Existing state of potassium chloride in agglomerated sintering dust and its water leaching kinetics

In order to examine the leaching rate of potassium chloride from the sintering dust by water,surface morphology and inner structure of the dust,especially the existing state of potassium chloride,were observed by scanning electron microscopy（SEM） and linear scanning technique via energy dispersive spectroscopy（EDS）.The characterization shows that the sintering dusts are mostly porous composites or agglomerates of the fine dust particles with size less than 10 μm,and the potassium chloride and sodium chloride particles are partly covered by other water insoluble matters in the dust which consist of elements iron,calcium and etc.Exposure of potassium chloride in the agglomerated dust matrix of this kind suggests that the leaching can be simply perceived as the dissolution of water soluble matters in the dust.On-line monitor of specific electrical conductivity of the leaching system verifies the prediction that leaching kinetics of potassium chloride from the sintering dust fits dissolution model well.Leaching equilibrium can be reached within 5 min with potassium leaching ratio more than 95%.

Leaching kinetics of zinc silicate in ammonium chloride solution

The leaching kinetics of zinc silicate in ammonium chloride solution was investigated. The effects of stirring speed （150？400 r/min）, leaching temperature （95-108 ℃, particle size of zinc silicate （61-150 μm） and the concentration of ammonium chloride （3.5-5.5 mol/L） on leaching rate of zinc were studied. The results show that decreasing the particle size of zinc silicate and increasing the leaching temperature and concentration of ammonium chloride can obviously enhance the leaching rate of zinc. Among the kinetic models of the porous solids tested, the grain model with porous diffusion control can well describe the zinc leaching kinetics. The apparent activation energy of the leaching reaction is 161.26 kJ/mol and the reaction order with respect to ammonium chloride is 3.5.

Hydrometallurgical processing of chalcopyrite:A review of leaching techniques

Copper,an essential metal for the energy transition,is primarily obtained from chalcopyrite through hydrometallurgical and pyrometallurgical methods.The risks and harmful impacts of these processes pose significant concerns for environmental and human safety,highlighting the need for more efficient and eco-friendly hydrometallurgical methods.This review article emphasizes current pro-cesses such as oxidative leaching,bioleaching,and pressure leaching that have demonstrated efficiency in overcoming the complicated chalcopyrite network.Oxidative leaching operates under benign conditions within the leaching media;nevertheless,the introduction of oxidizing agents provides benefits and advantages.Bioleaching,a non-aggressive method,has shown a gradual increase in copper extrac-tion efficiency and has been explored using both primary and secondary sources.Pressure leaching,known for its effectiveness and se-lectivity in copper extraction,is becoming commercially more viable with increased research investments.This research also provides im-portant data for advancing future research in the field.

Kinetics of simultaneous leaching of Ag and Pb from hydrometallurgical zinc residues by chloride

The leaching kinetics of silver and lead simultaneously from zinc residue by chloride was investigated.The effects of stirring speed,temperature,sodium chloride concentration,particle size and liquid/solid ratio on Ag and Pb dissolution in sodium chloride were studied.It was determined that the dissolution rates increased with increasing sodium chloride concentration,temperature and decreasing particle size.The dissolution kinetics followed a shrinking core model,with inter-diffusion through gangue layer as the rate determining step.This finding is in accordance with the apparent activation energy(E_a) of 26.8 kJ·mol^(-1)(Ag) and 26.5 kJ·mol^(-1)(Pb),and a linear relationship between the rate constant and the reciprocal of squared particle size.The orders of reaction with respect to sodium chloride concentration,temperature and particle size were also achieved.The rate of reaction based on diffusion-controlled process can be expressed by semi-empirical equations.

Effect of ammonium chloride on leaching behavior of alkaline anion and sodium ion in bauxite residue

This study focused on leaching behavior of alkaline anion and sodium in bauxite residue through ammonium chloride treatment.The results showed that the pH of bauxite residue decreased from 10.49 to 8.93,total alkaline anion(HCO3^-,CO3^2-,OH^-,AlO2^-)concentration reduced from 38.89 to 25.50 mmol/L,leaching rate of soluble sodium was 80.86%with ammonium chloride addition of 0.75%,liquid/solid(L/S)ratio of 3(mL/g),temperature of 30°C and reaction time of 18 h;L/S ratio was the main factor affecting the removal of alkaline anion and the leaching of sodium.Furthermore,ammonium chloride promoted the dissolution of diaspore and changed the micro/morphological characteristics with the increase of massive structure.The findings of this work will contribute to achieve soil-formation of bauxite residue.

Leaching of lead from zinc leach residue in acidic calcium chloride aqueous solution

A process with potentially reduced environmental impacts and occupational hazards of lead-bearing zinc plant residue was studied to achieve a higher recovery of lead via a cost-effective and environmentally friendly process. This paper describes an optimization study on the leaching of lead from zinc leach residue using acidic calcium chloride aqueous solution. Six main process conditions, i.e., the solution pH value, stirring rate, concentration of CaC12 aqueous solution, liquid-to-solid （L/S） ratio, leaching temperature, and leaching time, were inves- tigated. The microstructure and components of the residue and tailing were characterized using scanning electron microscopy （SEM） and X-ray diffraction （XRD）. On the basis of experimental results, the optimum reaction conditions were determined to be a solution pH value of 1, a stirring rate of 500 r·min-1, a CaC12 aqueous solution concentration of 400 g·L-1, a liquid-to-solid mass ratio of 7：1, a leaching tempera- ture of 80℃, and a leaching time of 45 min. The leaching rate of lead under these conditions reached 93.79%, with an iron dissolution rate of 19.28%. Silica did not take part in the chemical reaction during the leaching process and was accumulated in the residue.

Optimization of operating parameters and kinetics for chloride leaching of lead from melting furnace slag

The feasibility and kinetics of lead recovery from the slag of traditional lead melting furnace using chloride leaching were investigated.The effects of operating parameters such as leaching time,NaCl concentration,FeCl3concentration,liquid/solid ratio,stirring rate,temperature,and particle size on recovery of lead were studied and the optimization was done through the response surface methodology(RSM)based on central composite design(CCD)model.The optimum conditions were achieved as follows:leaching time60min,80°C,stirring rate800r/min,NaCl concentration200g/L,FeCl3concentration80g/L,liquid/solid ratio16,and particle size less than106μm.More than96%of lead was effectively recovered in optimum condition.Based on analysis of variance,the reaction temperature,liquid/solid ratio,and NaCl concentration were determined as the most effective parameters on leaching process,respectively.Kinetics study revealed that chloride leaching of galena is a first-order reaction and the diffusion through solid reaction product and chemical reaction control the mechanism.The activation energy of chloride leaching of galena was determined using Arrhenius model as27.9kJ/mol.

THE KINETICS OF FERRIC CHLORIDE LEACHING OF SPHALERITE IN THE MICROWAVE FIELD

The kinetics of ferric chloride leaching of sphalerite in the microwave field has being studied in this paper.According to the experimental data,the rate of dissolution of sphalerite microwave irradiation heating is faster than that with conventional heating.The dissolution of sphalerite in the microwave field was investigated in different condition of temperature,concentration of FeCl,and particle size and a nonisothermal kinetic equation has being obtained.

Enhanced extraction of scandium and inhibiting of iron from acid leaching solution of red mud by D2EHPA and sodium chloride

D2EHPA(P204),tri-butyl-phosphate(TBP)and sodium chloride(NaCl)were attractive for selective extraction of scandium from acid leaching solution of red mud.The extraction parameters of P204 concentration(X_(P204)),NaCl concentration(C_(NaCl)),pH value,reaction time,stirring speed and O/A were investigated to extract scandium and separate iron from the acid leaching solution.The extraction mechanism was analyzed by Fourier transform infrared spectroscopy(FT-IR)and thermodynamic theory.The single-stage extraction efficiency of scandium,iron andβ(Sc/Fe)were 99.1%,9.4%and 1061.2,respectively,with C_(NaCl) of 75 g/L and XP204 of 0.75 at solution pH value of 1.2 and stirring speed of 200 r/min for 6 min,in which a good separation effect of scandium and iron was obtained.The vibration absorption peak Sc─O was contributed to the extraction of scandium with P204.The complex[FeCln]^(3−n) existed in the solution with adding NaCl into the acid leaching solution.The value of n was higher and the valence state of the complex[FeCln]^(3−n) was lower with an increase of chloride concentration,which restricts the extraction efficiency of iron with P204.The extraction of three stages in the counter-current simulation experiments was carried out according to the McCabe-Thiele diagram.Gibbs free energy change(ΔG)of−5.93 kJ/mol,enthalpy change(ΔH)of 23.45 kJ/mol and entropy change(ΔH)of 98.54 J/(mol·K)were obtained in the solvent extraction proces,which indicate that the extraction reaction is easily spontaneous and endothermic and a proper increase of temperature is conducive to the extraction of scandium.

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

A dual cell system was used to study the influence of chloride ions on the electrogenerative leaching of sulfide minerals. The results show that the influences of chloride ions on a series of electrogenerative leaching system are similar, and chlorine ion is involved in the electrogenerative leaching process of sulfide minerals directly. The output power increases with the increase of Cl^- concentration. The influence on the electrogenerative leaching rate decreases when the Cl^- concentration reaches a certain value. The mechanisms of anodic reaction are deduced based on the reasonable hypothesis, and kinetic equations with respect to chlorine ions for each sulfide mineral are obtained. The kinetic equations show that when concentration of Cl^- is relatively low, the electrogenerative leaching rates are predicted to have 2/5,3/7,1/3 and 1/3 order dependence on Cl^- concentration for chalcopyrite concentrate,nickel concentrate, sphalerite and galena. As concentration of Cl^- increases, the correlative dependence of electrogenerative leaching rate on concentration of Cl^- becomes weak.

Dissolution kinetics of low grade complex copper ore in ammonia-ammonium chloride solution

The leaching kinetics of Tang-dan refractory low grade complex copper ore was investigated in ammonia-ammonium chloride solution.The concentration of ammonia and ammonium chloride,the ore particle size,the solid-to-liquid ratio and the temperature were chosen as parameters in the experiments.The results show that temperature,concentration of ammonia and ammonium chloride have favorable influence on the leaching rate of copper oxide ores.But,leaching rate decreases with increasing particle size and solid-to-liquid ratio.The leaching process is controlled by the diffusion of the lixiviant and the activation energy is determined to be 23.279 kJ/mol.An equation was also proposed to describe the leaching kinetics.

Leaching kinetics of low-grade copper ore with high-alkality gangues in ammonia-ammonium sulphate solution

The leaching kinetics of low-grade copper ore with high-alkality gangues was studied in ammonia-ammonium sulphate solution.The main parameters,such as ammonia and ammonium sulphate concentrations,particle size,solid-to-liquid ratio and reaction temperature,were chosen in the experiments.The results show that the increase of temperature,concentrations of ammonia and ammonium sulphate is propitious to the leaching rate of copper ore.The leaching rate increases with the decrease of particle size and solid-to-liquid ratio.The leaching rate is controlled by the diffusion through the ash layer and the activation energy is determined to be 25.54 kJ/mol.A semi-empirical equation was proposed to describe the leaching kinetics.

Behavior of silver and lead in selective chlorination leaching process of gold-antimony alloy

The behavior of silver and lead in the selective chlorination leaching process of gold-antimony alloy was analyzed in detail and appropriate recovery methods were developed.A reduction method by adding gold-antimony alloy powder was adopted to recover silver according to the thermodynamics calculation.The reducing rate of silver can exceed 99%at 80℃for 1.5 h when the dosage of gold-antimony alloy powder is 10%.The dissolution equilibrium curved surfaces of PbSO4 and PbCl2 under different conditions were drawn.The experimental results are well consistent with theoretical analysis that indicate lead may be precipitated in the form of lead chloride.The grade of gold in the residue can be further concentrated to 94.5%after being washed with hot water. These two methods have been applied successfully in the practice.

Extraction of metals from complex sulfide nickel concentrates by low-temperature chlorination roasting and water leaching

The recovery of valuable metals from complex sulfide concentrates was investigated via chlorination roasting followed by water leaching. A reaction process is proposed on the basis of previous studies and the results of our preliminary experiments. During the process, various process parameters were studied, including the roasting temperature, the addition of NH4Cl, the roasting time, the leaching time, and the liquid-to-solid ratio. The roasted products and leach residues were characterized by X-ray diffraction and vibrational spectroscopy. Under the optimum condition, 95% of Ni, 98% of Cu, and 88% of Co were recovered. In addition, the removal of iron was studied in the water leaching stage. The results demonstrate that this process provides an effective approach for extracting multiple metals from complex concentrates or ores. © 2017, University of Science and Technology Beijing and Springer-Verlag Berlin Heidelberg.

Electrochemical synthesis of Nb C-Sn composite powder in molten chloride

NbC-Sn composite powder was successfully prepared from SnO2,Nb2O5and carbon by electrochemical reduction andcarbonization in CaCl2-NaCl molten salt at900°C.The reaction pathway was investigated by terminating electrochemicalexperiments for various durations.The influence of carbon on the final products was considered.NbC particles were obtained byleaching the composite with acid.The results showed that the aggregated NbC-Sn composite powdev contained NbC particles about50-100nm and Sn particles about200nm.SnO2was reduced to Sn in the sintering process.Nb2O5was electrochemically reduced toNb in molten salt,experiencing some intermediate products of calcium niobates and niobium suboxides.Nb metal obtained wasconverted to NbC with assistance of carbon.The reduction of Nb oxides may be incomplete and Nb3Sn would be formed if carbon isinsufficient in the cathodic pellet.NbC with good dispersity is produced by leaching NbC-Sn with HCl.

Kinetic process of oxidative leaching of chalcopyrite under low oxygen pressure and low temperature

Kinetic process of oxidative leaching of chalcopyrite in chloride acid hydroxide medium under oxygen pressure and low temperature was investigated. The effect on leaching rate of chalcopyrite caused by these factors such as ore granularity, vitriol concentration, sodium chloride concentration, oxygen pressure and temperature was discussed. The results show that the leaching rate of chalcopyrite increases with decreasing the ore granularity. At the early stage of oxidative reaction, the copper leaching rate increases with increasing the oxygen pressure and dosage of vitriol concentration, while oxygen pressure affects leaching less at the later stage. At low temperature, the earlier oxidative leaching process of chalcopyrite is controlled by chemical reactions while the later one by diffusion. The chalcopyrite oxidative leaching rate has close relation with ion concentration in the leaching solution. The higher ion concentration is propitious for chalcopyrite leaching.

Effect of Roasting Temperature for Copper Leaching of Sulfide Concentrate by Combined Methods

This study was undertaken to develop a cost-effective method of copper leaching in sulfide concentrate involving minerals as chalcopyrite and pyrite. The combined methods involving low temperature roasting of sulfide copper minerals with potassium chlorides without the formation of sulfurous gases and their evolution into the atmosphere is suggested. The effect of experi-mental parameters such as a roasting temperature and time has been pre-sented and discussed in detail. This study was carried out in the roasting temperature range 400&#176C - 600&#176C and roasting time ranges 1 - 4 h with potas-sium chloride. The obtained cake is leached by an aqueous sulfuric acid 60 g/l concentrated at pH = 2 - 2.5 and 4 h. The concentrate, a roasting cake and after leaching solid residue were analyzed by chemical analysis, XRD and SEM-EDX. At temperature ranges 450&#176C - 550&#176C and 3 h of roasting, the pro-cess is activated. The recovery of copper into the solution at optimal roasting condition (500&#176C, roasting time 3 h) is 93.2%. The advantage of the devel-oped method is that, it not requires high roasting temperature and the use of autoclave for leaching. The method gives possibility to leach the concentrate at room temperature and atmospheric pressure, which gives possibility to reduce cost of the process.

ACTIVATION MECHANISM OF AlCl_3 DURING THE LEACHING OF Cu-Ni ORE WITH FeCl_3

After Cu-Ni ore powder pre-soaked in AlCl3 solution.the leaching ratios of copper andnickel can increase obviously.By X-ray diffraction analyses,electron energy spectrum analysesand electrochemical experiments,it is affirmed that,the activation of aluminum ion includestwo aspects:one is the surface change of the ore by the absorption of hydrolysates,and the oth-er is the change of semiconductor characteristics of the metal sulfides by impurity aluminum ionentering the lattice,so that leaching reactions are accelerated.

THERMODYNAMIC AND STRUCTURAL CHEMISTRY DISCUSSIONS FOR OXIDATIVE LEACHING OF Cu－Ni SULPHIDE ORE UNDER ATMOSPHERIC PRESSURE

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Kinetics of Magnesium Slag Leaching by NH_(4)Cl

The leaching kinetics of magnesium slag in ammonium chloride solutions was investigated.The effects of initial ammonium chloride concentration,liquid-solid ratio and reaction temperature on the leaching rate of calcium were determined.The results showed that the leaching rate increased with the increase in initial ammonium chloride concentration,reaction temperature and liquid-solid ratio.It was determined that the leaching rate fit the Avrami equation,and the leaching process was controlled by diffusion.The activation energy was 13.22 kJ/mol.