Water-insoluble polymer-clay nanocomposite ion exchange resin based on N-methyl-d-glucamine ligand groups for arsenic removal

The synthesis and arsenic-removal properties of nanocomposite ion-exchange resins based on N-methyl-d-glucamine groups are presented. First, the N-methyl-d-glucamine-based monomer was synthesised by reaction of 4-vinyl benzyl chloride and N-methyl-d-glucamine and was subsequently polymerised by in situ radical polymerisation in the presence of organic modified montmorillonite (as filler) and N,N-methylene-bis-acrylamide as crosslinker reagent. The nano-composite presented an intercalated morphology, and montmorillonite was dispersed at the nano-level, confirmed by X-ray diffraction and transmission electron microscopy. Arsenate sorption properties were evaluated as a function of pH, initial arsenic concentration, maximum retention capacity, and in the presence of interfering anions, such as phosphate and sulphate. The nano-composite presented high arsenic sorption efficiency, reaching final concentrations below the recommendation of the World Health Organization, even in the presence of interfering anions. Equilibrium sorption results are well described by Langmuir isotherms, and the sorption capacities were approximately 55 mg As/g resin. Finally, retention experiments were carried out using a real sample taken from the Camarones River in northern Chile.