Detoxification of photo-catalytically treated 2-chlorophenol: optimization through response surface methodology.

ABSTRACT

The present study was conducted to degrade and detoxify 2-chlorophenol (2-CP) under UV irradiation in the presence of titanium dioxide (TiO2) and hydrogen peroxide (H2O2). The treatment efficiency was evaluated on the basis of degradation and cytotoxicity reduction as well as biochemical oxygen demand (BOD), chemical oxygen demand (COD) and total organic carbon (TOC) removal. The process variables such as TiO2, pH, UV irradiation time and H2O2 were optimized. Central composite design in combination with response surface methodology was employed to optimize the process variables. A quadratic model was proposed to predict the treatment efficiency and analysis of variance was used to determine the significance of the variables. The correlation between the experimental and predicted degradation was confirmed by the F and P values (<0.05). The coefficient of determination (R2 = 0.99) were high enough to support the validity of developed model. At optimized conditions, up to 92% degradation of 2-CP was achieved with 3.5 × 10-4 s-1 rate constant. Significant reductions in BOD, COD and TOC values were also achieved. Cytotoxicity was evaluated using bioassays and it was observed that UV/TiO2/H2O2 reduced the cytotoxicity considerably. It is concluded that UV/TiO2/H2O2 could possibly be used to detoxify 2-CP in industrial wastewater.