Study On The Treatment Method And Mechanism For Industrial Wastewater Of Pearl Pigment Of Mica

Industrial wastewater of pearl pigment of mica, which has complex composition, high concentration of CODcr, chroma, salinity, acidity and basicity, is hard to biodegraded. At present, industrial wastewater of pearl pigment of mica in our country was discharged directly without any treatment, so it caused great environmental disruption.In this thesis, mineral kaolinite was used as substrate to prepare nano TiO₂/mineral compound photocatalyst by sol-gel method. Wastewater of azo dye was photodegraded by the photocatalyst TiO₂ and the optimal technique condition was obtained. Experimental results were characterized and analyzed by some modern measurements, such as UV-Vis, XRD, IR, Raman, TEM, AFM et al.Under UV irradiation, photocatalytic results of azo dye by TiO₂/mineral compound photocatalyst showed that when initial concentration of azo dye was 40mg/L, dosage of catalyst was lg/50ml, solution pH was 4, decolorization rate after 4h could get to 99.2%. Addition of oxidant could accelerate the reaction rate. The photocatalyst could be recycled several times and removal rate could get to 92.8% after reused 6 times.Nevertheless, under solar irradiation, removal rate of azo dye by TiO₂/mineral compound photocatalyst could get to 94%.The degradation course of azo dye by TiO₂ was that: the structure of azo dye was reduced to a new structure first, then naphthalene was oxidized to small molecular matters, which was next mineralized to harmless inorganic matters. But intermediate analysis needs further research because of limited measurement instruments at present.In order to compare with effect of photodegradation, methods of adsorption and chemical oxidation were used to degrade industrial wastewater of azo dye.Removal rate of azo dye could get to 80.17% by rectorite (74μm⁴4μm) which calcined 3h at 400℃, 96.98% by hydrated lime (-100μm) which calcined 3h at 350℃, 90% by Fenton method when FeSO4 was 0.7ml, H2O21.6ml, pH 4.The research indicated that the nano TiO₂/mineral composite photocatalyst had the best effect on the treatment of wastewater of azo dye. Photocatalysis is a kind ofmethod which has high activity, thorough degradation, without recontamination and is a new technology of ecotypic environmental protection. The research provided theoretic and practical reference for application of the technology.By comparison, hydrated lime has better adsorption effect than rectorite in the same condition. But no matter whether the effect is good or bad, adsorption is always a kind of phase transition which needs further treatment.