Long-term high temperature in conventional vanadium extraction process would cause particles to be sintered and wrapped, thus reducing extraction efficiency of vanadium. Based on the purpose of directional conversion ...Long-term high temperature in conventional vanadium extraction process would cause particles to be sintered and wrapped, thus reducing extraction efficiency of vanadium. Based on the purpose of directional conversion and process intensification, this work proposed a combination of low temperature sodium roasting and high efficiency selective oxidation leaching in vanadium extraction. The investigation of the reaction mechanism suggested that the structure of vanadium slag was changed by roasting, which also caused the fracture of spinel.The addition of MnO2 promoted the directional oxidation of low-valent vanadium into high valence. It also found that Na2S2O8 could oxidize low-valent vanadium effectively in leaching. The leaching efficiency of vanadium reached 87.74% under the optimum conditions, including a roasting temperature of 650 ℃, a roasting time of 2.0 h, a molar ratio of sodium-to-vanadium of 0.6, a MnO2(roasting additive) dosage of 5 wt% and a Na2S2O8(leaching oxidant) dosage of 5 wt%. This percentage is 7.18% higher than that of direct roasting-andleaching under the same conditions.展开更多
The fusion of the leaching and purification processes was realized by directly using microemulsion as the leaching agent.The bis-(2-ethyhexyl)phosphoric acid(DEHPA)/n-heptane/NaOH microemulsion system was established ...The fusion of the leaching and purification processes was realized by directly using microemulsion as the leaching agent.The bis-(2-ethyhexyl)phosphoric acid(DEHPA)/n-heptane/NaOH microemulsion system was established to directly leach vanadates from sodium-roasted vanadium slag.The effect of the leaching agent on the leaching efficiency was investigated,in addition to the molar ratio of H_(2)O/NaDEHP(W),DEHPA concentration,solid/liquid ratio,stirring time,and leaching temperature.In optimal situations,the vanadium leaching efficiency reaches 79.57%.The X-ray diffraction characterization of the leaching residue and the Raman spectrum of the microemulsion before and after leaching demonstrate the successful entry of vanadates from the sodium-roasted vanadium slag into the microemulsion.The proposed method successfully realizes the leaching and purification of vanadates in one step,thereby greatly reducing production costs and environmental pollution.It also offers a new way to achieve the green recovery of valuable metals from solid resources.展开更多
Tailings from the vanadium extraction process are discarded each year as waste,which contain approximately 30 wt%of Fe.In our previous work,we extracted Fe and Mn from vanadium slag,and Fe and Mn existed in the form o...Tailings from the vanadium extraction process are discarded each year as waste,which contain approximately 30 wt%of Fe.In our previous work,we extracted Fe and Mn from vanadium slag,and Fe and Mn existed in the form of FeCl_(2) and MnCl_(2) after chlorination by NH_(4) Cl to achieve effective and green usage of waste containing Fe and Mn.In this work,square wave voltammetry(SWV)and cyclic voltammetry(CV)were applied to investigate the electrochemical behaviors of Fe^(2+)and Mn^(2+)in Na Cl-KCl melt at 800℃.The reduction processes of Fe^(2+)and Mn^(2+)were found to involve one step.The diffusion coefficients of FeCl_(2) and Mn Cl_(2) in molten salt of eutectic mixtures Na Cl-KCl molten salt were measured.The electrodeposition of Fe and Mn were performed using two electrodes at a constant cell voltage.The Mn/Fe mass ratio of the electrodeposited product in Na Cl-KCl-2.13 wt%FeCl_(2)-1.07 wt%Mn Cl_(2) was 0.0625 at 2.3 V.After the electrolysis of NaCl-KCl-2.13 wt%Fe Cl_(2)-1.07 wt%MnCl_(2) melted at 2.3 V,the electrolysis was again started under 3.0 V and the Mn/Fe mass ratio of the electrodeposited product was 36.4.This process provides a novel method to effectively separate Fe and Mn from simulated chlorinated vanadium slag.展开更多
The chemical composition of vanadium slag significantly affects its element distribution and phase composition,which affect the subsequent calcification roasting process and vanadium recovery.In this work,seven kinds ...The chemical composition of vanadium slag significantly affects its element distribution and phase composition,which affect the subsequent calcification roasting process and vanadium recovery.In this work,seven kinds of vanadium slags derived from different regions in China were used as the raw materials to study the effects of different components on the vanadium slag’s elements distribution,phase composition,calcification roasting,and leaching rate of major elements using scanning electron microscope,X-ray diffraction analysis,and inductively coupled plasma-optical emission spectroscopy.The results show that the spinel phase is wrapped with silicate phase in all vanadium slag samples.The main elements in the spinel phase are Cr,V,and Ti from the interior to the exterior.The size of spinel phase in low chromium vanadium slag is larger than the other vanadium slags with higher chromium contents.The spinel phase of high-calcium and high-phosphorus vanadium slag is more dispersed.The strongest diffraction peak of vanadium spinel phase in the vanadium slag migrates to a higher diffraction angle,and(Fe_(0.6)Cr_(0.4))_(2)O_(3)is formed after calcification roasting as the chromium content increased.A large amount of Ca_(2)SiO_(4)is produced because excess Ca reacts with Si in high-calcium and high-phosphorus vanadium slag.The vanadium leaching rate reaches 88%in some vanadium slags.The chromium leaching rate is less than 5%in all vanadium slags.The silicon leaching rate of high-calcium and high-phosphorus vanadium slag is much higher than that of the other slags.The leaching rate of manganese is higher than 10%,and the leaching rates of iron and titanium are negligible.展开更多
Traditional processes for treating vanadium slag generate a huge volume of solid residue and a large amount of harmful gas,which cause serious environmental problems.In this study,a new process for the comprehensive u...Traditional processes for treating vanadium slag generate a huge volume of solid residue and a large amount of harmful gas,which cause serious environmental problems.In this study,a new process for the comprehensive utilization of vanadium slag was proposed,wherein zeolite A and a V2O5/TiO2 system were synthesized.The structural properties of the as-synthesized zeolite A and the V2O5/TiO2system were characterized using various experimental techniques,including X-ray diffraction,X-ray fluorescence,scanning electron microscopy,and infrared spectroscopy.The results reveal that zeolite A and the V2O5/TiO2 system are successfully obtained with high purity.The results of gas adsorption measurements indicate that the prepared zeolite A exhibits high selectivity for CO2 over N2 and is a candidate material for CO2 capture from flue-gas streams.展开更多
Calcification roasting–acid leaching of high-chromium vanadium slag(HCVS)was conducted to elucidate the roasting and leaching behaviors of vanadium and chromium.The effects of the purity of Ca O,molar ratio between C...Calcification roasting–acid leaching of high-chromium vanadium slag(HCVS)was conducted to elucidate the roasting and leaching behaviors of vanadium and chromium.The effects of the purity of Ca O,molar ratio between Ca O and V_2O_5(n(Ca O)/n(V_2O_5)),roasting temperature,holding time,and the heating rate used in the oxidation–calcification processes were investigated.The roasting process and mechanism were analyzed by X-ray diffraction(XRD),scanning electron microscopy(SEM),and thermogravimetry–differential scanning calorimetry(TG–DSC).The results show that most of vanadium reacted with Ca O to generate calcium vanadates and transferred into the leaching liquid,whereas almost all of the chromium remained in the leaching residue in the form of(Fe_(0.6)Cr_(0.4))_2O_3.Variation trends of the vanadium and chromium leaching ratios were always opposite because of the competitive reactions of oxidation and calcification between vanadium and chromium with Ca O.Moreover,Ca O was more likely to combine with vanadium,as further confirmed by thermodynamic analysis.When the HCVS with Ca O added in an n(Ca O)/n(V_2O_5)ratio of 0.5 was roasted in an air atmosphere at a heating rate of 10°C/min from room temperature to 950°C and maintained at this temperature for 60 min,the leaching ratios of vanadium and chromium reached91.14%and 0.49%,respectively;thus,efficient extraction of vanadium from HCVS was achieved and the leaching residue could be used as a new raw material for the extraction of chromium.Furthermore,the oxidation and calcification reactions of the spinel phases occurred at 592and 630°C for n(Ca O)/n(V_2O_5)ratios of 0.5 and 5,respectively.展开更多
To extract vanadium in an environment friendly manner, this study focuses on the process of leaching vanadium from vanadium slag by high pressure oxidative acid leaching. Characterizations of the raw slag, mineralogy ...To extract vanadium in an environment friendly manner, this study focuses on the process of leaching vanadium from vanadium slag by high pressure oxidative acid leaching. Characterizations of the raw slag, mineralogy transformation, and the form of leach residues were made by X-ray diffraction, scanning electron microscopy, and energy dispersive X-ray spectroscopy. The result shows that the vana-dium slag is composed of major phases of fayalite, titanomagnetite, and spinel. During the high pressure oxidative acid leaching process, the fayalite and spinel phases are gradually decomposed by sulfuric acid, causing the release of vanadium and iron in the solution. Meanwhile, unreacted silicon and titanium are enriched in the leach residues. With the initial concentration of sulfuric acid at 250 g·L^-1, a leaching tem-perature of 140℃, a leaching time of 50 min, a liquid-solid ratio of 10:1 mL·g^-1, and oxygen pressure at 0.2 MPa, the leaching rate of vana-dium reaches 97.69%.展开更多
The extraction of vanadium from high calcium vanadium slag was attempted by direct roasting and soda leaching. The oxidation process of the vanadium slag at different temperatures was investigated by X-ray diffraction...The extraction of vanadium from high calcium vanadium slag was attempted by direct roasting and soda leaching. The oxidation process of the vanadium slag at different temperatures was investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy dispersive spectroscopy (EDS). The effects of roasting temperature, roasting time, Na2CO3 concentration, leaching tem- perature, leaching time, and liquid to solid ratio on the extraction of vanadium were studied. The results showed that olivine phases and spinel phases in the vanadium slag were completely decomposed at 500 and 800℃, respectively. Vanadium-rich phases were formed at above 850℃. The leaching rate of vanadium reached above 90% under the optimum conditions: roasting temperature of 850℃, roasting time of 60 min, Na2CO3 concentration of 160 g/L, leaching temperature of 95℃, leaching time of 150 min, and liquid to solid ratio of 10:1 mL/g. The main impurities were Si and P in the leach liquor.展开更多
Microwave irradiation was used to investigate vanadium slag in place of traditional heating.Factors associated with vanadium extraction ratio were studied following the concentration of leaching agent,oxidant dosage,m...Microwave irradiation was used to investigate vanadium slag in place of traditional heating.Factors associated with vanadium extraction ratio were studied following the concentration of leaching agent,oxidant dosage,microwave power,microwave irradiation time and mass ratio of liquid to solid.Results indicated that leaching ratio based on microwave leaching at atmospheric pressure can get to 68.48% under the conditions following sulfuric acid concentration 30%,mass ratio of liquid to solid ratio 2∶1,mass ratio of vanadium slag to manganese dioxide dosage 25∶1.4,and microwave power 800W for 3.5 h at 95 ℃.While,leaching ratio based on microwave leaching under pressure was up to 45.79% under the conditions following sulfuric acid concentration 20%,mass ratio of liquid to solid ratio 2∶1,mass ratio of vanadium slag to manganese dioxide dosage 25∶0.9,microwave power 800W for 10 min.Results showed leaching based on microwave irradiation under pressure can shorten time 94.44% in comparison with that at atmospheric pressure,and the leaching extraction can improve about 20%.展开更多
To minimize the vanadium content in the vanadium extraction tailings, composite additive roasting with (CaO + MgO) and subsequent acid leaching process was carried out dealing with vanadium-bearing converter slag. The...To minimize the vanadium content in the vanadium extraction tailings, composite additive roasting with (CaO + MgO) and subsequent acid leaching process was carried out dealing with vanadium-bearing converter slag. The effect of additive with different MgO/(CaO + MgO) molar ratios on the roasting and leaching behaviours of vanadium slag was investigated, and the optimum process conditions were obtained. The results show that in the roasting experiment, under the conditions of roasting temperature of 850 ℃ and roasting time of 2 h, the main kinds of vanadate transformed from Ca_(2)V_(2)O_(7) to Ca_(5)Mg_(4)V_(6)O_(2)4 and then to Mg_(2)V_(2)O_(7) with the increase in the MgO/(CaO + MgO) molar ratio. In the leaching experiment, under the conditions of particle size less than 75 μm, leaching temperature of 50 ℃, pH of 2.5, liquid–solid ratio of 20:1, and MgO/(CaO + MgO) molar ratio of 1:3, the leaching efficiency of vanadium is increased by about 5%, but the substitution of MgO for most or all of CaO will significantly reduce the leaching efficiency of vanadium. Furthermore, the leaching efficiency of impurities (P and Cr) can also be decreased by a composite addictive (CaO + MgO) roasting process. The X-ray diffraction, scanning electron microscopy, energy dispersive spectrometry, and X-ray photoelectron spectroscopy of the original vanadium slag and solid products of both roasting and leaching processes were also evaluated.展开更多
The influence of V2O3, FeO, TiO2, MnO and MgO in vanadium slag on the corrosion mechanism of MgO-C bricks was studied by stationary immersion tests at vanadium-extracting temperature. Experimental results show that Fe...The influence of V2O3, FeO, TiO2, MnO and MgO in vanadium slag on the corrosion mechanism of MgO-C bricks was studied by stationary immersion tests at vanadium-extracting temperature. Experimental results show that FeO, TiO2, and MnO could enhance the corrosion rate and V2O3 and MgO could decrease it. Microstructure and phase composition of worn samples were investigated by SEM-EDS, revealing the presence of Fe particles, produced by graphite reduction, and (Mg,Fe,Mn)O solid solution at the interface. The formation process of (Mg,Fe,Mn)O solid solution was discussed and the corrosion mechnism of MgO-C bricks was thus proposed.展开更多
The sodium roasted-acid leaching tailing(SRALT)of vanadium slag with a certain amount of vanadium exhibits potential environmental risk.To investigate the leaching behavior of vanadium from the SRALT,neutral batch lea...The sodium roasted-acid leaching tailing(SRALT)of vanadium slag with a certain amount of vanadium exhibits potential environmental risk.To investigate the leaching behavior of vanadium from the SRALT,neutral batch leaching tests were performed.The evolution of vanadium concentration,pH,redox potential(Eh),dissolved oxygen,and conductivity as a function of time was measured.Pourbaix diagrams of V–H2O system with different vanadium concentrations were obtained to identify the ionic speciation of vanadium in leachate.X-ray diffraction,X-ray photoelectron spectroscopy,field emission-scanning electron microscopy,and thermogravimetry–differential scanning calorimetry analysis were conducted to investigate the mineralogical evolution of the SRALT during the leaching process.It was found that the major minerals of the original SRALT are titanomagnetite,spinel,olivine,and augite.The valence states of V existing in the original SRALT are V^(3+)and V^(5+).The pH and Eh values of the obtained leachates are 10.00–10.58 and(−43)–(+67)mV,respectively.In this pH and Eh region,the released vanadium is mainly present as HVO_(4)^(2−).The FeOOH and CaCO_(3)would form during the leaching process.The HVO_(4)^(2−)would be mainly adsorbed by the FeOOH and slightly incorporated into the CaCO_(3),resulting in the decline in the vanadium concentration.The vanadium concentration above 27 mg L^(−1)and the dissolved oxygen value below 5.0 mg L^(−1)can be obtained after a short leaching period.As a V(V)-releasing and oxygen-depleting substance,the leaching toxicity of the SRALT should not be ignored.展开更多
基金supported by the National Key Research and Development Program of China,China(2017YFB0603105)the Key Program of Key Program of National Natural Science Foundation of China,China(21636004)。
文摘Long-term high temperature in conventional vanadium extraction process would cause particles to be sintered and wrapped, thus reducing extraction efficiency of vanadium. Based on the purpose of directional conversion and process intensification, this work proposed a combination of low temperature sodium roasting and high efficiency selective oxidation leaching in vanadium extraction. The investigation of the reaction mechanism suggested that the structure of vanadium slag was changed by roasting, which also caused the fracture of spinel.The addition of MnO2 promoted the directional oxidation of low-valent vanadium into high valence. It also found that Na2S2O8 could oxidize low-valent vanadium effectively in leaching. The leaching efficiency of vanadium reached 87.74% under the optimum conditions, including a roasting temperature of 650 ℃, a roasting time of 2.0 h, a molar ratio of sodium-to-vanadium of 0.6, a MnO2(roasting additive) dosage of 5 wt% and a Na2S2O8(leaching oxidant) dosage of 5 wt%. This percentage is 7.18% higher than that of direct roasting-andleaching under the same conditions.
基金This work was financially supported by the National Natural Science Foundation of China(Nos.51474041 and 51674051)Chongqing Science and Technology Bureau(No.cstc2019jcyjjqX0006)Chongqing Talents Plan for Young Talents(No.CQYC201905050).
文摘The fusion of the leaching and purification processes was realized by directly using microemulsion as the leaching agent.The bis-(2-ethyhexyl)phosphoric acid(DEHPA)/n-heptane/NaOH microemulsion system was established to directly leach vanadates from sodium-roasted vanadium slag.The effect of the leaching agent on the leaching efficiency was investigated,in addition to the molar ratio of H_(2)O/NaDEHP(W),DEHPA concentration,solid/liquid ratio,stirring time,and leaching temperature.In optimal situations,the vanadium leaching efficiency reaches 79.57%.The X-ray diffraction characterization of the leaching residue and the Raman spectrum of the microemulsion before and after leaching demonstrate the successful entry of vanadates from the sodium-roasted vanadium slag into the microemulsion.The proposed method successfully realizes the leaching and purification of vanadates in one step,thereby greatly reducing production costs and environmental pollution.It also offers a new way to achieve the green recovery of valuable metals from solid resources.
基金the National Natural Science Foundation of China(Nos.51904286,51922003,51774027 and 51734002)the China Postdoctoral Science Foundation(No.2019M650848)。
文摘Tailings from the vanadium extraction process are discarded each year as waste,which contain approximately 30 wt%of Fe.In our previous work,we extracted Fe and Mn from vanadium slag,and Fe and Mn existed in the form of FeCl_(2) and MnCl_(2) after chlorination by NH_(4) Cl to achieve effective and green usage of waste containing Fe and Mn.In this work,square wave voltammetry(SWV)and cyclic voltammetry(CV)were applied to investigate the electrochemical behaviors of Fe^(2+)and Mn^(2+)in Na Cl-KCl melt at 800℃.The reduction processes of Fe^(2+)and Mn^(2+)were found to involve one step.The diffusion coefficients of FeCl_(2) and Mn Cl_(2) in molten salt of eutectic mixtures Na Cl-KCl molten salt were measured.The electrodeposition of Fe and Mn were performed using two electrodes at a constant cell voltage.The Mn/Fe mass ratio of the electrodeposited product in Na Cl-KCl-2.13 wt%FeCl_(2)-1.07 wt%Mn Cl_(2) was 0.0625 at 2.3 V.After the electrolysis of NaCl-KCl-2.13 wt%Fe Cl_(2)-1.07 wt%MnCl_(2) melted at 2.3 V,the electrolysis was again started under 3.0 V and the Mn/Fe mass ratio of the electrodeposited product was 36.4.This process provides a novel method to effectively separate Fe and Mn from simulated chlorinated vanadium slag.
基金financially supported by the National Natural Science Foundation of China (No. 51874077)the Opening Foundation of State Key Laboratory of Vanadium and Titanium Resources Comprehensive Utilization, China (No. 2019P4FZG00A)
文摘The chemical composition of vanadium slag significantly affects its element distribution and phase composition,which affect the subsequent calcification roasting process and vanadium recovery.In this work,seven kinds of vanadium slags derived from different regions in China were used as the raw materials to study the effects of different components on the vanadium slag’s elements distribution,phase composition,calcification roasting,and leaching rate of major elements using scanning electron microscope,X-ray diffraction analysis,and inductively coupled plasma-optical emission spectroscopy.The results show that the spinel phase is wrapped with silicate phase in all vanadium slag samples.The main elements in the spinel phase are Cr,V,and Ti from the interior to the exterior.The size of spinel phase in low chromium vanadium slag is larger than the other vanadium slags with higher chromium contents.The spinel phase of high-calcium and high-phosphorus vanadium slag is more dispersed.The strongest diffraction peak of vanadium spinel phase in the vanadium slag migrates to a higher diffraction angle,and(Fe_(0.6)Cr_(0.4))_(2)O_(3)is formed after calcification roasting as the chromium content increased.A large amount of Ca_(2)SiO_(4)is produced because excess Ca reacts with Si in high-calcium and high-phosphorus vanadium slag.The vanadium leaching rate reaches 88%in some vanadium slags.The chromium leaching rate is less than 5%in all vanadium slags.The silicon leaching rate of high-calcium and high-phosphorus vanadium slag is much higher than that of the other slags.The leaching rate of manganese is higher than 10%,and the leaching rates of iron and titanium are negligible.
基金supported by the Natural Science Foundation of China (Nos. 51406029 and 51474067)the Key Laboratory Project of Liaoning Province of Education (No.LZ2015032)
文摘Traditional processes for treating vanadium slag generate a huge volume of solid residue and a large amount of harmful gas,which cause serious environmental problems.In this study,a new process for the comprehensive utilization of vanadium slag was proposed,wherein zeolite A and a V2O5/TiO2 system were synthesized.The structural properties of the as-synthesized zeolite A and the V2O5/TiO2system were characterized using various experimental techniques,including X-ray diffraction,X-ray fluorescence,scanning electron microscopy,and infrared spectroscopy.The results reveal that zeolite A and the V2O5/TiO2 system are successfully obtained with high purity.The results of gas adsorption measurements indicate that the prepared zeolite A exhibits high selectivity for CO2 over N2 and is a candidate material for CO2 capture from flue-gas streams.
基金financially supported by the National Natural Science Foundation of China (Nos.51604065 and 51574082)the National Basic Research Program of China (No.2013CB632603)the Fundamental Funds for the Central Universities (Nos.150203003 and 150202001)
文摘Calcification roasting–acid leaching of high-chromium vanadium slag(HCVS)was conducted to elucidate the roasting and leaching behaviors of vanadium and chromium.The effects of the purity of Ca O,molar ratio between Ca O and V_2O_5(n(Ca O)/n(V_2O_5)),roasting temperature,holding time,and the heating rate used in the oxidation–calcification processes were investigated.The roasting process and mechanism were analyzed by X-ray diffraction(XRD),scanning electron microscopy(SEM),and thermogravimetry–differential scanning calorimetry(TG–DSC).The results show that most of vanadium reacted with Ca O to generate calcium vanadates and transferred into the leaching liquid,whereas almost all of the chromium remained in the leaching residue in the form of(Fe_(0.6)Cr_(0.4))_2O_3.Variation trends of the vanadium and chromium leaching ratios were always opposite because of the competitive reactions of oxidation and calcification between vanadium and chromium with Ca O.Moreover,Ca O was more likely to combine with vanadium,as further confirmed by thermodynamic analysis.When the HCVS with Ca O added in an n(Ca O)/n(V_2O_5)ratio of 0.5 was roasted in an air atmosphere at a heating rate of 10°C/min from room temperature to 950°C and maintained at this temperature for 60 min,the leaching ratios of vanadium and chromium reached91.14%and 0.49%,respectively;thus,efficient extraction of vanadium from HCVS was achieved and the leaching residue could be used as a new raw material for the extraction of chromium.Furthermore,the oxidation and calcification reactions of the spinel phases occurred at 592and 630°C for n(Ca O)/n(V_2O_5)ratios of 0.5 and 5,respectively.
基金supported by the National High Technology Research and Development Program of China(No.2012AA062303)the National Natural Science Foundation of China(Nos.U1202274,51004033,and 51204040)the Doctoral Fund Project of China(No. 20120042110011)
文摘To extract vanadium in an environment friendly manner, this study focuses on the process of leaching vanadium from vanadium slag by high pressure oxidative acid leaching. Characterizations of the raw slag, mineralogy transformation, and the form of leach residues were made by X-ray diffraction, scanning electron microscopy, and energy dispersive X-ray spectroscopy. The result shows that the vana-dium slag is composed of major phases of fayalite, titanomagnetite, and spinel. During the high pressure oxidative acid leaching process, the fayalite and spinel phases are gradually decomposed by sulfuric acid, causing the release of vanadium and iron in the solution. Meanwhile, unreacted silicon and titanium are enriched in the leach residues. With the initial concentration of sulfuric acid at 250 g·L^-1, a leaching tem-perature of 140℃, a leaching time of 50 min, a liquid-solid ratio of 10:1 mL·g^-1, and oxygen pressure at 0.2 MPa, the leaching rate of vana-dium reaches 97.69%.
基金financially supported by the National High-Tech Research and Development Program of China (No. 2008AA031104)the National Basic Research and Development Program of China (No. 2007CB13503)the National Natural Science Foundation of China(No. 51090382)
文摘The extraction of vanadium from high calcium vanadium slag was attempted by direct roasting and soda leaching. The oxidation process of the vanadium slag at different temperatures was investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy dispersive spectroscopy (EDS). The effects of roasting temperature, roasting time, Na2CO3 concentration, leaching tem- perature, leaching time, and liquid to solid ratio on the extraction of vanadium were studied. The results showed that olivine phases and spinel phases in the vanadium slag were completely decomposed at 500 and 800℃, respectively. Vanadium-rich phases were formed at above 850℃. The leaching rate of vanadium reached above 90% under the optimum conditions: roasting temperature of 850℃, roasting time of 60 min, Na2CO3 concentration of 160 g/L, leaching temperature of 95℃, leaching time of 150 min, and liquid to solid ratio of 10:1 mL/g. The main impurities were Si and P in the leach liquor.
基金Funded by the National High-tech Development and Research Program(2008AA0312)
文摘Microwave irradiation was used to investigate vanadium slag in place of traditional heating.Factors associated with vanadium extraction ratio were studied following the concentration of leaching agent,oxidant dosage,microwave power,microwave irradiation time and mass ratio of liquid to solid.Results indicated that leaching ratio based on microwave leaching at atmospheric pressure can get to 68.48% under the conditions following sulfuric acid concentration 30%,mass ratio of liquid to solid ratio 2∶1,mass ratio of vanadium slag to manganese dioxide dosage 25∶1.4,and microwave power 800W for 3.5 h at 95 ℃.While,leaching ratio based on microwave leaching under pressure was up to 45.79% under the conditions following sulfuric acid concentration 20%,mass ratio of liquid to solid ratio 2∶1,mass ratio of vanadium slag to manganese dioxide dosage 25∶0.9,microwave power 800W for 10 min.Results showed leaching based on microwave irradiation under pressure can shorten time 94.44% in comparison with that at atmospheric pressure,and the leaching extraction can improve about 20%.
基金supported by the National Natural Science Foundation of China(No.52004044)the Natural Science Foundation of Chongqing(Nos.cstb2022nscq-msx0801 and cstc2019jcyjqX0024)+3 种基金the Foundation of Chongqing University of Science and Technology(No.ckrc2022030)the Graduate Research Innovation Project of Chongqing University of Science and Technology(No.YKJCX2220216)the Science and Technology Innovation Training Program of Chongqing University of Science and Technology(No.2022046)the College Students'innovation and entrepreneurship training program of Chongqing University of Science and Technology(No.2022007).
文摘To minimize the vanadium content in the vanadium extraction tailings, composite additive roasting with (CaO + MgO) and subsequent acid leaching process was carried out dealing with vanadium-bearing converter slag. The effect of additive with different MgO/(CaO + MgO) molar ratios on the roasting and leaching behaviours of vanadium slag was investigated, and the optimum process conditions were obtained. The results show that in the roasting experiment, under the conditions of roasting temperature of 850 ℃ and roasting time of 2 h, the main kinds of vanadate transformed from Ca_(2)V_(2)O_(7) to Ca_(5)Mg_(4)V_(6)O_(2)4 and then to Mg_(2)V_(2)O_(7) with the increase in the MgO/(CaO + MgO) molar ratio. In the leaching experiment, under the conditions of particle size less than 75 μm, leaching temperature of 50 ℃, pH of 2.5, liquid–solid ratio of 20:1, and MgO/(CaO + MgO) molar ratio of 1:3, the leaching efficiency of vanadium is increased by about 5%, but the substitution of MgO for most or all of CaO will significantly reduce the leaching efficiency of vanadium. Furthermore, the leaching efficiency of impurities (P and Cr) can also be decreased by a composite addictive (CaO + MgO) roasting process. The X-ray diffraction, scanning electron microscopy, energy dispersive spectrometry, and X-ray photoelectron spectroscopy of the original vanadium slag and solid products of both roasting and leaching processes were also evaluated.
基金Item Sponsored by National Natural Science Foundation of China (51090382)
文摘The influence of V2O3, FeO, TiO2, MnO and MgO in vanadium slag on the corrosion mechanism of MgO-C bricks was studied by stationary immersion tests at vanadium-extracting temperature. Experimental results show that FeO, TiO2, and MnO could enhance the corrosion rate and V2O3 and MgO could decrease it. Microstructure and phase composition of worn samples were investigated by SEM-EDS, revealing the presence of Fe particles, produced by graphite reduction, and (Mg,Fe,Mn)O solid solution at the interface. The formation process of (Mg,Fe,Mn)O solid solution was discussed and the corrosion mechnism of MgO-C bricks was thus proposed.
基金supported by the Natural Science Foundation of Hebei Province(Nos.E2020209195,E2021209043,E2020209043),National Natural Science Foundation of China(No.51574108),Tangshan Municipal Project of Science and Technology(No.19150201E)Science and Technology Project of Hebei Education Department(Nos.BJ2020022,BJ2021034).
文摘The sodium roasted-acid leaching tailing(SRALT)of vanadium slag with a certain amount of vanadium exhibits potential environmental risk.To investigate the leaching behavior of vanadium from the SRALT,neutral batch leaching tests were performed.The evolution of vanadium concentration,pH,redox potential(Eh),dissolved oxygen,and conductivity as a function of time was measured.Pourbaix diagrams of V–H2O system with different vanadium concentrations were obtained to identify the ionic speciation of vanadium in leachate.X-ray diffraction,X-ray photoelectron spectroscopy,field emission-scanning electron microscopy,and thermogravimetry–differential scanning calorimetry analysis were conducted to investigate the mineralogical evolution of the SRALT during the leaching process.It was found that the major minerals of the original SRALT are titanomagnetite,spinel,olivine,and augite.The valence states of V existing in the original SRALT are V^(3+)and V^(5+).The pH and Eh values of the obtained leachates are 10.00–10.58 and(−43)–(+67)mV,respectively.In this pH and Eh region,the released vanadium is mainly present as HVO_(4)^(2−).The FeOOH and CaCO_(3)would form during the leaching process.The HVO_(4)^(2−)would be mainly adsorbed by the FeOOH and slightly incorporated into the CaCO_(3),resulting in the decline in the vanadium concentration.The vanadium concentration above 27 mg L^(−1)and the dissolved oxygen value below 5.0 mg L^(−1)can be obtained after a short leaching period.As a V(V)-releasing and oxygen-depleting substance,the leaching toxicity of the SRALT should not be ignored.