Study On Degradation Of Ammonia Nitrogen In Water By Ultrasonic Enhanced Catalytic Ozonation

Ammonia nitrogen has always been one of the focus of environmental problems.It is an important task for environmental workers to develop simple and efficient ammonia nitrogen treatment method.In this paper,the degradation of ammonia nitrogen wastewater by ultrasonic enhanced catalytic ozonation was studied,we can get the following conclusions:1)Six catalysts including alumina supports magnesium,barium,iron,copper,strontium and cobalt were prepared by impregnation method.And two kinds of better catalysts were screened out of alumina containing magnesium and strontium through analysising the performance of catalysts in the degradation of ammonia nitrogen wastewater by ultrasonic enhanced catalytic ozonation.The orthogonal experimental of catalyst preparation showed that the optimum preparation conditions for Mg/Al₂O₃ were calcining time 1 h,calcination temperature 500?and the concentration of Mg?NO₃?₂ in soaking solution 0.10 mol/L.The optimum preparation conditions for Sr/Al₂O₃ were calcining time 4 h,calcination temperature700?,and the concentration of Sr?NO₃?₂ in soaking solution 0.10 mol/L.The SEM and BET analysis results showed that the Mg/Al₂O₃ prepared in calcination temperature 500?contained a lot of small and uniform floc,with the specific surface area 218.4 m²/g.The Sr/Al₂O₃ prepared in calcination temperature 700?was particle linked,and the size was uniform,rough and uneven,with the specific surface area 253.3 m²/g.2)The study of ultrasonic reinforcement showed that with the introduction of ultrasound,the reaction time of simulated ammonia nitrogen wastewater degradation by Sr/Al₂O₃catalytic ozonation was shortened from 120 min to 60 min,the reaction temperature decreased from 45?to room temperature?25??,the catalyst dosage reduced from 2.5 g/L to 2 g/L,and the ozone flow rate dropped from 1.5 g/h to 0.75 g/h.The residual ammonia nitrogen concentration,nitrate nitrogen concentration and total nitrogen concentration after the degradation simulated ammonia wastewater by ultrasonic enhanced Sr/Al₂O₃ catalytic ozonation were 8.40 mg/L,15.64 mg/L and 24.15 mg/L respectively and degradation rate of ammonia nitrogen was 83.20%,under the conditions of the initial mass concentration of ammonia nitrogen was 50 mg/L,the solution pH 9.5,the ozone flow rate 0.75 g/h,the reaction time 60 min,the catalyst dosage 2 g/L,the reaction temperature 25?,ultrasonic frequency 25 kHz,ultrasonic power 270 W,ultrasonic mode of operation 1 s interval 2 s.The presence of SO₄^2-,HCO₃^-and CO₃^2-,due to their capture of·OH radicals,they inhibited the degradation of simulated ammonia nitrogen wastewater by ultrasonic enhanced catalytic ozonation.While the presence of Br^-,because it participated in the reaction cycle,the ammonia nitrogen degradation pathway is increased,resulting in a greater conversion of ammonia nitrogen to gaseous nitrogen,which will promote the degradation of simulated ammonia nitrogen wastewater by ultrasonic enhanced catalytic ozonation.Under the optimum reaction conditions,when the initial mass concentration of ammonia nitrogen was 50.38 mg/L,the degradation rate of ammonia nitrogen in the actual low concentration ammonia nitrogen wastewater by the ultrasonic enhanced Sr/Al₂O₃ catalytic ozone degradation can reach74.80%.3)The kinetic analysis indicated that the degradation of simulated ammonia nitrogen wastewater by Sr/Al₂O₃ catalytic ozonation was more consistent with the second-order kinetic equation,while the ultrasonic enhanced Sr/Al₂O₃ catalytic ozonation was more suitable for the first-order kinetic equation.The synergistic effect evaluation showed that there was not only synergistic effect between ultrasonic and catalytic ozonation,but also the enhancement of catalytic ozonation.The FIR spectra of Sr/Al₂O₃ catalyst before and after reaction showed that the introduction of ultrasound promoted hydroxyl generation on the catalyst surface and promoted the cracking of N-H bonds on the catalyst surface.Tert butanol experiments showed that the addition of tert butanol?0¹8 mg/L?resulted in a general decrease in the efficiency of ultrasonic enhanced catalytic ozonation for the degradation of simulated ammonia nitrogen wastewater.It preliminarily indicated that the degradation of ammonia nitrogen wastewater by ultrasonic enhanced catalytic ozonation followed the·OH oxidation mechanism.