ADSORPTION OF NICKEL (II) IONS ON A PEANUT SHELL
Thermally and chemically (with dimethylglyoxime) modified sorption materials based on peanut shells have been obtained. The effect of treatment with dimethylglyoxime on the structure and relief of the peanut shell was studied. The optimal conditions for the processes of sorption of nickel (II) ions by the original and modified peanut shells were selected: solution pH 6,0, dosage of sorption material 3 g/dm3, phase contact time 6 hours. The adsorption isotherms of nickel (II) ions in the initial and thermally and chemically modified peanut shells were obtained. The sorption capacity of the initial peanut shell (0,45 mmol/g), thermally modified (0,58 mmol/g) and modified with a 0,5M solution of dimethylglyoxime (0,53 mmol/g) with respect to nickel (II) ions in static conditions have been found. Equations and thermodynamic parameters (Gibbs energy and sorption energy) of the processes under study were determined by processing of the obtained adsorption isotherms within the framework of four monomolecular sorption models: Langmuir, Freundlich, Dubinin-Radushkevich, and Temkin. It has been established that the sorption processes are best described by the Freundlich and Temkin models, i.e. monomolecular adsorption occurs on a heterogeneous sorbent surface, and the sorption capacity of active centers depends on whether neighboring areas are occupied or not, in other words, sorbate-sorbate interaction is observed. The values of thermodynamic parameters indicate that the processes under study proceed spontaneously (∆G <0 kJ/mol) and have the nature of physical adsorption (E = 3-5 kJ/mol, ∆G = -2-0 kJ/mol).