Chemically modified magnetic chitosan microspheres for Cr(VI) removal from acidic aqueous solution

A bioadsorbent composed of magnetic silica nanoparticles encapsulated by chitosan microspheres was prepared by the emulsion cross-linking method, and it was then modified with quaternary ammonium groups by reaction with ethylenediamine and glycidyl trimethylammonium chloride. Characterization of the bioadsorbent indicated that it was highly acid resistant and magnetically responsive. The bioadsorbent was then used to remove Cr(VI) from acidic aqueous solution. The results of batch experiments indicated that the optimal pH value was 2.5, and the adsorbent exhibited low pH dependence. The maximum adsorption capacity was 233.1 mg/g at pH 2.5 and 25 degrees C, and the equilibrium time was determined to be 40-120 min depending on the initial Cr(VI) concentration. The adsorbent could be effectively regenerated using a mixture of 0.3 mol/L NaOH and 0.3 mol/L NaCl with a desorption efficiency of 95.6%, indicating high reusability. In conclusion, the bioadsorbent shows potential for Cr(Vl) removal from acidic wastewater. (C) 2016 Chinese Society of Particuology and Institute of Process Engineering, Chinese Academy of Sciences. Published by Elsevier B.V. All rights reserved.