Effect of Fe2+ on the performance of Anammox at low temperature

The effects of the addition of a certain concentration of Fe2+ on the activity of anammox bacteria in the system at neutral low temperature were investigated by detecting the contents of nitrate, conductance values and protein in the system. The results showed that when the temperature was set at 15°C and the concentration of Fe2+ was 0.16 mmol/L, the system operated in the best condition. After 60h, the denitration rate increased by 40%, the electrical conductivity value decreased the fastest, and the protein content increased by 24.5 mg/g compared with the control group. Zero valent iron has been widely concerned as a reducing agent for the treatment of nitrate wastewater, but the treatment efficacy is severely affected by temperature. The addition of anammox bacteria coupled with Fe0 can not only mutually promote the reaction activity to adapt to more non ideal environments but also reduce the secondary pollution, which provides a new idea for the practical application of nitrate wastewater treatment.

Study on the effect of Anammox/Fe0 coupling treatment of nitrate wastewater under neutral conditions

Batch experiments were conducted to explore the effect of Anammox bacteria on the nitrate reduction efficiency of Fe0 under neutral conditions and to analyze the ways of its enhancement. The effects of Fe2+ concentration on the activity of Anammox bacteria in the system were investigated by detecting the nitrate content in the system under neutral conditions. The upflow reactor was set to verify the possibility of stable operation of Fe0/Anammox system in continuous flow. The results showed that in neutral environment, Anammox bacteria can significantly promote the reduction of nitrate by Fe0, and the denitration rate can reach more than 75% under the dual biological and chemical effects. In the continuous flow system of nitrate reduction by Fe0/Anammox bacteria, the stable treatment period was about 7 days. Through regular replacement of iron powder, the denitration rate can be maintained at more than 75% for a long time, and the effluent NH4+, NO2- concentration is low. The treatment of nitrate wastewater by zero-valent iron as a reducing agent has been widely paid attention, but the treatment effect is seriously affected by pH. Anammox bacteria were added to coupling with Fe0 can not only promote each other’s reactivity to adapt to more non-ideal environment, but also reduce secondary pollution, which provides a new idea for the practical application of nitrate wastewater treatment.

Comparative Study on NH3-SCR of High Entropy Mineral Catalytic Materials for Different Ratios of Rare Earth Concentrate/Rare Earth Tailing

A series of high-entropy mineral catalytic materials were obtained by mixing rare earth tailings containing Fe oxide and rare earth concentrate rich in Ce in Baiyun Obo in different proportions, and by acid-base leaching and microwave roasting. The effects of different proportions of mixed rare earth minerals on the denitrification activity of the samples were analyzed by various techniques, including XRD, EDS and SEM. The mineral phase structure and surface morphology of the catalysts were analyzed. The surface properties of the samples were tested by TPD and XPS methods. The denitrification activity of the sample was simultaneously evaluated and compared in the microreactor. The results show that the denitration efficiency of the active powder is the best when the mixing ratio of rare earth tailings/rare earth concentrate is 1:1, the denitration rate can reach 82%. In summary, different proportions of optimization are extremely effective methods to improve catalyst performance.

Influence of Biochar Composition and Micro-Structure on the Denitration of Flue Gases at High Temperature

Biochar materials are good reducers of nitrogen oxides. The composition and structure of biochar affect significantly its ability to reduce C–NO. In order to study the denitration of flue gases by biochar at high temperature, three kinds of biochar (bamboo charcoal (BC), rice husk ash (RHA), and straw charcoal (SC)) were mixed with cement raw meal in a fixed-bed quartz reactor at the temperature of 800–900 °C and O2 concentration of 0.5%–2%. The results showed that the initial denitration rate of BC was higher than that of RHA, and that of SC was the lowest. RHA had the largest specific surface area, and BC the smallest. The elements C, N, and O and the functional groups of the three types of biochar had a greater influence on the denitration rate than their structures. The denitration rate decreased faster as the O/C ratio increased, and the increase in the relative content of the N element induced the formation of nitrogen-containing functional groups catalyzing C–NO reduction. The content of the C–C bond affected directly the rate of denitration, and both (NCO)x and C–O bonds had a positive effect on the reduction capability of biochar. It can be concluded that the composition of biochar has an important effect on the reduction of C–NO.

Effect of Cement Raw Material and Oxygen Concentration on SNCR Reaction

As the selective non-catalytic reduction denitration(SNCR denitration) was used in cement decomposition furnaces under the high concentration cement raw materials and complex flue gas composition , the denitration efficiency is poor and the reducing agent is largely consumed.In order to meet the more stricter requirements of environmental protection, there is an urgent need to improve the denitration efficiency of SNCR and reduce the escape of reducing agentsin order to prevent the unnecessary waste caused by excessive use of reducing agents and secondary atmospheric pollution.Therefore, studying the effect of cement raw materials and O2 concentration on SNCR process is very important. In this paper, the initial concentration of NO and the ammonium to nitrogen ration (CNH3/CNO) was 800ppm and 1.5, respectively. The effects of cement raw material and oxygen concentration on the reaction process of NH3+NO+O2 in the temperature range of 750°C -1100°C were investigated by means of denitration rate, in Situ DRIFTS analysis.The results demonstrate when O2 concentration was 5% and denitration temperature was 950°C, the deNOx rate reached a maximum of 89.64%, which due to O2 promoted NH3 and NO to react with O2 to produce N2 and H2O. However,under the effect of cement raw material, O2 can promote NH3 which was adsorbed on the surface of cement raw material to react with O2 and produce NO and H2O, and the reaction of oxidation of NH3 is dominant, therefore, the denitration reaction is inhibited. .When O2 concentration was 5% and temperature was 850°C, the deNOx rate reached a minimum value of -109.09%. the high concentration cement raw material and flue gas composition reduce the denitration efficiency of cement kiln.

Optimization of Preparation Process of La-Ce-Palygorskite Catalysts for NO Decomposition by Response Surface Methodology

Response surface methodology(RSM) was applied to optimize the preparation process of La-Ce-Palygorskite catalysts for NO decomposition. The method of three-factors-three-levels central composition experiments were designed. The pH value of the chemical blending, ratio of La/Ce and calcination treatment temperature of the catalysts were chosen as casual factors. With RSM, the effects of these 3 factors on the response value was investigated. It has been found that the most active La-Ce-Palygorskite catalyst for NO decomposition can be prepared when the rare earth content, La:Ce, pH value of the chemical blending and calcination treatment temperature were 2%, LaxCe(1-x)(x=0.55), 6.5 and 409 °C, respectively. The denitration rate of the catalyst could be up to 66.58% under reaction conditions.

Preparation and Catalytic Performance of Ce-Y-Palygorskite Catalysts for NO Decomposition

Ce-Y-palygorskite catalysts were prepared by chemical blending method. The effect of preparation conditions on catalytic performance of Ce-Y-palygorskite catalyst for NO decomposition was investigated in a fixed bed flow reactor. The characteristics of the Ce-Y-palygorskite catalysts were studied by X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FT-IR). The obtained results provided substantial evidence that the catalysts preparation conditions would have strong effect on the catalytic activity for NO decomposition. The Ce-Y-palygorskite catalyst prepared under the optimal conditions: rare earth content, Ce/Y, pH value of the chemical blending and calcination treatment temperature was 3%, CexY(1-x)(x=0.9), 7 and 350°C, respectively, was identified as the most active catalyst for the NO decomposition, and the denitration rate could be up to 67.3% under the experimental reaction conditions.