"Sono-Electro-Fenton Treatment" Oxidation of 4-chlorophenol using activated carbon electrodes

Abstract

In recent years the search for new technologies for the treatment of waste water hasadvanced at a greater rate due to three principal reasons:-Stricter controls limiting the production of waste water by commercial enterprise.-The lack of water resulting from imminent and progressive climatic change brings with it apolicy of reutilization of waste water.-A greater climatic consciousness means that there is a greater social acceptance of the needto treat waste water.Over the past few decades, advanced oxidation processes (AOPs) have been givenconsiderable attention as effective technologies for environmental remediation. Thecommon feature of these techniques is the generation of free hydroxyl radicals (HO°),which are very reactive since they have a high oxidation potential for the degradation ofpersistent pollutants from water and wastewater. Using H2O2, the production of hydroxylradicals is enhanced by the presence and action of ferrous ion (Fe2+), as a catalyst. In thiscase, hydrogen peroxide is decomposed to hydroxyl radical and hydroxyl ion, while ferrousion is transformed into ferric ion. This reaction is known as Fenton's reaction.The aim of this research was to develop a new method for the degradation of4-Chlorophenols (common waste constituents). A combination of adsorption,electrochemistry and Fenton 's reagent (Fe2+/H2O2) was studied in the absence and presenceof ultrasound. Though the combination of ultrasound with Fenton 's reagent looks to be apromising option to increase the generation of free radicals, not many studies have beenreported.Activated Carbon was employed for the development and characterization of theworking electrodes. Composites of activated carbon containing ferric oxide and ironpowder metal, and the modification of activated carbon with ferrous sulphate, are describedin detail, and were used to generate ferrous ions. Studies carried out on working electrodesusing the Cyclic Voltammetry demonstrated that all electrodes were capable of producing ferrous ions under acidic conditions. For the Activated Carbon Modified Electrode, thegeneration of ions was improved due to pre-impregnation with ultrasound. It has beenshown using Activated Carbon Ferric Oxide Composite Electrodes, that ions were absorbedon the electrode surface.Electrodes with large surface areas and high porosity, offered the best environmentfor Fenton's reaction, where by diffusion, adsorbed Chlorophenol reacted with formedHydroxyl Radicals.The Electro-Fenton treatment occurred in two electrochemical glass cells connectedvia a salt bridge. For Sono-Electro-Fenton treatment, a 40 KHz ultrasonic bath was usedwhile the potentiostat applied a potential on the working electrode over twelve minutes.Experiments were compared with Silent-Electro-Fenton treatment. The degradation ofChlorophenols was followed by HPLC analysis. It was shown that degradation rates of4-Chlorophenol improved with ultrasound when an Activated Carbon Ferric OxideElectrode was used. The erosion suffered by the electrode under ultrasonic conditions led toan improvement in its degradation. This erosion released ferric oxide into the workingsolution and these particles acted as a catalyst for Fenton's reaction

Date of Award	2007
Original language	English
Awarding Institution	Coventry University
Supervisor	Timothy Mason (Supervisor)