Sonophotocatalytic oxidation based treatment of phthalocyanine pigment containing industrial wastewater intensified using oxidising agents

In the present study, a novel treatment method based on the combination of ultrasonic and ultraviolet irradiation as well as various additives i.e. oxidants and catalysts has been developed for the treatment of real industrial wastewater containing copper phthalocyanine pigment. The progress of the treatment of wastewater has been monitored in terms of reduction in the chemical oxygen demand (COD), total organic content (TOC) and total dissolved salts (TDS) content. Initially, the effect of operating conditions as ultrasonic power, temperature and pH on the extent of COD reduction has been studied. The optimized conditions established were 100 W as the ultrasound power, pH of 2, temperature of 31 +/- 2 degrees C and reaction time of 120 min. Under these optimized conditions, the combination with photocatalytic oxidation (involving CuO and TiO2) with or without various additives like H2O2 and ozone has been studied. The efficacy of combined approaches was generally higher than individual treatment methods of sonolysis (51.52% as the COD reduction) and photolysis (45.65% as the COD reduction). The actual extent of COD reduction obtained for combined approaches of US/UV/CuO, US/UV/TiO2, US/UV/CuO/O-3 and US/UV/TiO2/O-3 was 78.5%, 85.5%, 91.67% and 94.44% respectively in 120 min of treatment. Sonophotocatalysis (catalyst as TiO2) combined with ozone established as the most efficient hybrid technique for COD reduction also resulted in maximum TOC removal of 89.17% and TDS removal of 75.74%. Overall, the combination of US + UV + TiO2 + O-3 has been established as the most efficient technique for the treatment of phthalocyanine pigment based industrial wastewater, yielding final effluent conforming to discharge standards.