Study On The Treatment Of Nitrogen-Contained Wastewater By Photocatalysis

With water bodies suffer increasing nitrogen pollution,wastewater discharge standards for emissions requirements for nitrogen continuously strengthened, using conventional technology to remove inorganic nitrogen is facing many problems, research and development of new technologies、new methods to remove inorganic nitrogen to become the subject of widespread concern. Photocatalysis is an attraetive,elean,low-temperature reaction and a nonenergy-intensitive approaeh,is widely used to remove contaminants from wastewater, photocatalysis also has high research valuein the degradation of inorganic nitrogen.TiO₂ as a catalyst for photocatalytic degradation of inorganic nitrogen in wastewater.First with industrial-grade TiO₂ as a catalyst, the effect of irradiation time、pH value and formic acid concentration are introduced on nitrogen translation.The results showe that, the irradiation time less 90 min is beneficial to the oxidation of nitrogen, with the extension of irradiation time the condition is beneficial to nitrogen reduction; acidic conditions are beneficial to the reduction of the nitrogen, alkaline conditions are beneficial to the oxidation of nitrogen;the formic acid is a good reducing agent,the concentration of formic acid less 50mmol/L is beneficial to the reduction of the nitrogen, greater than 50mmol/L is beneficial to the oxidation of nitrogen.According to the transforming rules of nitrogen in the photocatalysis treatment, this paper simulate biological nitrogen removal treatment: reduction in the acidic conditions at first and then oxidation in the alkaline conditions for degradation of inorganic nitrogen. The effects of reduction time, oxidation time, the amount of hydrogen peroxide, the amount of N2,the amount of air, light intensity and amount of catalyst were discussed.. The results showed that nitrogen removal rate were highest with reduction time of 30 min, oxidation time of 50 min, the amount of hydrogen peroxide of 5 mL, the amount of N2 of 3 L/min, the amount of air of 2 L/min, light intensity of 1000 W and amount of catalyst of 0.6 g/L,above 60% total nitrogen reduced in this study.In this paper, we prepared nano-TiO₂ with Ti（OC4H9）4 and C2H5 OH through sol-gel method. The catalyst was characterized by x-ray diffraction（XRD） and TEM. The influences of calcination temperature, calcination time and amount of catalyst on the removal rate of total nitrogen were investigated. The results indicated that the catalyst prepared at a calcination temperature of 500℃, calcination time of 2h and amount of catalyst of 0.4 g /L exhibited the best photocatalytic activity for total nitrogen removal and the nanoscale TiO₂ catalyst with an anatase phase structure. TEM characterization of catalyst particles dispersed displayed no agglomeration and sintering phenomena,a grain size of 15 20 nm.This paper also prepare nano-TiO₂ modified with chitosan（CS） by sol-gel method to improve the photocatalytic activity, The catalyst was characterized by x-ray diffraction（XRD）.The influences of chitosan content and the amount of TiO₂/CS nanoparticles were investigated. The results as follow:chitosan content was 2wt% and amount of TiO₂/CS nanoparticles of 1.2 g/L, chitosan is helpful to nano-crystalline titania.