(234x) Microwave Assisted Advanced Oxidation of Petrochemical Wastewater

New environmental policies apply stricter discharge limits, especially for industrial effluents. In order to meet these restrictions, new treatment processes or the intensification of the existing ones has become essential. Recently, Microwave (MW) has been coupled to Catalytic Wet Peroxide Oxidation (CWPO), an Advanced Oxidation Process (AOP) which uses H₂O₂ as a source of HO_X^â?¢ radicals for organic matter oxidation in water at mild working conditions. The most interesting phenomena produced by MW is the so called hot spot formation, which takes place on the surface of MW-absorbers such as activated carbon (AC). On these spots temperature over 1000ºC is reached. As a result, HO_X^â?¢ formation is enhanced and thus, oxidation rate is significantly increased in comparison to traditional heating methods. Therefore, MW presents multiple synergic effects on CWPO, heating aqueous medium and therefore reducing reaction time due to more effective process, turning MW-absorbing materials into feasible catalysts and, finally, reducing the amount of adsorbed compounds on catalytic surface, consequently degraded in the oxidation process.

This work addresses the use of MW-CWPO with activated carbon as catalyst upon different model compounds present in petrochemical wastewater. In this terms 100 mg/L of phenol, 4-chlorophenol, and toluene and 30 mg/L of naphthalene were subjected to this process. Catalyst dose and pH were optimized to 1 g/L of AC and pH 3. Under this conditions, complete removal of all pollutants after 5 min was achieved. Additionally mineralization degree above 90% was reached after 15 minutes except for toluene, which presented a maximum TOC removal of 77%. As this compounds are not likely to be found as individuals in petrochemical wastewater, several mixes were also treated upon MW-CWPO. In all trials aromatic compounds were completely depleted in the very first minutes of reaction, hence toxicity was eliminated.