Treatment of malachite green dye using combined oxidation techniques based on different irradiation

We investigated the treatment of malachite green (MG) dye using sonocatalytic, photocatalytic and sonophotocatalytic techniques. The percentage of decolorization for sonophotolysis (65.5 +/- 3.3%) was much higher than the individual effects of sonolysis (55.2 +/- 2.4%) and photolysis (52.1 +/- 2.6%). The efficiency of the sonophotocatalytic process increased in the presence of photocatalysts such as anatase TiO2 (82.2 +/- 4.1%) and ZnO (75.7 +/- 3.8%). The decolorization rate further enhanced in the presence of nano-TiO2 (anatase, rutile ratio 75: 25 and particle size 100 nm). The enhancement in decolorization was marginal for sonophotocatalysis (95.9 +/- 4.8%) as compared to sonocatalysis (93.0 +/- 4.3%) and photocatalysis (93.2 +/- 4.6%). The intensification of decolorization in the presence of nano-TiO2, due to lower recombination of hydroxyl ions on the photocatalytic surface and nano-particle size of a catalyst, increased cavitational activity. The total organic carbon was found to be maximum for sonophotocatalytic in the presence of nano-TiO2 (67.1 +/- 3.3%).