Study On Decolorization Of Azo Dye By Trichoderma Viride

Azo dyes are the most common and largest group of synthetic dyes in the world. They are resistant to fading on exposure to acid, alkali, light and microorganism due to their complex structures. The presence of dye in water can reduce photosynthesis and dissolved oxygen, which results in natural water pollution to cause a serious threat to the environment and human healthy.A number of physicochemical methods are available for the treatment of textile dyeing effluents containing azo dyes. However, these methods have their own limitations such as high cost, sludge generation and low efficiency. Bioremediation or biological methods have attracted considerable attention as they are eco-friendly, efficient and low cost characteristics.Because of the stability of fungal degradation, we need to breed fungus with strong degradation ability, and it has great application value for the biological treatment of dye wastewater. The purpose of this study is to screen degrading fungi which has the characteristics of antibacterial ability, fast growth and high decolorization efficiency. Then it is used for the decolorization of azo dyes and dyeing wastewater. The main contents are as follows:(1) The research work undertaken describes the isolation and screening of the fungal strains from soil and other samples. The dominant fungus was identified by morphology and molecular biology to determine the fungal species.(2) The fungus screened from soil was enclosed in the hydrogel beads made from polyvinyl alcohol and sodium alginate. The decolorization efficiency of the immobilized fungus on different artificial dyeing wastewater and real dyeing water from plant were investigated. And the repeated use of the immobilized fungus was studied.(3) The pH value, mycelia biomass and dye concentration during the decolorizing process of Acid Red 3R were optimized by response surface methodology (RSM). And the optimal conditions were verified by experiments.(4) The biodegradation of the fungus was evaluated by Ultraviolet Visible spectrophotometer (UV-VIS), Fourier transform infrared spectrometer(FTIR) and Gas chromatography-mass spectrometer (GC-MS). The activity of extracellular enzymes produced by the fungus were measured. Phytotoxicity study carried out upon two common plant seeds Glycine max (L.) Merr and Adenanthera microsperma demonstrated the less toxic nature of degraded metabolites.In this study, the fungus isolated from soil with remarkable dyes degradation ability was identified as Trichoderma atroviride. The Trichoderma atroviride enclosed in the hydrogel beads was used for the treatment of artificial dyeing wastewater and real dyeing water. Excellent decolorization effect and favourable repeatability were achieved in this process. Response surface methodology was employed through central composite design to investigate the effect of three influential factors, and the optimal conditions for processing azo dyes Acid Red 3R were as follows:pH was 8.44, mycelia biomass was 4.99g/100mL, initial dye concentration was 85.5mg/L. Several experiments were done under this condition, and the average value of decolorization rate was 99.1%. The study on the decolorization mechanism show that the decoloring approach of Trichoderma degradation was degradation. The manganese peroxidase played an important role in the process of dye degradation. The phytotoxicity test revealed the less toxic nature of the degraded metabolite compared to the toxic azo dye Acid Red 3R.