Research On New Catalyst Of Catalytic Reduction Removal Water Nitrate

Activities of nitrogen fixation which people take destroy the balance of nartrual nitrogen with the development of agriculture and industry.The increase of nitrate concentration in ground water has stimulated to intensive reserarch on denitrification. The conventional methods of removing nitrate from water exists some disadvantages. The nitrate is reduced into nitrogen with hydrogen, which is a new water treatment technology. Catalytic reduction method is known to have great potential for rapid reaction, high selectivity of generating nitrogen, low energy consumption and easy operation.Catalytic nitrate reduction is one of the most promising methods.Bimetal catalyst was prepared usingγ-Al2O3 as support and selecting non-precious metals as active component.Non-precious metal catalysts with high activity and selectivity was screened by means of control experiments of performance comparison. Trimetallic catalyst was prepared by adding Pd into bimetal catalyst. Compared with traditional Pd-Cu/γ-Al2O3, the timetallic catalyst contained lower amount of Pd. Comparison of activity and selectivity between the timetallic catalyst and traditional Pd-Cu/γ-Al2O3 was performed. Effects of calcination temperature, proportion of metal, sequence and way of impregnation on reaction performance were investigated. Catalysts were characterized by XRD and SEM. Effects of pH value, hydrogen flow, initial concentration of nitrate, catalyst amount on reduction of nitrate were studied.It was found that W-Cu/γ-Al2O3 with calcination temperature of 350℃and W:Cu ratio of 4:1 exhibited the optimal catalytic performance. Nitrate removal rate and ammonia nitrogen yield was respectively up to 52.49% and 4.38% under the condition of pH of 4, catalyst amount of 2g/L, initial nitrate concentration of 100mg/L, hydrogen flow of 100mL/min and reaction time of 3h. Compared with the traditional Pd-Cu/γ-Al2O3, not only content of Pd in Pd-Cu-W/γ-Al2O3 decreased, but also the catalytic activity and selectivity of Pd-Cu-W/γ-Al2O3 increased. Pd-Cu-W/γ-Al2O3 exhibited the optimal catalytic performance when the catalyst was prepared with mixed impregnation method using Pd:W:Cu ratio of 3:1:1 and calcination temperature of 400℃. Nitrate removal rate and ammonia nitrogen yield was respectively up to 100% and 7.8% under the condition of pH of 4, catalyst amount of 3g/L, initial nitrate concentration of 100mg/L, hydrogen flow of 100mL/min and reaction time of 1h.