Modeling and Optimization of Degradation of Dyes Present in Textile Waste Water using Supported Photocatalyst

Abstract

Synthetic dyes are mostly used in different industries like textile, paper etc. These dyes are discharged in the aqueous streams from the effluents of different industries like leather, textiles and paper etc. These dyes produce major environmental pollution problems by discharging polluting and potential carcinogenic substances. The dyeing and finishing industries are the major sources of pollutants in the industrial sector. Due to the toxicity and determination of the dyes, their removal from the textile wastewater has become an issue of interest during the last decades. The complete mineralization of the dyes is not possible by conventional methods. The present study of water decontamination processes are concerned with the oxidation of the dyes. These methods depend on the formation of highly reactive chemical species that mineralize a number of recalcitrant molecules into non-toxic compounds and are called advanced oxidation processes (AOPs). Heterogeneous photocatalytic process employs the near UV irradiation to photo-excite a semiconductor photocatalyst. Using semiconductor based photocatalysis, organic contaminants (textile dyes) can be totally mineralized, reacting with the oxidizers to produce carbon dioxide, water and dilute concentration of simple mineral acids. Among the various semiconductors employed, the anatase phase of TiO2 is known to be a good photocatalyst for the degradation of several pollutants due to its high photosensitivity and large bandgap. Despite the positive attributes of various photocatalysts, there are some drawbacks associated with their use. One of the major drawbacks is the band edge absorption threshold which does not allow the utilization of visible light. Bandgap tailoring by doping and codoping is the most efficient and frequently used approach. Photocatalytic degradation of organic dyes depends on temperature, agitation, catalyst loading, initial dye concentration, pH, geometry of reactor, flow behavior, radiation flux etc.