Study On Microwave The Treatment On Leachate By Catalytic Oxidation Technology

Landfill leachate is a kind of toxic wastewater with high concentration of organic chemicals. It will do harm to the ecological environment and human while drain to the nearby environment without proper disposal. Effluent from domestic landfill leachate treatment process can hardly reach the demands of sanitary landfill leachate emission standards because of the geographical variability of the water quality and quantity, and feasible and applicable full-treatment techniques are lacking both at home and abroad. Economic and effective leachate treatment technology and process is in urgent demand. In order to save cost, enhance the removal efficiency of organic compounds, speed up the reaction rate and shorten the reaction process, and based on the practical need, a new technology—microwave catalytic oxidation process was applied in the thesis to treat the landfill leachate. Catalyst was obtained from different methods: coprecipitation - roasting method, impregnation - roasting method and solid phase calcination method. Compared from the lab scale experiment, a best method from the four above was selected to prepare the catalyst and characterized; modification and reshaping was applied to the catalystwith the purpose to upgrade theremoval efficiency; a kinetic model was set up to formulate the degradation trend of organic compounds, and molecular classification was used to analyze the change of organic matters molecular, besides, spectral scanning was used to analyze the change of types in organic matters.Research on catalyst preparation showed that, Fe-Zr catalyst was the best choice from coprecipitationin the degradation of n-Butyric acid analogous wastewater, the removal efficiency of total organic carbon (TOC) was 75%.Potential mechanism might be due to its enhanced activity and stability by the modified phase by doped technique; Fe-O/CeO₂ catalyst was the best one obtained by impregnation - roasting. Removal efficiency of TOC was 67%. The activated constituents wasα-Fe2O3, with CeFe2; Ni-Co-Ce-O catalysts from low-temperature performed the best one by solid phase calcination. Removal efficiency of TOC was 68% in the treatment of n-Butyric acid analogous wastewater. Compared with Ni-Co-Ce-O catalysts that obtained under high- temperature, this catalysts has higher activity due to its smaller grain diameter and more specific surface areas.Water quality of reallandfill leachate (from Changsheng Bridge landfill) were as follows: COD concentration was 5736mg/L, and the molecular weight of the majority organic matter was below 1000 and it took 54.55%; the total solid concentration was 5477.0 mg/L, among which the dissolved solid was 87.33%; total nitrogen concentration was 2163.16mg/L, among which 80.61% is ammonia, and its concentration was 1743.62 mg/L; the concentration of Ni and Fe was 7.18 mg/L and 1.98mg/L, respectively, and they existed in grain and dissolved types.Fe-O/CeO₂ catalyst was the best catalyst to treat real landfill leachate, and its best working condition was as follows: the Fe-O/CeO₂ dosage is 10g/L, H₂O₂ dosage is 22.5ml/L, microwave power was 800w, microwave irradiation time is 8min and when the COD concentration was 5736mg/L, the removal efficiency of COD_Cr was 69%.Study on catalytic modification showed that the fluidity of round granule was better than that of columnar one, the catalysts was formed from powdered to round with diameter of 4.5mm;matter a was a dope agent in the modified catalysts, which was prepared by roasting at 350℃in muffle furnace for 4h after extrusion forming and air drying . The average aperture was 0.56nm, and main duct were micropores. The leachate was filtered through 0.45μm filter after treated by modified catalysts, its effluent COD_Cr and ammonia concentration are 257mg/L and 99.2mg/L, which meets the municipal wastewater effluent standardsâ…¢.Results of single-purpose matter catalysts experiment showed that the catalysis effectiveness of Ni-O/CeO₂ catalysts was higher than that of Fe-O/CeO₂; the catalysis effectiveness of Fe-O/CeO₂ catalysts was higher than that of Ni-O/CeO₂ when H₂O₂ served as oxidants. Compared with atmospheric pressure and ambient temperature catalytic oxidation and catalytic oxidation in a water bath, microwave catalytic oxidation has higher removal efficiency and greatly shortens the reaction time.The mechanism of modified Catalysts treating leachate through microwave catalytic oxidation showed that, for those rich in granular organic matters, microwave catalytic oxidation attains good pretreatment effect, while for those rich in dissolved organic matter, the effluent attained the municipal wastewater effluent standardsâ…¢after treated; Molecular weigh cutting experiments showed that the removal efficiency of organic matter changes disproportionally with different molecular weight. In the early stage of catalytic reaction, compared with large molecule organic matters, the smaller one might much more easily removed by catalytic oxidation, after the catalytic oxidation reaction, large molecule organic matters in leachate were oxidized into smaller molecule organic compounds, carbon dioxide and water. Spectrum scanning was done before and after the leachate was treated, result show that the types of organic matters decreased quickly step by step as the proceeded. From the treatment efficiency, microwave catalytic oxidation is an efficient way to remove ammonia. General kinetic formular of organic degradation in this study did not show a goodness of fit with Elovich equation, Double constant equation, first-degree kinetic equation and parabola- diffusion equation. However, the fitted degradation equation by SPSS package were Y=1852.4602-442.4124t+36.8971t²-1.0152t³;Y=216.5628+5060.8354exp (-0.5431t).