Electrochemical oxidation of aqueous phenol at a carbon black slurry electrode

The electrochemical oxidation of an aqueous phenol solution was studied via a novel process. Experiments were conducted by recirculating a slurry electrode made of the product to be treated (phenol) and a catalyst (carbon black) through a flow-by electrolyser with a vertical stack of perforated Ti/Pt electrodes. Both the capacity of high adsorption of organic compounds and gases and the conductivity properties of Carbon Black allowed the acceleration of the degradation. High pressure liquid chromatography (HPLC) analysis was used to follow phenol loss and the formation of by-products. Gas chromatography (GC) analysis revealed the presence of two gases: oxygen -electrogenerated by the oxidation of water- and carbon dioxide produced by both phenol and CB oxidation. Other experiments under nitrogen and oxygen flow were performed in a closed reactor cell and proved that oxygen generated by Ti/Pt electrodes is sufficient to obtain the full degradation of phenol. The effects of CB concentration (ranging from 0 to 4 gl(-1)), of the nature of CB and of the applied current (from 0 to 20 A) were investigated. An increase of CB concentration and applied current was found to shift product distribution to favour the formation of carbon dioxide. A removal efficiency of 100% was obtained in a reaction time of 15 min under the following conditions: an initial phenol concentration of 1 mmol 1(-1), 4 g 1(-1) of CB, an applied current of 10 A, a flow rate of 10 ml s(-1) and a temperature of 30 degrees C.