Recovery and separation of Fe and Mn from simulated chlorinated vanadium slag by molten salt electrolysis

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.

Measurement on Physicochemical Properties ofNaCl-KCl-ScCl_3 System for Manufacture of Al-Sc Alloy by Molten Salt Electrolysis

The physicochemical properties of the system, such as density, surface tension, specific conductance and melting point were measured. The results were discussed.

Preparation of Master Alloy Cu－Sr by Molten Salt Electrolysis with Copper Consumable Cathode

The influence of electrolyte composition and temperature. cathodie current density as well as someadditives on preparation process of alloy Cu-Sr by molten salt electrolysis with consumable cathode was stu-died in laboratory. Under optimum conditions determined experimentally. the current efficiency amountedto 70% and the master alloy contained 61% Sr After vacuum distillation or the cathodic product, metallicSr of 98% purity was obtained.

CO-DEPOSITION OF Li(Ⅰ)WITH RE(Ⅲ)AND ITS APPLICATION IN THE PRODUCTION OF Al-Li-Cu-RE ALLOY BY MOLTEN SALT ELECTROLYSIS

The possibility of co-deposition of Li(Ⅰ)and RE(Ⅲ)has been estimated by both theoretical analysis and experimental study on the influences of temperature and concen- tration of chloride on the deposition potential.Both the electrochemical and electrolytic results clearly show that Li(Ⅰ)and RE(Ⅲ)can co-deposit on the Al-Cu electrode under selected conditions.

U(VI) adsorption behavior onto polypyrrole coated 3R-MoS2 nanosheets prepared with the molten salt electrolysis method

To improve the separation capacity of uranium in aqueous solutions, 3R-MoS2 nanosheets were prepared with molten salt electro- lysis and further modified with polypyrrole (PPy) to synthesize a hybrid nanoadsorbent (PPy/3R-MoS2). The preparation conditions of PPy/3R- MoS2 were investigated and the obtained nanosheets were characterized with scanning electron microscope (SEM), high resolution transmis- sion electron microscope (HRTEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectro- scopy (XPS). The results showed that PPy/3R-MoS2 exhibited enhanced adsorption capacity toward U(VI) compared to pure 3R-MoS2 and PPy;the maximum adsorption was 200.4 mg/g. The adsorption mechanism was elucidated with XPS and FTIR: (1) negatively charged PPy/3R-MoS2 nanosheets attracted by an electrostatic interaction;(2) exposed C, N, Mo, and S atoms complexed with U(VI) through co- ordination;(3) Mo in the complex partly reduced the adsorbed U(VI) to U(IV), which further regenerated the adsorption point and continu- ously adsorbed U(VI). The design of the PPy/3R-MoS2 composite with a high adsorption capacity and chemical stability provides a new direc- tion for the removal of radionuclide.

Annihilating the Formation of Silicon Carbide:Molten Salt Electrolysis of Carbon-Silica Composite to Prepare the Carbon-Silicon Hybrid for Lithium-lon Battery Anode

Silicon(Si)and carbon(C)composites hold the promise for replacing the commercial graphite anode,thus increasing the energy density of lithium-ion batteries(LIBs).To mitigate the formation of SiC,this paper reports a molten salt electrolysis approach to prepare C-Si composite by the electrolysis of C-SiO2 composites.Unlike the conventional way of making a C coating on Si,C-SiO2 composites were prepared by pyrolyzing the low-cost sucrose and silica.The electrochemical deoxidation of the C-SiO2 composites not only produces nanostructured Si inside the C matrix but also introduces voids between the C and Si owing to the volume shrinkage from converting SiO2 to Si.More importantly,the use of Mg ion-containing molten salts precludes the generation of SiC,and the electrolytic Si@C composite anode delivers a capacity of about 1500 mAh g-1 after 100 cycles at a current density of 500 mA g-1.Further,the Si@C‖LiNi0.6Co0.2Mn0.2O2 full cell delivers a high energy density of 608 Wh kg-1.Overall,the molten salt approach provides a one-step electrochemical way to convert oxides@C to metals@C functional materials.

Preparation of Mg-Li alloys by electrolysis in molten salt at low temperature

A new technology for preparation of low cost Mg-Li alloys was studied. The alloys were prepared by electrolysis in molten LiCl-KCl （weight ratio is 1：1） electrolyte with Mg rod severing as the consumed cathode. Main factors that affect current efficiency were investigated, and optimal electrolysis parameters were obtained. Mg-Li alloys with low lithium Content （about 25%） were prepared by the unique method of a higher post-thermal treatment temperature after electrolysis at low temperature. The results showed that the electrolysis can be carried out at low temperature, which resulted in reducing preparation cost due to energy saving. The new technology for the oreoaration of Mg-Li alloy by electrolysis in molten salt was laroved to be feasible.

Cathodic reduction process of Al-Cu-Y alloy in fluoride-oxide eutectic system via molten salt electrolysis

Al-Cu-Y alloys were prepared by molten salt electrolysis in fluoride-oxide system composed of electrolyte（Na3 AlF6-AlF3-LiF-MgF2） and oxide（Al2 O3-CuO-Y2 O3）. Cathodic reduction process of Al2 O3,CuO and Y2 O3 were analyzed by cyclic voltammetry and chronoamperometry. Components and phase composition of alloy samples prepared by potentiostatic electrolysis were characterized by scanning electron microscopy and energy dispersive spectroscopy. The results show that the Al-Cu-Y alloy can be prepared in the AIF3-NaF-5 wt%LiF-5 wt%MgF2（NaF/AlF3 = 2.2, molecular ratio） eutectic system with mixed oxide（Al2 O3-CuO-Y2 O3） through 2 h at the conditions of a temperature of 1208 K, cell voltage3.0 V, cathode current density 0.7 A/cm^2. Al（Ⅲ） and Cu（Ⅱ） ions can be reduced to zero valence Al（0） and Cu（0） directly on carbonaceous electrode surface by instantaneous nucleation, respectively, the reduction process is controlled by diffusion. The reduction potential of Y（Ⅲ） ions is close to the active ions of fluoride melts, but strengthened phase AI3 Y can be formed through electrochemical reduction and alloyed process with active Al（Ⅲ） and Cu（Ⅱ） ions, meanwhile, the Al2 Cu and Al3 Y phases are distributed at the grain boundary of Al matrix.

Optimal V_(2)O_(3) extraction by sustainable vanadate electrolysis in molten salts

Recently,an environmentally friendly electrolysis process of soluble vanadates is proposed and successfully confirmed for V_(2)O_(3) extraction.In this paper,the solubilities of various vanadates(i.e.NaVO_(3),Na_(4)V_(2)O_(7) and Na_(3)VO_(4))in NaCl molten salt are measured.The dependences of V_(2)O_(3) extraction on vanadate form,anode material and molten salt system are studied.A long-term electrolysis is carried out.The result indicates that the solubilities of all vanadates are high and meet electrolytic requirements.Compared to Na_(4)V_(2)O_(7) and Na_(3)VO_(4),NaVO_(3) exhibits larger current efficiency and lower electricity consumption.By using SnO_(2) anode instead of graphite anode,the current efficiency of NaVO_(3) electrolysis can be increased to 58.1%and carbon pollution is avoided at 700℃.The extraction rate of V_(2)O_(3) reaches 81.3%after long-term electrolysis of 51 h.This work optimizes the electrochemical preparation process of V_(2)O_(3) from various vanadates and contributes to the improvement of current efficiency and extraction rate.

Towards a sustainable technology for production of extra-pure Ti metal:Electrolysis of sulfurized Ti(C,N)in molten CaCl_(2)

A new concept for producing highly pure Ti metal powder from ilmenite(FeTiO)_(3))is proposed in this article.Titanium nitride(TiN)or titanium oxycarbonitride(TiO_(x)C_(y)N_(z))could be synthesized in the first step via the simultaneous carbothermal reduction and nitridation(CTRN)of FeTiO3 to remove oxygen roughly.To separate oxygen completely,high-quality TiS2 samples were then synthesized from TiN and TiC using S2 gas,and the clean sulfides were finally reduced toα-Ti powders with spherical morphology using electrolysis in molten CaCl_(2).Xray diffraction(XRD),scanning electron microscopy(SEM)in conjunction with energy-dispersive X-ray spectroscopy(EDS),and elemental LECO analysis were used to study the phases and microstructures of the sulfides and the electrochemically reduced powders.The Ti powder showed no carbon contamination and consisted of high-purity foil-like Ti sheets with very low oxygen,carbon,and nitrogen contents of less than 0.15 wt%O,0.02 wt%C,and 0.003 wt%N,respectively.The quality of the Ti powder was much higher than that of the powder obtained using the conventional OS process(proposed by K.Ono and R.O.Suzuki)starting directly from the oxides.

Electrolysis of Magnesia from Bischofite in Qinghai Salt Lakes

A new technique of magnesia electrolysis from bischofite in Qinghai salt lakes was investigated experimentally. Magnesia was prepared by ammonia processing. On an electrolysis cell of about 100 A capacity at 700degreesC, magnesium metal was obtained with a current efficiency of 90.23% and a specific energy consumption of 11.5 kW(.)h. The new technique has the advantages of energy saving, high current efficiency and environmental amity.

Direct electrochemical N-doping to carbon paper in molten LiCl-KCl-Li3N

Graphite materials are widely used as electrode materials for electrochemical energy storage.N-doping is an effective method for enhancing the electrochemical properties of graphite.A novel one-step N-doping method for complete and compact carbon paper was proposed for molten salt electrolysis in the Li Cl-KCl-Li3 N system.The results show that the degree of graphitization of carbon paper can be improved by the electrolysis of molten salts,especially at 2.0 V.Nitrogen gas was produced at the anode and nitrogen atoms can substitute carbon atoms of carbon paper at different sites to create nitrogen doping during the electrolysis process.The doping content of N in carbon paper is up to 13.0 wt%.There were three groups of nitrogen atoms,i.e.quaternary N(N-Q),pyrrolic N(N-5),and pyridinic N(N-6)in N-doping carbon paper.N-doping carbon paper as an Al-ion battery cathode shows strong charge-recharge properties.

Preparation of Al-Si-Ti Master Alloys by Electrolysis of Silica and Titania in Cryolite-Alumina Melts

Aluminum silicon titanium master alloys were prepared in the laboratory by electrolysis of silica and titania dissolved in cryolite alumina melts. Alloys containing up to 12 mass% Si and 2.6 mass% Ti were formed after about 90 min of electrolysis at 950℃. The current efficiency for the preparation of the Al Si Ti alloys varied with time, temperature and cathodic current density. It is concluded that this electrolytic method may be an interesting alternative to the direct metal mixing process for formation of Al Si Ti master alloys.

Electrochemical codeposition of typical α+β phases Mg-Li alloys from the molten LiCl-KCl-MgCl_2 system

Electrochemical codeposition of Mg-Li alloys on molybdenum electrodes was investigated in LiCl-KCl（50 wt.%：50 wt.%） melts containing different concentrations of MgCl2 at 973 K.Cyclic voltammograms show that the underpotential deposition of lithium on pre-deposited magnesium leads to the formation of liquid Mg-Li alloys.The deposition potentials of Mg（II） and Li（I） ions gradually near each other with MgCl2 concentration decreasing.Mg-Li alloys with typical α ＋ β phases could be obtained by potentiostatic electrolysis from LiCl-KCl melts containing 5 wt.% MgCl2 at -2.25 V vs.Ag/AgCl（cathodic current density 1.70 A·cm-2） for 2.5 h.α phase, α ＋ β phases, and β phase Mg-Li alloys with different lithium contents were obtained by potentiostatic electrolysis from LiCl-KCl melts with the different concentrations of MgCl2.The samples were characterized by X-ray diffraction and scanning electron microscopy.

Electrochemically exfoliated WS_(2)in molten salt for sodium-ion battery anode

The poor crystallinity and unstable crystal structure of tungsten disulfide(WS2)limit its application in practice.In this paper,a molten salt electrolysis method is proposed to intercalate metal ions into the interlayers of layered WS2 to obtain few-layer sheetlike structures.The effect of the molten salt system,applied constant current and electrolysis duration on the exfoliation degree of WS2 bulk has been investigated.The results show that the products electrolyzed in molten LiCl-NaCl-KCl and NaClKCl salts under 25 mA were more transparent and thinner flakes sheets due to the uniform intercalation of Li^+and Na^+with smaller size.The exfoliated WS_(2)was used as an anode material for sodium-ion batteries with a potential of 0.01-2.50 V.In comparison,the WS_(2)-NaCl-25 mA electrode displays a high reversible capacity of 373 mAh·g^(-1)at0.1 A·g^(-1)after cycling for 100 cycles at the same time showing great rate and cycle performance.It also presents a high capacitive ratio of 90.65%at 1.0 mV·s^(-1).The molten salt electrolysis provides a new perspective on the exfoliation of layered material,while demonstrating the great potential of WS2 as an anode material for sodium-ion battery.

Rare metals preparation by electro-reduction of solid compounds in high-temperature molten salts

Direct electro-reduction of solid compounds in molten salts is a simple and straightforward electrolytic metallurgical method, which outperforms traditional pyrometallurgical methods such as carbothermic and met- allothermic reductions in terms of economic viability, energy efficiency and carbon footprint. To better highlight the features of the direct electro-reduction of solid com- pounds in molten salts in extraction of rare metals, the scope of this paper is focused on the know-how of the cathodic process of the direct electro-reduction of solid compounds in molten salts in extraction of rare refractory metals including Ti, Zr, Hf, V, Nb, Ta, Mo and W, and rare disperse metals including Ga and Ge. In line with an introduction of the basic concept of the method, the char- acteristics of reaction paths in different systems are sum- marized and the corresponding strategy on tailoring energy efficiency and microstructure of electrolytic products are rationalized. The economic competence of the method might be enhanced by extending the method to controllable production of rare metals with high added values, well- defined microstructure and intriguing functionality.

Enhanced electrodeposition and separation of metallic Cr from soluble K2CrO4 on a liquid Zn cathode

Carbon contamination and the formation of low-valence oxides limit the preparation of refractory metals by molten salt electrolysis.In this paper,a liquid Zn cathode is adopted for the electrochemical reduction of soluble K2CrO4 to metallic Cr in CaCl2-KCl molten salt.It is found that CrO4^2-can be directly electrochemically reduced to Cr via a six-electron-transfer step and low-valence Cr oxides is hardly produced.The reduction rate is obviously increased from 16.7 mgCrh^-1cm^-2 on the solid Mo cathode to58.7 mgCrh-1cm-2on liquid Zn cathode.The electrodeposited Cr is distributed in liquid Zn cathode.Carbon contamination is effectively avoided due to the negligible solubility of carbon in the liquid Zn cathode.Furthermore,Cr can be effectively separated and enriched to the bottom of liquid Zn under supergravity field,realizing the efficient acquisition of metallic Cr and recycling of liquid Zn.The method herein provides a promising route for the preparation of refractory metals with high-purity by molten salt electrolysis.

Electrolytic silicon/graphite composite from SiO_(2)/graphite porous electrode in molten salts as a negative electrode material for lithium-ion batteries

Nano-silicon(nano-Si)and its composites have been regarded as the most promising negative electrode materials for producing the next-generation Li-ion batteries(LIBs),due to their ultrahigh theoretical capacity.However,the commercial applications of nano Si-based negative electrode materials are constrained by the low cycling stability and high costs.The molten salt electrolysis of SiO_(2)is proven to be suitable to produce nano-Si with the advantages of in-situ microstructure control possibilities,cheap affordability and scale-up process capability.Therefore,an economical approach for electrolysis,with a SiO_(2)/graphite porous electrode as cathode,is adopted to produce nano-Si/graphite composite negative electrode materials(SGNM)in this study.The electrolytic product of the optimized porous electrode is taken as the negative electrode materials for LIBs,and it offers a capacity of 733.2 mAh·g^(-1)and an initial coulombic efficiency of 86.8%in a coin-type cell.Moreover,the capacity of the SGNM retained 74.1%of the initial discharging capacity after 50 cycles at 0.2C,which is significantly higher than that of the simple mixture of silicon and graphite obtained from the formation of silicon carbide(SiC)between nano-Si and graphite particles.Notably,this new approach can be applied to a large-scale production.

Electrochemical Preparation of V2O3 from NaVO3 and Its Reduction Mechanism

Vanadium trioxide（V2O3） was directly prepared by NaVO3 electrolysis in Na Cl molten salts. Electrolysis products were characterized by X-ray diffraction（XRD）, scanning electron microscopy（SEM） and energy dispersive spectroscopy（EDS）. The existing state and electrochemical behavior of NaVO3 were also studied. The results indicated that V2O3 can be obtained from NaVO3. VC and C were also formed at high cell voltage, high temperature, and long electrolysis time. During electrolysis, NaVO3 was dissociated to Na＋ and VO3-in Na Cl molten salt. NaVO3 was initially electro-reduced to V2O3 on cathode and Na2O was released simultaneously. Na2CO3 was formed due to the reaction between Na2O and CO2. The production of C was ascribed to the electro-reduction of CO3（2-）. VC was produced due to the reaction between C and V2O3.

Preparation of Rarc Earth Alloys by Cathodic Alloying

The electrode processes of La(Ⅲ), Ce(Ⅲ), Pr(Ⅲ), Nd(Ⅲ) and Y(Ⅲ) reduced on iron, cobalt, nickel andcopper electrodes in chloride melts were investigated by cyclic voltammetry, potential- time curve afterpotentiostatic electrolysis and current-time curve at potential step. The diffusion coefficient of deposited metalatom in the alloyed cathode and the free energy of formation of intermetallic compound were determined.Thirteen surface alloy layers were obtained by electrolysis at constant potential. The alloys of La-Fe, La-Ni,La-Cu, Pr-Fc, Pr-Co. Pr-Ni. Pr-Cu, Nd-Fe, … were prepared by consumpable cathode.