Precursors of chromium oxide （p-Cr203） were prepared by reducing hexavalent chromium in the presence of sodium carbonate solution under hydrothermal conditions. Methanal was used as the reductant, and carbon dioxide...Precursors of chromium oxide （p-Cr203） were prepared by reducing hexavalent chromium in the presence of sodium carbonate solution under hydrothermal conditions. Methanal was used as the reductant, and carbon dioxide was the acidulating agent. The influences of reaction temperature, initial pressure of carbon dioxide, isothermal time and methanal coefficient on Cr（VI） reduction were investigated. Ex- perimental results showed that Cr（VI） was reduced to Cr（III） with a yield of 99%. Chemical titration, thermogravimetry （TG）, X-ray diffrac- tion （XRD） analysis, and scanning electron microscopy （SEM） were used to characterize the p-Cr203 and Cr203. The series of p-Cr203 were found to be multiphase even if they presented different colors, from gray green to lavender. After these p-Cr203 samples were calcined, the product of rhombohedral Cr203 with a purity of 99.5wt% was obtained.展开更多
Boron-bearing magnetite concentrate is typically characterized by low grade of iron and boron （wTFe = 51%- 54%, WB2O3 =6%-8%）, as well as the close intergrowth of ascharite phase and magnetite phase. A promising tec...Boron-bearing magnetite concentrate is typically characterized by low grade of iron and boron （wTFe = 51%- 54%, WB2O3 =6%-8%）, as well as the close intergrowth of ascharite phase and magnetite phase. A promising technology was proposed to separate iron and boron by coupling the direct reduction of iron oxides and Na activation of boron minerals together. The influence of Na2CO3 as additive on the direct reduction of boron-bearing magnetite was studied by chemical analysis, kinetic analysis, XRD analysis and SEM analysis. The results showed that the ad- dition of Na2CO3 not only activated boron minerals, but also reduced the activation energy of the reaction and pro- moted the reduction of iron oxides. Besides, the addition of Na2CO3 changed the composition and melting point of non-ferrous phase, and then promoted the growth and aggregation of iron grains, which was conducive to the subse- quent magnetic separation. Thus, the coupling of the two processes is advantageous,展开更多
基金the National Science Foundation for Distinguished Young Scholars of China(No.51125018)the National Key Technologies R&D Program(No.2011BAC06B07)+1 种基金the National High-Tech R&D Program of China(No.2011AA060704)Henan Yongtong Nickel Industry Co.,Ltd
文摘Precursors of chromium oxide （p-Cr203） were prepared by reducing hexavalent chromium in the presence of sodium carbonate solution under hydrothermal conditions. Methanal was used as the reductant, and carbon dioxide was the acidulating agent. The influences of reaction temperature, initial pressure of carbon dioxide, isothermal time and methanal coefficient on Cr（VI） reduction were investigated. Ex- perimental results showed that Cr（VI） was reduced to Cr（III） with a yield of 99%. Chemical titration, thermogravimetry （TG）, X-ray diffrac- tion （XRD） analysis, and scanning electron microscopy （SEM） were used to characterize the p-Cr203 and Cr203. The series of p-Cr203 were found to be multiphase even if they presented different colors, from gray green to lavender. After these p-Cr203 samples were calcined, the product of rhombohedral Cr203 with a purity of 99.5wt% was obtained.
基金Item Sponsored by National Natural Science Foundation of China(51304181)National Science Foundation for Distinguished Young Scholars of China(51125018)
文摘Boron-bearing magnetite concentrate is typically characterized by low grade of iron and boron （wTFe = 51%- 54%, WB2O3 =6%-8%）, as well as the close intergrowth of ascharite phase and magnetite phase. A promising technology was proposed to separate iron and boron by coupling the direct reduction of iron oxides and Na activation of boron minerals together. The influence of Na2CO3 as additive on the direct reduction of boron-bearing magnetite was studied by chemical analysis, kinetic analysis, XRD analysis and SEM analysis. The results showed that the ad- dition of Na2CO3 not only activated boron minerals, but also reduced the activation energy of the reaction and pro- moted the reduction of iron oxides. Besides, the addition of Na2CO3 changed the composition and melting point of non-ferrous phase, and then promoted the growth and aggregation of iron grains, which was conducive to the subse- quent magnetic separation. Thus, the coupling of the two processes is advantageous,
