Electrolytic Oxidation of Polynuclear Aromatic Hydrocarbons from Creosote Solution Using TI/IRO2 and TI/SNO2 Circular Mesh Electrodes

The electrooxidation of polynuclear aromatic hydrocarbons (PAHs) in solution was investigated. Most of the PAHs compounds are toxic and hardly biodegradable, so that a chemical or physicochemical treatment is required. In this paper, we reported treatment of synthetic creosote oily effluent (COE) containing several PAHs by using Ti/IrO2 and Ti/SnO2 circular or cylindrical mesh anode electrodes. COE was prepared with distilled water and a commercial creosote solution in the presence of an amphoteric surfactant (CAS). In addition to anode material, different operating parameters were investigated such as current density, reaction time, recycling flow rate, and oxygen injection flow rate. The first series of experiments carried out in the recirculating batch reactor showed that circular Ti/SnO2 electrode was found to be more effective in removing PAHs than circular or cylindrical Ti/IrO2 electrodes. Current density and retention time played important roles for PAHs degradation efficiency, whereas circulation flow rate and oxygen injection slightly influenced the removal efficiency. Finally, the best and simplest operating conditions (82-84% of PAHs removal) determined for PAHs degradation in COE were obtained at a current density of 15 mA/cm(2) through 90 min of treatment with a recycling rate of 3.6 L/min but without O-2 injection in the close loop. Likewise, in the recirculating batch tests, PAHs decomposition exhibited behaviors of the fist-order reaction with a rate coefficient (k) of 0.015 min(-1). The energy consumption was 7.5 kWh/m(3). The second series of experiment using successively batch and continuous treatment of COE shows that the percentage of PAHs degradation could be maintained above 80% up to 18 h of treatment, thereafter, removal efficiency decreased owing to the formation of organic substances on the electrodes surface.