Zinc Extraction Rate Research Articles

Bioleaching of Sulfide Concentrates with Different Copper and Zinc Contents and Evaluation of Bioleach Residue Grade

Bioleaching of sulfide concentrates with different copper and zinc contents using two cultures of acidophilic chemolithotrophic microorganisms, which were grown at 30 and 35°C, was studied. The average leaching rate of copper was shown to be directly dependent on the copper content in the concentrate. The leaching rate of zinc was found to depend not only on the zinc content but also on the copper content. At the same time, the specific leaching rate of copper varied insignificantly (28–45 mg/(g day)), while the change in the specific leaching rate of zinc was much more pronounced (107–319 mg/(g day)) and depended on the metal contents in the concentrates. Under all conditions of bioleaching, the specific rate of zinc extraction into the aqueous phase increased significantly with an increase in the copper content in the concentrates, which indicated galvanic interactions between sulfide minerals. The possibility of the obtainment of the copper concentrates containing negligible amounts of zinc after bioleaching of the concentrates, in which the content of copper exceeded that of zinc and was not less than 10%, was shown. Bioleaching of the concentrates containing more zinc than copper is impractical.

Extracting bio-zinc and taurine from Pinctada martensii meat.

Recently, intensive processing of marine resources has attracted considerable attention. In order to further utilize the byproducts of aquatic shellfish (Pinctada martensii meat) with high value, this study proposes a method of extracting zinc and taurine from P. martensii meat. Zinc was first extracted from P. martensii meat with an ultrasonic crusher, and then taurine was further extracted by ultrasonic-assisted water extraction from the remaining shellfish. After optimization, the biological zinc extraction rate reached 8.63%, and the taurine extraction rate reached 0.71%. Meanwhile, the parameters for cation exchange separation and taurine purification were optimized, in which the injection volume, pH value, and elution rate were set to 8.0mL, 4.5, and 3.0mL/min, respectively. Ultimately, the purity the extracted taurine reached 98.16%. This study provides a novel method for the extraction of biological zinc and taurine by deep processing of shellfish meat.

Leaching Kinetics of Hemimorphite in Ammonium Chloride Solution

The leaching kinetics of hemimorphite (Zn4Si2O7(OH)2·H2O) in ammonium chloride solution was presented in detail. Effects of stirring speed (150–350 rpm), leaching temperature (75–108 °C), particle size of hemimorphite (45–150 μm), and the concentration of ammonium chloride (3.5–5.5 mol/L) on the zinc extraction rate were studied. The zinc extraction rate enhanced slightly with the increase in stirring speed, but increased significantly with an increase in the leaching temperature and ammonium chloride concentration. Zinc extraction was enhanced significantly in the first 60 min with decreasing particle size, but had little effect on the leaching process after 60 min. Scanning electron microscopy (SEM) analysis showed that some silica gel formed in the leaching process was not separated from the hemimorphite surface, but covered some of the active particle surface. The Elovich equation successfully described the leaching kinetics of hemimorphite in ammonium chloride solution with an apparent activation energy of 405.14 kJ/mol at temperatures of 75–90 °C and 239.61 kJ/mol at temperatures of 95–108 °C, which is characteristic for a chemically-controlled process. Silica gel is generated at temperatures of 75–90 °C and decomposed into silica at temperatures of 95–108 °C.

Selective reduction process of zinc ferrite and its application in treatment of zinc leaching residues

The traditional zinc hydro-metallurgy generates a large amount of zinc ferrite residue rich in valuable metals. The separation of iron is crucial for resource recycling of valuable metals in zinc ferrite residue. A novel selective reduction roasting–leaching process was proposed to separate zinc and iron from zinc leaching residue which contains zinc ferrite. The thermodynamic analysis was employed to determine the predominant range of Fe3O4 and ZnO during reduction roasting process of zinc ferrite. Based on the result of thermodynamic calculation, we found that V(CO)/V(CO+CO2) ratio is a key factor determining the phase composition in the reduction roasting product of zinc ferrite. In the range of V(CO)/V(CO+CO2) ratio between 2.68% and 36.18%, zinc ferrite is preferentially decomposed into Fe3O4 and ZnO. Based on thermogravimetric (TG) analysis, the optimal conditions for reduction roasting of zinc ferrite are determined as follows: temperature 700–750 °C, volume fraction of CO 6% and V(CO)/V(CO+CO2) ratio 30%. Based on the above results, zinc leaching residue rich in zinc ferrite was roasted and the roasted product was leached by acid solution. It is found that zinc extraction rate in zinc leaching residue reaches up to 70% and iron extraction rate is only 18.4%. The result indicates that zinc and iron can be effectively separated from zinc leaching residue.

Leaching and recovery of zinc from leaching residue of zinc calcine based on membrane filter press

The feasibility of leaching and recovery of zinc from zinc leaching residue (ZLR) based on a membrane filter press (MFP) was investigated. Experimental results show that zinc calcines with particle sizes of less than 106 μm and chambers of widths of 30 mm are appropriate for establishing uniform filter cakes to obtain acceptable leaching and recovery results. The leaching of zinc from ZLR performed via washing at 90 to 96 °C for 90 min with spent electrolyte using a MFP results in a zinc extraction rate of 97%, and almost all of the zinc leached are recovered after water washing with MFP, thereby avoiding any loss in the ZLR. Compared with the traditional hot concentrated acid leaching process, the process based on MFP as a leaching reactor is able not only to ensure a high extraction rate but also to reduce the leaching time. Moreover, the thickening, pulping, second leaching, washing, filtering and pressing could be integrated and realized using a single MFP.

Bioleaching of complex polymetallic sulfide ores by mixed culture

Bacterial leaching of single sulfide minerals and polymetallic sulfide ores was operated in shake flasks and small-scaled columns. The results show that bioleaching of jamesonite is not accessible, the iron extraction rate of pyrrhotite bioleaching reaches 98.2% after 26 d, and the zinc extraction rate of marmatite bioleaching reaches 92.3%, while the corresponding iron extraction reaches only 13.6% after 29 d. Pulp density has a significant effect on metal extraction of pyrrhotite and marmatite bioleaching. The corresponding metal extraction rate decreases with the increase of pulp density. For the polymetallic sulfide ores, zinc extraction of 97.1% is achieved after bioleaching in shake flasks for 10 d, while only 7.8% is obtained after bioleaching in small-scaled column. Analytical results of scanning electron microscopy (SEM) and energy dispersive X-ray analysis (EDX) reveal that large amount of calcium sulfate is formed on the mineral surface.

Effects of mechanical activation on physicochemical properties and alkaline leaching of hemimorphite

Effects of mechanical activation on physicochemical properties and alkaline leaching of hemimorphite from Lanping, Yunnan province were studied. The results showed that both dry milling and mechano-chemical milling could enhance zinc extraction rate and shorten the leaching time. Scanning electron microscope (SEM), particle size distribution (PSD), X-ray diffraction (XRD) analysis demonstrated that different milling times and modes could form different morphologies, particle size distributions and crystal structures, thus influence zinc recovery differently.

Effect of Cu 2+ ions on bioleaching of marmatite

The effect of Cu 2+ ions on bioleaching of marmatite was investigated through shake leaching experiments. The bacteria inoculated are a mixed culture of Acidithiobacillus ferrooxidans, Acidithiobacillus thiooxidans and Lepthospirillum ferrooxidans. The results show that zinc is selectively leached, and the addition of appropriate content of Cu 2+ ions has positive effect on the bioleaching of marmatite. SEM and EDX analyses of the leaching residue reveal that a product layer composed of iron sulfide, elemental sulfur and jarosite forms on the mineral surface. The biooxidation of elemental sulfur is catalyzed by the Cu 2+ ions, which eliminate the barrier to bioleaching of marmatite and keep low pH value. With the addition of 0.5 g/L Cu 2+ ions, the maximum zinc extraction rate reaches 73% after 23 d at the temperature of 30 °C with the pulp density of 10%, while that of iron is only about 10%.

Dynamics in simultaneous electro-generative leaching for sphalerite-MnO 2

The principle for the electro-generative leaching was applied to simultaneous leaching of sphalerite-MnO 2. A galvanic system for the bio-electro-generative leaching was set up. The effects of grain size and temperature on rate of zinc extraction from sphalerite under the conditions of presence and absence of Acidithiobacillus ferrooxidans (A. ferrooxidans) were studied, respectively. The results show that with bacteria, the maximum extraction of zinc from the ores with grain size of 16.6 urn can reach 32.01% after leaching for 12 h, while to obtain the same extraction ratio in the traditional bio-leaching route (i.e. not electro-generative one) 10 d is needed to ore granules with same size. The unreacted shrinking core model was used for describing the reaction-relative and diffusion-relative phenomena presented in the process of the electro-generative leaching with and without bacteria, which is considered to be diffusion controlled. The activation energies of the anodic reaction for leaching system in the presence and absence of bacteria are 11.97 and 14.39 kJ/mol, respectively, indicating that leaching rate can be decreased by A. ferrooxidans. SEM was used to study the effect of A. ferrooxidans on the ores in the simultaneous electro-generative leaching, which indicates that the produced sulfur on the surface of the sulfides can be oxidized by A. ferrooxidans after bio-electro-generative leaching for 24 h, and the transferred charge due to the bacterial oxidation is up to 17.86%, which is an important part of the output electric quantity.

Solvent extraction of copper and zinc from bioleaching solutions with LIX984 and D2EHPA

The solvent extraction of copper and zinc from the bioleaching solutions of low-grade sulfide ores with LIX984 and D2EHPA was investigated. The influences of extractant content, aqueous pH value, phase ratio and equilibration time on metals extraction were studied. The results show that LIX984 has a higher selectivity for copper than for iron, zinc and other metals, and has the copper extraction rate above 97%, while the zinc and iron extraction rate is less than 1.6% respectively. Zinc extraction is carried out following the copper extraction from the raffinate. The zinc extraction with di(2-ethylhexyl) phosphoric acid (D2EHPA) is low due to its poor cation exchange. A sodium salt of D2EHPA is used and the zinc extraction rate is enhanced to above 98%. Though iron (III) is strongly extracted before the extraction of zinc by D2EHPA, it is difficult to strip iron from the organic phase by sulfuric acid. The zinc stripping rate is above 99% with 100 g/L sulfuric acid, while that of iron is 0.16%. Hence, the separation of zinc from iron can be achieved by the selective stripping.

Relative importance of diffusion and reaction control during the bacterial and ferric sulphate leaching of zinc sulphide

A study has been undertaken on the bacterial and ferric sulphate leaching of sphalerite, with the aim of observing the relative importance of both diffusion and reaction control, across a range of operating conditions. To facilitate this kinetic analysis a mixed-control rate equation was developed based upon the shrinking particle and shrinking core models, featuring both an intrinsic rate of zinc extraction and a product layer diffusion coefficient. The ferric sulphate oxidation of a pure sphalerite sample was first studied, and the process was found to be mainly controlled by surface diffusion, thought to be due to formation of the elemental sulphur product layer. The mesophilic bacterial oxidation of a high-grade zinc ore was studied at 35 °C, and the process was observed to be controlled by both chemical reaction and diffusion. However, during the mesophilic bacterial oxidation of a low-grade zinc ore at 25 °C, diffusion was found to be rate limiting. It was proposed that this diffusion resistance arises from an unreacted layer of gangue material.

Test cells for plating

The traditional zinc hydro-metallurgy generates a large amount of zinc ferrite residue rich in valuable metals. The separation of iron is crucial for resource recycling of valuable metals in zinc ferrite residue. A novel selective reduction roasting–leaching process was proposed to separate zinc and iron from zinc leaching residue which contains zinc ferrite. The thermodynamic analysis was employed to determine the predominant range of Fe3O4 and ZnO during reduction roasting process of zinc ferrite. Based on the result of thermodynamic calculation, we found that V(CO)/V(CO+CO2) ratio is a key factor determining the phase composition in the reduction roasting product of zinc ferrite. In the range of V(CO)/V(CO+CO2) ratio between 2.68% and 36.18%, zinc ferrite is preferentially decomposed into Fe3O4 and ZnO. Based on thermogravimetric (TG) analysis, the optimal conditions for reduction roasting of zinc ferrite are determined as follows: temperature 700–750 °C, volume fraction of CO 6% and V(CO)/V(CO+CO2) ratio 30%. Based on the above results, zinc leaching residue rich in zinc ferrite was roasted and the roasted product was leached by acid solution. It is found that zinc extraction rate in zinc leaching residue reaches up to 70% and iron extraction rate is only 18.4%. The result indicates that zinc and iron can be effectively separated from zinc leaching residue.

The kinetics of zinc extraction in the di(2-ethylhexyl) phosphoric acid, n-heptane-Zn(ClO 4) 2, HClO 4, H 2O system using the rotating diffusion cell

The kinetics of zinc extraction from perchlorate solutions by di(2-ethylhexyl) phosphoric acid in n-heptane were measured using the rotating diffusion cell technique. The extraction of zinc is controlled by the mass transfer of reactants (Zn 2+ and D2EHPA) to the interface: bulk pH has little effect. It appears that the chemical reaction rate is so fast that it has a negligible effect on the overall extraction rate. A mass transfer mathematical model was developed which is adequate for predicting the extraction rate under variable conditions of zinc concentration, D2EHPA concentration and pH. The effect of using a partially loaded organic extractant was investigated and the system was found to be mass transfer controlled. A second mathematical model was developed which predicts that the speciation of organic-complexed zinc changes with increasing preload and, at high loadings, the direction of ZnL 2·HL and ZnL 2·(HL) 2 flux reverses, with these species providing extractant to the interface. At very high loadings, ZnL 2·HL provides almost all the extractant to the interface. Experimental studies of the effect of temperature on the rate of zinc extraction resulted in calculation of an activation energy of 12.4 kJ/mol, which is consistent with a diffusion-controlled mechanism. The extraction rate decreases significantly for a very small filter pore size, while there appears to be little or no effect for larger filter pore sizes. It was therefore concluded that, for the filter pore size used in this study, the filter pores do not pose an additional resistance to mass transfer.

Analysis of Transport Rate of Zinc Extraction through Liquid Surfactant Membrane

Abstract Analysis of the transport rate of a metal ion through a liquid surfactant membrane is important for understanding an extraction system. A facilitated transport model for zinc extraction through a liquid surfactant membrane is proposed for the analysis of the transport rate. Based on the model, the transport rates, including the interfacial reaction rates and the diffusion rate of the zinc ion, are analyzed. From an analysis of the model, it is shown that the reactions at both interfaces are not in equilibrium before extraction is complete. It is also shown that the transport rates are not equal value in the early stage of a run. Parametric effects on the transport rates are also illustrated.

Extraction kinetics of zinc from aqueous perchlorate solution by D2EHPA dissolved in Isopar-H

The rate of extraction of zinc(II) from aqueous perchlorate solutions at 1 M ionic strength by di(2-ethylhexyl) phosphoric acid (DEHPA) in Isopar-H (ESSO chemicals) was studied. The study was performed using a modified Lewis cell at 25°C. The experimental hydrodynamic conditions were chosen so that the contribution from diffusion on the measured rate of reaction was minimized. The rate of zinc extraction was measured at different chemical composition by varying zinc, hydrogen ion and DEHPA concentrations. The data were analysed in terms of pseudo-first order constants and a reaction mechanism was developed where a zinc-DEHPA complex is formed at the interface. The results of this kinetic model are in agreement with the equilibrium study reported previously for the same system.

THE KINETICS OF ZINC, COBALT AND NICKEL EXTRACTION IN THE D2EHPA-HEPTANE-HC104 SYSTEM USING THE ROTATING DIFFUSION CELL TECHNIQUE

ABSTRACT The kinetics of the extraction of zinc, cobalt and nickel from perchlorate solutions using di 2-ethyl-hexyl phosphoric acid (D2EHPA) dissolved in heptane were studied using the Rotating Diffusion Cell technique. The extraction of each metal was investigated individually over a wide range of metal concentration, extractant concentration, pH and temperature conditions. The data were analysed in terms of a mass transfer with chemical reaction (MTWCR) mechanism. Hughes and Rod'/s generalized MTWCR model was used to fit the cobalt data using kinetic and equilibrium parameters. The zinc and nickel data were quantitatively described within the framework of the MTWCR model. The zinc extraction rate was so fast that mass transfer alone was rate controlling. The nickel extraction experiments were so slow that the metal-ligand complex formation was incomplete in the aqueous film. Some reaction was determined to be occurring in the aqueous bulk solution as well.

A kinetic study on the pressure leaching of sphalerite

The dissolution of sphalerite (ZnS) in sulfuric acid solution under oxygen pressure was investigated. Effects of temperature, percent solids, agitation, sample size, oxygen partial pressure and foreign ions were evaluated. The effect of hydrogen pretreatment on sphalerite leaching rate was also examined. Leaching of sphalerite at 90°C and 150 psi oxygen pressure was found to occur at a constant rate. This rate was determined from the experimental data observed under the different leaching conditions mentioned above. The constant leaching rate was attributed to the chemical reaction occurring on the surface of the flat-plate type sphalerite sample. The rate-controlling step of the reaction was determined to be the oxidation of hydrogen sulfide to elemental sulfur. Oxidation of hydrogen sulfide was studied through the addition of iron and through the observation of the change in iron concentration during leaching. The oxidation was concluded to be by reaction with ferric ion rather than by direct oxygen oxidation. Leaching tests run with samples pretreated with hydrogen do not show any increase in the rate of zinc extraction.

The effect of carbon dioxide and particle surface area on the microbiological leaching of a zinc sulfide concentrate

AbstractThe effects of carbon dioxide‐enriched air on the rate of zinc extraction during the microbiological leaching of a, high‐grade zinc sulfide concentrate by Thiobacillns ferrooxidans have been studied. Under normal air‐aeration conditions, the leach rate is limited initially by the availability of solid substrate surface area per unit volume of leach liquor, then by availability of carbon dioxide. If carbon dioxide‐enriched air is supplied, along with excess substrate, the zinc extraction rate increases as the carbon dioxide content increases until some other, as yet unknown, factor becomes limiting.

Microbiological leaching of a zinc sulfide concentrate

AbstractThe microbiological extraction of zinc from a high‐grade zinc sulfide concentrate has been investigated, using a pure strain of Thiobacillus ferrooxidans. Conditions such as temperature, pH, pulp density, nutrient, concentration, and specific surface of solids have been studied in terms of their effects on zinc extraction rate and in some instances on final zinc concentration in solution. Where appropriate, optimum conditions for leaching have been specified.