Photocatalytic Degradation Of Paraquat Using TIO2 and Photo-Fenton

Abstract

Pesticide paraquat dichloride is most widely used as herbicide in the world, it kills a wide range of annual grasses and broad leaved weeds and it is very fast reacting therefore it is mostly used in farming to protect plants and foods. But on the other hand it is a highly toxic substance. It causes contamination of air, water and soil. It enters the food chain and cause bioaccumulation and biomagnifications. Exposure can lead to diseases of eyes, skins, inhalation and ingestion. Therefore an alternate solution must be there so it can be used as an environmentally friendly product. One of the methods is by photo degradation. Photo degradation was performed in a UV chamber. During experiment TiO2 was used as photo catalyst degradation of paraquat dichloride as it is the best photo catalyst due to its chemical and biological inertness when compare to other photo catalyst. During experiment it was found that degradation of 20ppm paraquat with proper agitation and aeration for 420min. with pH 11 and TiO2 content 0.4gm in 250ml solution showed maximum degradation of 98%. When same experiment was conduct in sunlight it show even higher degradation of 98% as compared to UV light. This showed that optimum catalytic properties enable demonstrate TiO2 has good behavior to photo catalytically degrade paraquat dichloride to relatively safe and tolerable compounds in the environment. To reduce the paraquat impact, more powerful treatment processes as compared to traditional treatment for its degradation in environmental water are needed. Photo Fenton is one of the clean technologies based on the generation of extremely reactive and non-selective hydroxyl radicals, with very high oxidative power. Due to their powerful capability to oxidize numerous organic compounds into CO2 and H2O. Fenton’s reagent is a solution of hydrogen peroxide and ferrous ions. Experiment conducted with Photo Fenton showed higher degradation as compared to TiO2. Result obtained by the degradation of paraquat when performed with optimum conditions by addition of 20ppm paraquat, pH 3, Fe2+ 5.5mg and H2O2 0.1ml in 500ml solution for 300 min. showed maximum degradation of 89% which is more than degradation done by TiO2 which showed 77% degradation in 300min. This result showed that with Photo Fenton process even better and faster degradation can be obtained as compared to TiO2. Even it is possible to achieve complete degradation of paraquat by Photo Fenton process by increasing reaction time.