N-(2-Carboxybenzyl) grafted chitosan as adsorptive agent for simultaneous removal of positively and negatively charged toxic metal ions.

A chitosan material, cross-linked and grafted with N-(2-carboxybenzyl) groups, was evaluated as adsorbent to sufficiently remove both positively charged ions (Cu(II), Ni(II)) and negatively charged ones (Cr(VI), As(V)) from aqueous solutions. After complete characterization study with FTIR, SEM and BET analysis, the evaluation of adsorption was done with experiments at pH range 2-12 and then varying the initial concentrations of ions. Langmuir-Freundlich equation was used to fit the adsorption data and showed maximum adsorption capacities 308 mg/g at 25 °C for copper and 381 mg/g for nickel ions. The adsorption capacity of As(V) was 208 mg/g and 175 mg/g for Cr(VI). Also, a mechanistic (phenomenological) model of adsorption kinetics is employed to fit the kinetic data found using parameters with physical meaning, and clearly understand the process dynamics. The regeneration of adsorbents was presented in ten cycles of reuse (adsorption-desorption), showing the strong reuse potential of the adsorbent used.