[Adsorption of Pb2+ onto chitosan-grafted-poly (acrylic acid )/sepiolite composite]

A composite adsorbent chitosan-grafted-poly(acrylic acid)/sepiolite was prepared, and its pH-dependence for removing Pb2+, as well as adsorption isotherm and kinetics were estimated. The results indicate that poly (acrylic acid) has been grafted onto the backbone of chitosan, forming an organic-inorganic composite adsorbent. As-prepared adsorbent shows a coarse, porous and accidented surface, which can contribute to its adsorption kinetics. Under the conditions of pH 6.00, contact time of 30 min, initial Pb2+ concentration of 0.02 mol x L(-1) and amount of adsorbent of 0.10 g, the adsorption capacity of developed adsorbent for Pb2+ is found to be 638.9 mg x g(-1), about three times than that of sepiolite. When five cycles of adsorption-desorption process were carried out, the adsorption capacity decreased to 489.2 mg x g(-1), 76.6% to its original adsorption capacity. However, when sepiolite was used as the adsorbent, no sorption can be observed after three cycles of adsorption-desorption process. Compared to sepiolite, this composite adsorbent presents higher adsorption capacity, faster adsorption rate and better reusable ability.