Electrochemical Degradation of Phenol in Aqueous Solutions Using Activated Carbon-ZnO Composite

Abstract

Olive mill wastewater (OMWW) has high added-value compounds namely phenolic alcohols, phenolic acid, flavonoids, and lignans. OMWW causes a certain amount of toxicity/phytotoxicity because of its phenolic compounds, which demands removal to acceptable levels before being discharged into water bodies. Therefore, the treatment of phenolic compounds of OMWW is very much needed. Actually, electrochemistry method is becoming a substitute method for wastewater treatment using modified carbon as an electrode. The modification of granular activated carbon with zinc oxide (ZnO) nanoparticles was done based on the deep-coating procedure. Electrochemistry degradation of phenol, with a molecular formula C6H5OH, was studied using an activated carbon modified by ZnO as an electrode. The composite activated carbon-ZnO was characterized by Scanning Electron Microscope, X-ray Diffraction, Transformer Fourier Infrared Spectroscopy, and the measure of pHPZC. The techniques used in this work confirmed that ZnO was immobilized onto activated carbon surface. The morphology and the chemical composition of activated carbon have been changed after the ZnO grafting. Electrochemical performances of the electrochemical process were determined under different conditions, like pH, nature, and concentration of the supporting electrolyte. In this work, NaCl is used as a supporting electrolyte; phenol groups were oxidized by indirect electrochemical oxidation. The degradation of 95% of phenol was achieved after 30 min at the optimal operating conditions (pH = 2 in 3% NaCl). It was concluded that electrochemical oxidation using activated carbon-ZnO is a promising process for the destruction of all phenolic compounds present in OMWW. This opens new perspectives in the field of adsorbent materials, to prepare very efficient carbon for environmental phenol remediation.