Treatment of Textile Industrial Wastewater by the Heterogeneous Solar Photo-Fenton Process Using Copper Slag

The treatment of textile industrial wastewater was assessed by applying for the first time a metallurgical copper slag (CS) as a non-conventional Fenton-type catalyst in the heterogeneous photo-Fenton process (HPF) under solar irradiation. The effect of pH, CS and H 2 O 2 doses, as well as liquid depth, on color and COD removal was evaluated using a central composite design. The best results were obtained using 80 g CS (133.3 g/L), 6290 mg/L H 2 O 2 , pH 7 and a liquid depth of 0.5 cm. Under these conditions, the process achieved a total discoloration and a depletion of the organic matter content (measured as COD) of 85.7% at 240 min of treatment. In addition, when evaluating the individual components of the system, color and COD removals of 25% and 20% were obtained with CS and 49% and 32% with H 2 O 2 , respectively. The pH adjustment and the exposure to sunlight did not have a significant effect on the response variables. It was found that CS can be used up to six consecutive cycles without altering its removal efficiency without any pretreatment, or up to nine cycles with an intermediate washing. It was determined that raw and treated water are harmful to aquatic organisms mainly due to the presence of residual H 2 O 2 and dissolved salts. CS and exposure to sunlight do not contribute to water toxicity. This water can be reused in the textile industry process if the sun exposure time is increased to eliminate residual H 2 O 2 . Finally, a total treatment cost of 8.7 USD/m 3 of treated water was calculated, which was competitive with respect data reported for photo-Fenton and solar photo-Fenton processes.