Magnetic chitosan modified with cysteine-glutaraldehyde as adsorbent for removal of heavy metals from water

New cross-linked chitosan magnetic beads modified with cysteine-glutaraldehyde schiff's base (Chi-CG) were utilized as a possible adsorbent for the elimination of Cu(II) and Cr(VI) from aqueous solutions. The prepared magnetic beads were investigated by several techniques including FTIR, SEM, XPS, TGA and magnetism. The effects of the main analytical parameters (e.g. pH, temperature, contact time, adsorption isotherms, conditions of desorption and the effect of electrolyte) were investigated in detail. At optimum conditions, the adsorption equilibrium was achieved after almost 90 min in case of Cu(II) and 110 min in case of Cr(VI). The surface characteristics of the prepared magnetic beads were varied with different pH ranges. The maximum adsorption capacities for Cu(II) and Cr(VI) were 156.49 and 138.53 mg g(-1), respectively. The adsorption isotherms fit well with Langmuir equation that indicates the monolayer adsorption. Also, pseudo-2nd order equation governs the overall kinetics, indicating chemical reaction as that the rate limiting step. Spontaneous nature of the adsorption process was indicated according to the positive and the negative values of Delta H degrees and Delta G degrees; respectively. The adsorption rate decreased to 90% of the primary adsorption amount after three regeneration cycles. Additionally, no significant reduction in the sorption performance of either Cu(II) or Cr(VI) in the presence of solutions containing K+, Na+, Mg2+, Ca2+, Cl-, NO3-, SO42- or PO43- ions. The accuracy was examined by analyzing some spiked samples. The proposed procedure was applied effectively for the removal of studied toxic ions in some natural and industrial samples. (C) 2016 Elsevier Ltd. All rights reserved.