Reduction roasting with sodium sulfate fol- lowed by magnetic separation was investigated to utilize vanadium tailings with total iron grade of 54.90 wt% and TiO2 content of 17.40 wt%. The results show that after redu...Reduction roasting with sodium sulfate fol- lowed by magnetic separation was investigated to utilize vanadium tailings with total iron grade of 54.90 wt% and TiO2 content of 17.40 wt%. The results show that after reduction roasting-magnetic separation with sodium sul- fate dosage of 2 wt% at roasting temperature of 1150℃ for roasting time of 120 min, metallic iron concentrate with total iron grade of 90.20 wt%, iron recovery rate of 97.56 % and TiO2 content of 4.85 wt% is obtained and high-titanium slag with TiO2 content of 57.31 wt% and TiO2 recovery rate of 80.27 % is also obtained. The results show that sodium sulfate has a catalytic effect on the reduction of tailings in the novel process by thermody- namics, scanning electron microscopy （SEM） and X-ray diffraction （XRD） and reacts with silica and alumina in the tailings to form sodium silicate and sodium aluminosili- cate. Migration of elements and chemical reactions destroy the crystal structures of minerals and promote the reduction of vanadium tailings, resulting in that iron grains grow to large size so that metallic iron concentrate with high total iron grade and low TiO2 content is obtained.展开更多
The reduction of vanadium titano-magnetite pellets by H_2-CO at temperatures from 850 to 1050°C was investigated in this paper. The influences of pre-oxidation treatment, reduction temperature, and V_（H_2）/（V_...The reduction of vanadium titano-magnetite pellets by H_2-CO at temperatures from 850 to 1050°C was investigated in this paper. The influences of pre-oxidation treatment, reduction temperature, and V_（H_2）/（V_（H_2） ＋ VCO） on the metallization degree were studied. The results showed that pre-oxidation played a substantial role in the reduction of vanadium titano-magnetite pellets. During the reduction process, the metallization degree increased with increasing temperature and increasing V_（H_2） /（V_（H_2） ＋ VCO）. The phase transformation of pre-oxidized vanadium titano-magnetite pellets during the reduction process under an H_2 atmosphere and a CO atmosphere was discussed, and the reduced samples were analyzed by scanning electron microscopy（SEM） in conjunction with back scatter electron（BSE） imaging. The results show that the difference in thermodynamic reducing ability between H_2 and CO is not the only factor that leads to differences in the reduction results obtained using different atmospheres. Some of Fe_（3-x）Ti_xO_4 cannot be reduced under a CO atmosphere because of the densification of particles＇ structure and because of the enrichment of Mg in unreacted cores. By contrast, a loose structure of particles was obtained when the pellets were reduced under an H_2 atmosphere and this structure decreased the resistance to gas diffusion. Moreover, the phenomenon of Mg enrichment in unreacted cores disappeared during H_2 reduction. Both the lower resistance to gas diffusion and the lack of Mg enrichment facilitated the reduction of vanadium titano-magnetite.展开更多
LiVPO_(4) F has attracted increasing research interest in the field of Li-ion batteries due to its high working voltage platform and high theoretical energy density.However,the construction of stable LiVPO_(4) F catho...LiVPO_(4) F has attracted increasing research interest in the field of Li-ion batteries due to its high working voltage platform and high theoretical energy density.However,the construction of stable LiVPO_(4) F cathode material with excellent electrochemical properties is still a major challenge.Herein,we successfully synthesized spherically shaped LiVPO_(4) F/C via a spray dryingroasting method.X-ray diffraction(XRD)and scanning electron microscopy(SEM)results indicate that the well crystallized LiVPO_(4) F/C with triclinic structure shows spherical morphology with an average diameter of 1-3μm.The spherically shaped LiVPO_(4) F/C delivers a discharge capacity of 137.9 mAh·g^(-1) at 0.1 C rate in the range of3.0-4.5 V and remains 91.4%capacity retention of its initial discharge capacity after 50 cycles.These results reveal that spray drying-roasting method is a promising approach to synthesize spherically shaped LiVPO_(4) F/C cathode material with stable crystal structure and excellent performance.展开更多
基金financially supported by Fundamental Research Funds for the Central Universities (No. 2014zzts273)the National Professional Senior Researchers and Visiting Scholar Programs (No. [2013]3018)
文摘Reduction roasting with sodium sulfate fol- lowed by magnetic separation was investigated to utilize vanadium tailings with total iron grade of 54.90 wt% and TiO2 content of 17.40 wt%. The results show that after reduction roasting-magnetic separation with sodium sul- fate dosage of 2 wt% at roasting temperature of 1150℃ for roasting time of 120 min, metallic iron concentrate with total iron grade of 90.20 wt%, iron recovery rate of 97.56 % and TiO2 content of 4.85 wt% is obtained and high-titanium slag with TiO2 content of 57.31 wt% and TiO2 recovery rate of 80.27 % is also obtained. The results show that sodium sulfate has a catalytic effect on the reduction of tailings in the novel process by thermody- namics, scanning electron microscopy （SEM） and X-ray diffraction （XRD） and reacts with silica and alumina in the tailings to form sodium silicate and sodium aluminosili- cate. Migration of elements and chemical reactions destroy the crystal structures of minerals and promote the reduction of vanadium tailings, resulting in that iron grains grow to large size so that metallic iron concentrate with high total iron grade and low TiO2 content is obtained.
基金financially supported by the Fundamental Research Funds for the Central Universities(2014zzts273)
文摘The reduction of vanadium titano-magnetite pellets by H_2-CO at temperatures from 850 to 1050°C was investigated in this paper. The influences of pre-oxidation treatment, reduction temperature, and V_（H_2）/（V_（H_2） ＋ VCO） on the metallization degree were studied. The results showed that pre-oxidation played a substantial role in the reduction of vanadium titano-magnetite pellets. During the reduction process, the metallization degree increased with increasing temperature and increasing V_（H_2） /（V_（H_2） ＋ VCO）. The phase transformation of pre-oxidized vanadium titano-magnetite pellets during the reduction process under an H_2 atmosphere and a CO atmosphere was discussed, and the reduced samples were analyzed by scanning electron microscopy（SEM） in conjunction with back scatter electron（BSE） imaging. The results show that the difference in thermodynamic reducing ability between H_2 and CO is not the only factor that leads to differences in the reduction results obtained using different atmospheres. Some of Fe_（3-x）Ti_xO_4 cannot be reduced under a CO atmosphere because of the densification of particles＇ structure and because of the enrichment of Mg in unreacted cores. By contrast, a loose structure of particles was obtained when the pellets were reduced under an H_2 atmosphere and this structure decreased the resistance to gas diffusion. Moreover, the phenomenon of Mg enrichment in unreacted cores disappeared during H_2 reduction. Both the lower resistance to gas diffusion and the lack of Mg enrichment facilitated the reduction of vanadium titano-magnetite.
基金financially supported by the National Natural Science Foundation of China(51774207,51774210 and 51904194)the Prospective Applied Research from the Technological Innovation Project of Key Industry of Suzhou(SYG201931)+1 种基金Natural Science Research of Jiangsu Higher Education Institutions of China(19KJB450001)Guangxi Key Laboratory of Electrochemical and Magnetochemical Functional Materials(EMFM20182202)。
文摘LiVPO_(4) F has attracted increasing research interest in the field of Li-ion batteries due to its high working voltage platform and high theoretical energy density.However,the construction of stable LiVPO_(4) F cathode material with excellent electrochemical properties is still a major challenge.Herein,we successfully synthesized spherically shaped LiVPO_(4) F/C via a spray dryingroasting method.X-ray diffraction(XRD)and scanning electron microscopy(SEM)results indicate that the well crystallized LiVPO_(4) F/C with triclinic structure shows spherical morphology with an average diameter of 1-3μm.The spherically shaped LiVPO_(4) F/C delivers a discharge capacity of 137.9 mAh·g^(-1) at 0.1 C rate in the range of3.0-4.5 V and remains 91.4%capacity retention of its initial discharge capacity after 50 cycles.These results reveal that spray drying-roasting method is a promising approach to synthesize spherically shaped LiVPO_(4) F/C cathode material with stable crystal structure and excellent performance.
