Water polishing of phenol by walnut green hull as adsorbent: an insight of adsorption isotherm and kinetic

Abstract

The present paper aims to investigate water purification of phenol by walnut green hull adsorbent. The surface characteristics of the adsorbent were studied using Fourier transform infra-red (FTIR), scanning electron microscope, and X-ray diffraction (XRD) techniques. The presence of functional groups such as hydroxyl and carbonyl onto walnut green hull surface was proved by FTIR analysis. Also quartz, cellulose and hematite were detected in the XRD analysis of samples by an X-ray diffractometer. The maximum sorption was achieved at pH 4.0. Data were evaluated for compliance with the Langmuir, Freundlich, Temkin and Dubinin–Radushkevich isotherm models. The results indicate that the data for adsorption of phenol onto walnut green hull fitted well with the Langmuir isotherm. The maximum adsorption capacity of the adsorbent was achieved by Langmuir isotherm 17.8 mg g–1. Also, the adsorption kinetics of phenol on the adsorbent were studied. The rates of sorption were found to conform to pseudo-second-order kinetics with good correlation.