Immobilised TiO2 application for pesticides degradation using a solar still

Abstract

Pesticides are recalcitrant contaminants, which are bioaccumulative in nature. A good number of pesticides, particularly organochlorines, have been listed among the Persistent Organic Pollutant list of Stockholm convention. Organochlorine pesticides were significantly used in the past, however, their footprints still exist in environmental matrices.In the present study, degradation of pesticides using a solar still, with immobilised TiO2, is performed. Existing solar remediation systems have a limitation of utilizing ultraviolet portion of solar energy and the thermal energy remains unutilized in most cases. Solar distillation with a TiO2 photocatalysis enhances the purification properties of the solar still in terms of treatment of recalcitrant pollutants.Organochlorine pesticides like isomers of Hexachlorocyclohexane (HCH), Endosulphan and Dichlorodiphenyltrichloroethane (DDT) can be significantly degraded using a thermo-photocatalytic solar still described in the study. Besides this, degradation of synthetic pyrethroids like fenpropathrin, cyhalothrin, cyfluthrin, cypermethrin and fenvalerate is also studied. Combination of solar distillation and photocatalysis was effective for the treatment of water contaminated with pesticides, achieving more than 21–82% degradation for the studied pesticides. For Organochlorine pesticides, pp DDE’ was the compound which showed least degradation (21.4%) and maximum degradation was achieved for Alpha HCH (82.9%). In the synthetic pyrethroid group, fenpropathrin showed least degradation among all the compounds (60.4%) and fenvalerate showed a maximum degradation (96.4%).Solar photocatalytic distillation can find application in recycling of wastewater generated from agriculture-intensive areas and pesticide manufacturing industries.

Keywords

• Solar distillation
• Photocatalysis
• Pesticides
• Organochlorines
• Synthetic pyrethroids
• Solar still