Mathematical modeling of the Ni(II) removal from aqueous solutions onto pre-treated rice husk in fixed-bed columns: a comparison

Abstract

One of the efficient techniques for the removal of heavy metals from wastewater is adsorption. In this paper, the adsorption of Ni on a new porous carbonaceous adsorbent, pre-treated rice husk particles, was investigated in both batch and column experiments. The equilibrium isotherm was described well by both the Langmuir and Freundlich isotherm. The Langmuir constants, qm and b, were estimated to be 8.0 and 0.15 l/mg, respectively. Different conditions of flow rate, bed heights, and initial nickel concentrations were considered in the column experiments. It was observed that the adsorption capacity of the packed-bed column and the breakthrough time were increased with an increase in the bed height and a decrease in the flow rate and the influent Ni concentration. The traditional Bohart–Adams, Thomas, and Yoon–Nelson models in accompany with the mass transport model were used to describe the adsorption process in the columns. The experimental breakthrough curves were described satisfactorily by all the aforementioned continuous models. However, the predicted maximum adsorption capacity using Bohart–Adams and Thomas models was less than the one obtained from batch equilibrium experiments. Whereas, there was a good agreement between the batch equilibrium results and the continuous mass transport model regarding the maximum adsorption capacity, indicating the prediction of column performance using batch experiments.