Sorption of copper (II) ions by a composite sorbent based on chitosan and montmorillonite

Abstract

A composite sorbent based on chitosan and montmorillonite has been developed for the extraction of heavy metal ions from aqueous solutions. The optimal chitosan / montmorillonite ratio for obtaining sorbent granules has been determined. Equilibriumkinetic studies of the process of copper (II) ions extraction in the heterophase system "aqueous solution of metal sulphate - modified sorbent" have been carried out.The treatment of sorption isotherms of copper (II) ions by the initial chitosan and a chitosan based composite according to the Langmuir equation made it possible to determine the maximum sorption capacities of these materials (А∞). It has been established that A∞ of the chitosan/montmorillonite composite sorbent exceeds the maximum sorption capacity for the original chitosan by more than two times.The effect of pH on the sorption of copper ions by chitosan-based sorbents is due to the competition of metal cations and protons for sorption sites. In the course of competitive chemisorption, protons deactivate amino groups - the main sorption centers, converting them into an inactive, H-salt form, which leads to a decrease in the sorption capacity of chitosan in relation to copper ions.Changes in the composition of the modified sorbent compared to the original chitosan are confirmed by infrared spectroscopy data. Microscopic studies using the method of scanning electron microscopy show the presence of changes in the surface structure of chitosan granules when montmorillonite is introduced into the composition of the sorbent.