Decomposition of phenol and trichloroethylene by the ultrasound/H2O2/CuO process

The combination of sololysis at 520 kHz and oxidation with H2O2 using heterogeneous catalysis was investigated in aqueous solution. To select a convenient heterogeneous catalyst, degradation of 100 mM H2O2 in the presence of 1 mg ml(-1) Al2O3, ZnO, Ni2O3 and CuO was determined. The high est apparent first-order degradation rate was measured for CuO. The most intensive luminescence was observed as well with CuO, and therefore this metal oxide was used as heterogeneous catalyst. No effect of sonication was measured on the CuO-catalysed degradation of 100 mM H2O2 although sonication affects strongly the specific surface of the CuO-particles. The combination of sonolysis and oxidation with H2O2/CuO was tested on the degradation of the hydrophilic compound phenol and the hydrophobic volatile compound trichloroethylene (TCE). The degradation of phenol was slower than if additivity of both degradation mechanisms is assumed. Addition of CuO/H2O2 on the other hand did not enhance the degradation rate of TCE at all. TCE does not react with the radicals, probably superoxide radicals, formed by the CuO-catalysed H2O2 decomposition and the formation of cavitations is apparently not increased by adding CuO-particles. (C) 1999 Elsevier Science Ltd. All rights reserved.