Ethylenediamine grafted poly(glycidylmethacrylate-co-methylmethacrylate) adsorbent for removal of chromate anions

The removal of chromate anions (CrO42-) from aqueous solutions under different experimental conditions using cross-linked poly(glycidylmethacrylate-co-methylmethacrylate), poly(GMA-co-MMA), adsorbent was investigated in this study. The epoxy group containing adsorbent in the beads form was prepared from glycidylmethacrylate and methylmethacrylate via suspension polymerization. The epoxy groups of the poly (GMA-co-MMA) beads were used for grafting with ethylenediamine to prepare specific adsorbent (poly(GMA-co-MMA)-ED) for CrO42- anions removal from aqueous solutions. Adsorption equilibrium was achieved in approximately 120 min. The removal was favored at low pH, with a maximum adsorption at pH 2.0. Isotherm studies showed that CrO42- anions could be effectively removed by poly(GMA-co-MMA)-ED beads. The maximum adsorption capacities of the poly(GMA-co-MMA) and poly(GMA-co-MMA)-ED beads were 0.044 and 0.441 mmol CrO42- anions/g of dry adsorbents, respectively. The experimental data of the adsorption equilibrium from CrO42- anions aqueous solution correlated well with the Langmuir-Freundlich isotherm model. The experimental data were analyzed using the first- and the second-order kinetic models. The rate constants of adsorption for both kinetics models have been calculated. The second-order model provides the best correlation of the data. Desorption experiments show that the process of adsorption of CrO42- anions was reversible and the adsorbent was easily regenerated with 0.1 M NaOH up to 96% recovery. (C) 2005 Elsevier B.V. All rights reserved.