Search

The behavior of zinc (Zn), copper (Cu), and indium (In) during the precipitation of lead jarosite (Pb-J) was investigated. At a temperature of 150°C and sulfuric acid concentration of 20 g/L, increasing concentrations of Zn, Cu, and In in the solution facilitated the formation of lead jarosite in the solid product. However, the incorporation of Zn remained consistently low, with less than 3% Zn present in precipitates from solutions containing ~ 150 g/L Zn. Mass balance calculations indicated that less than 1.2% of Zn precipitated into the solid products under all experimental conditions. The precipitation of Cu decreased with increasing concentration, while ~ 25% of In precipitated and remained stable across different concentrations. The order of substitution into Pb-J was approximately: In > Cu > Zn. The incorporation of Zn, Cu, and In influenced the morphology of the solid products, with Cu and In exhibiting similar morphologies. Additionally, PbSO4 was encapsulated within the jarosite structure, resulting in the distribution of Zn, Cu, and In between PbSO4 and Pb-J phases, predominantly within Pb-J. [ABSTRACT FROM AUTHOR]

In the Lanping lead–zinc mine area, hazardous jarosite residue produced by the jarosite process seriously threatens the remaining capacity of the tailings pond and the local ecological environment. Therefore, the hematite process has been recommended as an alternative to the jarosite process to overcome the challenge of the hazardous jarosite residue. The recommended reaction conditions for the hematite process are: initial pH = 3.0–4.5, reaction temperature = 150°C, oxygen partial pressure = 0.4 MPa, agitation speed = 500 rpm, and reaction time = 3 h. For the zinc leaching solution containing about 19 g/L Fe2+, the Fe concentration after iron removal via the hematite process was reduced to 2 g/L, and the corresponding iron removal efficiency reached 89%. The Fe content in the hematite product is higher than 55%, and the Zn loss and S pollution in the hematite products were below 1% and 3%, respectively. According to the China Non-Ferrous Metals Association for group standard (T/CNIA 0147-2022), the hematite products produced in this study reached the third grade and can be sold as steelmaking raw materials. Therefore, iron ions in zinc leaching solution can be resourced through the hematite process so as to avoid the stockpiling of iron removal residue. The challenges posed by the limited storage capacity of the tailings pond and the threat of jarosite residue to the local ecology can thus be perfectly solved. [ABSTRACT FROM AUTHOR]

This study employed low-grade hematite acquired from zinc hydrometallurgy to synthesize α-Fe2O3 pigment via high-temperature hydrothermal treatment. This study investigated the effects of hydrothermal conditions on α-Fe2O3 pigment. The results indicate that hydrothermal treatment causes the internal rearrangement of Fe (oxyhydr)oxides into Fe oxides. A high-quality α-Fe2O3 pigment with a Fe content > 69% and Zn and S content < 0.15% and 0.25% was successfully synthesized using the HCl-H2O medium at > 260°C. The average crystal size of α-Fe2O3 pigment was found to be between 45 nm and 80 nm. The α-Fe2O3 pigment consists of prismatic crystals with a smooth surface and distinct edges. The UV-VIS-NIR spectra demonstrated that the α-Fe2O3 pigment strongly absorbs light in the wavelength range of 200–420 nm, and its absorption edge falls between 420 nm and 550 nm. Additionally, the α-Fe2O3 pigment has chromatic values of L* = 37.27–38.69, a* = 5.07–6.26, and b* = 1.70–2.49. All α-Fe2O3 products show similar colors. This work introduces an environmentally friendly method for synthesis of high-quality α-Fe2O3 pigment using iron removal residue in zinc hydrometallurgy. [ABSTRACT FROM AUTHOR]

The controlled synthesis of recyclable hematite in the leaching solution of secondary zinc oxide powder is an urgent problem in the chemical industry and metallurgy fields. In this paper, the effects of the temperature, agitation speed, and seed addition on the contents of iron, sulfur, potassium, sodium, and zinc in the iron removal residues, as well as the iron concentration in the supernatant after iron removal were systematically studied. In addition to the temperature control already reported, we found that the agitation speed can also control the transformation between jarosite and hematite phases. The content of jarosite in the residues can be effectively controlled by adjusting the agitation speed, thereby significantly improving the quality of hematite product, as indicated by SEM-EDS and XRD results. Under temperature of 185 °C, an agitation speed of 500 rpm, and a seed addition of 15 g/L, the iron, sulfur and zinc contents in the filter residues and the iron concentration in the supernatant were 59%, 3.22%, 0.92%, and 4.182 g/L, respectively. Kinetic studies show that the rapid oxidation kinetics is not conducive to the formation of high-quality hematite products. These results can directly guide the process of transformation of harmful jarosite into recyclable hematite from the leaching solution of secondary zinc oxide powder, which is of great practical significance for the controlled and waste-free removal of iron from aqueous solutions in the chemical industry and metallurgy fields. [ABSTRACT FROM AUTHOR]

In response to the problem of additive zinc concentrate consumption and inefficient reduction of ferric ion (Fe3+) in the acid-leaching solution of zinc hydrometallurgy when employing zinc sulfide concentrate, various parameters were examined. These included particle size, temperature, addition coefficient of the concentrate, and sulfuric acid concentration, all aimed at enhancing the rate of Fe3+ reduction. The results indicated that increasing the temperature from 80 to 120°C enhanced the Fe3+ reduction rate from 93.3 to 98%, reducing the time from 180 to 60 min. Furthermore, enlarging the particle size of the concentrate from below − 58/+ 48 μm to − 246/+ 150 μm, lowering the Fe3+ concentration in the reduction solution to < 0.5 g/L, and decreasing the addition coefficient from 1.8 to 1.5 further enhanced the reduction process. Additionally, employing a pressure process to increase the reduction temperature proved to be an effective strategy for enhancing the utilization rate of the zinc sulfide concentrates and the Fe3+ reduction rate, thereby reducing the amount of reduction residue and facilitating its subsequent treatment. [ABSTRACT FROM AUTHOR]

The re-dissolution of unstable iron oxides during the low-temperature hematite process significantly increases the iron ions concentration in solution after iron removal in zinc hydrometallurgy. The reason for the re-dissolution of precipitated hematite was determined through simulated iron removal experiments in an autoclave. It was caused by e.g., weak acid solubility resistance in high acidity and the poor crystallinity of hematite. In order to solve the problem of re-dissolution of hematite precipitated in a short time, three improving methods, namely increasing the reaction temperature, extending the reaction time in the autoclave, and reducing the acidity of hematite process, have been systematically studied. Increasing the reaction temperature is not economical from the perspective of industrial production, and extending the reaction time does not meet the original intention of the zinc smelter to increase production capacity. Although zinc sulfide concentrate as a neutralizing agent can increase the pH of the slurry, the hematite produced does not have the potential for sales. When 12 g/L zinc calcine was added, the residual Fe concentration in solution after iron removal within 90 min can be controlled below 1 g/L, and high-grade hematite with Fe, Zn, and S contents of 56.62%, 2.09%, and 2.78% can be produced. [ABSTRACT FROM AUTHOR]

Iron in the leaching solution with high K+ and Na+ concentrations was usually precipitated as the typical hazardous and toxic jarosite residues. However, this method of treatment has been greatly restricted by increasingly strict environmental regulations. Here we propose that iron can be precipitated from the solution with high K+ and Na+ concentrations as recyclable hematite products by adjusting the concentration ratio of sodium and potassium ions in the solution. The transformation behavior of jarosite into hematite in high concentration potassium ion and sodium ion solution was explained based on collision theory. The results indicated that in instances where the concentration ratio of Na+/K+ is ≥ 4:1, the iron present in the solution can be effectively precipitated as a recyclable hematite product, as opposed to forming the conventional hazardous jarosite residue, even under conditions where the potassium ion concentration reaches levels as high as 4 g/L. On the other hand, thermodynamic and molecular dynamics simulations indicate that at a temperature of 185 °C, the decomposition transformation of Na-jarosite (32.64 kJ and 7.25 eV) is more energetically advantageous compared to that of K-jarosite (61.07 kJ and 15.31 eV). The results were verified by the leaching solution from smelting industry. The iron content in the residues is above 58%, the sulfur content is below 4%, the zinc content is below 1%, and the total iron concentration in the supernatant is about 4 g/L, reaching the production index of the smelting industry. The green, environmentally friendly, and recyclable separation of iron in a solution with high concentrations of potassium and sodium ions is achieved, which is of great significance for the treatment of iron-containing solution and wastewater in the chemical industry and metallurgy fields. [ABSTRACT FROM AUTHOR]

The component solubilities of FeSO4·7H2O–ZnSO4·xH2O–H2O (x = 6, 7) systems at 25 and 40°C were calculated using Pitzer's ion-interaction model and its Harvie–Weare extension. The calculated results of FeSO4 · 7H2O–ZnSO4· xH2O–H2O (x = 6, 7) systems are in good agreement with the experimental data both at 25 and 40°C. The model can be extended to a wider range of temperatures for single- or multi-component systems using temperature-dependent binary parameters, providing an alternative approach for the prediction of electrolyte solubilities. [ABSTRACT FROM AUTHOR]

In this study, hydrometallurgical processes involving pressure acid leaching and solvent extraction were developed to aid recovery of indium from zinc slag, which is produced in the imperial smelting process. Four different acid leaching methods were studied, namely atmospheric leaching, atmospheric leaching with KMnO4, roasting-atmospheric leaching, and oxygen pressure leaching in a sulfuric acid medium. Oxygen pressure acid leaching is the most effective method for indium extraction, and 94.1% of indium was leached under the optimum conditions, i.e., 300 g/L H2SO4,oxygen pressure 0.4 MPa, liquid/solid ratio 10 mL/g, and temperature 100°C for 5 h. X-ray diffraction and scanning electron microscopy examination of the raw material and leaching residue samples indicated that the intermetallic compounds Cu5Zn8and Cu2Zn, metallic zinc, and iron in the raw material dissolved, leaving the insoluble components PbSO4 and Pb as the major compounds in the leaching residue. A 98.5% proportion of the indium in the leaching solution was selectively extracted with 30% bis(2-ethylhexyl) phosphate and 70% kerosene by three-stage counter-current extraction, and 99.5% of the indium in the loaded organic phase was stripped by 6 mol/L HCl through four-stage counter-current stripping. The overall recovery yield of indium through all processes was approximately 92%. [ABSTRACT FROM AUTHOR]

Nickel was separated and precipitated with potassium nickel sulfate hexahydrate [K2Ni(SO4)2·6H2O] from acidic sulfate solution, a leach solution from molybdenum-nickel black shale. The effects of the potassium sulfate (K2SO4) concentration, crystallization temperature, solution pH, and crystallization time on nickel(II) recovery and iron(III) precipitation were investigated, revealing that nickel and iron were separated effectively. The optimum parameters were K2SO4 concentration of 200 g/L, crystallization temperature of 10°C, solution pH of 0.5, and crystallization time of 24 h. Under these conditions, 97.6% nickel(II) was recovered as K2Ni(SO4)2·6H2O crystals while only 2.0% of the total iron(III) was precipitated. After recrystallization, 98.4% pure K2Ni(SO4)2·6H2O crystals were obtained in the solids. The mother liquor was purified by hydrolysis-precipitation followed by cooling, and more than 99.0% K2SO4 could be crystallized. A process flowsheet was developed to separate iron(III) and nickel(II) from acidic-sulfate solution. [ABSTRACT FROM AUTHOR]

The dissolution kinetics of hemimorphite with low sulfuric acid solution was investigated at high temperature. The dissolution rate of zinc was obtained as a function of dissolution time under the experimental conditions where the effects of sulfuric acid concentration, temperature, and particle size were studied. The results showed that zinc extraction increased with an increase in temperature and sulfuric acid concentration and with a decrease in particle size. A mathematical model able to describe the process kinetics was developed from the shrinking core model, considering the change of the sulfuric acid concentration during dissolution. It was found that the dissolution process followed a shrinking core model with 'ash' layer diffusion as the main rate-controlling step. This finding was supported with a linear relationship between the apparent rate constant and the reciprocal of squared particle radius. The reaction order with respect to sulfuric acid concentration was determined to be 0.7993. The apparent activation energy for the dissolution process was determined to be 44.9 kJ/mol in the temperature range of 373 K to 413 K (100 °C to 140 °C). Based on the shrinking core model, the following equation was established: [ABSTRACT FROM AUTHOR]

Iron in the leaching solution with high K+ and Na+ concentrations was usually precipitated as the typical hazardous and toxic jarosite residues. However, this method of treatment has been greatly restricted by increasingly strict environmental regulations. Here we propose that iron can be precipitated from the solution with high K+ and Na+ concentrations as recyclable hematite products by adjusting the concentration ratio of sodium and potassium ions in the solution. The transformation behavior of jarosite into hematite in high concentration potassium ion and sodium ion solution was explained based on collision theory. The results indicated that in instances where the concentration ratio of Na+/K+ is ≥ 4:1, the iron present in the solution can be effectively precipitated as a recyclable hematite product, as opposed to forming the conventional hazardous jarosite residue, even under conditions where the potassium ion concentration reaches levels as high as 4 g/L. On the other hand, thermodynamic and molecular dynamics simulations indicate that at a temperature of 185 °C, the decomposition transformation of Na-jarosite (32.64 kJ and 7.25 eV) is more energetically advantageous compared to that of K-jarosite (61.07 kJ and 15.31 eV). The results were verified by the leaching solution from smelting industry. The iron content in the residues is above 58%, the sulfur content is below 4%, the zinc content is below 1%, and the total iron concentration in the supernatant is about 4 g/L, reaching the production index of the smelting industry. The green, environmentally friendly, and recyclable separation of iron in a solution with high concentrations of potassium and sodium ions is achieved, which is of great significance for the treatment of iron-containing solution and wastewater in the chemical industry and metallurgy fields. [ABSTRACT FROM AUTHOR]