Experimental Study On Photocatalytic Reduction Of Nitrate In Water By TiO₂

With the rapid development of industry and agriculture, nitrate pollution of groundwater is becoming more and more serious. Since the chemical properties of nitrate is more stable, the general approach difficult to remove it from the water. Commonly used methods for the removal of nitrate include physicochemical method, biological denitrification method, catalytic reduction method and photocatalytic reduction method. In this study, the photocatalytic reduction method adopted for the removal of nitrate. In order to provide more methods and experience for removal of nitrate.The effects of Sinopharm Ti O₂, metal-doped Sinopharm Ti O₂ and metal-doped homemade Ti O₂ have been investigated.Through the experimental study on photocatalytic reduction of nitrate in Sinopharm Ti O₂ found that, no matter how the reaction conditions were changed, the efficiency of the photocatalytic reduction reaction was very low. The highest removal rate of total nitrogen was only 5.29%, and the concentration of ammonia nitrogen was not high.Metal-doped Sinopharm Ti O₂ as a catalyst for photocatalytic reduction of nitrate, the effects of metal doping content and doping methods, type of light source and light intensity, hole scavenger type and amount, the amount of catalyst, calcination temperature, p H, DO, metal cation and inorganic anion have been investigated. The results showed that:catalyst doped by chemical reduction method has a higher photocatalytic activity, and the best doping amount of metal is 2%. Nitrate can be removed efficiently under the combination of Ultra Violet?365nm,308 nm,254nm?, the higher the light intensity, the higher the reduction efficiency of nitrate. Best catalytic activity for photocatalytic reduction of nitrate with the presence of formic acid was obtained when the concentration of formic acid was 30mmol/L. The best dosage of Ti O₂ was 1g/L, the optimum calcination temperature is 500 ?. Acidic condition and introduction of nitrogen is more conducive to the reaction. Fe2+ and HCO3— promote the reduction of nitrate, other ions inhibits the reduction of nitrate. Metal-doped indeed improved the activity of the catalyst, the removal rate of nitrate was increased to 20.81% by Ag-doped Ti O₂,and the removal rate of nitrate was increased to 16.82% by Pd-doped Ti O₂.Ti O₂ catalyst was prepared using Ti Cl4 and dilute ammonia by precipitation method and characterized by SEM. Effects of the Ag content, the dosage of catalyst, the amount of formic acid, the calcination temperature of Ti O₂,the concentration of ammonia, the ratio of Ti Cl4 and ammonia,the feeding methods have been investigated.The results of experiments showed that best catalytic activity for photocatalytic reduction of nitrate with the content of Ag was 1%, the concentration of formic acid was 50mmol/L, the dosage of Ti O₂ was 1.5g/L, the calcination temperature was 650 ?, the ammonia concentration was 1mol/L,the ratio of Ti Cl4 and ammonia was1:?5⁶?,the feeding methods was inverse,the removal rate of nitrate was19.96%.