Isotherm and kinetic studies on the adsorption of humic acid onto chitosan-H2SO4 beads

A batch adsorption system was applied to study the adsorption of humic acid onto chitosan-H2SO4 beads. Different parameters affecting the adsorption capacity such as initial pH, agitation period, different temperatures and different initial concentrations of humic acid were studied. The adsorption of humic acid onto chitosan-H2SO4 beads agreed well with the non-linear Langmuir, Freundlich and Sips isotherm models. Based on the Langmuir isotherm model, the maximum adsorption capacities attained by chitosan-H2SO4 beads at 300, 310 and 320 K were 377.40, 363.50 and 342.50 mg/g, respectively. Different temperatures affected the adsorption process and it was found that the adsorption process was endothermic in nature. The pseudo-second-order kinetic model, which assumed that chemisorption, was the rate-limiting step best described the adsorption of humic acid onto chitosan-H2SO4 beads. (C) 2011 Elsevier B.V. All rights reserved.