Comparative Studies on the Photocatalytic Degradation of 2,4,6- Trichlorophenol Under Various Irradiation Sources

Abstract

With the increasing industrialization because of the development taking place all around the globe the large amount of industrial waste water is being produced and discharged in nearby water streams. Restoring waste water quality is essential to avoid further pollution of the environment. Biodegradable pollutants present in industrial wastewater can be treated by various biological treatment technologies available and are already being used, but there are few biorecalcitrant organic contaminants which can’t be degraded in conventional waste water treatment plants and need special attention. AOPs are the promising technologies which degrade organic compound by hydroxyl radicals. The versatility of AOPs is also enhanced by the fact that they offer different possible ways for OH radical production, thus allowing a better compliance with the specific treatment requirements. Among AOPs heterogeneous photocatalysis has been emerged as an effective way for degradation of organic contaminants.It involes the acceleration of the photoreaction in the presence of semiconductor, photocatalyst and UV irradiation.Chlorophenols (CPs) are a group of special interest due to their high toxicity and low biodegradability. CPs are resistant to biodegradability and even a low concentration can pose health problem. 2,4,6-trichlorophenol was chosen as a model compound, which is also listed in EPA's list of priority pollutants. 2,4,6-trichlorophenol which(TCP) is used as a wood and glue preservative, as an antimildew agent for textiles, in pesticide formulations (herbicides, fungicides, bactericides) and in leather tanning and fishing industries. It has been detected in the emission from fossil fuel combustion, municipal waste incineration, and chlorination of water containing phenols or certain aromatic acids with hypochlorite or during the disinfection of drinking water sources, river water, landfill leachate, chemical plant and sew-age treatment plant effluents and in ambient air. 2,4,6-TCP is a toxic, mutagenic and carcinogenic pollutant. 2,4,6-trichlorophenol is a weak acid which can easily permeate into the human skin in vitro and is readily absorbed by the gastro-intestinal tract. It is also very harmful to the aquatic life if it is discharged into the river, lake and sea as well. The stable carbon-chlorine bond and the position of chlorine atoms relative to the hydroxyl group are responsible for their toxicity, carcinogenic properties, structural stabilization and persistence in the environment, making the removal of 2,4,6-trichlorophenol from the environment very crucial.