Chromium removal using poly(4-vinylpyridinium)-modified treated clay salts

New composite materials, able to remove hexavalent chromium [Cr(VI)] ions from aqueous solutions, were obtained by reacting poly(4-vinylpyridine) (P4VP) with treated clay [TC]. Two composite samples [TCP4VP-5-0.5] and [TCP4VP-5-1.5], were prepared by varying initial amounts of P4VP and TC and characterized. The retention of Cr(VI) was investigated by batch equilibrium procedure. The good efficiency in removing chromium ions from acidic solutions was demonstrated by adsorption kinetics. Freundlich and Langmuir isotherm models were used to determine adsorption capacity of the TC and of the modified composites [TCP4VP-5-0.5] and [TCP4VP-5-1.5], at 25 degrees C and at pH = 1. The specific role of P4VP salt in new composite materials was evaluated by comparing the kinetics of the TC and [TCP4VP-5-0.5] and [TCP4VP-5-1.5] composites. The obtained results showed clearly that the pyridinium positive charges on the polymer were efficient in hexavalent chromium removal from aqueous solutions. The thermodynamics of the rate processes showed the adsorption of chromium ions to be endothermic, accompanied by decreases in Gibbs free energy. The results showed these composites as potential adsorbent for the chromium ions from aqueous solutions.