Determination of lindane in surface water samples and its degradation by hydrogen peroxide and persulfate assisted TiO 2 -based photocatalysis.

Organochlorine pesticides (OCPs) have been used extensively as insecticides and herbicides. This study investigates the occurrence of lindane in surface water from the Peshawar valley ( i.e. , Peshawar, Charsadda, Nowshera, Mardan and Swabi districts of Khyber Pakhtunkhwa, Pakistan). Out of 75 samples tested ( i.e. , 15 samples from each district), 13 samples (including 2 from Peshawar, 3 from Charsadda, 4 from Nowshera, 1 from Mardan, and 3 from Swabi) are found to be contaminated with lindane. Overall, the detection frequency is 17.3%. The maximum concentration of lindane is detected in a water sample from Nowshera and found to be 2.60 μg L -1 . Furthermore, the degradation of lindane in the water sample from Nowshera, containing the maximum concentration, is investigated by simulated solar-light/TiO 2 (solar/TiO 2 ), solar/H 2 O 2 /TiO 2 and solar/persulfate/TiO 2 photocatalysis. The degradation of lindane by solar/TiO 2 photocatalysis is 25.77% after 10 h of irradiation. The efficiency of the solar/TiO 2 process is significantly increased in the presence of 500 μM H 2 O 2 and 500 μM persulfate (PS) (separately), represented by 93.85 and 100.00% lindane removal, respectively. The degradation efficiency of lindane is lower in natural water samples as compared to Milli-Q water, attributed to water matrix effect. Moreover, the identification of degradation products (DPs) shows that lindane follows similar degradation pathways in natural water samples as the one in Milli-Q water. The results show that the occurrence of lindane in surface waters of Peshawar valley is a matter of great concern for human beings and the environment. Interestingly, H 2 O 2 and PS assisted solar/TiO 2 photocatalysis is an effective method for the removal of lindane from natural water.