The microstructure evolution and electrolysis behavior of(Cu_(52)Ni_(30)Fe_(18))–x Ni Fe_2O_4(x=40wt%,50wt%,60wt%,and 70wt%)composite inert anodes for aluminum electrowinning were studied.Ni Fe_2O_4 was synthesized b...The microstructure evolution and electrolysis behavior of(Cu_(52)Ni_(30)Fe_(18))–x Ni Fe_2O_4(x=40wt%,50wt%,60wt%,and 70wt%)composite inert anodes for aluminum electrowinning were studied.Ni Fe_2O_4 was synthesized by solid-state reaction at 950°C.The dense anode blocks were prepared by ball-milling followed by sintering under a N_2 atmosphere.The phase evolution of the anodes after sintering was determined by scanning electron microscopy and energy-dispersive X-ray spectroscopy.The results indicate that a substitution reaction between Fe in the alloy phase and Ni in the oxide phase occurs during the sintering process.The samples were also examined as inert anodes for aluminum electrowinning in the low-temperature KF–NaF–AlF_3 molten electrolyte for 24 h.The cell voltage during electrolysis and the corrosion scale on the anodes were analyzed.The results confirm that the scale has a self-repairing function because of the synergistic reaction between the alloy phase with Fe added and the oxide phase.The estimated wear rate of the(Cu_(52)Ni_(30)Fe_(18))–50Ni Fe_2O_4 composite anode is 2.02 cm·a^(-1).展开更多
Effect of added Co2 +(aq)on copper electrowinning was studied using doped polyaniline(Pani)and Pb-Ag(1%)anodes and a stainless steel cathode.The presence of added Co2+ (aq)in the electrolyte solution was found to decr...Effect of added Co2 +(aq)on copper electrowinning was studied using doped polyaniline(Pani)and Pb-Ag(1%)anodes and a stainless steel cathode.The presence of added Co2+ (aq)in the electrolyte solution was found to decrease the anode potentials.The optimum level of Co2 +(aq)concentration in the electrolyte,with respect to the maximum saving of power consumption was established.Linear sweep voltammetry(LSV)was used to study the influence of added Co2 +(aq)on the anodic processes in a copper sulfate-sulfuric acid electrolyte.The oxygen-evolution potential for Pani anode is depolarised at lower current densities(≤0.01 A/cm2)and attains saturation atρ(Co 2+ )o≈0.789 g/L;whilst the oxygen-evolution potential for Pb-Ag(1%)anode is depolarised at higher current densities(≤0.02 A/cm2)and attains saturation atρ(Co 2+ )o≈1.315 g/L.The preferred orientations of the copper deposits change from(220)to(111)with the addition of 0.394?0.789 g/L Co 2+ but higher concentrations favor(220)orientation again.展开更多
In order to eliminate the pitting and improve the surface morphology of cathode nickel,the influence of additives of boric acid and dodecyl sodium sulfate(SDS)on the process of nickel electrowinning from sulfate syste...In order to eliminate the pitting and improve the surface morphology of cathode nickel,the influence of additives of boric acid and dodecyl sodium sulfate(SDS)on the process of nickel electrowinning from sulfate system was studied by cathode polarization tests and nickel electrodeposition experiments.The experimental results show that the addition of boric acid can increase the cathode polarization while SDS can decrease the cathode polarization.Both boric acid and SDS are useful to eliminate the pitting on nickel deposits and improve the morphology of surface.Good deposit morphology with rare pitting and high current efficiency is favored by adding 10 g/L boric acid and 40 mg/L SDS in the electrolyte under the condition of nickel ion concentration of 80 g/L, sodium ion concentration of 10 g/L,pH of 3,current density of 220 A/m 2 and temperature of 70℃.展开更多
The objective of this work was to study the effect of different rolling technologies on the properties of Pb-0.06wt%Ca-1.2wt%Sn anodes during copper electrowinning and to determine the relationship between the propert...The objective of this work was to study the effect of different rolling technologies on the properties of Pb-0.06wt%Ca-1.2wt%Sn anodes during copper electrowinning and to determine the relationship between the properties of the anodes and rolling techniques during copper electrowinning. The anode process was investigated via anodic polarization curves, cyclic voltammetry curves, electrochemical impedance spectra, and corrosion tests. The microscopic morphology and phase composition of the anodic oxide layers were observed by scanning electron microscopy and X-ray diffraction, respectively. Observable variations in the electrocatalytic activity and reaction kinetics of anodes during electrowinning indicated that the electrochemical behavior of the anodes was strongly affected by the rolling technology. An increase in the rolling number tended to decrease the oxygen evolution overpotential and the corrosion rate of the anodes. These trends are contrary to that of the apparent exchange current density. Furthermore, the intensities of diffraction peaks associated with PbO, PbOx, and α-PbO2 tended to increase with increasing rolling number. In addition, the rolled anodes exhibited a more uniform microstructure. Compared with one-way rolled anodes, the eight-time cross rolled anodes exhibited better electrocatalytic activity and improved corrosion resistance.展开更多
The properties of Al/conductive coating/α-PbO2-CeO2-TiO2/β-PbO2-WC-ZrO2 composite anode for zinc electrowinning were investigated. The electrochemical performance was studied by Tafel polarization curves(Tafel), e...The properties of Al/conductive coating/α-PbO2-CeO2-TiO2/β-PbO2-WC-ZrO2 composite anode for zinc electrowinning were investigated. The electrochemical performance was studied by Tafel polarization curves(Tafel), electrochemical impedance spectroscopy(EIS) and corrosion rate obtained in an acidic zinc sulfate electrolyte solution. Scanning electron microscopy(SEM), X-ray diffraction(XRD), and energy dispersive X-ray spectroscopy(EDXS) were used to observe the microstructural features of coating. Anodes of Al/conductive coating/α-PbO2-CeO2-TiO2/β-PbO2, Al/conductive coating/α-PbO2-CeO2-TiO2/β-PbO2-WC, Al/conductive coating/α-PbO2-CeO2-TiO2/β-PbO2-ZrO2, and Pb-1%Ag anodes were also researched. The results indicated that the Al/conductive coating/α-PbO2-CeO2-TiO2/β-PbO2-WC-ZrO2 showed the best catalytic activity and corrosion resistant performance; the intensity of diffraction peak exhibited the highest value as well as a new PbWO4 phase; the content of WC and ZrO2 in coating showed the highest value as well as the finest grain size.展开更多
The influences of cupric ion concentration (5-35 g/L),current density (500-2000 A/m2),circulation rate of the electrolyte solution (15-120 mL/min),and temperature (25-60℃) on the physical and chemical propert...The influences of cupric ion concentration (5-35 g/L),current density (500-2000 A/m2),circulation rate of the electrolyte solution (15-120 mL/min),and temperature (25-60℃) on the physical and chemical properties of copper powders obtained in electrolysis cells were investigated.Two industrial processes,electrorefining (ER) cells with a synthetic electrolyte and electrowinning (EW) cells with an original solution of coppermineral leaching,were utilized to produce copper powders.Finally,the statistical full factorial method of design of experiments (DOE) was employed to investigate the interaction or the main effects of processes.The results show that increasing the copper concentration and temperature can increase the grain size,apparent density,and electrical energy consumption.On the other hand,increasing the current density and circulation rate of the electrolyte can decrease them.This production process is optimized via DOE to control the interactive and main effects to produce copper powders with favorable properties.展开更多
In order to study the anodic behavior and microstructures of Al/Pb-Ag-Co anode during zinc electrowinning,by means of potentiodynamic investigations,scanning electron microscopy(SEM) and X-ray diffraction(XRD)analyses...In order to study the anodic behavior and microstructures of Al/Pb-Ag-Co anode during zinc electrowinning,by means of potentiodynamic investigations,scanning electron microscopy(SEM) and X-ray diffraction(XRD)analyses,the mechanism of the anodic processes playing on the surface of Al/Pb-0.8%Ag and Al/Pb-0.75%Ag-0.03%Co anodes prepared by electro-deposition from methyl sulfonic acid bath for zinc electrowinning from model sulphate electrolytes have been measured.On the basis of the cyclic voltammograms obtained,information about the corrosion rate of the composite in PbO2 region has been concluded.The microstructures were also observed by means of SEM and XRD which showed Pb-0.75%Ag-0.03%Co alloy composite coating has uniform and chaotic orientation tetragonal symmetry crystallites of PbSO4,but Pb-0.8%Ag alloy composite coating has well-organized orientation crystallites of PbSO4 concentrated in the certain zones after 24 h of anodic polarization.It is important that Al/Pb-0.75%Ag-0.03%Co anode oxide film consists of non-conductive dense MnO2 and PbSO4 and α,β-PbO2 penetrated into which,in fact,are the active centers of the oxygen evolution after 24 h of anodic polarization.展开更多
The anodic reaction kinetics of zinc electrowinning was investigated on the titanium base RuO2 anode in the system of Zn(Ⅱ)-NH3-NH4Cl-H2O. The effects of stirring speed, ammonium chloride concentration and temperat...The anodic reaction kinetics of zinc electrowinning was investigated on the titanium base RuO2 anode in the system of Zn(Ⅱ)-NH3-NH4Cl-H2O. The effects of stirring speed, ammonium chloride concentration and temperature on anodic reaction rate were studied through the curve measurement of potentiostatic polarization. The results reveal that the electrochemically controlled anodic reaction obeys Tafel equation and the anodic reaction order for ammonium chloride is 1.056, with the apparent activation energy of 40.17 kJ/mol. The general equation of anodic reaction kinetics was obtained.展开更多
Consumable carbon anodes are used in the electrowinning of aluminium by the Hall-Heroult process.Emissions of CO2 may be eliminated by introducing an inert oxygen evolving anode,which however will require a higher ano...Consumable carbon anodes are used in the electrowinning of aluminium by the Hall-Heroult process.Emissions of CO2 may be eliminated by introducing an inert oxygen evolving anode,which however will require a higher anode potential.An alternative approach is to use a natural gas or hydrogen gas anode to reduce the CO2 emissions and lower the anode potential.Preliminary laboratory experiments were carried out in an alternative molten salt electrolyte consisting of CaCl2-CaO-NaCl at 680 °C.Porous anodes of platinum and tin oxide were tested during electrolysis at constant current.The behaviour of inert anode candidate materials such as tin oxide and nickel ferrite were also studied.展开更多
The effect of lead anode, rotating cylinder electrode (RCE), amount of 1,2-dihydroxypropane (12-DHP), temperature and rotation on the electrowinning of copper from low concentration acidified copper sulphate solution ...The effect of lead anode, rotating cylinder electrode (RCE), amount of 1,2-dihydroxypropane (12-DHP), temperature and rotation on the electrowinning of copper from low concentration acidified copper sulphate solution has been investigated. Copper powder was electrodeposited onto RCE that made of pure copper. From cyclic voltammetry experiments, an empirical parameter called the departure percent, S, was obtained which may represent the stability of the organic additive in the given medium and under the experimental conditions. The inhibition percentage, P, was 0.00 - 89.91% depending on the experimental variables. P was affected by temperature and mole fraction of 12-DHP, while rotation did not show any influence on it. Values of activation energy of electrodeposition process, Ea, were found to be less than 28 kJ mol-1 indicating diffusion controlled process. The overall mass transfer correlations under the present conditions have been computed using the dimensional analysis method. The data were valid for 90 < Sh < 1098, 737 < Sc < 59284 and 271 < Re < 7046 and the results agreed with the previous studies of mass transfer to rotating cylinders in turbulent flow regimes. The effect of time, content of 12-DHP, temperature and the speed of rotation on the morphological changes of the electrodeposited copper powder as well as deposits composition and crystallite size have been studied. Various crystallite sizes ranged 7.1 nm - 250.6 nm were obtained and characterized by EDS and XRD. Different topographs proved that the rate of copper electrodeposition increased by increasing deposition time, temperature and the speed of rotation. Also, they proved that the deposition rate decreased by adding 12-DHP to the solution. Therefore, the results obtained by SEM supported those achieved by measuring the limiting current density and follow the normal manner when organic solvents were added to the electrodeposition bath.展开更多
A new anodic material of ternary Pb-0.8%Ag-(0-5.0%)Bi alloy for zinc electrowinning was obtained by doping Bi.The anodic oxygen evolution potential,corrosion rate,surface products after polarization,and microstructure...A new anodic material of ternary Pb-0.8%Ag-(0-5.0%)Bi alloy for zinc electrowinning was obtained by doping Bi.The anodic oxygen evolution potential,corrosion rate,surface products after polarization,and microstructures before and after polarization were studied and compared with those of Pb-0.8%Ag anode used in industry.The results show the anodic overpotential decreases with the increase of Bi content in the alloys.When the content of Bi is 1.0%(mass fraction),the anodic overpotential is 40-50 mV lower than that of Pb-0.8%Ag anode.While the corrosion rate decreases and then increases with the increase of Bi content.The Pb-0.8%Ag-0.1%Bi anode has the lowest corrosion rate(0.090 6 mg/(h·cm2).Doping Bi influences the structure of the anodic layer,but does not change the phase.The Pb-0.8%Ag-1.0%Bi anode layer is of a more fine-grained structure compared with Pb-0.8%Ag anode.展开更多
A new type of lead-based porous anode in zinc electrowinning was prepared by negative pressure infiltration. The anodic polarization potential and corrosion rate were studied and compared with those of traditional fla...A new type of lead-based porous anode in zinc electrowinning was prepared by negative pressure infiltration. The anodic polarization potential and corrosion rate were studied and compared with those of traditional flat anodes (Pb-0.8%Ag) used in industry. The anode corrosion rate was determined by anode actual current density and microstructure. The results show that the anodic oxygen evolution potential decreases first and then increases with the decrease of pore diameter. The anodic potential decreases to the lowest value of 1.729 V at the pore diameter of 1.25-1.60 mm. The porous anode can decrease its actual current density and thus decrease the anodic corrosion rate. When the pore diameter is 1.60-2.00 mm, the anodic relative corrosion rate reaches the lowest value of 52.1%.展开更多
An A1/Pb-0.3%Ag alloy composite anode was produced via composite casting. Its electrocatalytic activity for the oxygen evolution reaction and corrosion resistance was evaluated by anodic polarization curves and accele...An A1/Pb-0.3%Ag alloy composite anode was produced via composite casting. Its electrocatalytic activity for the oxygen evolution reaction and corrosion resistance was evaluated by anodic polarization curves and accelerated corro- sion test, respectively. The microscopic morphologies of the anode section and anodic oxidation layer during accelerated corrosion test were obtained by scanning electron microscopy. It is found that the composite anode (hard anodizing) dis- plays a more compact interracial combination and a better adhesive strength than plating tin. Compared with industrial Pb-0.3%Ag anodes, the oxygen evolution overpotentials of A1/Pb-0.3%Ag alloy (hard anodizing) and A1/Pb-0.3%Ag alloy (plating tin) at 500 A.m-2 were lower by 57 and 14 mV, respectively. Furthermore, the corrosion rates of Pb-0.3%Ag alloy, A1/Pb-0.3%Ag alloy (hard anodizing), and A1/Pb-0.3%Ag alloy (plating tin) were 13.977, 9.487, and 11.824 g.m-2.h-1, respectively, in accelerated corrosion test for 8 h at 2000 A-m-2. The anodic oxidation layer of A1/Pb-0.3%Ag alloy (hard anodizing) is more compact than Pb-0.3%Ag alloy and A1/Pb-0.3%Ag alloy (plating tin) after the test.展开更多
The separating efficiency of Sb from As and Sn in jamesonite concentrate could be improved by changing the composition of leaching solution and other conditions.The related kinetic parameters of electrode reaction wer...The separating efficiency of Sb from As and Sn in jamesonite concentrate could be improved by changing the composition of leaching solution and other conditions.The related kinetic parameters of electrode reaction were evaluated under discussion on the form of complex ion AsS_3^(3-)in extract and the reduction at amalgam electrode.It was also discussed about the ef- fect of eoncentration of Na_2S and SbS_3^(3-)in solution on the current efficiency of SnS_4^(4-) reduction.展开更多
The effects of arsenic on the cathode polarization process in zinc electrowinning,its kinetics equation,parameters and polarization mechanism were studied by multiple electrochemistry approaches.The experimental resul...The effects of arsenic on the cathode polarization process in zinc electrowinning,its kinetics equation,parameters and polarization mechanism were studied by multiple electrochemistry approaches.The experimental results show that,if[As 3+]≥3 mg/L,electrowinning first enters into stationary passivation range,and then enters into precipitation range,which indicates that the depolarization function of impurity arsenic is zinc electrowinning.展开更多
Polyaniline(Pani)anode is tested to highlight the feasibility of reduction of both energy consumption and capital costs in zinc electrowinning from sulfate solution without any modification to the existing plant.Curre...Polyaniline(Pani)anode is tested to highlight the feasibility of reduction of both energy consumption and capital costs in zinc electrowinning from sulfate solution without any modification to the existing plant.Current density,electrolyte temperature, added gelatin,added Mn 2+ ,oxygen-evolution potential,cell potential and long duration tests were investigated.The zinc deposits were also studied by means of scanning electron microscope(SEM)and X-ray diffraction(XRD).The results show that current density and added gelatin change the preferred crystal orientations of the zinc deposits.Compared with Pb-Ag(1%)anode used in industry,the cell voltage decreases by 0.15-0.30 V,energy consumption of Zn is 2.46-2.70 kW·h/kg which results in 20%energy savings.Long duration tests show that Pani anode can represent a good alterative ability for zinc electrowinning.Zinc deposits obtained have no Pb pollution.The additions of Mn2 +ions and gelatin also change the surface morphology and deposit quality of the electrodeposited zinc,affecting the crystal orientation.These researches demonstrate that Pani anode has distinct advantages over acidic electrowinning process.展开更多
基金financially supported by the Major Science and Technology Programs of CHALCO(ZB2013CBBCe1)the Zhengzhou Non-ferrous Metals Research Institute Co.Ltd.of CHALCO for supporting this work
文摘The microstructure evolution and electrolysis behavior of(Cu_(52)Ni_(30)Fe_(18))–x Ni Fe_2O_4(x=40wt%,50wt%,60wt%,and 70wt%)composite inert anodes for aluminum electrowinning were studied.Ni Fe_2O_4 was synthesized by solid-state reaction at 950°C.The dense anode blocks were prepared by ball-milling followed by sintering under a N_2 atmosphere.The phase evolution of the anodes after sintering was determined by scanning electron microscopy and energy-dispersive X-ray spectroscopy.The results indicate that a substitution reaction between Fe in the alloy phase and Ni in the oxide phase occurs during the sintering process.The samples were also examined as inert anodes for aluminum electrowinning in the low-temperature KF–NaF–AlF_3 molten electrolyte for 24 h.The cell voltage during electrolysis and the corrosion scale on the anodes were analyzed.The results confirm that the scale has a self-repairing function because of the synergistic reaction between the alloy phase with Fe added and the oxide phase.The estimated wear rate of the(Cu_(52)Ni_(30)Fe_(18))–50Ni Fe_2O_4 composite anode is 2.02 cm·a^(-1).
基金Project(50974065)supported by the National Natural Science Foundation of ChinaProject(2009009)supported by the Analysis and Testing Foundation of Kunming University of Science and Technology,China
文摘Effect of added Co2 +(aq)on copper electrowinning was studied using doped polyaniline(Pani)and Pb-Ag(1%)anodes and a stainless steel cathode.The presence of added Co2+ (aq)in the electrolyte solution was found to decrease the anode potentials.The optimum level of Co2 +(aq)concentration in the electrolyte,with respect to the maximum saving of power consumption was established.Linear sweep voltammetry(LSV)was used to study the influence of added Co2 +(aq)on the anodic processes in a copper sulfate-sulfuric acid electrolyte.The oxygen-evolution potential for Pani anode is depolarised at lower current densities(≤0.01 A/cm2)and attains saturation atρ(Co 2+ )o≈0.789 g/L;whilst the oxygen-evolution potential for Pb-Ag(1%)anode is depolarised at higher current densities(≤0.02 A/cm2)and attains saturation atρ(Co 2+ )o≈1.315 g/L.The preferred orientations of the copper deposits change from(220)to(111)with the addition of 0.394?0.789 g/L Co 2+ but higher concentrations favor(220)orientation again.
文摘In order to eliminate the pitting and improve the surface morphology of cathode nickel,the influence of additives of boric acid and dodecyl sodium sulfate(SDS)on the process of nickel electrowinning from sulfate system was studied by cathode polarization tests and nickel electrodeposition experiments.The experimental results show that the addition of boric acid can increase the cathode polarization while SDS can decrease the cathode polarization.Both boric acid and SDS are useful to eliminate the pitting on nickel deposits and improve the morphology of surface.Good deposit morphology with rare pitting and high current efficiency is favored by adding 10 g/L boric acid and 40 mg/L SDS in the electrolyte under the condition of nickel ion concentration of 80 g/L, sodium ion concentration of 10 g/L,pH of 3,current density of 220 A/m 2 and temperature of 70℃.
基金financial support of the National Natural Science Foundation of China (No.51004056)the Applied Basic Research Foundation of Yunnan Province (No. 2010ZC052)the Specialized Research Fund for the Doctoral Program of Higher Education of China (No. 20125314110011)
文摘The objective of this work was to study the effect of different rolling technologies on the properties of Pb-0.06wt%Ca-1.2wt%Sn anodes during copper electrowinning and to determine the relationship between the properties of the anodes and rolling techniques during copper electrowinning. The anode process was investigated via anodic polarization curves, cyclic voltammetry curves, electrochemical impedance spectra, and corrosion tests. The microscopic morphology and phase composition of the anodic oxide layers were observed by scanning electron microscopy and X-ray diffraction, respectively. Observable variations in the electrocatalytic activity and reaction kinetics of anodes during electrowinning indicated that the electrochemical behavior of the anodes was strongly affected by the rolling technology. An increase in the rolling number tended to decrease the oxygen evolution overpotential and the corrosion rate of the anodes. These trends are contrary to that of the apparent exchange current density. Furthermore, the intensities of diffraction peaks associated with PbO, PbOx, and α-PbO2 tended to increase with increasing rolling number. In addition, the rolled anodes exhibited a more uniform microstructure. Compared with one-way rolled anodes, the eight-time cross rolled anodes exhibited better electrocatalytic activity and improved corrosion resistance.
基金Funded by the National Natural Science Foundation of China(Nos.51564029,51504111,51504231,51364019)the Key Project of Yunnan Province Applied Basic Research Plan of China(No.2014FA024)
文摘The properties of Al/conductive coating/α-PbO2-CeO2-TiO2/β-PbO2-WC-ZrO2 composite anode for zinc electrowinning were investigated. The electrochemical performance was studied by Tafel polarization curves(Tafel), electrochemical impedance spectroscopy(EIS) and corrosion rate obtained in an acidic zinc sulfate electrolyte solution. Scanning electron microscopy(SEM), X-ray diffraction(XRD), and energy dispersive X-ray spectroscopy(EDXS) were used to observe the microstructural features of coating. Anodes of Al/conductive coating/α-PbO2-CeO2-TiO2/β-PbO2, Al/conductive coating/α-PbO2-CeO2-TiO2/β-PbO2-WC, Al/conductive coating/α-PbO2-CeO2-TiO2/β-PbO2-ZrO2, and Pb-1%Ag anodes were also researched. The results indicated that the Al/conductive coating/α-PbO2-CeO2-TiO2/β-PbO2-WC-ZrO2 showed the best catalytic activity and corrosion resistant performance; the intensity of diffraction peak exhibited the highest value as well as a new PbWO4 phase; the content of WC and ZrO2 in coating showed the highest value as well as the finest grain size.
文摘The influences of cupric ion concentration (5-35 g/L),current density (500-2000 A/m2),circulation rate of the electrolyte solution (15-120 mL/min),and temperature (25-60℃) on the physical and chemical properties of copper powders obtained in electrolysis cells were investigated.Two industrial processes,electrorefining (ER) cells with a synthetic electrolyte and electrowinning (EW) cells with an original solution of coppermineral leaching,were utilized to produce copper powders.Finally,the statistical full factorial method of design of experiments (DOE) was employed to investigate the interaction or the main effects of processes.The results show that increasing the copper concentration and temperature can increase the grain size,apparent density,and electrical energy consumption.On the other hand,increasing the current density and circulation rate of the electrolyte can decrease them.This production process is optimized via DOE to control the interactive and main effects to produce copper powders with favorable properties.
基金Project(51004056)supported by the National Natural Science Foundation of China
文摘In order to study the anodic behavior and microstructures of Al/Pb-Ag-Co anode during zinc electrowinning,by means of potentiodynamic investigations,scanning electron microscopy(SEM) and X-ray diffraction(XRD)analyses,the mechanism of the anodic processes playing on the surface of Al/Pb-0.8%Ag and Al/Pb-0.75%Ag-0.03%Co anodes prepared by electro-deposition from methyl sulfonic acid bath for zinc electrowinning from model sulphate electrolytes have been measured.On the basis of the cyclic voltammograms obtained,information about the corrosion rate of the composite in PbO2 region has been concluded.The microstructures were also observed by means of SEM and XRD which showed Pb-0.75%Ag-0.03%Co alloy composite coating has uniform and chaotic orientation tetragonal symmetry crystallites of PbSO4,but Pb-0.8%Ag alloy composite coating has well-organized orientation crystallites of PbSO4 concentrated in the certain zones after 24 h of anodic polarization.It is important that Al/Pb-0.75%Ag-0.03%Co anode oxide film consists of non-conductive dense MnO2 and PbSO4 and α,β-PbO2 penetrated into which,in fact,are the active centers of the oxygen evolution after 24 h of anodic polarization.
文摘The anodic reaction kinetics of zinc electrowinning was investigated on the titanium base RuO2 anode in the system of Zn(Ⅱ)-NH3-NH4Cl-H2O. The effects of stirring speed, ammonium chloride concentration and temperature on anodic reaction rate were studied through the curve measurement of potentiostatic polarization. The results reveal that the electrochemically controlled anodic reaction obeys Tafel equation and the anodic reaction order for ammonium chloride is 1.056, with the apparent activation energy of 40.17 kJ/mol. The general equation of anodic reaction kinetics was obtained.
文摘Consumable carbon anodes are used in the electrowinning of aluminium by the Hall-Heroult process.Emissions of CO2 may be eliminated by introducing an inert oxygen evolving anode,which however will require a higher anode potential.An alternative approach is to use a natural gas or hydrogen gas anode to reduce the CO2 emissions and lower the anode potential.Preliminary laboratory experiments were carried out in an alternative molten salt electrolyte consisting of CaCl2-CaO-NaCl at 680 °C.Porous anodes of platinum and tin oxide were tested during electrolysis at constant current.The behaviour of inert anode candidate materials such as tin oxide and nickel ferrite were also studied.
文摘The effect of lead anode, rotating cylinder electrode (RCE), amount of 1,2-dihydroxypropane (12-DHP), temperature and rotation on the electrowinning of copper from low concentration acidified copper sulphate solution has been investigated. Copper powder was electrodeposited onto RCE that made of pure copper. From cyclic voltammetry experiments, an empirical parameter called the departure percent, S, was obtained which may represent the stability of the organic additive in the given medium and under the experimental conditions. The inhibition percentage, P, was 0.00 - 89.91% depending on the experimental variables. P was affected by temperature and mole fraction of 12-DHP, while rotation did not show any influence on it. Values of activation energy of electrodeposition process, Ea, were found to be less than 28 kJ mol-1 indicating diffusion controlled process. The overall mass transfer correlations under the present conditions have been computed using the dimensional analysis method. The data were valid for 90 < Sh < 1098, 737 < Sc < 59284 and 271 < Re < 7046 and the results agreed with the previous studies of mass transfer to rotating cylinders in turbulent flow regimes. The effect of time, content of 12-DHP, temperature and the speed of rotation on the morphological changes of the electrodeposited copper powder as well as deposits composition and crystallite size have been studied. Various crystallite sizes ranged 7.1 nm - 250.6 nm were obtained and characterized by EDS and XRD. Different topographs proved that the rate of copper electrodeposition increased by increasing deposition time, temperature and the speed of rotation. Also, they proved that the deposition rate decreased by adding 12-DHP to the solution. Therefore, the results obtained by SEM supported those achieved by measuring the limiting current density and follow the normal manner when organic solvents were added to the electrodeposition bath.
基金Project(2007SK2009)supported by the Science and Technology Research Project of Hunan Province,China
文摘A new anodic material of ternary Pb-0.8%Ag-(0-5.0%)Bi alloy for zinc electrowinning was obtained by doping Bi.The anodic oxygen evolution potential,corrosion rate,surface products after polarization,and microstructures before and after polarization were studied and compared with those of Pb-0.8%Ag anode used in industry.The results show the anodic overpotential decreases with the increase of Bi content in the alloys.When the content of Bi is 1.0%(mass fraction),the anodic overpotential is 40-50 mV lower than that of Pb-0.8%Ag anode.While the corrosion rate decreases and then increases with the increase of Bi content.The Pb-0.8%Ag-0.1%Bi anode has the lowest corrosion rate(0.090 6 mg/(h·cm2).Doping Bi influences the structure of the anodic layer,but does not change the phase.The Pb-0.8%Ag-1.0%Bi anode layer is of a more fine-grained structure compared with Pb-0.8%Ag anode.
基金Project(2007SK2009) supported by the Science and Technology Research Project of Hunan Province, China
文摘A new type of lead-based porous anode in zinc electrowinning was prepared by negative pressure infiltration. The anodic polarization potential and corrosion rate were studied and compared with those of traditional flat anodes (Pb-0.8%Ag) used in industry. The anode corrosion rate was determined by anode actual current density and microstructure. The results show that the anodic oxygen evolution potential decreases first and then increases with the decrease of pore diameter. The anodic potential decreases to the lowest value of 1.729 V at the pore diameter of 1.25-1.60 mm. The porous anode can decrease its actual current density and thus decrease the anodic corrosion rate. When the pore diameter is 1.60-2.00 mm, the anodic relative corrosion rate reaches the lowest value of 52.1%.
基金financially supported by the National Natural Science Foundation of China(No.51004056)the Opening Foundation of the Key Laboratory of Inorganic Coating Materials,Chinese Academy of Sciences(No.KKZ6201152009)+2 种基金the Specialized Research Fund for the Doctoral Program of Higher Education(No.20125314110011)the Applied Basic Research Foundation of Yunnan Province,China(No.2010ZC052)the Analysis and Testing Foundation of Kunming University of Science and Technology(Nos.2010203 and 2011173)
文摘An A1/Pb-0.3%Ag alloy composite anode was produced via composite casting. Its electrocatalytic activity for the oxygen evolution reaction and corrosion resistance was evaluated by anodic polarization curves and accelerated corro- sion test, respectively. The microscopic morphologies of the anode section and anodic oxidation layer during accelerated corrosion test were obtained by scanning electron microscopy. It is found that the composite anode (hard anodizing) dis- plays a more compact interracial combination and a better adhesive strength than plating tin. Compared with industrial Pb-0.3%Ag anodes, the oxygen evolution overpotentials of A1/Pb-0.3%Ag alloy (hard anodizing) and A1/Pb-0.3%Ag alloy (plating tin) at 500 A.m-2 were lower by 57 and 14 mV, respectively. Furthermore, the corrosion rates of Pb-0.3%Ag alloy, A1/Pb-0.3%Ag alloy (hard anodizing), and A1/Pb-0.3%Ag alloy (plating tin) were 13.977, 9.487, and 11.824 g.m-2.h-1, respectively, in accelerated corrosion test for 8 h at 2000 A-m-2. The anodic oxidation layer of A1/Pb-0.3%Ag alloy (hard anodizing) is more compact than Pb-0.3%Ag alloy and A1/Pb-0.3%Ag alloy (plating tin) after the test.
文摘The separating efficiency of Sb from As and Sn in jamesonite concentrate could be improved by changing the composition of leaching solution and other conditions.The related kinetic parameters of electrode reaction were evaluated under discussion on the form of complex ion AsS_3^(3-)in extract and the reduction at amalgam electrode.It was also discussed about the ef- fect of eoncentration of Na_2S and SbS_3^(3-)in solution on the current efficiency of SnS_4^(4-) reduction.
基金Project(2008049)supported by Personal Training of Kunming University of Science and TechnologyProject(2008ZC013M)supported bythe Basic Research Program of Scientific and Technological Department Yunnan Province
文摘The effects of arsenic on the cathode polarization process in zinc electrowinning,its kinetics equation,parameters and polarization mechanism were studied by multiple electrochemistry approaches.The experimental results show that,if[As 3+]≥3 mg/L,electrowinning first enters into stationary passivation range,and then enters into precipitation range,which indicates that the depolarization function of impurity arsenic is zinc electrowinning.
基金Project(50974065)supported by the National Natural Science Foundation of ChinaProject(2009009)supported by the Analysis and Testing Foundation of Kunming University of Science and Technology,China
文摘Polyaniline(Pani)anode is tested to highlight the feasibility of reduction of both energy consumption and capital costs in zinc electrowinning from sulfate solution without any modification to the existing plant.Current density,electrolyte temperature, added gelatin,added Mn 2+ ,oxygen-evolution potential,cell potential and long duration tests were investigated.The zinc deposits were also studied by means of scanning electron microscope(SEM)and X-ray diffraction(XRD).The results show that current density and added gelatin change the preferred crystal orientations of the zinc deposits.Compared with Pb-Ag(1%)anode used in industry,the cell voltage decreases by 0.15-0.30 V,energy consumption of Zn is 2.46-2.70 kW·h/kg which results in 20%energy savings.Long duration tests show that Pani anode can represent a good alterative ability for zinc electrowinning.Zinc deposits obtained have no Pb pollution.The additions of Mn2 +ions and gelatin also change the surface morphology and deposit quality of the electrodeposited zinc,affecting the crystal orientation.These researches demonstrate that Pani anode has distinct advantages over acidic electrowinning process.
基金supported by the National Natural Science Foundation of China (Nos. 52074363, 52104355, 51922108, U20A20273)the National Key R&D Program of China (No. 2019YFC1907402)。