Comparison of different TiO2 samples as photocatalyst for the degradation of a mixture of four commercial pesticides

BACKGROUND The presence of pesticides in surface and ground waters can trigger serious environmental problems, particularly in those areas where agriculture is the major economic activity. In this respect, photochemical advanced oxidation processes may be employed to decontaminate such matrices. RESULTS Semiconductor photocatalysis was employed to treat a mixture of four commercial pesticides (oxydemethon‐methyl, methidathion, carbaryl and dimethoate at 25 mg L−1 each). Laboratory scale experiments under UV‐A irradiation were performed to evaluate the relative activity of six commercially available titania samples at 0.5 g L−1 concentration, with Evonik P25 (a 75:25 mixture of anatase:rutile) being the most effective one in terms of pesticides degradation. Experiments were then performed in a pilot plant reactor under natural sunlight leading to quantitative removal of pesticides in less than 300 min; this was accompanied by a substantial reduction of acute toxicity to Vibrio fischeri (i.e. from an initial value of 50% to 15%), as well as moderate mineralization, i.e. 40% COD and 25% DOC removal. CONCLUSIONS The use of sunlight, a renewable energy source, alongside a commercially available, inexpensive and active titania photocatalyst may offer a sustainable treatment option to detoxify this type of wastewater.