Intrinsic adsorption properties of raw coal fly ash for quinoline from aqueous solution: kinetic and equilibrium studies

Abstract

Fly ash and quinoline are two major waste materials produced by the large scale utilization of coal. This study describes the investigation into the intrinsic adsorption properties of raw coal fly ash toward quinoline in the aqueous solution. The adsorbent was characterized using XRF, SEM, BET, and XRD. Batch experiments were performed to detect the influences of adsorption conditions on the adsorption capacity of coal fly ash. The results show that the amounts of adsorbed quinoline increase with the increment of initial quinoline concentration and contact time. The potential adsorption mechanism and rate-determining steps were illustrated by analyzing adsorption equilibrium with Langmuir, Freundlich and Redlich-Peterson isotherm models and correlating the experimental results with several kinetic models. It was noticeable that the adsorption process experiences an initial rapid and a subsequent slow uptake stages. Moreover, the adsorption of quinoline on coal fly ash complies with the pseudo-second-order kinetics, and the adsorption isotherm is well described by the Langmuir adsorption model.