Adsorption of humic acid from aqueous solutions on crosslinked chitosan–epichlorohydrin beads: Kinetics and isotherm studies

The adsorption of humic acid on crosslinked chitosan–epichlorohydrin (chitosan–ECH) beads was investigated. Chitosan–ECH beads were characterized by Fourier transform infrared spectroscopy (FTIR), surface area and pore size analyses, and scanning electron microscopy (SEM). Batch adsorption experiments were carried out and optimum humic acid adsorption on chitosan–ECH beads occurred at pH 6.0, agitation rate of 300 rpm and contact time of 50 min. Adsorption equilibrium isotherms were analyzed by Langmuir and Freundlich models. Freundlich model was found to show the best fit for experimental data while the maximum adsorption capacity determined from Langmuir model was 44.84 mg g−1. The adsorption of humic acid on chitosan–ECH beads was best described with pseudo-first-order kinetic model. For desorption study, more than 60% of humic acid could be desorbed from the adsorbent using 1.0 M HCl for 180 min.