Batch adsorption of some phenolic acids from aqueous solution by means of natural bentonite clay: equilibrium and kinetic studies

Abstract

In the present study, adsorption of some polyphenolic acids encountered in olive mill waste waters was carried out on natural bentonite clay. Many techniques, namely X-Ray Diffraction, X-Ray Fluorescence, and Transmission Electron Microscopy equipped with Energy Dispersive X-Ray spectroscopy were used to characterize sampled clay. Results revealed the presence of montmorillonite clay in addition of some impu-rities such as quartz, feldspar and mica. Kinetics and equilibrium adsorption of caffeic acid, tannic acid and a mixture of soluble phenolic compounds extracted from olive mill waste waters were studied. Results showed that the adsorption kinetic model of all tested compounds is the same and it follows pseudo-second-order reaction. However, the adsorption isotherms are different, while caffeic acid adsorption fitted well to the Langmuir model, Tannic acid and polyphenols extract are taken up according to the Freundlich isotherm. pH and Chemical Oxygen