Removal Of Ammonia-nitrogen And Dimethoate By Nano-TiO₂ And TiO₂/Biochar

There are various kinds of contaminants in farmland wastewater. The most serious contaminants are ammonia nitrogen and pesticide. High photocatalytic properties of nano-TiO2 and TiO2/Biochar were successfully prepared by hydrothermal method. Then, the removal rate of ammonia nitrogen and pesticide were evaluated by simulation experiment. This study provided theoretical basis to remove contaminants using new functional materials. This issue was studied from the following several aspects:(1) Nano-TiO2 was prepared by hydrothermal method, and the result of ammonia nitrogen removal in the simulative ammonia nitrogen wastewater. The removal efficiency was evaluated under 254 nm UV irradiation. The influence of initial concentration of ammonia-nitrogen, photocatalyst concentration, pH and temperature on removing ammonia-nitrogen was discussed. And the final products was detected. The optimum factors for ammonia-nitrogen (50 mg·L-1) removal are 1.0 g·L-1 photocatalyst dose, initial pH 11 and 150 mL·min-1 of aeration rate. The removal efficiency is up to 90% at 60℃ and over 45% at room temperature. The content of nitrate and nitrite in the final products were low. It reflects that the catalyst has good photocatalytic oxidation selectivity, which can oxide ammonia-nitrogen to N2. Meantime, the catalyst also shows effective removal ability of total nitrogen and ammonia-nitrogen in domestic sewage.(2) Nano-TiO2 was prepared by hydrothermal method, and the result of dimethoate’s degradation in the simulative ammonia nitrogen wastewater. The degradation efficiency was evaluated under 254 nm UV irradiation. The influence of initial concentration of dimethoate, photocatalyst concentration, pH and light intensity on degradating dimethoate was discussed. And the degradation degree was detected. The optimum factors for dimethoate (10 mg·L-1) degradation are 1.0 g·L-1 photocatalyst dose, the pH is not adjusted, light power is 40 W and 150 mL·min-1 of aeration rate. The degradation efficiency is 100% at room temperature. The degradation degree is incomplete, there are some by-products. It reflects that the catalyst has good photocatalytic oxidation selectivity, degradation efficiency of dimethoate is decline and initial degradation rate is rise with the rise of dimethoate degradation.(3) TiO2/Biochar was prepared by hydrothermal method, and the result of ammonia nitrogen removal in the simulative ammonia nitrogen wastewater. The removal efficiency was evaluated under 254 nm UV irradiation. The influence of initial concentration of ammonia-nitrogen, capacity of TiO2, pH and temperature on removing ammonia-nitrogen was discussed. And the final products was detected. The optimum factors for ammonia-nitrogen (50 mg·L-1) removal are 20% TiO2’s capacity, initial pH 11 and 150 mL·min-1 of aeration rate. The removal efficiency is up to 100% at 60℃ and over 70% at room temperature. The content of nitrite in the final products were low, and there is not nitrate. It reflects that the catalyst has good photocatalytic oxidation selectivity, which can oxide ammonia-nitrogen to N2.(4) TiO2/Biochar was prepared by hydrothermal method, and the result of dimethoate degradation in the simulative dimethoate wastewater. The degradation efficiency was evaluated under 254 nm UV irradiation. The influence of initial concentration of ammonia-nitrogen, capacity of TiO2, pH and temperature on removing ammonia-nitrogen was discussed. And the final products was detected. The optimum factors for ammonia-nitrogen (10 mg·L-1) removal are 20% TiO2’s capacity, the pH is not adjusted, the light power is 40 W and 150 mL·min-1 of aeration rate. The degradation efficiency is up to 100% at room temperature in 90 min. The degradation degree is incomplete, there are some by-products.