Photocatalytic degradation of textile dyes by hydrogel supported titanium dioxide nanoparticles

Background: Textile industry has been condemned as one of the world’s worst offenders in terms of pollution because 10-15% of all the dyes used in the industry are lost within wastewater during processing. The presence of even very low concentrations of dyes in effluent is highly visible and degradation products of these textile dyes are often carcinogenic. Owing to the complex nature of synthetic dyes, conventional biological treatment methods are ineffective. Hence there exist needs for developing treatment techniques that can lead to the complete destruction of the dye molecules from waste stream. The current study focused to develop a new photocatalytic reactor using immobilized TiO2 capacity to decolourise and degrade textile industry effluent in an effective way. Methods: TiO2 nanoparticles synthesized by simple precipitation method at pH 5 was successfully entrapped in biopolymer calcium (Ca)-alginate and used as heterogeneous photocatalyst for the degradation of various textile dyes using UV radiations. Photocatalyst was characterized by scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). The influence of previous operational parameters on the photodegradation has been studied by setting up a laboratory scale photocatalytic reactor. Results: The scanning electron microscopic images indicate that, the alginate gel acts as a bridge that binds the nanoparticles together. The experimental results showed that the rate of degradation depends on the chemical structure of different dyes as well as adsorption of dyes by TiO2 which is directly proportional to the surface area and dispersion of the catalyst, the adsorption of light by the dye. The kinetics of COD disappearance was slower than the discoloration of the solution. The supported TiO2 can be used several times without lose of efficiency Conclusions: The results of this study have shown that the degradation of different textile dyes was successfully carried out in laboratory scale photoreactor containing coated TiO2 as photo catalyst. Calcium alginate can be used as a green support for immobilizing TiO2 nanoparticles and can be used for developing a new environment friendly immobilization system for large scale water treatment.