Substance use among people living with HIV is associated with poor health, social, and psychological outcomes. This study assessed the prevalence of substance use and associated factors among youth attending HIV care and treatment centers (CTCs) in Dodoma, Tanzania.This cross-sectional study was carried out in Dodoma, Tanzania, from February to April 2020 among youth aged 15–24 attending HIV CTCs. Data was collected using sociodemographic, WHO ASSIST Version 3.0, BDI II, and SERAD questionnaires. Data analysis was done using Stata 17. Descriptive statistics were used to summarize continuous and categorical variables. Univariable and multivariable logistic regression analyses were conducted to determine factors independently associated with substance use.The prevalence of substance use was relatively low (6.6%). Older youth (20 to 24 years) were 2% less likely to use substances compared to the younger ones (15 to 19 years) . There were statistically significant decreasing odds of substance use with every year increase in age at HIV diagnosis . Being unemployed was statistically significantly associated with decreased odds of substance use among this population . Youth who had detectable viral loads were significantly more likely to use substances compared to those with undetectable viral loads .Despite the low prevalence of substance use found in this study, it is important to note that late age of HIV diagnosis, employment, and detectable viral load negatively impacted HIV positive youth with regards to substance use. It is recommended that CTCs emphasize routine screening for substance use among youth who have detectable viral loads. HIV infection disproportionately affects young people, with individuals between the ages of 16 and 24 demonstrating the highest rates of new HIV infections compared to other age groups –5.Substance use has become one of the major growing public health and socioeconomic issues worldwide, particularly in developing countries , 7. SubsA study conducted in the United States of America assessing the prevalence and correlates of substance use among youth (ages 12–26) living with HIV found that 32.9% used tobacco, 27.5% used marijuana, 21.3% used alcohol, and 22.5% reported any other illicit drug use . A studyThe majority of studies addressing the use of substances among YLWH have been carried out in high-income countries , 36. StuThis was an analytical cross-sectional study conducted across 4 care and treatment centers (CTCs) in Dodoma, the capital city of Tanzania, from February to April 2020. The prevalence of HIV in the Dodoma region is 2.9%, and that of substance use among youth (regardless of HIV status) is 14.6% , 41. TheWe enrolled youth ages 15–24 who were confirmed to be HIV positive and attending selected HIV care and treatment centers in Dodoma. They were aware of their HIV status and were able to give consent (18–24 years), as were emancipated minors (< 18 years). Youth aged 15–17 years gave their assent with the consent of their guardians. In instances where the guardians were unable to present to the clinic to give assent, mostly citing transportation challenges, the youth was excluded from participation in the study. Using the Leslie Kish formula for cross-sectional studies, a total sample of 211 participants was recruited from the 4 centers using a probability proportionate to size sampling technique per center followed by a systematic sampling method for each sampling frame .3 and ≥ 200 cells/mm3. This categorization helps guide clinicians in making decisions about issues such as treatment failure and HIV disease progression to AIDS and allows them to intervene accordingly.Sociodemographic variables comprised of age (completed years), sex , race/tribe (Gogo or other), religion (Muslim or Christian), education level , occupation status , orphan status , and marital status . Information on clinical variables was obtained from patients’ CTC records; information was collected about the most recent viral load (within the last 6 months), most recent CD4 count (within the last 6 months), World Health Organization (WHO) HIV clinical staging, the ART regimen that they were currently on, the duration of ART use, and their age at diagnosis of HIV. Cut-offs for viral load and CD4 counts were adopted based on the Standard Treatment Guidelines and the National Essential Medicines List for Tanzania Mainland designates a viral load of < 40 copies/mL as undetected and ≥ 40 copies/mL as detected. The Standard Treatment Guidelines for Tanzania also categorize CD4 counts into two groups: < 200 cells/mmSubstance use was assessed using the Alcohol, Smoking, and Substance Involvement Screening Test (ASSIST). In this study, "substance use" referred to the non-medical use of any substance falling into categories of the ASSIST over the past 3 months prior to the study. These substances were: alcoholic beverages, tobacco products, cannabis, cocaine, amphetamine-type stimulants, inhalants, sedatives, hallucinogens, opioids, and others. The ASSIST is an 8–item questionnaire that assesses lifetime use of substances, substance use in the past 3 months, and injection drug use. The ASSIST also assesses the frequency of substance use. The ASSIST was developed by the World Health Organization and an international team of substance use researchers. It was designed for use by health care workers in a range of health care settings . The ASSParticipants were assessed for depressive symptoms using Beck’s Depression Inventory, Second Edition (BDI-II). The BDI-II is designed for individuals aged 13 and above. It is a 21–item multiple-choice self-report instrument intended to assess the existence and severity of symptoms of depression as listed in the American Psychiatric Association’s Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition . The BDIAntiretroviral therapy (ART) adherence over the past month was assessed using the Self-Reported Adherence (SERAD) questionnaire. The SERAD is a self-reported instrument designed to provide easier adherence measurement. It is a 14-item tool that evaluates different time frames and possible reasons for medication non-adherence. The SERAD has been validated for use in the adult HIV-positive population . The SERp-value < 0.25 and priori confounders from the crude analysis were entered into the multivariable model to determine independent factors associated with substance use . Confounders that were controlled in the multivariable model included marital status, occupation, education level, age at diagnosis of HIV, duration on ART, and viral load [Data were entered using Epidata and analyzed using Stata 17 . Measureral load . All varral load –53.The mean age of participants was 19 years (SD = 2.5); a majority (63.5%) were aged 15 to 19 years. More than half (59%) were female, and a majority (66.8%) had secondary education or above . The median depressive symptom score was 1 . The median age at diagnosis of HIV was 11 years IQR = 9,12) with the majority of the study participants (81.2%) being diagnosed with HIV below the age of 10 years  compared to unemployed youth 3.8%). Youth that were diagnosed with HIV before the age of 10 had a significantly lower prevalence of substance use (1.2%) compared to those diagnosed at ages above 10 (28.9%). The prevalence of substance use was also significantly higher among youths with a CD4 count of less than 200 cells/mm.8%. Yout3 of viral load were significantly more likely to use substances compared to those whose copies/mm3 of viral load were undetected  (Table 4).In the crude analysis, youth characteristics including current age, occupation, age at diagnosis of HIV, WHO clinical staging, duration on ART, CD4 count, and viral load were significantly associated with substance use. In the adjusted analysis, however, fewer characteristics—current age, occupation, age at diagnosis of HIV, and viral load were significantly associated with substance use. Older youth (20–24 years) were less likely to use substances compared to the younger ones (15–19 years) . Unemployed youth were less likely to use substances compared to their employed counterparts . With regard to the age at diagnosis of HIV, the odds of substance use increased by 1.7 times  for youth diagnosed with HIV after the age of 10. It was observed that youth who had detected copies/mmThis study found a prevalence of 6.6% for substance use among HIV positive youth attending CTC. This prevalence is similar to a study done in Dar es Salaam among youth in the general population, which reported a prevalence of 7% . The preUnemployed youth and students were observed to have significantly lower odds of substance use compared to employed youths. This is similar to other studies that have been conducted among YLWH in clinical settings , 34. A pTo the best of our knowledge, this study is one of the first to address both injectable and non-injectable drug use among YLWH. Our study is not without limitations. Due to the cross-sectional nature of this study, temporal relationships between HIV infection and substance use could not be established. Some of the study instruments used, such as the BDI II and the SERAD, for the assessment of depressive symptoms and adherence to ART, respectively, have not been validated in the Tanzanian setting. Nonetheless, previous studies conducted in Tanzania have used the BDI II to assess for depressive symptoms among PLWH , 73. TheThe prevalence of substance use among HIV-positive youth attending CTCs in Dodoma was 6.6%. The decreasing odds of substance use with every year increase in age at HIV diagnosis and among employed youth were observed to be statistically significant. This study highlights important aspects of substance use among youth living with HIV. We recommend routine screening for substance use among youth attending CTCs and providing continued psychoeducation and counseling to enable timely detection of the behavior and promote abstinence from substance use. Concerned health care providers should engage with policymakers to enact and promote policies against substance use as the vice plays a role in late presentation to clinical settings, particularly for YLWH.Clients at CTC who consistently present with low CD4 counts, detectable viral loads, higher WHO HIV clinical staging, and suboptimal adherence to ART should be monitored closely for the possibility of the use of substances. We also recommend that further studies be done to explore other psychosocial aspects associated with substance use among HIV-positive youth, such as mode of transmission, adverse childhood experiences, and caregiver/family dynamics.


Vaccinium corymbosum L.) leaf tissues was studied by using different concentrations of colchicine and oryzalin. Oryzalin was found to be highly toxic to this species, while the adventitious shoot organogenesis media enriched with 25 and 250 µM colchicine was able to induce polyploidization, with significant differences among the treatments used. Higher concentrations of both antimitotic agents led to the browning and death of the leaf tissues. The polyploids obtained showed several morphological differences when compared with the diploid shoots. Flow cytometry analysis was used to confirm the ploidy level of the regenerated shoots, demonstrating that a total of 15 tetraploids and 34 mixoploids were obtained. The stomatal sizes (length and width) of the tetraploids were larger than those of the diploids, but a reduced stomatal density was observed as compared to the controls. These shoots will be acclimatized and grown until they reach the reproductive phase in order to test their potential appeal as new varieties or their use for breeding and genetic improvement.Polyploid induction is of utmost importance in horticultural plants for the development of new varieties with desirable morphological and physiological traits. Polyploidy may occur naturally due to the formation of unreduced gametes or can be artificially induced by doubling the number of chromosomes in somatic cells. In this experiment, a protocol for in vitro polyploid induction of highbush blueberry ( V. corymbosum L.) is a species with escalating production worldwide and a commercially valuable minor fruit crop in Italy since it is a much sought-after species used to differentiate crops, utilize marginal lands and meet the increasing consumer demand. The potential uses of blueberries are manifold: from fresh consumption to processing for juices, jams, and even the pharmaceutical and cosmetics industries, since it is one of the richest sources of antioxidants with high potential to reduce the incidence of several degenerative diseases. Breeding of the highbush blueberry is focused mainly on low-chilling requirements, superior fruit quality [The highbush blueberry , which have the advantage of accelerating and enhancing classical breeding programs. These techniques are mainly based on somaclonal variations obtained through appropriate protocols from cells and tissues grown in vitro. In blueberries, various PGRs such as zeatin, zeatin riboside, zeatin trans-isomers, 2iP, TDZ and NAA are routinely used for inducing the regeneration of lueberry ,16. Therlueberry . Inducedlueberry . Adventilueberry .In this context, there is growing interest in obtaining plants with a higher level of ploidy, which could lead to phenotypic changes in plants as a result of alterations in gene expression . MoreoveIn this study, we evaluated the efficiencies of antimitotic agents in inducing polyploidy in highbush blueberry, obtaining polyploid and mixoploid shoots. This experiment aimed to develop a protocol for in vitro polyploid induction and to identify diverse breeding materials of highbush blueberry with improved traits that can be used as parent material in its future breeding programs.V. corymbosum L. by using colchicine and oryzalin was achieved. Shoots of the M5 variety were successfully established in vitro and, after three subcultures, they were used as explants for the experiments.In this study, the successful induction of artificial polyploidy in Vaccinium vitis idaea L.) [V. virgatum) [The incidence of de novo shoot organogenesis was observed just 5–6 days after the explants were placed in the culture medium, as validated with SEM images, in which single a or groudaea L.) ,28 and rirgatum) . Surprisirgatum) , who desBased on these preliminary results, the leaves used for polyploidy induction were cultured with the abaxial side up and were used to evaluate the effect of different concentrations of both antimitotic mutagens for the induction of polyploidy studies .As shown in Leaves cultured on colchicine- and oryzalin-free media started showing the first organogenesis events just after 9–10 days in culture medium f, whereaPassiflora edulis), the highest concentration used (30 μM) applied for 15 days resulted in 98% viable explants, with a tetraploid regeneration frequency of 2%. However, contrary to our results, colchicine has been reported to be more phytotoxic than oryzalin in several species [Furthermore, colchicine significantly inhibited the shoot organogenesis of the explants, in line with what has been observed by other authors ,31,32,33 species ,36,37.n = 48) shoot and a representative tetraploid (2n = 96) shoot. The tetraploid induction rates are presented in At completion of the experiments, a total of 409 regenerated shoots had been obtained (165 from both 25 and 250 µM colchicine treatments) . The plo2) , trifoliate orange (Poncirus trifoliata L. Raf.) and precocious trifoliate orange (P. trifoliata). They conclude that primary metabolism takes priority over secondary metabolism in doubled-diploid plants to relieve the “genomic stress” encountered during the early stages of genome doubling, probably to promote vitality and growth of plants.To better understand the stomatal traits with respect to the ploidy level, stomatal length, width and density were compared, and the results are listed in 2) e. On the2) f correspdization ,47, and dization . In addidization , observe® for 40 min [® for 20 min and rinsed three times with sterile distilled water under a laminar flow hood. The explants were cultured for 15 days in a hormone-free WPM medium [The plant material used in our study was a clonal selection named M5. Uniform twigs were collected from the greenhouse and rinsed under running tap water to remove the dirt after leaf removal. After washing, the twigs were immersed in aqueous solution containing 250 mg/L of ascorbic acid, 250 mg/L of citric acid and 0.1% PPM M medium , at pH 5Sterilized shoots were transferred to the proliferation medium, containing WPM medium including vitamins, 3% sucrose, 250 mg/L of L-glutamine, 2.28 µM zeatin riboside (ZR) and 0.25 µM indole-3-butyric acid (IBA).To induce polyploidy, fully expanded leaves were collected from 21-day-old in vitro growing shoots and cultured in the adventitious shoot organogenesis medium (SOM) consisting of WPM medium including vitamins , 3% sucr−2s−1 at 24 ± 1 °C.A stock solution of colchicine  was prepared by dissolving 100 mg of colchicine powder in 10 mL of sterile deionized water and filter-sterilized with a 0.22 μm Millipore filter, and then added to the above-described SOM medium to reach the final concentrations of 25, 250 and 500 μM. Similarly, a stock solution of oryzalin (2500 mg/L) was prepared by dissolving 25 mg of powdered oryzalin in 1.5 mL of dimethyl sulfoxide (DMSO), and brought to a final volume of 10 mL with sterile deionized water and then filter-sterilized following the same procedure mentioned above. The stock solution of oryzalin was also added to the SOM medium to obtain the final concentrations of 25 and 250 μM. Twenty-five milliliters of the media containing different concentrations of colchicine and oryzalin were poured into Petri dishes (Ø 96 mm), and 26 leaves were cultured in each plate. Six plates were used for each treatment. Before the setup of the experiment, a test was carried out with the aim of investigating the organogenetic ability of the explants with adaxial or abaxial side up. The Petri dishes were kept in the dark for 10 days, and then, the plates were transferred to oryzalin- and colchicine-free media and then exposed to the light condition, with a 16 h photoperiod with a PPFD of 40 μmol mDuring all the experiments, the plates were regularly checked for contamination and under the stereomicroscope for the appearance of the first buds.At the end of the experiments, the percentage of explants forming shoots and the number of adventitious shoots were determined. Regenerated shoots showing atypical visual morphology  were selected as possible polyploids or mixoploids.®. All chemicals were purchased from Duchefa Biochemie NL .The pH of the media was adjusted to 5.4 with 1N HCl or 1N KOH before autoclaving at 121 ± 1 °C, 1 atm for 20 min, and all the media were supplemented with 0.6% Plant AgarAllium cepa was used as an internal standard.Flow cytometric analysis of putative polyploid shoots was performed according to , after tFor scanning electron microscopy (SEM), leaves used for adventitious shoot organogenesis were collected and cut in transversal sections, and then treated by following the protocol described by . The obsp ≤ 0.01).The data were subjected to analysis of variance (ANOVA) performed using the SPSS software, version 20.0. Percentage data were transformed as the arcsine of the square root of p/100 before analysis of variance. Fisher’s test and Student’s test were used for mean separation and to provide homogeneous groups for the means (at A suitable protocol for shoot regeneration from the leaf tissue of highbush blueberry has been obtained using the WPM medium including vitamins , 3% sucrAs far as we know, this is the first evidence of novel and successful induction of polyploidy in highbush blueberry. The genetic material developed in the present work is being used for further selection and crosses.


At the optimum salinity and dilution conditions, compared with other salinities, there was less scale formation with more nanofluid stability. Obtained results from ZP measurements and dynamic light scattering (DLS) showed that by removing divalent ions (Mg2+ and Ca2+) of water-based nanofluid  composition), more NPs were attached to the surface due to the reduction in repulsive forces between the NPs. Therefore, at optimum low salinity soft water (OLSSW), more wettability alteration occurred compared with optimum low salinity hard water (OLSHW) due to the more stability of NPs in OLSSW. The obtained results from the contact angle measurements, surface adsorption of the NPs by FESEM images, and ZP measurements showed that the predominant mechanism in enhancing oil recovery by nanofluid was the wettability alteration by disjoining pressure. According to wettability alteration results, the silica NPs with an optimized concentration in the optimized LSHW and LSSW compositions could be improved the wettability alteration by up to 23.37% and 55.81% compared with the without NPs. The optimized LSSW compared with LSHW composition could be improved the wettability alteration by up to 11.69%. In addition, OLSSW-based nanofluid compared with OLSHW could be increased wettability alteration toward strongly water-wet by up to 33.44%.Recent studies showed the high potential of nanofluids as an enhanced oil recovery (EOR) agent in oil reservoirs. This study aimed to investigate the effects of salts and ions, the salinity of aqueous solution, total dissolved solids (TDS), scale deposition of mixing brines, surface charge as zeta potential (ZP) value, and pH of injected brines as low salinity water (LSW) on the stability of silica nanoparticles (NPs). The experiments were conducted on the stability of silica NPs at different concentrations and brines to determine optimum salinity, dilution, cations, and anions concentrations. The results showed that 10 times diluted seawater (SW#10D) was optimum low salinity water (OLSW) as injected LSW and water-based nanofluids. Results showed that by decreasing the salinity, increasing seawater dilution, and removing Mg The chemistry of the injected water in the form of salinity as low salinity water (LSW) or modified ionic composition in the form of smart water (SW) has an effective impact on the EOR4. In the LSW injection method, by changing the composition and concentration of ions (cations and anions) present in the water, the injected fluid is shifted to high compatibility with the rock and reservoir fluids7. The dominant mechanisms of LSW flooding are reservoir rock wettability alteration 9, fine migration 11, interfacial tension (IFT) reduction 12, multi-ion exchange 15, and double-layer expansion 16. However, the main mechanism is addressed as wettability alteration in most publications 17.In recent years, due to growth in the energy demand, it is remarkably important to improve oil recovery obtains before abanding currently oil wells to the newly discovered ones. Numerous enhanced oil recovery (EOR) technologies have increased in the past decades to improve the oil recovery of remaining oil trapped in the oil reservoir18. NPs, as nanofluids, are proposed as alternative flooding water-based EOR  due to their specific characteristics, small size, high surface area, high surface-to-volume ratio, free movability, and dispersion ability in porous media 21. Numerous studies have been done on the application of NPs in EOR. Hendraningrat et al.22 studied the silica NPs possibility to improve oil recovery in sandstone rocks and examined effective concentration. They concluded that higher concentrations of NPs had more formation damage in the rocks. However, increasing NPS concentration illustrated a change in wettability, and their results have shown that more recovery is not assured. Bazazi et al.23 investigated the influence of silica NPs on wettability alteration. They conducted a series of experiments on the impact of silica nanofluids on EOR. They observed that the efficiency of NPs obtained more oil recovery factors than water flooding and chemical flooding methods. Yuyang et al.24 studied the impact of modified silica NPs on wettability alteration of oil-wet cores. They used the UV-spectroscopy and dynamic light scattering (DLS) methods to determine NPs stability, contact angle, and imbibition tests to investigate the efficiency NPs in improving EOR. The results showed that modified silica NPs could enhance wettability alteration from oil-wet to water-wet. Olayiwola and Dejam 25 studied the efficiency of silica NPs on the wettability alteration during LSW and surfactant flooding in carbonate reservoirs. They observed that injection of NPs after LSW could alter wettability from oil-wet to water-wet. They examined important mechanisms for improving EOR performance: wettability alteration, reduction of IFT, and viscosity modification. They reported that using NPs during the LSW was more efficient and economical for improved EOR mechanisms in carbonate reservoirs. Rafiei and Khamehchi26 presented similar outcomes in artificial sandstone core samples. Mahmoudpour et al.9 investigated silica NPs' effect and SW on oil recovery. Their results showed that the dispersed silica NPs in SW could remarkably improve the wettability alteration mechanism; also, it was the best influence on oil recovery by raising the liquid viscosity. Ezzati and Khamehchi27 studied the stability of silica NPs in low salinity brine and investigated the ZP  effect on stability at different salts. They concluded that nanofluids without Mg2+ and Ca2+ ions had the highest stability. Songolzadeh and Moghadasi28 investigated stabilizing silica NPs in saline environments for wettability alteration of oil-wet reservoir rocks. They used two surfactants Cetyl Trimethyl Ammonium Bromide (CTAB) and Sodium Dodecyl Sulfate (SDS), for stabilizing NPs in high saline waters. Their results showed that nanofluid with 0.05 wt.% silica NPs and SDS was the highest efficiency on wettability alteration. In addition, silica NPs have a remarkable impact on oil/brine contact angle; as a result, NPs can be applied to improve oil production by changing the wettability. Al-Anssari et al.29 studied the impact of salinity on silica NPs stability in saline environments. Their results showed that increasing salt NaCl concentration had a considerable impact on the ZP value of nanofluids.One of the aspects of nanotechnology is applying the new chemical enhanced oil recovery (C-EOR) in oil reservoirs. The application of nanoparticles (NPs) rather than other chemical materials shows this method's efficiency and economic advantages. The NPs can be applied in nanofluid, and LSW flooding operations contain NPs, ions, and optimum composition as EOR agents in the injection water (IW) 36, this study has tried to extend the investigation of the effective parameters on the stability of silica NPs at different LSW compositions. These parameters included the effect of salinity, times diluted seawater, formation damage as scale deposition, type and concentration of ions and salts, pH, surface charge, and NPs concentration in aqueous solution.Unlike the previous experimental works This paper has the following novel points: (1) unlike the previous experimental works, the paper provides physiochemical insights comprehensively  to examine nanofluid utilization to improve wettability alteration and enhance oil recovery; (2) investigation of essential and effective factors on stability and compatibility of dispersed NPs in optimum low salinity hard water (OLSHW) and optimum low salinity soft water (OLSSW) with minimum scale deposition during LSW flooding is confirmed as an effective method to improve wettability alteration in sandstone oil reservoirs.This study investigates the potential of silica NPs at different concentrations as the new agent and wettability modifier in a sandstone reservoir through contact-angle, Field Emission Scanning Electron Microscopy (FESEM), ZP, DLS, pH, and brine compatibility measurements. Experimental tests are conducted with and without NPs to study the compatibility and scaling potential, stability of NPs in LSW brines, and wettability alteration of different LSW compositions before and after dispersing with NPs. In addition to examining different LSW compositions associated with NPs considering wettability alteration, scale-risk, and surface charge perspectives. Experimental investigations into the rock/fluid (nanofluid and brine) and nanofluid/brine interactions are also conducted through the contact angel test, FESEM, and nanofluid stability behavior by compatibility test, ZP, and DLS measurements. A schematic diagram of the workflow of this study is shown in Fig. 2.2 H2O, NaCl, KCL, Na2SO4, NaHCO3, and MgCl.6H2O dispersed in deionized water. The brine compositions of the IW (seawater) and formation water (FW) as a candidate for reservoir water are tabulated in Table The brine samples were made in the laboratory by dissolving specified quantities of different salts, salts at high purity from Merck Chemicals (purity of 99.5%). The salts included CaCl2O3), magnesium (MgO), zinc (ZnO), copper (CuO) oxides, and silicon dioxide (SiO2) were used. The NPs used in this work were purchased from the US Research Nanomaterial Inc, Houston, TX, USA. The characteristics of the metal oxide NPs are listed in Table In this study, types of metal oxide NPs, including aluminum Al2O, magnesiThin sections of specimens at a 3.6 cm diameter from sandstone rock were provided for contact angle tests. FESEM images of surface rock were taken to investigate surface adsorption of NPs and surface changes due to the effect NPs and LSW. Also, the rock powder was prepared from the sandstone rock sample for investigation of surface charge and ZP tests. The rock powder was prepared in the same procedure with thin slices aged with a strong fatty acid (0.1 molars of stearic acid) and normal heptane at a temperature reservoir in the oven for four days until rock powders were obtained from oil-wet. An x-ray fluorescence spectrometry (XRF) analysis was conducted to evaluate the core's rock composition because rock lithology could directly affect surface charge analysis. Table In this study, crude oil from one of the southwestern Iranian reservoirs was used in the experiments. Tables 2 NPs in the ranges of 500, 1000, 2000, and 2500 ppm were first added to 1000 ml of the seawater and LSW compositions  and mixed by magnetic stirrers for 30 min. Then, the solutions were endured for 1 h of ultrasonic radiation using the Ultrasonic Probe DA UP-400  apparatus. The ultrasonic probe apparatus with breaking nanoparticle clusters could improve nanofluids stability and inhibit NPs agglomeration and deposition in the base fluid30.The observational investigation performed the experiments on nanofluids' stability at different LSW and times diluted seawater (SW#XD) compositions at reservoir temperature (65 °C). In this study, for the preparation of different nanofluids, five different concentrations of SiOAn experimental test for evaluating the compatibility of FW with injected brines was applied to the evolution of the amount of scale deposition and the determination of optimum low salinity water (OLSW). This test was conducted at a reservoir temperature (65 °C). First, the Persian Gulf was considered a candidate for IW. Also, LSW samples with different dilution times were prepared according to this composition, including SW#0D, SW#2D, SW#5D, and SW#10D brines. All synthetic brines included FW and injection waters made in 1-L volume for experiments. After, these samples were mixed with formation brine at a mixing proportion of 1:1 or a mixing ratio of 50% IW/FW. 100 cc of each brine was filtered, poured into a glass bottle, and mixed with formation brine at a 0.5 mixing proportion for each compatibility test.37. After 3 days, mixed brine samples were filtered by 0.22 µm filter paper, and then the mass of the scale was measured. As the main purpose was to investigate the mineral scale weight, a membrane filtration apparatus was used to filter the samples. Furthermore, the filters were cleaned with deionized water, and the mineral scale was free of sodium chloride (NaCl) to ensure measures of exact filter weighting. After the filters were dried in an oven at 65 °C to evaporate associated with water, only the precipitated scales remained on the filters. The laboratory scale was utilized to weigh filters' accurate mass and measure the total suspended solids (TSS) in mixed brine samples.Moreover, every sample was put in an oven at 65 °C for three days. Reaching the different equilibrium conditions can be associated with scale formation. Scale formation occurred due to the supersaturation of one or more types of salt in a liquid38. When the ZP has sufficient high values (without regard to the negative or positive charges), it can make sure the stability of the NPs in an aqueous solution. In contrast, lower ZP values cause NPs agglomeration in aqueous solution39.ZP is the main parameter in the NPs distribution for the nano-suspensionsIn this study, the ZP, the hydrodynamic diameter, and the dispersion stability of NPs by DLS  were examined. In addition, the surface charge of solutions was estimated by the Malvern Zeta-sizer Nano ZS instrument concerning sandstone grains dispersed in the wanted brine. The surface charge value was listed in the ZP value of various samples. The dispersed sandstone grains in brines were provided by combining 0.5 g of milled sandstone particles with 50 ml of brine, representing 1% weight of the liquid suspension. The solutions were sonicated for 30 min with a sonication tool and allowed to hold for 2 days to give the equilibration condition. An adequate value of ZP was elected about the average of three analyses for each sample.44. Utilizing this method could extensively decrease the time needed for aging the samples. The sandstone rock samples were oil wetted by 0.01 molarity of stearic acid/n-heptane liquid at 65 °C for 4 days  apparatus was utilized to measure the equilibrium oil contact angle/aqueous solution on the sandstone rock surface at the reservoir temperature and ambient pressure conditions. Contact angle values of thin section specimens before and after nanofluids injection at different NPs concentrations and LSW compositions were estimated at reservoir temperature. Figure To examine the effect of pH values on the surface charge and stability of NPs in LSW brines, the pH values of aqueous solutions were measured with a pH lab. The average particle size and ZP values in brines with and without the rock powders were measured immediately. While these measurements were in progress, the pH of solutions was changed and modified by adding diluted HCl or NaOH solutions. The LSW brines with and without NPs were dispersed in rock powders on magnetic stirring and after sonicated in an ultrasonic apparatus for 30 min at room temperature.2O3), magnesium oxide (MgO), zinc oxide (ZnO), and copper oxide (CuO) that all NPs settled in tubes in different injected waters with different salinities and dilution times seawater after ultra-sonication. Eventually, only silicon dioxide (SiO2) NPs were stabilized in SW#10D, and silica NPs did not stabilize in SW#0D, SW#2D, and SW#5D brines. As shown in Table The stability of NPs in electrolyte solutions is an essential parameter in the performance evaluation of nanofluids. Experiments on nanofluids' stability in various injected waters were performed by observation under reservoir temperature (65 °C). According to this approach, each NPs was weighed at the relevant weights and added to the brines. After ultra-sonication of the solutions, they were kept in the oven at reservoir temperature for 7 days. Table 46. The potential of mineral scale deposits due to the incompatibility of injected water and the FW during the injection of LSW and SW flooding has been less considered 6.One of the main problems during water injection projects is formation damage by inorganic scale formation due to mixing the incompatible injected water with FW at reservoir conditions 2 flooding operations 48. As a result, this software was used to determine the minimum scale deposition that could occur during the LSW samples for scale-up to oil reservoirs. It is noticed that the prediction and control of scale deposition are essential problems in LSW flooding operations 47. The software can calculate saturation ratio (SR) and saturation index (SI) terms to predict scale formation for an aqueous solution. SR and SI are defined as follows 46 :The obtained results from the compatibility tests due to mixing FW and injection waters in SW#0D, SW#2D, SW#5D, and SW#10D compositions with a mixing ratio 1:1 (% 50 to % 50 WI/FW) of one of the oil fields in southwestern Iran indicated that the minimum scale formation happened in SW#10D as OLSW composition. These results correspond to the effects of salinity and dilution times on the stability of NPs in different brines. Table ,The activity of the ion species37. As shown in Table 51. Also, scale deposition is inversely related to the stability of NPs in brine 49.The aqueous solution is supersaturated, and the scale tends to form when the SR and SI are greater than 1.0 and 0, respectively. In contrast, the aqueous solution is unsaturated, and mineral scales cannot be formed when the SR and SI are lower than 1.0 and 0, respectively 52. As shown in Tables 56. Therefore, it is recognized that the high salinity of solution has a screening impact on the electrostatic repulsion forces between NPs in solution, leading to an accelerated coalescence and deposition of NPs. As can be seen in Table 54. Also, Tables The NPs concentrations in base fluids can change after injection into oil reservoirs because of the deposition and adsorption of NPs on the rock surface 2+ and Mg2+ ions. Results of the ZP measurements of silica NPs in LSSW and LSHW compositions are given in Table 2+ and Mg2+ ions was higher than low salinity hard water-based nanofluid (LSHWN). As cation valency was increased, therefore nanofluid instability was increased. Table 2+ and Mg2+ in OLSW composition could reduce the nanofluid stability55. As shown in Fig. 2 and CaCl2 salts compared with NaCl, KCl, Na2SO4, and NaHCO3 salts had a negative effect on the stability of SiO2 nanofluids. The mean particle size of nanofluid in the presence of CaCl2 and MgCl2 salts was about 1.5 times higher than NaCl after 7 days. Also, as can be seen in Tables 2 and MgCl2 salts than in brines containing NaCl, KCl, Na2SO4, and NaHCO3 salts that leads to a silica nanofluid with less stability. Also, the results showed that the type of salt could control the efficient concentration of NPs and change the size of dispersed NPs in the LSW as a carrier fluid.Table 53. At this point, the net electric charge on the particles' surface is zero since the electrostatic repulsion force between the particles is insufficient; as a result, the sediment and lumps of NPs 57. If the pH of the nanofluid solution is higher than IEP, then the NPs in the solution can have a negative electrical potential. According to the literature, the IEP of the silica nanofluids is between 1.75 and 3.5 58. While the pH value is higher than this value, the NPs receive a negative charge, and the ZP value increases negatively. Ionization of the reactive silanol groups (-SiOH) is the main source of the surface charge 59. Thus, hydroxyl groups can be adsorbed with neutral silanol groups at pH values above IEP (pH  8), and particles shift negatively charged  2 and MgCl2 salts to LSW composition as divalent cations (Ca2+ and Mg2+) could decrease the ZP values and surface charges. The reason might be due to the selective adsorption of ions on the surface of the NPs, which could prevent the particle charge. Therefore, divalent cation (Mg2+ and Ca2+) could negatively affect silica nanofluids' stability compared with OLSSW in the presence of monovalent ions (Na+ and HCO3−) and divalent anion of SO42−. Moreover, as shown in Fig. 2 and CaCl2 salts had a negative impact on the stability of silica nanofluid as opposed to NaCl, KCl, Na2SO4, and NaHCO3 salts. As can be seen in Tables 2 and MgCl2 salts were higher than other salts after 7 days. As mentioned above, this difference was due to lower strength of repulsive forces between silica NPs in brines containing CaCl2 and MgCl2 salts than in brines containing NaCl, KCl, Na2SO4, and NaHCO3 salts, led to nanofluids with less stability.Also, screening effects of the LSHW and LSSW compositions can be seen in Tables 61. The results of average particle size measurements agree with ZP measurements .With the increasing silica NPs concentration in LSW and according to ZP measurements in Fig. n-Heptane and 0.1 M stearic acid at 65 °C temperature and 14.7 psi pressure until rock powders became oil-wet. The ZP values shown here were the mean of 3 measurements for the sample.The ZP values were measured in the sandstone rock/brine (R-B) systems. The results of ZP measurements are illustrated in Figs. 2+, Mg2+, and SO42- to attach and alter the rock-brine interface charge. Therefore, when the salinity of injection brines changes, the ionic compositions for binding sites and their reaction with OH− and H+ ions in solution also change, resulting in ZP values that can differ 49. The OLSW solution prompted a higher negative surface charge due to ions adsorption on the rock particles' surface. As the salinity of LSW composition had an optimum salinity, ZP values changed negatively. As a result, by reducing salinity and ionic strength of brine (OLSHW > OLSSW), the ZP gives more negative values  can increase the surface concentration of CaSO4- complexes, leading to a negative surface charge on the surface rock. When the pH value of the solution increases, this process can be reversed. In this condition, the surface concentration of CaSO4− decreases and CaOH0 complexes increase, but CO3Ca+ and CO3Mg+ complexes do not change and cannot be significantly influenced by pH.The ZP behavior was in agreement with previous experimental studies, which recommend more reduction in salinity of IW changed rock wettability to a less oil-wetting state62. When divalent cations remove from brine composition, therefore the salinity and TDS of LSSW compared with LSHW are reduced. As a result, a reduction in the ZP value toward additional negative values can obtain in this condition. The main reason was the expansion of the double layer at more down salinity and increasing negative surface charge owing to the alteration in the value of surface complexes70. As can be seen in Figs. Consequently, the net surface charges shift from minor negative to high positive, resulting in an enhancement in ZP value versus a rise in pH 71.Figure Figure Figure 72. Table 2+ and Mg2+ decrease ZP value because they tend to aggregate particles  analysis, showing that the presence of MgCl2 and CaCl2 salts was more significant than other salts. Therefore, the strength of the repulsive forces between silica NPs in the presence of MgCl2 and CaCl2 salts in LSHW was lower than of KCl, NaCl, Na2SO4, and NaHCO3 salts in LSSW, leading to more instability of silica nanofluid.The particle size distribution (DLS) of nano-suspensions in the presence of MgCl2–4 ions were higher than divalent ions in LSHW. Furthermore, the highest surface charge of silica NPs was obtained in optimal salinity and two optimum concentrations with high stability in the presence of rock at pH  4.5. With increasing pH, this amount was decreased in the presence of rock. Also, according to ZP results that the dispersed silica NPs with optimized concentration into the optimized LSW composition at pH  4.5 could improve the surface charge value by up to 15.71 mV compared with the without NPs.The ZP results at different pH showed that the ZP values of LSSW solutions in the presence of monovalent and SO+2 and Ca+2 ions could reduce the nanofluid stability.The ZP measurements showed that by removing divalent cation ions in the nano-aqueous solution, more NPs were attached to the rock surface, and the disjointing pressure increased. As a result, in the presence of Nanosilica in LSSW compared with LSHW, the rock wettability altered to strongly water-wet and water-wet conditions because divalent MgFESEM and contact angle results confirmed ZP results, and it was mean that dispersed NPs in OLSW solutions were able to make sandstone surface more negative wettability changes from oil-wet toward water-wet. Also, according to WAI results, the silica NPs with an optimized concentration in the optimized LSHW and LSSW compositions could improve the wettability alteration by up to 23.37% and 55.81% compared with the without NPs.According to WAI results Table , the OLSThe principal conclusions from this study are summarized as follows:


At a pH representative of mine effluents, where Cd presents its greatest mobility and risk as a pollutant, grape and flax waste showed capacity for effective bulk water treatment due to rapid removal kinetics and moderate adsorption properties: reaching equilibrium within 183 and 8 min – adsorption capacities were determined as 3.99 and 3.36 mg Cd per g, respectively. The capacity to clean contaminated effluents was not correlated with the surface area of the biosorbents. Surface chemistry analysis indicated that Cd removal is associated with exchange with Ca, and chemisorption involving CdCO3, CdS and CdO groups. This work indicates that some AWBs can be directly (i.e. without pre-treatment or modification) used in bulk to remediate effluents contaminated with heavy metals, without requiring further cost or energy input, making them potentially suitable for low-cost treatment of persistent (e.g. via mine drainage) or acute (e.g. spillages) discharges in rural and other areas.Agricultural production results in wastes that can be re-used to improve the quality of the environment. This work has investigated for the first time the use of abundant, un-modified agricultural wastes and by-products (AWBs) from grape, wheat, barley and flax production, to reduce the concentration of Cd, a highly toxic and mobile heavy metal, in contaminated water. At concentrations of 1.1 mg Cd per L, flax and grape waste were found superior in removing Cd compared with a granular activated carbon used in water treatment, which is both more expensive and entails greater CO Agricultural production results in wastes that can be re-used to improve the quality of the environment. Several heavy metals are micronutrients while others are potent cell toxins but almost all are harmful if critical thresholds for toxicity are exceeded.4,5 Furthermore, Cd ions are considered to be more mobile in aquatic environments than most other heavy metals.4 The global extraction of Cd was 20 100 tons in 2009 6 and a fraction of this ends up being released to the environment, and Cd is found at toxic concentrations in some rivers.2 Indirect sources of Cd to surface water can be emissions or products from industries such as electroplating, pigment/textile, plastics production (i.e. with up to 2 g Cd per kg PVC), Ni–Cd batteries, and photovoltaic technologies (in the form of Cd–tellurium).7 Mineral fertilisers are derived from phosphate rock where Cd occurs naturally at concentrations of 1–92 mg Cd per kg rock,8,9 consequently Cd can also enter directly to surface water, soil and the food chain through direct application of phosphatic fertilisers, which represents 60% of the emissions of Cd to soils.10,11 Among the heavy metals in phosphate rock, Cd has the highest transfer factor in plants,8 and therefore its concentration in water and soil is of high concern. Cd can also be present in mine effluents which, in origin, may be very acidic (pH 2.2–3.1),12 conditions in which Cd presents its highest mobility. The pH of these effluents rises later to 4–5 when mixing with pristine waters.12Among heavy metals, Cd has special relevance due to its broad use, mobility and toxicity .13 The discharge of Cd from various industrial sectors into surface water is to be ceased by 2020,14 and its limit in drinking water is 5 μg L−1.15 The removal of Cd from industrial effluents, mine waters or other Cd sources is therefore of high importance to prevent its discharge and accumulation in the environment. A recent review has discussed the current technologies used for the removal of Cd and other heavy metals from industrial wastewater.16 Chemical precipitation is the most widely used technique in industry for Cd removal, and ion exchange techniques are also commonly used. Other techniques include membrane filtration, coagulation and flocculation, flotation, electrochemical treatment and adsorption via activated carbon. However, despite being highly effective, there are practical drawbacks that limit the applicability of these approaches such as the high volumes of chemical sludge generated in chemical precipitation; and the high cost  of ion exchange and membrane filtration-based processes.16 Adsorption has become a popular treatment for the removal of Cd and is considered one of the most efficient and economical contaminant removal techniques.17 Biochar and activated carbons have been used for the adsorption of Cd, and although effective, they are relatively expensive to produce, which limits their use.18 Numerous low-cost materials have been investigated for their potential as alternatives to activated carbon, and these include natural materials such as zeolite19 and montmorillonite;20 or industrial wastes such as fly ash.21 There has also been recent interest in the application of agricultural wastes and by-products (AWBs) for the removal of Cd such as leaves from camphor tree22 or garlic peel.23 These sorbents typically have low preparation costs, and potentially greener credentials than activated carbons, i.e. they use natural agricultural residues rather than coal-derived products as a feedstock and can be applied to divert wastes from landfill or other disposal. Much of the published data however have focused on processed or modified AWBs, and on adsorption capacity and kinetics rather than fundamental adsorption mechanisms.Cd is identified as a priority hazardous substance, listed among the 33 substances identified as such by the European Commission.This study aims to evaluate abundant, un-modified agricultural wastes and by-products as cost-effective sorbents for the removal of Cd from water. Surface chemistry analysis is used to assess adsorption mechanisms for Cd, and adsorption kinetics and capacities compared to those previously reported for processes or modified AWBs. This research contributes to the environmentally sustainable initiative of the development of a more circular economy, where the utilisation of food wastes can be used to improve water quality (water-food nexus).22.1−1 Cd solution   was further diluted to make up all solutions with deionized water. Where pH has been adjusted it was done so dropwise using 1 M NaOH and HNO3 solutions.AWBs were selected to represent a range of bulk agricultural products and wastes from cereal, wine and oil production. Six AWBs: grape wastes (GW), flax wool (FW), flax mat (FM), flax shive (FS), barley straw (BS) and wheat straw (WS), all dried in air, were sourced directly from producers. The grape wastes were mainly skins, with some seeds and stalks attached, and were by-products from the production of Tempranillo (red) wine sourced from DO Penedès (NE Spain). The flax (Linum usitatissimum) materials, were obtained from the FP7 Interreg IVA (South) project 4044 “Flax – Increasing its value for society” through the collaboration of the University of Brighton with Linière de Bosc Nouvel S.A., Seine-Maritime (France). The wheat and barley straws were sourced from the John Innes Centre (UK) and NE Spain (Penedès), respectively. The sorbents were further dried in a vacuum oven at 40 °C before use. The AWBs were cut to achieve approximately equal particle sizes (1 cm) and their different natural widths were not modified. A commercial granular activated carbon (GAC), provided by Anglian Water (UK), was also used in the study as a commercially used sorbent for comparison. A stock solution 1000 mg L2.2SBET) of the AWBs were obtained using N2 adsorption isotherms at 77 K, after degassing the airdried samples (2 g) for 24 h at 90 °C and treating adsorption/desorption data with BET (Brunauer–Emmett–Teller) and BJH  modelling as described elsewhere using an Autosorb adsorption analyser .24Surface area measurements  operating at 3–5 KV for all sorbents.ca. 900 × 600 μm2 was defined by the microfocused X-ray source. Full survey scans  and narrow scans  of the C 1s , O 1s (BE ∼ 531 eV), P 2p (BE ∼ 130 eV), Cd 3d (BE ∼ 410 eV), Ca 2p (BE ∼ 350 eV), and Cu 2p (BE ∼ 940 eV) regions were acquired from three separate areas on each sample. Data were transmission function corrected and analyzed using Thermo Avantage Software (Version 5.952) using a smart background. The XPS analysis was carried out on dry grape waste before and after Cd adsorption studies.XPS was performed using an ESCALAB 250 Xi system (Thermo Scientific) equipped with a monochromated Al Kα X-ray source, a hemispherical electron energy analyzer, a magnetic lens and a video camera for viewing the analysis position. The standard analysis spot of 2.312,25 and 0.2 g of each individual AWB in 50 mL polypropylene centrifuge tubes. These were shaken at 100 rpm at a temperature of 22 ± 2 °C in an orbital shaker for 48 h before separation by centrifugation. The mass of Cd sorbed per mass of AWB was calculated from the difference between the initial (Ci) and final (Ceq) concentration in solution. Sorption removal efficiency (%) and capacity, qeq , were calculated as follows:V (L) is the volume of solution and w (g) is the amount of sorbent used. In all studies, control samples (solution without AWB added) were conducted under the same experimental conditions – the resulting Cd concentration in the control is used as Ci in Batch uptake studies aimed at screening the performance of the AWBs were carried out by mixing 40 mL of contaminated aqueous solutions representative of mine effluent (19.3 mg Cd per L at pH 2.2)26,27 and is representative of acidic soils and mine effluents that have been attenuated.12 No effort was made to maintain pH throughout the process. The experimental data obtained was modelled using kinetic models (pseudo-first- and pseudo-second-order).For investigation of sorption kinetics, uptake was measured over several predetermined time intervals  in duplicate from an initial concentration of 18.4 mg Cd per L. The pH was adjusted to 5.5 as described in Section 2.1 – this has been indicated as the optimal acidity for Cd adsorptionThe effect of the concentration of contaminant on its removal was assessed using initial concentrations of ∼1.1, 6.8 and 21.5 mg Cd per L at pH 5.5, performed at equilibria with a contact time of 4 hours (determined through the kinetics experiments). A commercial granular activated carbon (AC) was introduced here to provide a comparison against the AWBs at low concentration. The quantification of Cd was carried out using an ICP-OES Perkin Elmer Optima™ 2100 DV with detection limit in the analysis of Cd at <10 ppb.328 309 000 tonnes of flax fibre in 2015;29 136 million tonnes of barley in 2007;30 and 754 million tonnes of wheat production forecast for 2018/19.31Derived products from the production of grapes/wine, flax, barley, and wheat were selected because these crops have high global production rates, for example: 247 million hectolitres of wine produced in 2017;3.12 adsorption isotherms and the surface areas are presented in SBET values of the AWB materials were all <10 m2 g−1, excluding flax wool which had a surface area of 75.1 m2 g−1. Commercial GAC showed much higher surface area (552 m2 g−1). Hence, AWBs are all characterised by relatively low surface areas, which may decrease their value as an adsorbent; however, their low or zero cost economically favours their use in a large scale.High surface area is an advantageous characteristic in sorbents, as the abundance of active sites involved in the uptake of contaminants is maximised. The six AWBs tested were characterised by N2, and leads to increase of micro and mesoporosity, resulting in greater surface area.SEM observations  showed t3.232 although this is at significantly greater concentrations of Cd than typically found in environmental waters. Use of such high concentrations however allows comparison of the different sorbents at or near to their maximum adsorption capacities. The removal efficiency of Cd by the AWBs is presented in The capacity of the AWBs to uptake Cd was primarily determined in a screening study under conditions using Cd concentrations typical of those found in mine drainage,The Cd sorption efficiency of grape waste was significantly higher than the other AWBs tested, giving a removal of 74.6 ± 4.3% Cd in this study, despite the very low surface area of this material . In cont33 Grape wastes are also known to be rich in phenolic moieties.The lack of correlation between surface area and Cd removal efficiency  indicateBased on these preliminary results, grape and flax wool were chosen for further study. They represent the two most efficient waste materials studied (in terms of sorption properties) and incorporate varying features amongst the AWBs which may be important for further understanding mechanisms driving the adsorption of Cd to these biosorbents.3.334 Activated carbon was also tested at the lowest initial concentration and was found to be less efficient than both agricultural materials tested (removing 34 ± 4.9% of Cd from solution). This indicates that AWBs and GAC have different adsorption mechanisms, with the AWBs having a higher heat of adsorption and offering better performance than GAC at this concentration, and at lower cost.i.e. not found in environmental/waste effluents. The uptake is compared with the performance of other (modified) waste materials in 3 nanoparticles deposited onto porous sewage sludge biochar, which is a more energy intensive and costly material than AWBs, achieved about 10 times greater removal capacity.35The maximum adsorption capacities found in this study are 3.99 and 3.36 mg Cd per g for grape waste and flax wool respectively. At much higher initial concentrations this value would be higher, albeit at unrealistic conditions, i.e. classification of the material as a waste or usable biomass) and thresholds, and the potential of the AWBs for further processing and valorisation.36Further study is required however into the overall cost of pre-treatments and modifications to determine if the improved capacity and performance they provide are worth the costs, complexity and chemicals added to the process. Maximum adsorption capacity, although being highly valued for adsorbent materials, may not be as important for AWBs materials since their low cost or presence as by-products otherwise requiring disposal mean that larger masses of sorbent may be applied in the adsorption process, offsetting their lower adsorption capacities. Conversely, this means that higher post-treatment disposal volumes of adsorbent are generated, although the final disposal route will depend on local regulatory classifications (3.4r2 > 0.998), respectively).Kinetic experiments were undertaken to establish the period taken by each adsorbent to reach equilibrium. The results are presented in 42 and is partly complex in nature as it does not fit as well to a pseudo first-order model. Other studies using AWB materials as sorbents have also found kinetic experimental data to fit this model, possibly owing to chemisorption due to the interaction of the contaminants with the functional groups in cellulose and hemicellulose material.43 Interestingly, the uptake here was not related to the surface area, whereas in chemisorption uptake would generally be correlated with this parameter. This lack of correlation was observed in other sorption processes elsewhere,44 and it was attributed to the existence of specific sites within the sorbent with affinity for the contaminant.The experimental data were fitted using different models  to eluci−1) was greater than the equivalent rate for grape wastes (0.0196 mg (g minute)−1). This lower rate for grape wastes may indicate that chemisorption processes such as ion-exchange dominate in grape waste whereas van der Waals forces may dominate in the uptake of Cd in flax wool.45 These results point out the important potential of flax wool for its use in the filtration of contaminated effluents, or either flax wool or grape waste (in a suitable form) for the passive treatment of diffuse contamination such as leachates in mine sites where other more expensive technologies like dispersed alkaline substrate are currently implemented.46The sorption kinetics rate associated with flax wool (0.340 mg (g minute)3.5i.e. following batch adsorption studies), was investigated for the first time via XPS as detailed in via XPS due to its fibrous nature, which made sample immobilisation  impractical. The survey scan for grape waste (33) groups  groups  present 4−1), and as the rate of sorption is very important in adsorption systems, flax wool shows a higher potential if used practically in filtration systems. The mechanism of removal of Cd using grape waste relates to the chemical interaction of Cd with oxygen (possibly from polyphenols), sulphur, and carbonate groups, and possible displacement of Ca from the original sorbents.The efficiency of various globally abundant AWBs for the adsorption of Cd has been investigated for the first time. Cd is a priority pollutant that causes damage to multiple organs and can leach to freshwater in effluents from a wide range of industries, landfills and mines. The clean-up properties of the AWBs have been studied under conditions relevant to effluents contaminated with Cd, such as mine run off, which is one of the environmental problems where they could be used. Grape wastes and flax wool are very effective in the removal of Cd from aqueous solution, the former removing >90% of Cd from initial concentrations from 1.1–21.5 mg Cd per L and outperformed the more expensive GAC used in tertiary treatment . Flax wool has exceptionally fast kinetics  material in contaminated waters). AWBs are often available in large quantities, and so can be useful at large scale as they require minimal technical provision/input and reduce the need for chemical additions or costlier processes. While further work is required on their application to other divalent metal cations, this research indicates that some AWBs can be directly (i.e. without pre-treatment or modification) used in bulk to remediate effluents contaminated with heavy metals, without requiring further cost or energy input, making them potentially suitable for low-cost treatment of persistent (e.g. via mine drainage) or acute (e.g. spillages) discharges in rural and other areas.This study has demonstrated the potential of low cost and low/un-processed sorbents for effective removal of Cd: flax wool and grape waste but also flax shive, wheat and oat straw. Further work should address optimising their final form for their application in environmental remediation (There are no conflicts to declare.


Due to widespread use of nanoparticles in surfactant-based formulations, their release into the environment and wastewater is unavoidable and toxic for biota and/or wastewater treatment processes. Because of concerns over the environmental impacts of nanofluids, studies of the fate and environmental impacts, hazards, and toxicities of nanoparticles are beginning. However, interactions between nanoparticles and surfactants and the biodegradability of these mixtures have been little studied until now. In this work, the environmental impacts of nanofluids containing mixtures of surfactants and silica nanoparticles were valuated. The systems studied were hydrophilic silica nanoparticles (sizes 7 and 12 nm), a nonionic surfactant , an anionic surfactant (ether carboxylic acid), and mixtures of them. The ultimate aerobic biodegradation and the interfacial and adsorption properties of surfactants, nanoparticles, and mixtures during biodegradation were also evaluated. Ultimate biodegradation was studied below and above the CMCs of the individual surfactants. The interfacial and adsorption properties of surfactant solutions containing nanoparticles were influenced by the addition of silica particles. It was determined that silica nanoparticles reduced the capability of the nonionic surfactant alkyl polyglucoside to decrease the surface tension. Thus, silica NPs promoted a considerable increase in the surfactant CMC, whereas the effect was opposite in the case of the anionic surfactant ether carboxylic acid. Increasing concentrations of surfactant and nanoparticles in the test medium caused decreases in the maximum levels of mineralization reached for both types of surfactants. The presence of silica nanoparticles in the medium reduced the biodegradability of binary mixtures containing nonionic and anionic surfactants, and this effect was more pronounced for larger nanoparticles. These results could be useful in modelling the behaviour of nanofluids in aquatic environments and in selecting appropriate nanofluids containing nanoparticles and surfactants with low environmental impact. Despite the many applications and numerous advantages of surfactants in industrial and economic fields, from an environmental point of view, they are considered an important contaminant of aquatic environments, and high volumes of these substances are released daily into this medium. Once used, the surfactants reach treatment plants through urban and industrial wastewater and in certain cases are directly discharged into surface waters. During treatment of wastewater, a high percentage of the surfactants present in the aquatic environment are eliminated by aerobic biodegradation and adsorption onto particulate material, while the metabolites generated and the remaining nondegraded surfactants are dispersed in different environmental compartments. A growing problem is currently arising at wastewater treatment plants due to mixing of domestic wastewater and hospital and industrial effluent containing significant surfactant loads, and the mixtures may contain surfactants with different properties. The concentrations of surfactants present in domestic wastewater can vary between 1 and 10 mg/L, while they can reach levels of 300 mg/L in industrial wastewater  analysed in this study. The consumption of these surfactants is increasing year by year due to their remarkable environmental profiles. The fast-moving consumer goods industry demands products with low environmental impact, and consumers pay special attention to their components. Recent market reports Fact.Mr.  predict The surfactant ether carboxylic acid is used in cleaning and cosmetic products that come in contact with the skin. These surfactants improve the foaming capacity of surfactant formulations and decrease levels of irritation  and the advantages they offer in processes related to catalysis, new materials, or biomedicine have led to increased use in consumer products such as detergents , a nonionic surfactant  whose individual environmental impacts have been previously assessed , specific surface area (S), tapped density (d), and pH. Nanoparticles were observed by TEM using an ultrahigh-resolution scanning transmission electron microscope (S/TEM) and a high-angle annular dark-field imaging (HAADF) system (FEI TITAN G2 60-300). The images showed amorphous structures for both nanoparticles, and these tended to be spherical in shape ) were used. Table ape Fig. , but botThe nonionic surfactant alkyl polyglucoside (APG) was supplied by Sigma-Aldrich , and the anionic surfactant ether carboxylic acid (EC) was provided by KAO Corporation . Table A magnetic stirrer was used to wet the silica particles with aqueous media, and then dispersion and deagglomeration were performed by ultrasonication for 30 min  in 1 L of ultrapure water. Subsequently, the surfactant was aggregated to obtain a suitable concentration. Ultrasonic cavitation helped to disperse particles since it generates high shear that breaks particle agglomerates. The interfacial tension, superficial tension, and biodegradability of surfactant solutions with silica nanoparticles were assessed as described in the following sections.Surface and interfacial tensions were determined for nanoparticles and surfactants. Additionally, during the biodegradability tests, surface and interfacial tension were determined over time. Surface tension was measured at 25 °C using the Wilhelmy plate method with a Krüss KSV tensiometer equipped with a 2-cm platinum plate . The platinum plate was cleaned by heating it to a reddish orange colour with a burner prior to use. Standard deviations were calculated by carrying out successive measurements, resulting in values less than 0.1 mN/m. The interfacial tensions (IFT) between dodecane and aqueous solutions were determined at 25 °C by a pendant drop tensiometer . Measurements were performed in triplicate.3 mg/L). The break point in the plot indicates the formation of micelles. CMC results for anionic and nonionic surfactants are shown in Table The critical micellar concentration CMC was calculated by plotting the surface tension vs. surfactant concentration 0 to 5·10 mg/L. Th2PO4, 217.5 mg K2HPO4, 334.0 mg Na2HPO4.2H2O, 5.0 mg NH4Cl, 27.5 mg CaCl2, 22.5 mg MgS04.7H20, and 0.25 mg FeCl3.6H20. The test medium was previously aerated for 30 min with carbon dioxide-free air and prepared according to guidelines for glass-distilled water and mineral salts. Duplicate tests were run for each test solution, along with the positive control and blank samples. The solution for which biodegradability was to be determined was inoculated with 0.5 mL of fresh activated sludge inoculum obtained from a municipal wastewater treatment plant that operates with active sludge ; this plant was selected because it deals predominantly with nonindustrial, municipal wastewater. This water sample was a mixed aerobic culture of faecal microorganisms, including, for the most part, total coliforms, faecal coliforms, and enterococcus. The microbial activity of the supernatant was determined to be 105 to 106 CFU/mL. Supernatant microbial sludge was added to the test medium.Ultimate ready biodegradability tests followed OECD 301E test guidelines OECD . Ready bBiodegradation was determined from the residual surfactant concentration over time by measuring dissolved organic carbon (DOC) in samples filtered through a 0.45-μm Millipore membrane. In the reference tests, the initial concentration of surfactant was 5 mg/L in all cases, and the average biodegradability reached at the end of the test was 98.34%; this fulfilled the 90% criterion set by the OECD for 5 days for soft standards and thus indicated the validity of the assay.2SO4 (98%).Test surfactant concentrations ranged from 25 to 50 mg/L in order to ensure at least 40 mg ThOD/L . The test temperature was maintained at 25 °C ± 1 °C (with minor deviations of less than 1 °C). All test vessels were stirred constantly with magnetic stir bars at 125 sweeps/min. All glassware was cleaned using a solution of ammonium persulfate in HAdsorption experiments were carried out under the same conditions as biodegradation tests but in the absence of microorganisms.Surface and interfacial tensions of nanoparticle dispersions in Milli-Q® water were determined in the concentration range 0−1.000 mg/L at 25 °C. For both nanoparticle dispersions, the surface and interfacial tensions did not change with concentration, and the values were approximately 44.6 ± 0.4 mN/m for interfacial tension and 71.3 ± 0.6 mN/m for surface tension Table  and VataAnionic and nonionic surfactants decrease the surface tensions of air–water interfaces and the interfacial tensions of liquid–liquid interfaces. As shown by the results in Table The surface and interfacial tensions for solutions of surfactant containing nanoparticles were measured, and CMCs were determined at 25 °C. Solutions containing nanoparticles and nonionic surfactant (APG) showed a CMC larger than that of pure surfactant solution, whereas solutions containing nanoparticles and anionic surfactant (EC) showed considerably reduced CMCs. Similar results were obtained by Rios et al. , half-life time (t1/2), mean biodegradation rate (VM), percentage of primary biodegradation reached at 50 h of assay (B), and mineralization (Min). Table When comparing the influence of nanoparticle size on the biodegradability, it was observed that larger particles caused greater biodegradability independent of the character of the surfactant Fig. . Both sufe time t/2, mean L; this value varied between 15.96 h for the APG-A200 assay and 78.24 h for the EC-A200 assay. The latency time and half-life time were notably augmented for nanofluids containing A200 nanoparticles. The presence of nanoparticles in the biodegradability test did not alter the form of the resulting curve except for anionic surfactant EC and A200 nanoparticles, the shape of the curve was exponential, the biodegradation process became slower (B = 2.55%), and a long lag phase was observed, although the final mineralization level reached was the highest among the tests carried out with nanoparticles (Min = 87.02%). Therefore, it was possible to establish a dependence of biodegradability on silica particle size. The ZP of A200 particles was less negative than the ZP of A380 particles, revealing the greater stability of the smallest nanoparticles. On the other hand, the TEM image of A380 silica nanoparticles used in this study corroborated the aggregation phenomenon that has a direct effect on even minor biodegradation.The nanoparticles affected the acclimation time of the microorganisms, tM, tL, t½, and B. Therefore, the average velocity of biodegradation VM and biodegradability B was greater for lower initial concentrations, and the latency time tL and half-life time t½ were greater.The influence of initial surfactant concentration on biodegradability was demonstrated Fig. . In geneFor nanofluids containing A200, the reduction in biodegradability, which was attributed to an increase in surfactant concentration, was more pronounced for the nonionic surfactant.The biodegradabilities of anionic/nonionic surfactant mixtures were evaluated to understand the interactions and synergies among different kinds of surfactants. Surfactants are used as cosurfactants in many formulations, and therefore, the ecotoxicological and interfacial interactions in binary mixtures with a 1:1 weight ratio of ether carboxylic derivative surfactants and alkyl polyglucosides were investigated. Mixtures of surfactants in detergents, household care products and industrial formulations generally include nonionic/nonionic, cationic/cationic, anionic/anionic, and amphoteric/amphoteric surfactant pairs. However, it has been demonstrated that the synergistic effects between them increase with increasing charge difference  decreased the surface tensions of air–water interfaces. The inclusion of negatively charged hydrophilic silica nanoparticles reduced the efficiency of the nonionic surfactant and considerably increased its CMC, but the effect was opposite for the case of the anionic surfactant. Increasing concentrations of surfactant and nanoparticles in the test medium resulted in decreases in the relative maximum mineralization for both surfactants. These results imply that surfactants assayed at low concentrations may be considered safe for the environment when formulated as nanofluids with or without nanoparticles and with an initial surfactant concentration of 25 mg/L. Measurements of binary mixtures indicated that the mixture with the lowest biodegradability was formed with the surfactant APG-EC and larger nanoparticles. Since biodegradation is the main mechanism for removing organic compounds, knowledge of the biodegradability of surfactants in combination with other additives is necessary for understanding the environmental behaviour of these mixtures before designing a detergent formula. These results can lead to a useful methodology for development of more biodegradable formulations.