Adsorptive removal of Cu(II) from aqueous solutions using non-crosslinked and crosslinked chitosan-coated bentonite beads

Batch experiments were executed to investigate the removal of Cu(II) from aqueous solutions using non-crosslinked (CCB) and crosslinked chitosan-coated (CCB-ECH) bentonite beads. CCB and CCB-ECH beads were characterized by BET surface area and pore diameter analysis and X-ray diffraction (XRD). The percentage removal and adsorption capacity of Cu(II) ions were examined as a function of initial concentration and pH. The equilibrium data of CCB agreed well with the Langmuir model while CCB-ECH beads showed a better fit with the Freundlich model. Based on the isotherm study, CCB is a homogenous adsorbent, whereas CCB-ECH is a heterogeneous adsorbent. The adsorption capacities of CCB and CCB-ECH at pH 4 are 12.21 and 9.43 mg/g, respectively. The kinetic data correlated well with the pseudo-second order equation, which implies that chemisorption is the rate-limiting step. The desorption study was performed using eluent solutions, tap water (pH 7) and HCl solution (pH 1 and pH 3). The best Cu(II) recovery was obtained using HCl solution (pH 1).

Research highlights
► The removal of Cu(II) from aqueous solution using non-crosslinked (CCB) and crosslinked (CCB-ECH) chitosan-coated bentonite has been studied.
► The isotherm data for CCB and CCB-ECH is best fit for Langmuir and Freundlich model, respectively.
► The adsorption capacities of CCB and CCB-ECH are 12.21 mg/g and 9.43 mg/g, respectively.
► The kinetic data correlated well with the pseudo-second order equation.
► Crosslinked CCB beads have better regeneration capacity over CCB even in acidic media.