The effects of the initial framework SiO2/Al2O3 ratio and temperature on the structural changes of NaY zeolites during hydrothermal treatments are studied. Two samples with different framework SiO2/Al2O3 ratios are ...The effects of the initial framework SiO2/Al2O3 ratio and temperature on the structural changes of NaY zeolites during hydrothermal treatments are studied. Two samples with different framework SiO2/Al2O3 ratios are subjected to hydrothermal treatment at four different temperatures. For zeolite with a lower initial SiO2/Al2O3 ratio of 4.2, mesopores are easily formed because more framework aluminum is detached. Moreover, two kinds of mesopores are produced at a higher temperature due to the interconnection of vacancies and smaller mesopores. For zeolite with a higher initial SiO2/Al2O3 ratio of 6.0, there are less mesopores formed as compared with the lower initial SiO2/Al2O3 ratio sample, but there are some macropores formed. This may be attributed to the isolation of vacancies and the different distributions of aluminum in the crystal lattice of the zeolite. The experiment data show that NaY with the SiO2/Al2O3 ratio of 6.0 retains a high relative crystallinity during the hydrothermal treatment. This proves that a high framework SiO2/Al2O3 ratio benefits the stability of zeolite.展开更多
A multi-phase slag containing Na2O is potential to efficiently dephosphorize high-P hot metal.After dephosphorization,the generated slag with high P2O5 content is regarded as a P resource.Because P2O5 was mainly conce...A multi-phase slag containing Na2O is potential to efficiently dephosphorize high-P hot metal.After dephosphorization,the generated slag with high P2O5 content is regarded as a P resource.Because P2O5 was mainly concentrated in the 2CaO SiO2-3CaO P2O5 solid solution,the recovery of P from dephosphorization slag primarily depends on the separation of the solid solution from other phases.The distribution ratios of P2O5 between solid solution and liquid phase in the CaOSiO2-FeO-P2O5-Nslag system were investigated.The results indicated that the addition of Na2O facilitated the enrichment of P2O5 in the solid solution because it increased not only the distribution ratio of P2O5 but also the mass fraction of the solid solution.The distribution ratio of P2O5 was independent of the P2O5 content in slag.A higher P2O5 content in slag resulted in higher P2O5 and Na2O contents in the solid solution.The distribution ratio of P2O5 increased with the total Fe content in the liquid phase,regardless of the valence of Fe.An increase in the FeO content in slag brought a higher P2O5 content in the solid solution.As slag basicity increased,the distribution ratio of P2O5 increased,but the P2O5 content in the solid solution decreased.展开更多
Fine Al（OH）3 crystals were aggregated from supersaturated aluminate solution in the batch reaction tanks. By means of laser particle size analyzer and scanning electron microscopy, the influences of temperature and ...Fine Al（OH）3 crystals were aggregated from supersaturated aluminate solution in the batch reaction tanks. By means of laser particle size analyzer and scanning electron microscopy, the influences of temperature and initial molar ratio of Na2O to Al2O3 （aK） on agglomeration of fine seed in Bayer process were investigated. The results show that agglomeration is almost finished in 8 h, and seeds with size less than 2 μm are easily aggregated together, and almost disappear in 8 h under the optimal process conditions. In the aluminate solution with the same moderate initial aK, when the reaction temperature reaches 75 ℃, the secondary nucleation does not occur, and the effect of agglomeration is better. And at the same reaction temperature, when the initial aK is 1.62, the initial supersaturation of aluminate solution is moderate, the binders on the surfaces of the seed are enough to maintain the agglomeration process, and the agglomeration degree is better. From SEM images, agglomeration mainly occurs in the fine particles, the combinations among the fine particles are loose and the new formed coarse crystal shapes are irregular.展开更多
In order to improve the dephosphorization efficiency of low-basicity converter slag and decrease the consumption of solid CaO,the effect of high Na2O addition(0-15 mass%)on the distribution of P2O5 between solid solut...In order to improve the dephosphorization efficiency of low-basicity converter slag and decrease the consumption of solid CaO,the effect of high Na2O addition(0-15 mass%)on the distribution of P2O5 between solid solution and matrix phase was investigated.The thermodynamic properties of slag samples were calculated by FactSage 7.0 software.Then,the dissolution behavior of phosphorus element from slag was studied.The results show that the mass fraction of 2CaO*SiO2-2CaO*Na2O*P2O5 solid solution increases when the Na2O content is increased in slag.However,the amount of formed solid solution changes little when the Na2O addition is more than 10 mass%.Moreover,the content of Na2O in solid solution would reach saturation when adding 15 mass%Na2O into the slag.With the increase in Na2O content in slag,the distribution ratio of P2O5 between solid solution and matrix phase increases.The values are evidently higher than the results reported in the literature.Meanwhile,the activity of P2O5 in matrix phase and the activity coefficient of P2O5 in solid solution are decreased with increasing the Na2O content in slag.Furthermore,the dissolution ratio of phosphorus in citric acid solution could be improved by adding Na2O into slag,but the increment of dissolution ratio would decrease when the Na2O content exceeds 10 mass%in slag.展开更多
以Ferrihydrite(又称水合氧化铁hydrous iron oxide)为反应前驱物,Fe(II)为催化剂,在微量Na2SiO3存在下,控制pH=6～9范围内合成出了亚微米级纺锤形和准立方形α-Fe2O3微粒.研究了初始pH,Na2SiO3浓度,Ferrihydrite老化方式对相转化时间...以Ferrihydrite(又称水合氧化铁hydrous iron oxide)为反应前驱物,Fe(II)为催化剂,在微量Na2SiO3存在下,控制pH=6～9范围内合成出了亚微米级纺锤形和准立方形α-Fe2O3微粒.研究了初始pH,Na2SiO3浓度,Ferrihydrite老化方式对相转化时间和产物形貌的影响,利用XRD,SEM等手段对产物进行了表征.结果表明,Na2SiO3对Ferriihydrite催化相转化有一定的抑制作用,是影响其相转化过程及产物形貌的关键.在弱碱性条件下,[Si]/[Fe3+]为0.01时可直接获得纺锤形(轴比≥2)或准立方形(300～400nm)α-Fe2O3粒子,并对形成机理进行了初步讨论.展开更多
文摘The effects of the initial framework SiO2/Al2O3 ratio and temperature on the structural changes of NaY zeolites during hydrothermal treatments are studied. Two samples with different framework SiO2/Al2O3 ratios are subjected to hydrothermal treatment at four different temperatures. For zeolite with a lower initial SiO2/Al2O3 ratio of 4.2, mesopores are easily formed because more framework aluminum is detached. Moreover, two kinds of mesopores are produced at a higher temperature due to the interconnection of vacancies and smaller mesopores. For zeolite with a higher initial SiO2/Al2O3 ratio of 6.0, there are less mesopores formed as compared with the lower initial SiO2/Al2O3 ratio sample, but there are some macropores formed. This may be attributed to the isolation of vacancies and the different distributions of aluminum in the crystal lattice of the zeolite. The experiment data show that NaY with the SiO2/Al2O3 ratio of 6.0 retains a high relative crystallinity during the hydrothermal treatment. This proves that a high framework SiO2/Al2O3 ratio benefits the stability of zeolite.
基金This work was financially supported by the National Natural Science Foundation of China(Nos.51704010,51604003,U1760117)Key Laboratory Open Project Fund of Metallurgical Emission Reduction and Resources Recycling(Anhui University of Technology)Ministry of Education(JKF18-02).
文摘A multi-phase slag containing Na2O is potential to efficiently dephosphorize high-P hot metal.After dephosphorization,the generated slag with high P2O5 content is regarded as a P resource.Because P2O5 was mainly concentrated in the 2CaO SiO2-3CaO P2O5 solid solution,the recovery of P from dephosphorization slag primarily depends on the separation of the solid solution from other phases.The distribution ratios of P2O5 between solid solution and liquid phase in the CaOSiO2-FeO-P2O5-Nslag system were investigated.The results indicated that the addition of Na2O facilitated the enrichment of P2O5 in the solid solution because it increased not only the distribution ratio of P2O5 but also the mass fraction of the solid solution.The distribution ratio of P2O5 was independent of the P2O5 content in slag.A higher P2O5 content in slag resulted in higher P2O5 and Na2O contents in the solid solution.The distribution ratio of P2O5 increased with the total Fe content in the liquid phase,regardless of the valence of Fe.An increase in the FeO content in slag brought a higher P2O5 content in the solid solution.As slag basicity increased,the distribution ratio of P2O5 increased,but the P2O5 content in the solid solution decreased.
基金Project(2005CB623702)supported by the Major State Basic Research and Development Program of ChinaProject(20476107) supported by the National Natural Science Foundation of China
文摘Fine Al（OH）3 crystals were aggregated from supersaturated aluminate solution in the batch reaction tanks. By means of laser particle size analyzer and scanning electron microscopy, the influences of temperature and initial molar ratio of Na2O to Al2O3 （aK） on agglomeration of fine seed in Bayer process were investigated. The results show that agglomeration is almost finished in 8 h, and seeds with size less than 2 μm are easily aggregated together, and almost disappear in 8 h under the optimal process conditions. In the aluminate solution with the same moderate initial aK, when the reaction temperature reaches 75 ℃, the secondary nucleation does not occur, and the effect of agglomeration is better. And at the same reaction temperature, when the initial aK is 1.62, the initial supersaturation of aluminate solution is moderate, the binders on the surfaces of the seed are enough to maintain the agglomeration process, and the agglomeration degree is better. From SEM images, agglomeration mainly occurs in the fine particles, the combinations among the fine particles are loose and the new formed coarse crystal shapes are irregular.
基金National Natural Science Foundation of China(51604003,51704010)Natural Science Research Project of Anhui Province Universities(KJ20I6A089)Key Laboratory Open Project Fund of Metallurgical Emission Reduction and Resources Recycling(Anhui University of Technology),Ministry of Education(JKF18-02).
文摘In order to improve the dephosphorization efficiency of low-basicity converter slag and decrease the consumption of solid CaO,the effect of high Na2O addition(0-15 mass%)on the distribution of P2O5 between solid solution and matrix phase was investigated.The thermodynamic properties of slag samples were calculated by FactSage 7.0 software.Then,the dissolution behavior of phosphorus element from slag was studied.The results show that the mass fraction of 2CaO*SiO2-2CaO*Na2O*P2O5 solid solution increases when the Na2O content is increased in slag.However,the amount of formed solid solution changes little when the Na2O addition is more than 10 mass%.Moreover,the content of Na2O in solid solution would reach saturation when adding 15 mass%Na2O into the slag.With the increase in Na2O content in slag,the distribution ratio of P2O5 between solid solution and matrix phase increases.The values are evidently higher than the results reported in the literature.Meanwhile,the activity of P2O5 in matrix phase and the activity coefficient of P2O5 in solid solution are decreased with increasing the Na2O content in slag.Furthermore,the dissolution ratio of phosphorus in citric acid solution could be improved by adding Na2O into slag,but the increment of dissolution ratio would decrease when the Na2O content exceeds 10 mass%in slag.
文摘以Ferrihydrite(又称水合氧化铁hydrous iron oxide)为反应前驱物,Fe(II)为催化剂,在微量Na2SiO3存在下,控制pH=6～9范围内合成出了亚微米级纺锤形和准立方形α-Fe2O3微粒.研究了初始pH,Na2SiO3浓度,Ferrihydrite老化方式对相转化时间和产物形貌的影响,利用XRD,SEM等手段对产物进行了表征.结果表明,Na2SiO3对Ferriihydrite催化相转化有一定的抑制作用,是影响其相转化过程及产物形貌的关键.在弱碱性条件下,[Si]/[Fe3+]为0.01时可直接获得纺锤形(轴比≥2)或准立方形(300～400nm)α-Fe2O3粒子,并对形成机理进行了初步讨论.
