The effect of pH on the sorption of humic acids on bentonite

Abstract

This article evaluates the impact of pH (4.0-8.5) on the sorption capacity of bentonite for humic acids. The sorption capacity of bentonite was higher in an acidic solution. The maximum sorption efficiency was observed at pH 5. Pseudofirst and pseudo-second order kinetic models, as well as the Freundlich isotherm were applied to fit the experimental results at pH 7.5, which was compared to sorption efficiency at pH 5.5. The equilibrium was achieved after 49 and 32 hours for pH 5.5 and 7.5, respectively. Within the experimental concentration scale of humic acid, the sorption capacity expressed by the values of Freundlich constants at pH 5.5 (0.377 mg.g-1) and at pH 7.5 (0.142 mg·g-1) indicates a high affinity of humic acids for bentonite in diluted aqueous solutions. © by PSP.