Mechanism of influence of chloride ions on electrogenerative leaching of sulfide minerals

1 INTRODUCTIONElectrogenerative leaching process is a newtechnique in hydrometallurgy .ZHANG et al[1]in-troduced the principle and technique of electrogen-erative process to metallurgy field by the leachingof synthetic Ni3S2with FeCl3.In order to utilizethe chemical energy in leaching process reasonablyand si mplify the purifying process , Wang et al[2 8]studied the electrogenerative leaching of a series ofsulfide minerals through a dual cell system withFeCl3and acidic MnO2as oxidant…     

Bioleaching of chalcocite by mixed microorganisms subjected to mutation

Mixed microorganisms with elevated activity of chalcocite-leaching were screened by mutation methods. The original microorganisms collected from acid mine drainage of different sites were mixed and then treated with mutagens NO₂⁻, diethyl sulfate (DES), UV and their combinations, respectively. Five groups of mixed microorganisms with much stronger ore-leaching ability were obtained by screening on the leaching media. Among them, group E of mixed microorganisms (treated with 1% DES for 60 min) with the best performance on chalcocite-leaching, increases the content of Cu²⁺ by 101.4% in 20 d of leaching compared with the control culture. In addition, group E is more tolerant to Cu²⁺ in media than the control without mutation treatment. Analysis for the diversity of microbial clones indicates that half of operational taxonomic units (OTUs) in group E are Acidithiobacillus ferrooxidans. These observations suggest that group E might have potentials for industrial application. Foundation item: Project(50321402) supported by the National Natural Science Foundation of China; Project(2004CB619201) supported by the Major State Basic Research and Development Program of China     

Recovery of molybdenum from residues by simultaneous ultrafine milling and alkali leaching

A new technology of treating molybdenum residues by simultaneous ultmfme milling and alkali leaching was put forward to recover molybdenum from metallurgical residues. The effects of residue size, milling time, solid content, n(Na2CO3)/n(Mo) and slurry pH value on molybdenum leaching rate were investigated. The results indicate that a simpler process, lower slurry temperature, 50% shorter treating time, 60% decrease of Na2CO3 content and 15% increase of molybdenum leaching rate can be obtained by the new technology compared with the traditional process. The leaching kinetic equation was determined, and calculation of active energy (E = 56.2 kJ/mol) shows that the leaching process of molybdenum residues by simultaneous ultmfine milling and alkali leaching is controlled by chemical reaction. Potential exists for the new process to form the basis for an economically viable, environmentally friendly process to recover valuable elements from residues.     

Electrogenerative leaching of nickel sulfide concentrate with ferric chloride

In order to utilize the chemical energy in hydrometallurgical process of sulfide minerals reasonably and to simplify the purifying process, the electrogenerative process was applied and a dual cell system was introduced to investigate FeCl3 leaching of nickel sulfide concentrate. Some factors influencing the electrogenerative leaching, such as electrode structure, temperature and solution concentration were studied. The results show that a certain quantity of electrical energy accompanied with the leached products can be acquired in the electrogenerative leaching process.The output current and power increase with the addition of acetylene black to the electrode. Varying the components of electrode just affects the polarization degree of anode. Increasing FeCl3 concentration results in a sharp increase in the output of the leaching cell when c(FeCl3) is less than 0.1mol/L. The optimum value of NaCl concentration for electrogenerative leaching nickel sulfide concentrate with FeCl3 is 3.0 mol/L. Temperature influences electrogeneratire leaching by affecting anodic and cathodic polarization simultaneously. The apparent activation energy is determined to be 34.63 kJ/mol in the range of 298 K to 322 K. The leaching rate of Ni^2 is 29.3% after FeCl3 electrogenerative leaching of nickel sulfide concentrate for 620 min with a filter bag electrode.     

Influences of silver sulfide on the bioleaching of chalcopyrite, pyrite and chalcopyrite-containing ore

The effects of silver sulfide (Ag2S) on the bioleaching of chalcopyrite and pyrite were investigated in this paper. It has been shown that Ag2S enhanced the yields of bioleaching of chalcopyrite but inhibited the bio-oxidation of pyrite. The addition of Ag:S selectively increased the copper dissolution from the chalcopyritecontaining ores in shake flasks with a recovery of 85.3 % compared with 24.3 % without Ag2S, while slightly decreased the iron yields from 51% to 41.8%. The copper extraction of the chalcoopyrite-containing waste rock in column leaching charged with 18 kg mass increased up to 21.7% in the presence of Ag2S, while only 3.4% in the absence of the catalyst. The mechanism of Ag2S catalysis could be explained well by the “Mixedpotential model”.     

Selective leaching of vanadium from V-Ti magnetite concentrates by pellet calcification roasting-H_2SO_4 leaching process

A novel method of pellet calcification roasting-H_2 SO_4 leaching was proposed to efficiently separate and extract vanadium(V) from vanadium-titanium(V-Ti) magnetite concentrates.The leaching rate of V is as high as 88.98%,while the leaching rate of impurity iron is only 1.79%.Moreover,the leached pellets can be used as raw materials for blast furnace ironmaking after secondary roasting.X-ray photoelectron spectroscopy(XPS) and scanning electron microscopy with energy dispersive X-ray spectrometry(SEMEDS) analyses showed that V~(3+) was oxidized to V~(5+) after roasting at 1200℃,and V~(5+) was then leached by H_2 SO_4.X-ray diffraction(XRD) analyses and single factor experiment revealed a minimal amount of dissolved Fe_2 O_3 during H_2 SO_4 leaching.Therefore,a high separation degree of V and iron(Fe) from V-Ti magnetite concentrate was achieved through H_2 SO_4 leaching.Compared with the traditional roastingleaching process,this process can achieve a high selectivity of V and Fe,and has excellent prospects for industrial production.     

The Mechanism of Sol-Gel Synthesis of Normal Spinel LiMn2O4 with Chelation of Citric Acid

The sol-gel process of citric acid chelating with metal cations for the synthesis of normol spinel LiMn2O4 and the reaction mechanion mechavism were investigated by means of XRD,TG-DTA,and SEM ,the results show that at the beginning lithium citrate and chelate compound of citic acid with manganese ions formed ,and then with heating the esterification and condensation reacions occured between them and glyol ,The products obtained are polymers in which metal cations are distibuted homogeneously on atomic scale that ensur hight reacivity to cations of Li^ and Mn^2 ,Firing the gel grepared by this process ,the lattice diffusions of solid reactant ions caused by non-homogeneity of reactants are elinimated and avoided .At 400℃ phase-pure LiMn2O4 with nanometer scale crystallization having precise stoichiometry and perfect crystallization can be obtained ,The model of chelate coordinated of double -molecule between citric acid and Mn^2 in the gel network is proosed ,It is important for explaining the dispersion state of Mn^2 and the formaiton process of gel by this model.     

Study on solubility of Nb2O5 in KOH solution and alkali leaching of niobite

Solubility of Nb₂O₅ and leaching behaviors of Nb and Ta from niobite in KOH solution have been investigated in order to develop an alkali hydrothermal leaching process of Nb and Ta. The solubility of Nb₂O₅ was measured in the range of 40 °C to 200 °C at various molar ratios of K₂O to Nb₂O₅(n(K₂O)/n(Nb₂O₅)). It has been found that Nb₂O₅ shows the maximum solubility at the solution composition of n(K₂O)/n(Nb₂O₅)=4/3 at a given temperature; the rise of temperature increases the solubility of Nb₂O₅ below 120 °C, but decreases it above 120 °C. The leaching behaviors of Nb and Ta were studied in the range of 150 °C to 250 °C and 0.1 MPa to 5 MPa. With the rise of temperature, the leaching degree increases when the leaching temperature is below 200 °C, but it decreases when the leaching temperature is above 200 °C. The maximum leaching degree is about 90% at 200 °C. It was proved that the alkali hydrothermal leaching process is effective for the recovery of Nb and Ta from niobite concentrate. Foundation item: The Key Project of Science and Technology Agency of Japan, 1994 Biography of the first author: ZHOU Kang-gen, doctor of engineering, professor, born in 1963, majoring in extractive metallurgy of rare metals and application of membrane separation technology.     

Synthesis and adsorption properties of chitosan-crown ether resins

1　INTRODUCTIONTheeffectiveremovalorrecoveryoftoxicmetalsstillremainsamajortopicofpresentresearch .In creasedawarenessofthetoxicityofmetalshaspromptedtheimplementationofstrictregulationsforitsdisposal,causingtraditionaltreatmentprocessessuchaschemicalprecipitationtoundergochanges .Modernmetal removaltechnologiessuchasionex change ,reverseosmosis ,andmembranesystemsthatproduceeffluentsofbetterqualitymakeitpossibletorecoverandreusemetals[1,2 ] .Chitosan ,whichiseasilyderivedfromchitinbyN de…     

Mechanism of crud formation in copper solvent extraction

The authors investigated the mechanism of crud formation in copper solvent extraction. It is indicated that pH value of solution and the phase ratio (O/A) are the main factors affecting crud formation in solvent extraction. The amount of crud extraction increases with aqueous pH value increase, and reduces with the increase of the phase ratio. Fe3 , Mg2 , fine air bubble and suspended particulates in leaching solution contribute to crud formation. One case is that a series of reactions of hydrolization and polymerization occurs for Fe3 , while pH＞2.5, polyhydric complex or Fe-SO4 complex are formed. Then the complex-ions of FeOH2 , Fe2(OH)4 2 cause poly-reaction, which is likely to lead emulsion. The study on Zeta potential indicates the repulsion between electriferous droplets in solvent extraction prevents phase coalescence, which is one of the major reasons for emulsion.     

Local segregation in Cu-In precursors and its effects on microstructures of selenized CuInSe2 thin films

Local segregation in Cu-In precursors and its effects on the element distribution and microstructures of selenized CuInSe₂ thin films were investigated. Cu-In precursors with an ideal total mole ratio of Cu to In of 0.92 were prepared by middle frequency alternating current magnetron sputtering with Cu-In alloy target, then CuInSe₂ absorbers for solar cells were formed by selenization process in selenium atmosphere. Scanning electron microscope and energy dispersive X-ray spectroscope were used respectively to observe the surface morphologies and determine the compositions of both Cu-In precursors and CuInSe₂ thin films. Their microstructures were characterized by X-ray diffractometry and Raman spectroscope. The results show that Cu-In precursors are mainly composed of Cu₁₁In₉ phase with In-rich solid solution. Stoichiometric CuInSe₂ thin films with a homogeneous element distribution and single chalcopyrite phase can be synthesized from a segregated Cu-In precursor film with an ideal total mole ratio of Cu to In of 0.92. CuInSe₂ thin film shows P-type conductivity and its resistivity reaches 1.2×10³ Θ·cm. Foundation item: Project(2004AA513023) supported by the National High Technology Research and Development Program of China     

Leaching kinetics of low grade zinc oxide ore in NH3-NH4Cl-H2O system

The leaching kinetics of low grade zinc oxide ore in NH3-NH4Cl-H2O system was studied. The effects of ore particle size, reaction temperature and the sum concentration of ammonium ion and ammonia on the leaching efficiency of zinc were examined. The leaching kinetics of low-grade zinc oxide ore in NH3-NH4Cl-H2O system follows the kinetic law of shrinking-core model. The results show that diffusion through the inert particle pores is the leaching kinetics rate controlling step. The calculated apparent activation energy of the process is about 7.057 kJ/mol. The leaching efficiency of zinc is 92.1% under the conditions of ore particle size of 69μm, holding at 80℃ for 60 min, sum ammonia concentration of 7.5 mol/L, the molar ratio of ammonium to ammonia being 2：1, and the ratio （g/mL） of solid to liquid being 1：10.     

Preparation and antimicrobial ability of natural proous antibacterial materials

The liquid ion exchange method, solid salt melt method and dry-wet circulation method were used to prepare natural porous antimicrobial materials with natural minerals, such as zeolite, spilite, palygorskite and montmorillonite, respectively. Atomic absorption spectrum and X-ray diffraction analysis were carried out to investigate the effects of Ag⁺, Cu²⁺ and Zn²⁺ on antimicrobial abilities of natural porous minerals, and the effect of preparation method on ion exchange capacity of antimicrobial material, respectively. The results show that for the ion exchange capacity, clay mineral is higher than fibrous mineral, i. e. both zeolite and montmorillonite are higher; the antimicrobial ability of material with Ag⁺ is the best; the exchange capacities of materials with Cu²⁺ or Zn²⁺ are all higher, but the antimicrobial ability of Cu²⁺ is better than that of Zn²⁺. Foundation item: Project (40072020) supported by the National Natural Science Foundation of China; project (2001AA322070) supported by the National High Technology Research and Development Program of China     

Isolation of Leptospirillum ferriphilum by single-layered solid medium

According to physiological and biochemical characteristics of Leptospirillum ferriphilum,a strain of object bacteria was isolated successfully.Bacteria were enriched by selective liquid medium and plated on designed single-layered agar solid medium.Colony was cultured and bacteria were collected.The morphologies of the object bacteria were observed using crystal violet staining,scanning electron microscope(SEM)and transmission electron microscope(TEM).The result of 16S rDNA identification shows that this bacterium belongs to Leptospirillum ferriphilum and it is named as Leptospirillum ferriphilum strain D1.These results indicate that this new single-layered agar solid medium is efficient and simple for isolation of Leptospirillum ferriphilum.Additionally,physiological-biochemical characteristics show that the optimum initial pH value and its growth temperature are 1.68 and 40 ℃,respectively.The culture of it is used to leach a complex concentrate chalcopyrite,the leaching efficiencies of copper and iron are 1.93 % and 13.74 %,respectively,and it is more effective than the A.ferrooxidans culture in the leaching of the complex concentrate chalcopyrite.     

Determination of the entropy change for electrode reaction and dilute enthalpy of some ions by thermo-eletrochemical technology

Based on thermo-electrochemical equation for an electrode reaction, the entropy change of it can be obtained by the thermo - electrochemical technology (TECT). The entropy changes of Fe (CN) ₆ ⁻³ /Fe (CN) ₆ ⁻⁴ , H⁺/H₂(P⁰), Cu⁺²/Cu and Zn⁺²/Zn electrode reaction systems and the dilute enthalpies of the H⁺, Cu²⁺ and Zn²⁺ ions under the ion concentrations studied have been determined by a specially designed thermo-electrochemical equipment. The enthalpy change and entropy change for the five systems at unlimitedly diluted concentrations agree well with the literature. Project supporterd by the National Natural Science Foundation of China Synopsis of the first author Fang Zheng, Ph. D. and professor, born in April 1944, majoring the metallurgical thermodynamics and thermoelectrochemistry, supervised and participated in three projects supported by the National Natural Science Fundation of China and some other projects. More than 70 academic papers have been published.     

Electrochemical behaviors of gold and its associated elements in various complex agent solutions

1　INTRODUCTIONGoldisquitestableanddifficulttodissolveinacommonmineralacid .However ,becausethereisadelectroniclayerunfilledingoldatomicstructure ,goldcanbecombinedwithmanychemicalagentstoformstablecomplexions,causingthepotentialofgoldinasolutiontodecreaseandgoldtodissolveinthesolutioneasily .Basedonthisprinciple ,cyanideisanefficientlixiviatingagentofgold ,andhasbeenwidelyusedtoextractgoldfrom primaryandsecondaryresources .However ,itisthemosttoxicandnotbeneficialtoen vironmentprotection…     

Infrared-to-green upconversion properties of Er^3＋/Yb^3＋ co-doped TeO2-TiO2-K2O glasses upon excitation with 976 nm lasers diode

The energy transfer and upconversion of Er^3＋/Yb^3＋ co-doped TeO2-TiO2-K2O glasses upon excitation with 976 nm lasers diode were studied. The tellurite glasses were prepared by conventional melting methods. Their optical properties and sensitization upconversion spectra were performed. The dependence of green upconversion lu- minescence intensity on the mole ratio of Yb^3＋ to Er^3＋ and Er^3＋ concentration were discussed in detail. When the mole ratio of Yb^3＋ to Er^3＋ is 25/1 and Er^3＋ concentration is 0.1% （mole fraction）, or when the mole ratio of Yb^3＋ to Er^3＋ is 10/1 and Er^3＋ concentration is 0.15 %, the optimal upconversion luminescence intensity is obtained. The obtained glasses can be one of the potential candidates for lasers-diode pumping microchip solid-state lasers.     

Structure and electrochemical properties of LiMn<Subscript>2</Subscript>O<Subscript>4</Subscript>−<Emphasis Type="Italic">x</Emphasis>F<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>

LiMn₂O₄−_xF_x prepared by the sol-gel method has a perfect crystal formation. The crystal particle size of the material was medium and distributed uniformly. The substitution of F for O increased the specific capacity of the material at the cost of the cycleability. The explanation of this results is that the F decreases the valence of Mn, that is, more Mn³⁺ and less Mn⁴⁺ exist in the material. The increase of Mn³⁺ will improve the initial specific capacity and Mn³⁺ is the original reason for Jahn-Teller effect that caused the poor cycleability of the cathode material by the micro-distortion of the crystal structure. In addition, the expanded measurement of the crystal lattice is also the reason for the poor cycleability. Therefore, the results of F-substitution and cation-substitution are opposite. If the two methods are combined, they can compensate the inability each other and the satisfactory results may be obtained. XIA Jun-lei: Born in 1977 Funded by the National Natural Science Foundation of China (No. 59972026)     

Electrochemical behavior of CoCl2 in ionic liquid 1-butyl-3-methylimidazolium hexafluorophosphate

The electrochemical behavior of CoCl2 in 1-butyl-3-methylimidazolium hexafluorophosphate （[bmim]PF6） was investigated by cyclic voltammetry. The cyclic voltammograms were obtained from electrochemical measurement under different temperatures, and the reversible behavior for Co^2＋/Co^3＋ redox couple on glassy carbon electrode in [bmim]PF6 was confirmed by the characteristic of the peak currents. The diffusion coefficients （about 10^-11m^2/s） of Co^2＋ in [bmim]PF6 under different temperatures were evaluated from the dependence of the peak current density on the potential scan rates in cyclic voltammograms. It is found that the diffusion coefficient increases with increasing temperature. Diffusion activation energy of Co^2＋ in [bmim]PF6 is also calculated to be 23.4 kJ/mol according to the relationship between diffusion coefficient and temperature.     

New technique of comprehensive utilization of spent Al2O3 -based catalyst

A new technology was developed to recover multiple valuable elements from the spent Al2O3-based catalyst by X-ray phase analysis and exploratory experiments. The experimental results show that in the condition of roasting temperature of 750 ℃ and roasting time of 30 min, molar ratio of Na2O to Al2O3 of 1.2, the leaching rates of alumina, vanadium and molybdenum in the spent catalyst are 97.2%, 95.8% and 98.9%, respectively. Vanadium and molybdenum in sodium aluminate solution can be recovered by precipitators A and B, and the precipitation rates of vanadium and molybdenum are 94. 8% and 92. 6%. Al（OH）3 was prepared from sodium aluminate solution in the carbonation decomposition process, and the purity of Al2O3 is 99. 9% after calcination, the recovery of alumina reaches 90. 6% in the whole process; the Ni-Co concentrate was leached by sulfuric acid, a nickel recovery of 98. 2% and cobalt recovery over 98.5% can be obtained under the experimental condition of 30% H2SO4, 80 ℃, reaction time 4 h, mass ratio of liquid to solid 8, stirring rate 800 r/min.