Preparation Of Zinc Stannate And Their Application In Metallurgical Coking Wastewater Treatment

With the development of industrial production and the prosperity of social economy, the industrial wastewater emissions are increasing. There are some problems of the traditional water treatment method, such as secondary pollution, high processing cost and so on. As a kind of green, non-toxic and environmentally friendly advanced oxidation processes, the photocatalytic oxidation technology has attracted increasing interest among researchers. For the core part of the photocatalytic technology,photocatalyst is the focus of study. Since the large scale application of traditional photocatalyst still have some problems, the present important subject of photocatalytic oxidation technology is seeking new photocatalyst with high efficient and stable properties. Spinel type semiconductor materials serve as photocatalyst exhibiting excellent properties in the degradation of organic pollutant, from which is hopeful to find the highly active and stable photocatalytic materials.In this paper, on the basis of the hydrothermal method, Zn₂SnO₄ with regular geometry was successfully synthesized by ionic liquid-assisted hydrothermal method.The optimum preparation conditions of the hydrothermal method and ionic liquids-assisted hydrothermal method were as follows: pH 9, 24 h, 180 ℃ and 0.5mmol[Emim]BF4（Sn4+ : [Emim]BF4 = 5:1（mole ratio））, pH 9, 32 h, 220 ℃. At those conditions, the pure, well crystalline and dispersive Zn₂SnO₄ samples were obtained and the samples had the highest activity of photocatalytic degradation of MB.In order to further improve the photocatalytic activity of the Zn₂SnO₄, we use graphene to modify Zn₂SnO₄ prepared by hydrothermal method. Adding differentamount of GO to Zn₂SnO₄ prepared by hydrothermal method, then graphene/Zn₂SnO₄ has obtained after hydrazine hydrate reduction. The results showed that the addition of graphene had no influence on the structure and morphology of Zn₂SnO₄. And when the additive amount of GO is 4 wt%, it can exhibit the highest photocatalytic activity and the property have greatly improved compared with pure Zn₂SnO₄.Research on photocatalytic mechanism suggested that ?OH was the dominant photooxidant, and there are indirect reaction between ?OH and organic chemical dyes.With good photocatalytic stability, the as-prepared Zn₂SnO₄ and Graphene/Zn₂SnO₄ can be used repeatedly.Finally, the as-prepared graphene/Zn₂SnO₄ photocatalyst was applied to metallurgical coking wastewater treatment process. The results suggested that the photocatalytic oxidation method has certain advantages in treatment of low concentration metallurgical coking phenolic wastewater. When the concentration of phenolic wastewater was 15 mg/L, the solution pH was 3, temperature was 25 ℃, the dosage of graphene/Zn₂SnO₄ was 50 mg, the addition of H2O2 was 0.1 mg/L, after 3 h of UV irradiation, the phenolic residue rate was 28.96%.