Increase of chitosan selectivity and affinity toward the cadmium ions using xanthate functionalization: Application for cadmium removal from saline solutions

Abstract

A Xanthate functionalized magnetic chitosan nanocomposite (XFMCN) was used for Cd(II) adsorption from high salinity water samples. The Xanthate functionalization was confirmed using the CHNS analysis, showing the sulfur content of 2.28 % in the composition of the nanocomposite. BET surface area of 44.79 m2 g−1 was obtained for XFMCN. The functionalization process resulted in a decrease in University of Tehran isotherm model (UT) constant from 6.73 to 1.80 × 10-3, showing an increased affinity toward cadmium adsorption. The impacts of contact time, the initial concentration of cadmium, adsorbent dosage, pH, temperature, and interfering ions such as Ca2+, Mg2+, Na+, SO₄2−, CO₃2−, NO₃− were investigated. The highest performance was at a contact time of 60 min and initial pH 7. The xanthate functionalization enhanced the selectivity of the adsorbent. Freundlich, Redlich Peterson, University of Tehran (UT), and Radke-Prausnitzi isotherm models described the equilibrium data well, confirming multilayer adsorption. The maximum equilibrium adsorption capacity was 55 mg g-1. Intraparticle diffusion and second-order models were suitable for describing the experimental data. Thermodynamics results showed an exothermic and spontaneous process. The adsorbed cadmium ion could easily be desorbed using hydrochloric acid 0.1 mol L−1. The recovery was studied up to five cycles, exhibiting a slight decrease in the adsorbent performance.