Fluorinated rare earth molten-salt electrolytic slag contains a considerable amount of rare earth elements,as well as a variety of heavy metals and fluorides that cause environmental pollution.Therefore,it is of great...Fluorinated rare earth molten-salt electrolytic slag contains a considerable amount of rare earth elements,as well as a variety of heavy metals and fluorides that cause environmental pollution.Therefore,it is of great importance to fully utilise this resource.In this study,the transformation mechanism of fluorinated rare earth molten-salt electrolytic slag roasted with sodium carbonate,and the regulation mechanism of rare earth leaching under different roasting conditions were investigated with the help of thermodynamic calculation of the reactions and kinetic analysis.The thermodynamic and differential thermal thermogravimetric(DTA-TG)analysis shows that the transformation of rare earth fluoride to rare earth oxide is promoted at elevated temperature.Furthermore,the leaching experimental results show that increasing the temperature,time,hydrochloric acid concentration,and liquid-solid ratio can effectively promote the recovery of rare earths.The optimum experimental conditions are a roasting temperature of 700℃,roasting time of 2 h,and sodium carbonate to molten salt electrolytic slag mass ratio of 0.6,followed by leaching at 80℃with a liquid-solid ratio of 10:1 by adding 3 moI/L hydrochlo ric acid with stirring for 2 h.Under these conditions,the rare earths in the molten salt electrolytic slag are biologically transformed at a lower temperature and the leaching efficiency of rare earths exceeds 98%.展开更多
Heterogeneous photocatalysed reduction of aqueous Na_2CO_3 was carried out by using nano LaCoO_3 semiconductor powders. Formic acid and formaldehyde were identified as photoproducts,and were measured spectrophotometri...Heterogeneous photocatalysed reduction of aqueous Na_2CO_3 was carried out by using nano LaCoO_3 semiconductor powders. Formic acid and formaldehyde were identified as photoproducts,and were measured spectrophotometrically using Nash reagent. The effect of different parameters such as sodium carbonate concentration,amount of photocatalyst and different light sources on the yield of photoproducts was also investigated. It shows that nano LaCoO_3 has photocatalytic activity. Irradiation leads to the production of electrons in the conduction band of the LaCoO_3 semiconductor. It is likely that the photoproduced electrons initially reduce CO_3 (2-) to HCOO -,and then to HCHO and CH_3OH.展开更多
The research on the roast reaction mechanism of bastnasite concentrate mixture with Na 2CO 3 was carried out by means of thermal, X ray diffraction and chemical analyses. The isomorphous substitution, F -+Ce 3+...The research on the roast reaction mechanism of bastnasite concentrate mixture with Na 2CO 3 was carried out by means of thermal, X ray diffraction and chemical analyses. The isomorphous substitution, F -+Ce 3+ (Pr 3+ )→O 2- +Ce 4+ (Pr 4+ ), occurred and isomorphous mixed crystal, REO 1+x F 1-x (0< x <1), grew while roasting concentrate mixed with Na 2CO 3. REO 1+x F 1-x with different compositions were produced under different roasting conditions. It has been found that the lattice constant of REO 1+x F 1-x was a linear function of the content of fluorine: a 0=0 5499+0 00102 c F - (nm).展开更多
基金supported by the National Key Research and Development Project of China(2018YFC1903400)Key Research and Development Program of Jiangxi Province(20212BBG73049)+1 种基金Jiangxi Provincial Department of Education Science and Technology Research Project(GJJ190486)Excellent Doctoral Dissertation Cultivating Project of Jiangxi University of Science and Technology(202202400013)。
文摘Fluorinated rare earth molten-salt electrolytic slag contains a considerable amount of rare earth elements,as well as a variety of heavy metals and fluorides that cause environmental pollution.Therefore,it is of great importance to fully utilise this resource.In this study,the transformation mechanism of fluorinated rare earth molten-salt electrolytic slag roasted with sodium carbonate,and the regulation mechanism of rare earth leaching under different roasting conditions were investigated with the help of thermodynamic calculation of the reactions and kinetic analysis.The thermodynamic and differential thermal thermogravimetric(DTA-TG)analysis shows that the transformation of rare earth fluoride to rare earth oxide is promoted at elevated temperature.Furthermore,the leaching experimental results show that increasing the temperature,time,hydrochloric acid concentration,and liquid-solid ratio can effectively promote the recovery of rare earths.The optimum experimental conditions are a roasting temperature of 700℃,roasting time of 2 h,and sodium carbonate to molten salt electrolytic slag mass ratio of 0.6,followed by leaching at 80℃with a liquid-solid ratio of 10:1 by adding 3 moI/L hydrochlo ric acid with stirring for 2 h.Under these conditions,the rare earths in the molten salt electrolytic slag are biologically transformed at a lower temperature and the leaching efficiency of rare earths exceeds 98%.
文摘Heterogeneous photocatalysed reduction of aqueous Na_2CO_3 was carried out by using nano LaCoO_3 semiconductor powders. Formic acid and formaldehyde were identified as photoproducts,and were measured spectrophotometrically using Nash reagent. The effect of different parameters such as sodium carbonate concentration,amount of photocatalyst and different light sources on the yield of photoproducts was also investigated. It shows that nano LaCoO_3 has photocatalytic activity. Irradiation leads to the production of electrons in the conduction band of the LaCoO_3 semiconductor. It is likely that the photoproduced electrons initially reduce CO_3 (2-) to HCOO -,and then to HCHO and CH_3OH.
文摘The research on the roast reaction mechanism of bastnasite concentrate mixture with Na 2CO 3 was carried out by means of thermal, X ray diffraction and chemical analyses. The isomorphous substitution, F -+Ce 3+ (Pr 3+ )→O 2- +Ce 4+ (Pr 4+ ), occurred and isomorphous mixed crystal, REO 1+x F 1-x (0< x <1), grew while roasting concentrate mixed with Na 2CO 3. REO 1+x F 1-x with different compositions were produced under different roasting conditions. It has been found that the lattice constant of REO 1+x F 1-x was a linear function of the content of fluorine: a 0=0 5499+0 00102 c F - (nm).
