The separation and recovery of V from chromium-containing vanadate solution were investigated by a cyclic metallurgical process including selective precipitation of vanadium,vanadium leaching and preparation of vanadi...The separation and recovery of V from chromium-containing vanadate solution were investigated by a cyclic metallurgical process including selective precipitation of vanadium,vanadium leaching and preparation of vanadium pentoxide.By adding Ca(OH)_(2) and ball milling,not only the V in the solution can be selectively precipitated,but also the leaching kinetics of the precipitate is significantly improved.The precipitation efficiency of V is 99.59%by adding Ca(OH)_(2) according to Ca/V molar ratio of 1.75:1 into chromium-containing vanadate solution and ball milling for 60 min at room temperature,while the content of Cr in the precipitate is 0.04%.The leaching rate of V reaches 99.35%by adding NaHCO_(3) into water according to NaHCO_(3)/V molar ratio of 2.74:1 to leach V from the precipitate with L/S ratio of 4:1 mL/g and stirring for 60 min at room temperature.The crystals of NH_(4)VO_(3) are obtained by adjusting the leaching solution pH to be 8.0 with CO2 and then adding NH_(4)HCO_(3) according to NH_(4)HCO_(3)/NaVO_(3) molar ratio of 1:1 and stirring for 8 h at room temperature.After filtration,the crystallized solution containing ammonia is reused to leach the precipitate of calcium vanadates,and the leaching efficiency of V is>99%after stirring for 1 h at room temperature.Finally,the product of V_(2)O_(5) with purity of 99.6%is obtained by calcining the crystals at 560℃ for 2 h.展开更多
Direct phase transformation of flue gas desulfurization gypsum in hot salt solution at atmospheric pres-sure was investigated.The effects of temperature,salt species,salt concentration,solids content,pH and modifier w...Direct phase transformation of flue gas desulfurization gypsum in hot salt solution at atmospheric pres-sure was investigated.The effects of temperature,salt species,salt concentration,solids content,pH and modifier were examined.The crystals obtained under different conditions and solubility of calcium sulfate in contact with solid gypsum were also determined.α-Calcium sulfate hemihydrate crystals of stubby columnar shape and regular pentahedral sides were obtained under the following conditions：salt concentration 20%-30%,operation tempera-ture 95-100 °C,solids mass content in the slurry 10%-30% and neutral pH.Thermodynamic analysis revealed that phase transformation of calcium sulfate dihydrate to α-calcium sulfate hemihydrate occurs because of the difference in solubilities between the two solid gypsum phases in this system.展开更多
基金The authors are grateful for the financial supports from the National Natural Science Foundation of China(51974369)the Postgraduate Research Innovation Project of Central South University,China(2019zzts244).
文摘The separation and recovery of V from chromium-containing vanadate solution were investigated by a cyclic metallurgical process including selective precipitation of vanadium,vanadium leaching and preparation of vanadium pentoxide.By adding Ca(OH)_(2) and ball milling,not only the V in the solution can be selectively precipitated,but also the leaching kinetics of the precipitate is significantly improved.The precipitation efficiency of V is 99.59%by adding Ca(OH)_(2) according to Ca/V molar ratio of 1.75:1 into chromium-containing vanadate solution and ball milling for 60 min at room temperature,while the content of Cr in the precipitate is 0.04%.The leaching rate of V reaches 99.35%by adding NaHCO_(3) into water according to NaHCO_(3)/V molar ratio of 2.74:1 to leach V from the precipitate with L/S ratio of 4:1 mL/g and stirring for 60 min at room temperature.The crystals of NH_(4)VO_(3) are obtained by adjusting the leaching solution pH to be 8.0 with CO2 and then adding NH_(4)HCO_(3) according to NH_(4)HCO_(3)/NaVO_(3) molar ratio of 1:1 and stirring for 8 h at room temperature.After filtration,the crystallized solution containing ammonia is reused to leach the precipitate of calcium vanadates,and the leaching efficiency of V is>99%after stirring for 1 h at room temperature.Finally,the product of V_(2)O_(5) with purity of 99.6%is obtained by calcining the crystals at 560℃ for 2 h.
基金Supported by the National High Technology Research and Development Program of China（2006AA06Z385） the Science Foundation of Wuhan University of Science and Technology（2008RC06）
文摘Direct phase transformation of flue gas desulfurization gypsum in hot salt solution at atmospheric pres-sure was investigated.The effects of temperature,salt species,salt concentration,solids content,pH and modifier were examined.The crystals obtained under different conditions and solubility of calcium sulfate in contact with solid gypsum were also determined.α-Calcium sulfate hemihydrate crystals of stubby columnar shape and regular pentahedral sides were obtained under the following conditions：salt concentration 20%-30%,operation tempera-ture 95-100 °C,solids mass content in the slurry 10%-30% and neutral pH.Thermodynamic analysis revealed that phase transformation of calcium sulfate dihydrate to α-calcium sulfate hemihydrate occurs because of the difference in solubilities between the two solid gypsum phases in this system.
