Non-catalytic remediation of aqueous solutions by microwave-assisted photolysis in the presence of H2O2

Advanced oxidation processes have emerged as potentially powerful methods to transform organic pollutants in aqueous solutions into non-toxic substances. In this work, a comparison of degradation dynamics of five aromatic compounds (phenol, chlorobenzene, nitrobenzene, 4-chlorophenol, and pentachlorophenol) in aqueous solutions by non-catalytic UV, MW, and combined MW/UV remediation techniques in the presence of H2O2 is presented. Relative degradation rate constants have been monitored and the major products were identified. The combined degradation effect of UV and MW radiation was found larger than the sum of isolated effects in all cases studied. It is concluded that such an overall efficiency increase is essentially based on a thermal enhancement of subsequent oxidation reactions of the primary photoreaction intermediates. Optimizations revealed that this effect was particularly significant in samples with a low concentration of H2O2, however, a larger excess of H2O2 was essential to complete the destruction in most experiments. The absence of heterogeneous catalysts was in no doubt an additional advantage of the technique applied.