Little attention has thus far been paid to the potential effect of solution composition on the hydrothermal crystallization of calcium sulfate whiskers prepared from flue-gas desulfurization（FGD） gypsum.When purifie...Little attention has thus far been paid to the potential effect of solution composition on the hydrothermal crystallization of calcium sulfate whiskers prepared from flue-gas desulfurization（FGD） gypsum.When purified FGD gypsum was used as raw material,the morphology and phase structure of the hydrothermal products grown in pure water,H2SO4-H2O,NaCl-H2O,and H2SO4-NaCl-H2O solutions as well as the solubility of purified FGD gypsum in these solutions were investigated.The results indicate that calcium sulfate whiskers grow favorably in the H2SO4-NaCl-H2O system.When prepared using 10-70 g NaCl/kg gypsum-0.01 M H2SO4-H2O at 130 ℃ for 60 min,the obtained calcium sulfate whiskers had diameters ranging from 3 to 5 ｜xm and lengths from 200 to 600 ｜xm,and their phase structure was calcium sulfate hemihydrate（HH）.Opposing effects of sulfuric acid and sodium chloride on the solubility of the purified FGD gypsum were observed.With the co-presence of sulfuric acid and sodium chloride in the reaction solution,the concentrations of Ca2＋ and SO42- can be kept relatively stable,which implies that the crystallization of the hydrothermal products can be controlled by changing the concentrations of sulfuric acid and sodium chloride.展开更多
Calcium sulfate hemihydrate （CSH） whiskers were synthesized by phase transition in CaCl2 solution under atmospheric pressure. Analytical-grade calcium sulfate dihydrate （AR CSD） was used as the raw material for th...Calcium sulfate hemihydrate （CSH） whiskers were synthesized by phase transition in CaCl2 solution under atmospheric pressure. Analytical-grade calcium sulfate dihydrate （AR CSD） was used as the raw material for the synthesis of CSH whiskers, according to orthogonal experiments. The effects of reaction tem- perature, AR CSD content, H2SO4 content, and reaction time were investigated, and the crystallization conditions were optimized. The as-prepared CSH whiskers displayed a regular morphology and a highly uniform size, with an aspect ratio of 105, A simulation system was also established by blending various sulfates with AR CSD, to evaluate the effects of impurities in flue gas desulfurization （FGD） gypsum. The main aim was to prepare CSH whiskers directly from FGD gypsum, without any purification, using the optimized conditions. This is a facile potential alternative process for large-scale production of CSH whiskers using abundant FGD gypsum as source materials.展开更多
基金the Henan Provincial Natural Science Foundation(122102210431 and 132300410233)for their financial supportthe financial support of the Wall and Materials Innovation Fund of Henan Province(08120043)+1 种基金supported by the Public Welfare Program of Environmental Protection Ministry of China(201409069)the characterization test supported by the Analytical and Testing Center of Huazhong University of Science and Technology(HUST)
文摘Little attention has thus far been paid to the potential effect of solution composition on the hydrothermal crystallization of calcium sulfate whiskers prepared from flue-gas desulfurization（FGD） gypsum.When purified FGD gypsum was used as raw material,the morphology and phase structure of the hydrothermal products grown in pure water,H2SO4-H2O,NaCl-H2O,and H2SO4-NaCl-H2O solutions as well as the solubility of purified FGD gypsum in these solutions were investigated.The results indicate that calcium sulfate whiskers grow favorably in the H2SO4-NaCl-H2O system.When prepared using 10-70 g NaCl/kg gypsum-0.01 M H2SO4-H2O at 130 ℃ for 60 min,the obtained calcium sulfate whiskers had diameters ranging from 3 to 5 ｜xm and lengths from 200 to 600 ｜xm,and their phase structure was calcium sulfate hemihydrate（HH）.Opposing effects of sulfuric acid and sodium chloride on the solubility of the purified FGD gypsum were observed.With the co-presence of sulfuric acid and sodium chloride in the reaction solution,the concentrations of Ca2＋ and SO42- can be kept relatively stable,which implies that the crystallization of the hydrothermal products can be controlled by changing the concentrations of sulfuric acid and sodium chloride.
基金financially supported by the Shanghai Foundation of Excellent Young University Teachersthe Science and Technology Commission of Shanghai Municipality(13ZR1415100,13JC1402700,14195800600)the Science and Technology Development Fund of Pudong New Area(PKJ2012-C05)
文摘Calcium sulfate hemihydrate （CSH） whiskers were synthesized by phase transition in CaCl2 solution under atmospheric pressure. Analytical-grade calcium sulfate dihydrate （AR CSD） was used as the raw material for the synthesis of CSH whiskers, according to orthogonal experiments. The effects of reaction tem- perature, AR CSD content, H2SO4 content, and reaction time were investigated, and the crystallization conditions were optimized. The as-prepared CSH whiskers displayed a regular morphology and a highly uniform size, with an aspect ratio of 105, A simulation system was also established by blending various sulfates with AR CSD, to evaluate the effects of impurities in flue gas desulfurization （FGD） gypsum. The main aim was to prepare CSH whiskers directly from FGD gypsum, without any purification, using the optimized conditions. This is a facile potential alternative process for large-scale production of CSH whiskers using abundant FGD gypsum as source materials.
