Synthesis of CuO–GO/TiO2 visible light photocatalyst for 2-chlorophenol degradation, pretreatment of dairy wastewater and aerobic digestion

Abstract

In the present study, photocatalysts such as copper oxide (CuO) and titanium dioxide (TiO2) were coupled with graphene oxide (GO) for the synthesis of visible light active CuO–GO/TiO2 composite photocatalyst for the decomposition of 2-chlorophenol (2-CP) and complex aromatics in the real dairy wastewater. Photocatalytically decomposed dairy wastewater was further purified by aerobic digestion. The results revealed that composite material shows improved 2-CP degradation, as 86% removal was achieved with k = 0.0101 min−1 at pH 5.0. The effect of pollutant concentration showed that the decomposition of 2-CP increases with the increase in the irradiation time and decreases with the increase in the 2-CP concentration in the solution. The reusability test showed the high stability of CuO–GO/TiO2 composite where the 2-CP degradation was achieved 85.8% after the third run. For real dairy wastewater degradation, photocatalysis increases the solubilization of the organic matters and a 24% higher sCOD (from 5764 to 7536 mg/L after 6 h) was observed compared to photolysis (without catalyst) pretreatment. This improves the aerobic digestibility of dairy wastewater where tCOD was significantly lowered from 12747 to 134.8 mg/L within 27 days of the process. Overall, the present study revealed that the CuO–GO/TiO2 composite material could be an efficient catalyst for removal of toxic organic pollutants and treatment of dairy effluent, thus it can be applied in wastewater treatment plants with a dependency of extensively available visible light.