the same, without relative sliding or dislocation. Based on the Krajcinovic’s vector damage theory and the Clausius–Duhem inequality , the damAccording to the hypothesis, the growth of microcracks mainly occurs at the midpoint of the specimen in the vertical direction. According to the incremental formula, the following conclusions can be drawn:σ11 is the normal stress in the x direction; ε11, ε22, and ε33 are positive strains in x, y, and z directions, respectively.That is,Based on the Mohr–Coulomb criterion under bending conditions, a hyperbolic method is used to simplify the damage surface. At this time, the strain generated is the same as the damage evolution value.By combining Equations (14) and (15), the definite integral is obtained:By substituting Equation (14) into Equation (16) and Equation (10) into Equation (13), we yield the following:Setting:Then, Equation (17) can be modified into the following:The definite integral of Equation (19) can be solved as follows:εpk is the strain corresponding to the peak stress.During the loading process, the SCGC is only subjected to bending load, so the constitutive damage equation of the SCGC under the FTCs is written as follows:Ed0 of the specimen and the dynamic elastic modulus (End) of the SCGC after n FTCs were obtained from the test results. However, if we need to obtain the stress–strain curve of the SCGC under the FTCs, only the values of α and β are needed. According to ε = εpk, σ = σpk;When ε = εpk, dσ/dε = 0.When According to Equation (21) of the damage constitutive model of the SCGC, the dynamic elastic modulus σpk is the peak stress, and εpk is the peak strain.From relationship (1) in combination with Equation (11), it follows thatσpk is the peak stress; E is the elastic modulus; εpk is the peak strain; D is the damage variable; Ed0 is the dynamic elastic modulus of the SCGC without a FTC; End is the dynamic elastic modulus of the SCGC after n FTCs; and α and β are the scale and shape factors.From relationship (2) combined with Equation (22), it can be seen thatδ is the midspan deflection, in mm; l is the distance between the left and right supports under the specimen, in mm; h is the height of the cross-section of the specimen, in this paper h = 100 mm; M is the bending moment of the specimen, in kN·m; I is the moment of inertia of the specimen, in m4; b is the width of the cross-section of the specimen, in mm; and y is the distance from the center of the moment of inertia to the neutral axis of the specimen, in mm, in this paper for h/2.During the loading process, the SCGC is in a state of compression on the one side and tension on the other, and the maximum stress point is at a certain position in the upper loading area of the specimen. The flexural failure at this position conforms to the constitutive relationship of concrete damage in the tension-bending state. The load–deflection curve of the relationship between load and displacement in the vertical direction of the SCGC can be transformed into the corresponding stress–strain curve through the corresponding relationship ,40. AccoThe corresponding stress–strain curve can be obtained by the load–midspan deflection curve obtained from the test through Equations (25)–(28), and the peak data can be obtained thereupon. Substituting them into Equations (23) and (24), the distributive parameters of each specimen can be obtained, as shown in Substituting the data from 2) of each model curve was greater than 0.9, indicating that the stress–strain curve of the SCGC specimen under the FTCs is in good agreement with that of the theoretical damage constitutive model, but there is a slight difference at the peak. This is mainly due to the differences in the individual samples, that is, the differences between the test and the simulated values resulting from the difference in the fiber content of the fracture surface. The measured flexural strength of the test is greater than the theoretically (model) calculated flexural strength, but the curve of the constitutive damage model before the peak is well fitted with the test data curve. Thus, the proposed constitutive damage model of SCGC under FTCs can more accurately describe the stress–strain changes in SCGC under FTCs. Therefore, the practicability and rationality of the model is validated herewith.From the results shown in With an increasing mass substitution rate of coal gangue, the frost resistance durability of SCGC decreases. The mass loss and relative dynamic elastic modulus of SCGC can be significantly reduced. When the number of FTCs reaches 50 times, the mass loss rate of SCGC is in the range of 1.18% (MG2508)~5.06% (MG12), while the relative dynamic elastic modulus is in the range of 0.55 (MG12)~0.94 (MG2508). In order to make SCGC more frost-resistant, the mass substitution rate of coal gangue should be set to 25%.With different volumetric fractions of steel fiber, the frost resistance index of SCGC varies. When the volumetric fraction of the steel fiber is 0.8% or 1.0%, the frost resistance index of SCGC increases obviously . When the volumetric fraction of the steel fiber is 1.2%, the frost resistance of SCGC decreases , but the incorporation of steel fiber can increase the ductility and toughness of SCGC . In order to produce SCGC for cold regions with higher ductility and toughness, the volumetric fraction of the steel fiber should be set to 0.8%.FTCs can increase the internal cracks and pore size of concrete, the interfacial transition zone between the coarse aggregate and the cement mortar, and the damage degree of coal gangue and destroy the connection between the steel fiber and the concrete structure, loosening the SCGC and macroscopically lowering the frost resistance index.The stress–strain curves of the SCGC specimens under the FTCs agree well with those predicted by the theoretical constitutive damage model. This proves that the model can accurately describe the stress–strain changes in SCGC under FTCs.


Ovarian tissue extract (OTE) and sodium selenite (SS) enhance the growth and maturation of preantral follicles in a dose-dependent manner.The present study was designed to bring more information regarding the mechanism of OTE and SS on the mRNA expression of follicle-stimulating hormone receptors (FSHR) and the proliferation cell nuclear antigens (PCNA) of in vitro matured isolated follicles.PCNA and FSH receptor genes were analyzed.The tissue extract was prepared from adult ovaries. The preantral follicles (n = 266) were isolated from 12-16-day-old mice and cultured in the control, experimental I (10 ng/ml SS), and experimental II (OTE) groups for 12 days. The follicular diameter, survival, and maturation rates, also, the production of 17-β-estradiol and progesterone, and the follicular expression of The survival rate of follicles in the SS-treated group (84.58%) was significantly higher than that OTE  and control  groups. The mean diameter of culture follicles in experimental group I (403.8 μm) and experimental group II (383.97 μm) increased significantly in comparison with the control group . The developmental rate of follicles, percentages of antrum formation, released metaphase II oocytes , production of hormones and the expression of 2 studied genes were significantly increased in both experimental groups in compare with control group .FSHR and PCNA genes. The OTE and SS have a positive effect on development of mouse preantral follicles via over-expression of  Folliculogenesis in mammals is one of the most complex processes that involves direct interaction between somatic cells (such as granulosa and theca cells) and oocytes (1). Different factors such as hormones, growth factors, and antioxidants play critical roles in the growth and maturation of follicles and oocytes (2). Several culture systems, including 2- and 3-dimensional systems, were designed to investigate the effects of these factors during in vitro follicular culture. Culture media usually contain necessary supplementations such as serum, growth factors, hormones, and so on that improve follicular maturation (3).It has been reported that selenium salts as non-metal chemical elements in large amounts are very toxic, but trace amounts of selenium are necessary for animal cell function (4). The addition of selenium to the culture medium as an antioxidant leads to the maturation of follicles and oocytes (5-10). It was reported that the supplementation of culture media with sodium selenite (SS) could increase the growth and maturation of preantral follicles (5). Also, several studies have demonstrated that supplementation of mouse oocyte maturation media with SS improved not only the oocyte developmental rate but also enhanced its expression of mitochondrial transcription factor A and mitochondrial DNA (6-9). These studies have shown that the reactive oxygen species (ROS) level was decreased in the presence of SS, which acts as an antioxidant . It was also shown that selenium is one of the main critical factors in follicular fluid (11).Ovarian follicular development is also regulated by intra-ovarian factors such as steroid hormones, epidermal growth factor, vascular growth factor, fibroblast growth factor, and growth differentiation factor β that enhance follicular development . Some of these factors are produced by the ovarian stromal cells and follicular cells (12). The ovarian microenvironment could improve follicular development by providing these elements. However, the literature shows that supplementation of culture media with follicular fluid could enhance the development and the quality of cumulus-oocyte complex and embryo .Previously, we studied the effects of different concentrations of ovarian tissue extract (OTE) on mouse follicular development. The OTE contains components that mimic the natural composition of ovarian tissues and was obtained from adult mouse ovaries, which contain a lot of follicular fluid that has an impact on follicular development. Our results at the morphological level demonstrated that the OTE increased the development of follicles as its concentration increased within the culture medium (14).Moreover, this study was designed to bring some additional information and compare the effect of SS and OTE on follicular function and development. In addition, at the mRNA level, the expression of 2 critical genes including follicle-stimulating hormone receptor (FSHR) and proliferation cell nuclear antigen (PCNA) that are involved in the maturation and proliferation of were assessed.The reagents were prepared by Sigma Aldrich company  except those indicated in the text.FSHR and PCNA genes were analyzed and compared. In addition, the levels of 17-β-estradiol and progesterone in the collected media were analyzed.In this experimental study from mouse ovaries, the follicles were dissected with 145-155 μm diameter and divided into 3 groups as follows. In the control group the culture media  containing 1% insulin, transferrin, and selenium , 100 mIU/ml recombinant follicle-stimulating hormone , 100 IU/ml penicillin and 100 mg/ml streptomycin and 10% fetal calf serum . In experimental group I, the culture media was the same as the control, in addition, 10 ng/ml SS was added (5). In experimental group II, the described culture media was used and the FBS was replaced with OTE (14). After 12 days of culture, the survival and developmental rate of follicles and the expression of For this study, 12-16-day-old female NMRI mice (n = 20) ovaries that contain preantral follicles were used for follicular isolation and 6-8-wk-old adult mice (n = 15) for the preparation of OTE. The mice were maintained in the animal house of the university under standard conditions . The ovaries were obtained after mice cervical dislocation, then transferred to culture media consisting of 10% FBS, 100 IU/ml penicillin, and 100 mg/ml streptomycin until assessments.The OTE was prepared according to the previous study (14). After dissecting the adult mice ovaries under a stereomicroscope, they (n = 15) were collected and immersed in potassium ammonium chloride solution (pH = 7.2-7.4) for 1 min. Ovaries were then washed 3 times with phosphate-buffered saline (PBS) and put into a glass homogenizer tube. They were homogenized by adding 2 ml of Tris-HCL buffer (pH = 7) and 50 μL of protease inhibitor solution. Then the volume of the solution reached 10 ml after the homogenization of ovarian tissues by Tris-HCL buffer (pH = 7). The obtained solution was sonicated for 2 min under W50 sonication conditions. Finally, the solution was centrifuged at 12000 RPM for 15 min. The supernatant was collected as tissue extract and stored at -80 C until assay.500 μL of supernatant of OTE was used to measure the amount of protein. The amount of protein in fetal bovine serum (FBS) was used as a reference to select the concentration of OTE. According to our previous study, the OTE which contains ½ of the protein level in FBS was selected (14).A 3-dimensional culture system based on sodium alginate capsulation was used for follicular culture (14). A mixture of sodium alginate and activated charcoal in distilled water was prepared to eliminate organic pollution. After 24 hr it was diluted with PBS at a concentration of 0.5% (w/v), then each isolated follicle was individually transferred into 7 µL of sodium alginate and a cross-linking solution containing 50 mM CaClThe morphological changes of follicles were studied using inverted microscope, and the follicles that showed a dark appearance were considered dead. By supplementing the culture media with 1.5 IU/ml of human chorionic gonadotropin  the oocyte ovulation induction was induced on Day 12 of culture, then 18 hr later the oocyte staging was done. The germinal vesicle oocyte has the prominent nucleus that is arrested in the prophase of meiosis I; the nucleus and polar body were not visible in the germinal vesicle breakdown oocyte, and the presence of the first polar body was demonstrated in the metaphase II (MII) oocyte (13).At the end of the culture period, steroid hormones, including 17-β-estradiol and progesterone, were analyzed in the collected media (n = 3 in each group). The levels of 17-β-estradiol and progesterone  were measured by an enzyme immunoassay, and these experiments were done in triplicates.PCNA,FSHR, and  was summarized in table I.Total RNA was extracted from follicles in each studied group (n = 12 in 3 replicates) using a TRIzol reagent extraction method . By spectrophotometer, the quality of extracted RNA and its level were analyzed. The list of applied primers for After extraction of total RNA and cDNA synthesis, according to QuantiTect SYBR Green RT-PCR kit , real-time RT-PCR was performed. Thermal conditions for the process included 3 steps; holding stage (95ºC for 5 min), step 2 was performed at 95ºC for 15 s, 58ºC for 30 s, and 72ºC for 30 s, and the last step (melt curve step) was continued at 95ºC for 15 s, 60ºC for 1 min, and 95ºC for 15 s. Then, the relative quantification of target genes to housekeeping genes was determined.The animals were used and cared for according to the Ethical Guidelines of Tarbiat Modares University. The Ethics Committee for Animal Research of the Tarbiat Modares University, Tehran, Iran, approved this study (Code: IR.TMU.REC.1394.272).Statistical analysis was conducted by SPSS 18 software . Quantitative variables were expressed as Mean The morphology of cultured follicles in 3 studied groups under the inverted microscope is demonstrated in figure 1. During the culture period, the follicular size showed a remarkable increase, and their diameter changes during the culture period are summarized and compared in table II. No significant difference was observed in follicular diameters in all studied groups at the beginning of the culture. Moreover, on day 12 of the culture period, these ranges were significantly increased in all groups, and the mean diameter of culture follicles in the 2 experimental groups was significantly higher in comparison with the control group (p = 0.032). However, this mentioned parameter was higher in the SS-treated group (p = 0.019).The survival and antrum formation rates in follicles and the rate of released MII oocytes are summarized in table III. At the end of the culture period, amongst the studied follicles in control, SS, and OTE-supplemented groups, the survival rates were found to be higher in SS supplemented group (p = 0.032). In the control group the percentages of antrum formation and the rate of released MII oocytes were significantly lower than in other studied groups (p = 0.027); but there was no statistical difference between SS and OTE groups.The levels of estradiol and progesterone in the group that was treated with SS and those treated with OTE were increased (p = 0.021) but there was no significant difference between these groups in this regard (Table IV).PCNA and FSHR genes were evaluated by real-time RT-PCR. The expression ratio of these target genes relative to the housekeeping  gene and the representative figure of PCR product electrophoresis are shown in figures 2A and B. This figure shows the expression of these studied genes was lower in the control group in comparison with both experimental groups (p = 0.023). Also, the representative figure of gel electrophoresis of PCR products in studied groups was demonstrated in figure 2C.The mRNA levels of .The present study aimed to evaluate the effect of OTE obtained from the adult mouse on preantral follicular growth, development, and gene expression. For better evaluation of this effect, in another set of experiment, in parallel, the preantral follicles were treated with SS and their development and pattern of gene expression were compared with another experimental and control groupOur results showed the survival, growth, and developmental rates of cultured follicles in 2 experimental groups that were treated with SS or OTE were higher than the control group, and these results revealed that the positive effects of these components on the follicular development.In agreement with our results, several reports demonstrated the positive effects of SS as an antioxidant, proliferative, and maturation factor that improved follicular development and oocyte maturation (4-10). It was reported that a culture medium supplemented with different concentrations of SS  promoted mouse in vitro follicular growth and maturation in a 2-dimensional culture system. Moreover, they demonstrated that 10 ng/ml of SS had better effects on the growth and maturation of the follicle (4).Another study showed that the activity of glutathione peroxidase of oocytes and the DNA integrity of cumulus cells were increased in the presence of SS during IVM of oocytes (6). Selenium as an integral part of the enzyme glutathione peroxidase improves the survival rate of the cells by the decrease in the level of ROS (5).In the present study, our results also confirm the similar effects of SS for enhancing follicular development in the 3D culture system. These results may be related to the antioxidant effects of SS by reducing the ROS or by reducing cell apoptosis .According to the results of another part of this study, it is suggested that the positive effects of OTE to improve follicular and oocyte development may be related to components within this extract, such as several types of growth factors that could enhance the follicular diameters by increasing the number of granulosa and theca cells . These factors are directly and indirectly involved in follicular growth and development. An increase in the number of follicular cells resulted in progress in follicular size that was demonstrated in both experimental groups during the culture period. It is suggested that SS as a proliferative factor and an antioxidant reagent enhances follicular development, while the OTE based on its component that mimics the natural condition and ovarian microenvironment showed the same effect.However, this effect is more prominent in SS-supplemented group. One explanation for these results is that the presence of some additional components in OTE that are remained or produced during its preparation, interferes with the follicular development. Moreover, in the present study, we did not assay and analyze the content of OTE based on some limitations, thus more additional studies are needed to prove the mentioned suggestions.The functional potential of granulosa and theca cells can be evaluated by measuring estradiol and progesterone production, and our observations showed that the levels of these hormones were increased in the culture media in both experimental groups in comparison with the control group. However, it was demonstrated that SS by stimulation of estradiol production could support in vitro and in vivo folliculogenesis (19). Also, it is suggested that the similar effect of OTE produces estradiol and progesterone by granulosa and theca cells; however, further study is needed to prove this suggestion.PCNA and FSHR genes. As the follicular development proceeded, the expression and production of these proteins was increased and could be a good indicator of follicular growth (20-22). However, in the present study, our results showed the treatment of follicles in vitro by SS and OTE led to increased expression of PCNA, and FSHR genes. This observation confirmed again the beneficial effects of SS and OTE on the in vitro maturation of follicles.Moreover, the molecular analysis in our study confirmed this suggestion and in this part of the study, we have evaluated the expression of 2 maturation markers in cultured follicles including PCNA expression markedly enhanced in the irradiated rats that were treated with SS in comparison with the non-treated once (23). From the other point of view, FSHR is a G-protein coupled with 7 transmembrane domain receptors and is expressed in the granulosa cells (24). Moreover, the nuclear and cytoplasmic maturation of oocytes could be controlled by the content of OTE via the expression of maturation genes such as FSHR. FSHR is necessary for follicular development and is also responsible for producing androgens (25). It has been reported that when the transition from the primordial to primary follicle occurred, FSHR expresses progressively (26). The presence of FSHR in the early follicular stages has an indirect effect on follicular development via paracrine factors released by ovarian stromal cells .A similar effect of SS was reported in an in vivo study by investigating the effects of SS on radiation-induced rat ovaries, which showed FSHR and PCNA genes.The OTE and SS have a positive effect on in vitro growth and maturation of mouse preantral follicles via over-expression of The authors declare that there is no conflict of interest.


The choice of crystals of these lanthanides is due to the fact that they have intense luminescence during mechanical action, and also do not dissolve in hydrocarbon solvents. During ultrasonic exposure to suspensions in pure alkanes, bands of Ln3+ ions and N2 in the UV region are recorded in the luminescence spectrum. When aromatic hydrocarbon molecules are added, bands of benzene, toluene and p-xylene molecules, coinciding with their photoluminescence spectra, are recorded in the sonotriboluminescence spectra in the UV region. The high sensitivity of the luminescence of suspensions to arene additives made it possible to obtain the dependence of the characteristic fluorescence of arene molecules in the sonotriboluminescence spectra on their concentration in suspensions. The limits of detection of benzene, toluene and p-xylene in the composition of this suspension were established. The lower limits of detection from the sonotriboluminescence spectra for xylene, toluene and benzene are 0.1, 3 and 50 ppmv, respectively. Fluorescence bands of these molecules were also recorded in the sonotriboluminescence spectra of suspensions in commercial dodecane and heptane with additives of commercial gasoline (up to 1%). The results obtained can be used for luminescent detection of aromatic compounds in saturated hydrocarbons.The sonotriboluminescence of suspensions of terbium(III) and europium(III) sulfates in decane without and in the presence of benzene, toluene and  Previously, we reported the registration of multiemitter sonotriboluminescence that occurs during sonication of suspensions of terbium sulfate in certain hydrocarbons [2(SO4)3 crystals significantly exceeds the intensity of sonoluminescence (SL) of a homogeneous solution of Tb2(SO4)3. Moreover, the STL spectra, in addition to narrow emission of Tb3+, contain intense fluorescence bands of aromatic hydrocarbons  in the region of 280–290 nm [Sonotriboluminescence (STL), a sonogenerated emission that occurs during the destruction of crystals in suspensions, is of not only fundamental  but also of practical interest for the development of new luminescent applications, especially in the field of analytical chemistry. Today, one of the most promising classes of sono- and triboluminophores are lanthanide compounds with intense luminescence in the near-UV 3∙8H2O and Tb2(SO4)3∙8H2O crystals in alkanes with the addition of different concentrations of arene molecules and commercial hydrocarbons to these liquids to identify patterns of acoustic influence, concentration dependences of luminescence intensities of arenes and the composition of sonotriboluminescence emitters.Here, for the first time, we present the results of a comparative study of ultrasonic influence on suspensions of Eu3+ and Tb3+ ions, N2 lines are also recorded in the STL spectra , 288 nm (toluene) and 292 nm (p-xylene), caused by singlet–singlet transitions, are recorded in the spectrum [In this work, alkanes are considered when benzene, toluene and spectrum ,20. As c3+ and N2), the generated electrons enter the volume of the liquid base of the suspension, and produce radiolysis, exciting the luminescence of aromatic compounds when they are present in alkanes.Recall that, in contrast to sonoluminescence , the mechanism of STL excitation of crystal suspensions is close to the mechanism of triboluminescence, namely, it is associated with electrification and the occurrence of discharges during friction and destruction of crystals ,21,22,23p-xylene from fluorescence spectra. The main maxima of these aromatic hydrocarbons are located very close together, and the bands also have a vibrational structure. When these spectra are superimposed on each other, it is difficult to deconvolute and assign fluorescence bands to one or another arena. However, based on the results obtained individually for each arena on the STL spectra, curves of the dependence of the luminescence intensity of aromatic hydrocarbon molecules on their content in decane were constructed  without additional purification, commercial dodecane (99%) and commercial gasoline (octane number 92) were used in the work. Suspensions were prepared by adding Eu2(SO4)3∙8H2O and Tb2(SO4)3∙8H2O crystals  to liquids. Sonotriboluminescence was excited in 7 mL of a solvent containing 250 mg of crystals in a thermostated stainless steel reactor with a quartz window at the bottom [−1. The temperature in the cuvette during recording of STL of suspensions was maintained using a circulation thermostat LT-105a . Sonotriboluminescence spectra were recorded using a Zolix OmniFluo-900 spectrofluorimeter (Detector TE-cooled PMT).Heptane and decane (≥99.99%), benzene, toluene, e bottom ,2. UltraAll measurements were carried out in a series of similar experiments 3–5 times. The average relative measurement error was no more than 5%.The identification of dodecane was carried out on a Chromatec-Crystal-5000 gas chromatograph with an Agilent DB-1 50 m × 0.25 mm × 0.25 µm capillary column . The chromatograph was attached by interface to the computer where the data were acquired with the program Chromatec Analitic 3.0.0.2.p-xylene molecules in the composition of decane were established. The lower limits of detection from the sonotriboluminescence spectra for xylene, toluene and benzene are 0.1, 3 and 50 ppmv, respectively. Fluorescence bands of these molecules were also recorded in the sonotriboluminescence spectra of suspensions in commercial dodecane and heptane with additives of commercial gasoline (up to 1%). The results obtained can be used for luminescent detection of aromatic compounds in saturated hydrocarbons.Thus, the sonotriboluminescence of suspensions of lanthanide salts in heptane and decane with the addition of arene molecules and commercial gasoline, as well as a suspension in commercial dodecane, was studied. The dependences of the intensities of characteristic fluorescence were obtained and limits of detection of benzene, toluene and