Adsorption characteristics of copper(II) onto non-crosslinked and cross-linked chitosan immobilized on sand

In this study, Cu(II) removal using non-crosslinked and cross-linked chitosan-coated sand (CCS) from aqueous solution was investigated. To improve the mechanical and chemical stability, chitosan was coated onto sand (CCS) and cross-linked using epichlorohydrin (ECH) and ethylene glycol diglycidyl ether (EGDE). The effect of pH (2.0-5.0) on the adsorption capacity was examined. The maximum adsorption capacity of CCS, CCS-ECH, and CCS-EGDE occurred at an initial pH of 5.0, 4.0, and 5.0, respectively. The kinetic experimental data agreed well with pseudo-second order equation (R² > 0.988), which implies that chemisorption is the rate controlling step. Langmuir, Freundlich and Dubinin-Radushkevich were used to analyze the equilibrium data, where the Langmuir model provided the best fit for the isotherm data obtained using CCS, CCS-ECH, and CCS-EDGE (R² > 0.990). Adsorption-desorption was carried out using HCl solution (pH 1.0 and 3.0) and tap water (pH 7.0), where HCl solution (pH 1.0) provided the greatest recovery of Cu(II) at 98.3, 87.5 and 83.5% for CCS, CCS-ECH and CCS-EDGE, respectively. The removal of Cu(II) from real groundwater samples were studied, where removal of 57.4, 62.4 and 77.5% were achieved using CCS, CCS-ECH and CCS-EDGE.