Photochemical Degradation of Organic Pollutants in Wastewaters

In the present work, the photochemical treatment of a synthetic wastewater in a batch recycle photochemical reactor using ultraviolet irradiation (254 nm, 6 W), hydrogen peroxide and ferric ions was studied. Reactor volume was 250 mL with 55.8 mL of irradiated volume in the annular photoreactor. The synthetic wastewater was composed mainly of organic carbon. The effect of initial total carbon (136-1080 mg L^-1), initial H₂O₂ amount (1332-5328 mg L^-1), pH, and Fe(III) presence (2-40 ppm), on total carbon (TC) removal was studied. Each experiment lasted 120 min, and the process was attended via pH and TC concentration. Direct photolysis in the absence of any oxidant had practically no effect on TC removal. Regarding the effect of initial TC concentration in the wastewater keeping the same initial hydrogen peroxide concentration (2664 mg L^-1), it was observed that for 136-271 mg L^-1 TC, around 60% TC removal was achieved, while when initial TC was increased at 528 mg L^-1, the TC removal observed decreased to 50%. For a further increase in TC at 1080 mg L^-1, TC removal dropped to 14%. Initial pH adjustment of the wastewater resulted in slight variations of the TC removals achieved. Finally, adding Fe(III) in the process was beneficial in terms of TC removal obtained. Particularly, the addition of 40 ppm Fe(III) in the presence of 2664 mg L^-1 H₂O₂ and initial TC equal to 528 mg L^-1 increased the TC removal from 50% to 72%.