Research On The Photocatalytic Degradation Of Ammonia Nitrogen Wastewater With Modification Of TiO₂

In recent years, environmental pollution of ammonia-nitrogen wastewater in Gannan region is serious increasingly with the over exploitation of rare earth ore.It is very necessary to look for an efficient and feasible method to remove. In this paper, photocatalyst of TiO2 prepared by sol gel is to treat ammonia-nitrogen wastewater. All influencing factors during the preparation of catalysts was studied, including temperature, the choice of metal elements and rare earth elements, doping ratio; Compared with commercial P25 in catalyst, optimizing catalysts and analyzing its Characterization; In the process of degradation of ammonia-nitrogen wastewatei, analyzing light intensity, pH value, initial concentration of ammonia nitrogen, catalyst dosing quantity, common ion of cations and anions, plus the oxidant H2O2 on the influence of ammonia-nitrogen wastewater degradation; Through the determination and analysis about the degradation products,speculating the mechanism that photocatalyst of TiO2 degrade ammonia-nitrogen wastewater. Detailed experimental results are as follows:(1) Preparing metal ions doped with Fe, Cu, rare earth ions doped with La,’Ce and metal ions,rare earth ions all doped in TiO2 using the sol gel method. Analyzing from characterization that TiO2 catalysts after doping increases the specific surface area, makes the adsorption ability of catalyst increase; elements doped is also very good to load the catalyst surface, reduce the phenomenon of reunion, homemade pure TiO2 catalyst and catalyst modified compared with P25, all make its absorption wave red shift, expanded its moving in the direction of the visible light.(2) Compared with the catalyst photocatalytic experiment:blank group after 3 h which removal rate reach 14.6% can be in a state of dynamic balance; Catalyst adsorption process are mainly concentrated in the first 30 min when the removal rate of ammonia-nitrogen reach 15.9% then in a state of dynamic balance; Compared with the experimental TiO2 catalyst, the blank removal effect to ammonia-nitrogen is far less than the catalyst for ammonia nitrogen removal efficiency. The reaction rate of catalyst is largest before 1h, the part reason is due to the existence of the adsorption.(3) By investigating all the influence factors that the homemade pure TiO2 degradation of ammonia-nitrogen, it is concluded that:catalyst activity is highest under the 500 "C calcination temperature; best removal efficiency condition to remove ammonia-nitrogen is 500 W uv lamp irradiation, pH 10.1, catalyst dosing quantity is 1 g/L, removal ratio for 100.67 mg/L of ammonia nitrogen can reach 46.1%. Examined that the modified TiO2 compared with pure TiO2 have different degree increase of catalytic activity, and obtained the optimum doping ratio is 2% under the experiment, discussed the effect that respective catalyst degraded all the influenced factors to ammonia-nitrogen. Compared different rare earth ions and metal ions doped the same condition to degrade ammonia nitrogen-wastewater effect, come that La/Fe/TiO2 has best removal effect to ammonia-nitrogen, can reach 64.2%. H2O2 and eight normal anion-cation ions in water has important effect on ammonia-nitrogen photocatalytic degradation:when the volume of addition of H2O2 is 2mmol/L, the degradation is best, whereby La/Fe/TiO2 under the synergy of H2O2 has the best degradation, the rate can reach 78.3%; when Na+, K+, Ca2+,Mg2+, Cl-, SO42- and NO3-HCO3- joines with 1 mmol/L respectively, has all blocking effect on the degradation of ammonia nitrogen.(4) Through analyzing products that photocatalyst of La/Fe/TiO2 degrade ammonia-nitrogen, deduced about 38.48% transformed into N2 in the process of reaction.