Equilibrium and kinetic study of arsenic sorption by water-insoluble nanocomposite resin of poly[N-(4-vinylbenzyl)-N-methyl-d-glucamine]-montmorillonite

This research presents the kinetic and equilibrium performance of arsenic sorption by a novel polymer-clay nanocomposite ion exchange resin. The monomer N-(4-vinylbenzyl)-N-methyl-d-glucamine was previously synthesised and subsequently polymerised via radical initiation in the presence of crosslinking reagent N,N-methylene-bis-acrylamide and organic-modified montmorillonite. The sorption of arsenic(V) was studied as a function of time, initial concentration and pH. Experiments as a function of pH revealed that arsenic sorption was favoured in the pH range from 3 to 6. The experimental data were fitted to kinetic and diffusion models, such as pseudo-first order, pseudo-second order, Elovich, and the intra-particle diffusion model. The pseudo-second order model presented the best correlation with the experimental data. The model indicated that high percentages of retention could be achieved in a short time (>90%, 1 h of contact) at pH 6 when the initial arsenic concentration was between 5 and 50 mg/L. Intra-particle diffusion and the Boyd relationship showed that arsenic sorption was controlled by the film diffusion mechanism. The Langmuir, Freundlich, and Dubinin–Radushkevitch isotherms were fitted to experimental data, and the Langmuir isotherm presented the best fit. Thermodynamic parameters (ΔG°, ΔH°, ΔS°) showed that the arsenic sorption process was a spontaneous process, endothermic, and produced an increase in entropy.

► Nanocomposite based on N-methyl-d-glucamine and montmorillonite for arsenic sorption. ► Arsenic sorption capacity above 70 mg As/gresin was reached. ► Low arsenic concentration and pH 6 are the optimal retention experimental conditions.