In order to achieve the dual goals of complete deamination of magnesium ammonium phosphate（MAP） and ensure the pyrolysate＇s good removal properties towards ammonia-nitrogen, a temperature-programmed method for the ...In order to achieve the dual goals of complete deamination of magnesium ammonium phosphate（MAP） and ensure the pyrolysate＇s good removal properties towards ammonia-nitrogen, a temperature-programmed method for the pyrolysis of MAP was studied, as well as the thermodynamic and kinetic processes involved in the removal reaction system between MAP pyrolysate and aqueous ammonium. It was found that the pyrolysis method and pyrolysis final temperature had significant effects on the MAP pyrolysate＇s removal properties towards aqueous ammonium, and the following conditions were deemed to be more appropriate： pyrolysis final temperature and heating rate at 180 ℃ and 5 ℃/min, respectively, and a pH level of 9.5 for the removal reaction system. The resultant ammonium removal capacity by the MAP pyrolysate was 95.62 mg/g. After 120 min, the removal rate with an initial concentration of 1000 mg/L was 82%. The kinetic and thermodynamic results indicated that the removal of aqueous ammonium by MAP pyrolysate was the exchange process between H^＋ and NH4^＋ via MAP precipitation. The kinetics complied with the Lagergren quasi second-order model with an equilibrium time of 120 min, while the isothermal curves complied with the Freundlich model.展开更多
Hollow B–SiO2@TiO2 composites were prepared by the wet chemical deposition method starting from TiCl4 and hollow B–SiO2 microspheres.TiO2 layers composed of anatase TiO2 nanoparticles were coated on the surfaces of ...Hollow B–SiO2@TiO2 composites were prepared by the wet chemical deposition method starting from TiCl4 and hollow B–SiO2 microspheres.TiO2 layers composed of anatase TiO2 nanoparticles were coated on the surfaces of the hollow B–SiO2 microspheres probably through the formation of Ti—O—Si and Ti—O—B bonds.A great number of—OH groups were also present at the TiO2 coating layers.The presence of Ti—O—Si bonds and Ti—O—B bonds resulted in the formation of defects in the TiO2 coating layers,which decreased the band gap of the TiO2 coating layers to ca.3.0 eV and endowed the TiO2 coating layers with visible light absorption performance.The buoyancy hollow B–SiO2@TiO2 composites exhibited high photocatalytic activities for the degradation of ammonia-nitrogen and green algae.The conversion of ammonia-nitrogen reached 65%when the degradation of ammonia-nitrogen(43 mg·L-1 at pH value of 8)was catalyzed by the B–SiO2@TiO2(100:10)composite under the simulated solar light irradiation at 35°C for 660 min.The green algae(5 mg·L-1)were almost completely degraded over the B–SiO@TiO2(100:20)photocatalyst under the visible light irradiation at 35°C for 510 min.展开更多
The riverbank soil is a natural purifying agent for the polluted river water(Riverbank filtration, RBF). This is of great importance to groundwater safety along the riverbank. This paper examines the migration and tra...The riverbank soil is a natural purifying agent for the polluted river water(Riverbank filtration, RBF). This is of great importance to groundwater safety along the riverbank. This paper examines the migration and transformation rules of ammonia-nitrogen in three typical types of sand soil using the indoor leaching experiment of soil column, and then makes comparison with the indoor experiment results in combination with the numerical simulation method. The experiment process shows that the change in ammonia-nitrogen concentration goes through three stages including "removal-water saturation-saturation". As the contents of clay particles in soil sample increase, the removal of ammonia-nitrogen from soil sample will take more time and gain higher ratio. During the removal period, the removal ratio of Column 1, Column 2 and Column 3 averages 68.8%(1-12 d), 74.6%(1-22 d) and 91.1%(1-26 d). The ammonia-nitrogen removal ratio shows no noticeable change as the depth of soil columns varies. But it is found that the ammonia-nitrogen removal ratio is the least of the whole experiment when the soil columns are at the depth of 15 cm. It can be preliminary inferred that the natural purifying performance of soil along the river for ammonia-nitrogen in river water mainly depends on the proportion of fine particles in soil. HYDRUS-1D model is used to simulate this experiment process, analyze the change of the bottom observation holes by time and depth in three columns(the tenth day), and make comparison with the experiment result. The coefficients of determination for fitting curves of Column 1, Column 2 and Column 3 are 0.953, 0.909, 0.882 and 0.955, 0.740, 0.980 separately. Besides, this paper examines the contribution of absorption, mineralization and nitrification in the simulation process. In the early removal stage, mineralization plays a dominant role and the maximum contribution rate of mineralization is 99%. As time goes by, absorption starts to function and gradually assumes a dominant position. In the middle and late removal stage, nitrification in Column 1 and Column 2 makes more contribution than mineralization. So the experiment result of the ammonia-nitrogen concentration is 0.6% and 2.4% lower than that in effluent and the maximum contribution ratio of nitrification is -4.53% and -5.10% respectively when only the function of absorption is considered. The mineralization in Column 1 and Column 2 in the middle and late removal stage still plays a more important role than nitrification. So the experiment result is 1.4% higher than that in effluent and the maximum contribution ratio of nitrification is -2.51% when only the function of absorption is considered. Therefore, absorption, mineralization and nitrification make different contributions during different part of the stage. This means that the natural purifying performance of soil along the river for ammonia-nitrogen in river water not only depends on the proportion of fine particles in soil, but depends on the mineralization and nitrification environment. This can offer some insights into the protection and recovery of groundwater along the riverbank.展开更多
基金Project(ZDSY20120619093952884)supported by Shenzhen Strategic New Industry Development,China
文摘In order to achieve the dual goals of complete deamination of magnesium ammonium phosphate（MAP） and ensure the pyrolysate＇s good removal properties towards ammonia-nitrogen, a temperature-programmed method for the pyrolysis of MAP was studied, as well as the thermodynamic and kinetic processes involved in the removal reaction system between MAP pyrolysate and aqueous ammonium. It was found that the pyrolysis method and pyrolysis final temperature had significant effects on the MAP pyrolysate＇s removal properties towards aqueous ammonium, and the following conditions were deemed to be more appropriate： pyrolysis final temperature and heating rate at 180 ℃ and 5 ℃/min, respectively, and a pH level of 9.5 for the removal reaction system. The resultant ammonium removal capacity by the MAP pyrolysate was 95.62 mg/g. After 120 min, the removal rate with an initial concentration of 1000 mg/L was 82%. The kinetic and thermodynamic results indicated that the removal of aqueous ammonium by MAP pyrolysate was the exchange process between H^＋ and NH4^＋ via MAP precipitation. The kinetics complied with the Lagergren quasi second-order model with an equilibrium time of 120 min, while the isothermal curves complied with the Freundlich model.
基金Supported by the National Natural Science Foundation of China(21506078).
文摘Hollow B–SiO2@TiO2 composites were prepared by the wet chemical deposition method starting from TiCl4 and hollow B–SiO2 microspheres.TiO2 layers composed of anatase TiO2 nanoparticles were coated on the surfaces of the hollow B–SiO2 microspheres probably through the formation of Ti—O—Si and Ti—O—B bonds.A great number of—OH groups were also present at the TiO2 coating layers.The presence of Ti—O—Si bonds and Ti—O—B bonds resulted in the formation of defects in the TiO2 coating layers,which decreased the band gap of the TiO2 coating layers to ca.3.0 eV and endowed the TiO2 coating layers with visible light absorption performance.The buoyancy hollow B–SiO2@TiO2 composites exhibited high photocatalytic activities for the degradation of ammonia-nitrogen and green algae.The conversion of ammonia-nitrogen reached 65%when the degradation of ammonia-nitrogen(43 mg·L-1 at pH value of 8)was catalyzed by the B–SiO2@TiO2(100:10)composite under the simulated solar light irradiation at 35°C for 660 min.The green algae(5 mg·L-1)were almost completely degraded over the B–SiO@TiO2(100:20)photocatalyst under the visible light irradiation at 35°C for 510 min.
基金supported by Special Scientific Research Expenditure for Public Charity Industry of Ministry of Water Resources(No.201501008)Institute of Resources and Environment of North China University of Water Resources and Electric Power
文摘The riverbank soil is a natural purifying agent for the polluted river water(Riverbank filtration, RBF). This is of great importance to groundwater safety along the riverbank. This paper examines the migration and transformation rules of ammonia-nitrogen in three typical types of sand soil using the indoor leaching experiment of soil column, and then makes comparison with the indoor experiment results in combination with the numerical simulation method. The experiment process shows that the change in ammonia-nitrogen concentration goes through three stages including "removal-water saturation-saturation". As the contents of clay particles in soil sample increase, the removal of ammonia-nitrogen from soil sample will take more time and gain higher ratio. During the removal period, the removal ratio of Column 1, Column 2 and Column 3 averages 68.8%(1-12 d), 74.6%(1-22 d) and 91.1%(1-26 d). The ammonia-nitrogen removal ratio shows no noticeable change as the depth of soil columns varies. But it is found that the ammonia-nitrogen removal ratio is the least of the whole experiment when the soil columns are at the depth of 15 cm. It can be preliminary inferred that the natural purifying performance of soil along the river for ammonia-nitrogen in river water mainly depends on the proportion of fine particles in soil. HYDRUS-1D model is used to simulate this experiment process, analyze the change of the bottom observation holes by time and depth in three columns(the tenth day), and make comparison with the experiment result. The coefficients of determination for fitting curves of Column 1, Column 2 and Column 3 are 0.953, 0.909, 0.882 and 0.955, 0.740, 0.980 separately. Besides, this paper examines the contribution of absorption, mineralization and nitrification in the simulation process. In the early removal stage, mineralization plays a dominant role and the maximum contribution rate of mineralization is 99%. As time goes by, absorption starts to function and gradually assumes a dominant position. In the middle and late removal stage, nitrification in Column 1 and Column 2 makes more contribution than mineralization. So the experiment result of the ammonia-nitrogen concentration is 0.6% and 2.4% lower than that in effluent and the maximum contribution ratio of nitrification is -4.53% and -5.10% respectively when only the function of absorption is considered. The mineralization in Column 1 and Column 2 in the middle and late removal stage still plays a more important role than nitrification. So the experiment result is 1.4% higher than that in effluent and the maximum contribution ratio of nitrification is -2.51% when only the function of absorption is considered. Therefore, absorption, mineralization and nitrification make different contributions during different part of the stage. This means that the natural purifying performance of soil along the river for ammonia-nitrogen in river water not only depends on the proportion of fine particles in soil, but depends on the mineralization and nitrification environment. This can offer some insights into the protection and recovery of groundwater along the riverbank.
