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A choline chloride/urea natural deep eutectic solvent (ChCl NADES) was prepared via a green chemistry method and used to leach Zn and Mn oxides from conventional Zn–C scrap batteries. FTIR and 1H NMR spectroscopy were used to characterize the NADES. The leaching kinetics of the Zn and Mn oxides was monitored at isothermal conditions (80, 100, 125, and 150 °C) and at two solid/NADES ratios: 3.3 and 10 g dm−3. It was possible to dissolve Zn and Mn oxides under all of tested conditions, reaching more than a 95% recovery for both metals at 150 °C after 90 min, whereas, at 25 °C, it was possible to leach up to 90% of the Zn and 30% of the Mn after 4320 min (72 h). Furthermore, the leaching kinetics was controlled by the boundary layer, coincident with a shrinking core model. According to the Arrhenius plot, the activation energy for Zn ranges from 49.13 to 52.21 kJ mol−1, and that for Mn ranges from 46.97 to 66.77 kJ mol−1.

Biological methods for leaching of nonferrous and noble metals from its sulfide ores are widely applied at industrial enterprises of different countries. This process is based on the use of the oxidative activity of acidophilic microorganisms. Since all bio systems are quite sensitive to the temperature, bacterial leaching process also significantly effects. In the present study, the impact of temperature on bacterial leaching of Zn from its sulphide ore, sphalerite, was investigated using ore adapted iron oxidizing bacteria. The bacteria were isolated from mine drainage samples and subjected to gene sequencing. The acquired nucleotide sequence revealed that the isolate was Leptospirillum ferriphilum . The nucleotide sequence of L. ferriphilum isolate was submitted to National Center for Biotechnology Information (NCBI) and accession number KF743135 was assigned. Using the isolate, the Zn leaching data were collected in the 298–318 K temperature range. The results showed that leaching of Zn increases with temperature until optimum temperature of 313 K and achieves highest leaching efficiency of 96.96% within 20 days. Since bioleaching of minerals have become increasingly applied in different mining industries, there is immense important to analyze mechanistically-based kinetics for the design, optimization, operation, and control of biochemical processes. The kinetic study showed that the rate of Zn leaching was maximized at the optimum temperature. Further, the leaching data were analyzed using shrinking core model which revealed that the rate of leaching was inhibited by diffusion through product layer. Reaction kinetics is also to be contrasted with thermodynamics. Using Arrhenius law of thermodynamics, it was found that activation energy for Zn bioleaching reaction was 39.557 kJ mol −1 . Such investigations will be necessitated for designing and implanting the ideal bioleaching system for metal bio-mining industries.

A mathematical model based on the computational fluid dynamics method, heat and mass transfer in porous media and the unreacted shrinking core model for the oxidation reaction of an individual magnetite pellet during preheating was established. The commercial software COMSOL Multiphysics was used to simulate the change in the oxidation degree of the pellet at different temperatures and oxygen concentrations, and the simulated results were compared with the experimental results. The model considered the influence of the exothermic heat of the reaction, and the enthalpy change was added to calculate the heat released by the oxidation. The results show that the oxidation rate on the surface of the pellet is much faster than that of the inside of the pellet. Temperature and oxygen concentration have great influence on the pellet oxidation model. Meanwhile, the exothermic calculation results show that there is a non-isothermal phenomenon inside the pellet, which leads to an increase in temperature inside the single pellet. Under the preheating condition of 873–1273 K (20% oxygen content), the heat released by the pellet oxidation reaction in a chain grate is 7.8 × 10 6 –10.8 × 10 6  kJ/h, which is very large and needs to be considered in the magnetite pellet oxidation modelling.

Kinetics of the attack of a Tunisian phosphate ore by phosphoric acid solution was calorimetrically investigated using a differential reaction calorimeter. Determination of the time constants (τ1 and τ2) and the transfer function of this device allowed calculation of the thermogenesis curves which were used for the kinetic study at different temperatures. It was found that the attack rate increased with increasing temperature and the kinetic results agree with the shrinking-core model with an ash layer diffusion control. The resulting apparent activation energy equals 25.4 ± 1.8 kJ mol−1, which is in the range determined by the isoconversional model (11.1–26.3 kJ mol−1).

In this paper, magnesium sulfate was used as a lixiviant to recover rare earth from kaolin. The effects of column leaching conditions, such as the concentration of magnesium sulfate, liquid/solid ratio, flow rate, and pH of the magnesium sulfate solution on the leaching efficiency of rare earth and aluminum, were investigated. In addition, the leaching kinetics of rare earth and aluminum were analyzed based on the magnesium concentration. The results showed that the optimal leaching conditions 0.2 mol/L magnesium sulfate solution with no pH adjustment, 1.2:1 for the liquid/solid ratio, and at a flow rate of 0.5 mL/min led to an 89% rare earth leaching efficiency and an 81% aluminum leaching efficiency. The aluminum leaching efficiency by magnesium sulfate was 7% less than that by ammonium sulfate. Moreover, the equilibrium time for rare earth was 33 min shorter than aluminum, which is of benefit to reduce the leaching time of aluminum. The leaching kinetic data fitted an unreacted shrinking-core model. Semi-empirical equations based on the apparent rate constant and magnesium concentration of rare earth and aluminum were established, and the reaction orders for rare earth and aluminum were determined to be 1.69 and 1.61, respectively. The results of this study could help to better understand and optimize the leaching process by magnesium sulfate.

The removal of heavy metals from industrial sludge through biosolubilization using sulfur-oxidizing bacteria has been shown to be a promising technology, but the process with surplus concentration of sulfur causes re-acidification of the treated residues and creates environmental issues. Thus, the study for investigating the effect of sulfur concentration on the heavy metal biosolubilization system, with an emphasis on optimizing the sulfur concentration, is of immense importance. In this study, the experiments to investigate the effect of sulfur concentration on the performance of biosolubilization were carried out using 2–10 g/L elemental sulfur on heavy metal-laden electroplating sludge (50 g/L). The sludge-acclimatized, sulfur-grown Acidithiobacillus ferrooxidans isolate was used as sulfur-oxidizing bacteria. For the type of sludge used in this study, high pH reduction, short lag phase, and high heavy metal solubilization efficiencies were obtained in the treatment with 6 g/L sulfur. The kinetic study showed that the rate constant values of heavy metal solubilization were relatively high while using sulfur concentration of 6 g/L. The analysis using shrinking core model of fluid–particle reaction kinetics explicated that chemical reaction step controls the rate of heavy metal biosolubilization. The study provides an optimized strategy to design an efficient biosolubilization system for anticipated energy source.

Basic oxygen furnace (BOF) slag is an industrial waste produced from steel-making. It can be utilized as building material, but its high content of free CaO (f-CaO) causes volume expansion of materials and limits its utilization. However, carbonation of BOF slag can decrease the f-CaO content, improve stability, and reduce carbon emissions. This study investigated the influence of temperature, pressure, liquid to solid, reaction time, and stirring pattern on f-CaO consumption and CO2 sequestration, which reached a maximum f-CaO consumption and C02 sequestration of 99.58% and 5.12% (51.2 g COs/Kg BOF slag), respectively, under optimum conditions. According to the results of the XRD patterns of carbonated slag, no peaks of CaO were detected, the peaks of Ca2Fe205 and Ca2Si04 were slightly reduced, and new peaks of CaC03 were detected. The reaction process has been described by a shrinking core model revealing that the diffusion of reactants through the product layer was the rate-limiting step for carbonation. The kinetic equation for C02 sequestration was derived as: InK = - 2132.83T_1-9.1543. This approach presents a green, cost-effective, and rapid method for enhancing steel slag utilization while capturing and storing C02. The method proposed in this paper holds significant potential for wider adoption.

This article mainly studies the process optimization and kinetics of leaching magnesium from low-grade magnesite in ammonium bisulfate (NH4HSO4) solution. The effects of leaching time, leaching temperature, ammonium bisulfate concentration and excess rate of ammonium bisulfate on the magnesium leaching rate were investigated, and the composition and microstructure of magnesite before and after leaching were analyzed. Through optimization based on the response surface method based on the center combination design, the optimal leaching conditions are determined as follows: the leaching time is 7.7 h, the leaching temperature is 94°C, the mass concentration of NH4HSO4 is 19.2%, and the excess rate of NH4HSO4 is 18.7%. Under the optimal conditions, the leaching rate of magnesium was 95.9%. Using a shrinking core model, dissolution curves were evaluated. The leaching kinetics of magnesite in ammonium bisulfate solution show that the leaching was controlled by a surface chemical reaction with an activation energy of 43.40 kJ/mol.

High gold-containing material (HGCM) is the product of waste printed circuit boards (WPCBs) by pyrometallurgy and electrolytic refining. This paper proposes a mixing method based on variable stirring speed to enhance the leaching of gold and copper. The leaching behavior of gold and copper in the chlorination system from HGCM under variable stirring speed was studied, and the results showed that a variable stirring speed can enhance liquid flow and save reaction time. Temperature and acid concentration affect the leaching of metals. Under optimum conditions, gold and copper can be completely leached. Moreover, the gold leaching process was found to conform to the surface chemical-controlled shrinking core model, according to the kinetic curve and an activation energy of 49.47 kJ/mol. In addition, combined with XRD analysis of the raw material and leaching residue, the main phases in HGCM are AuCu3, Au, and Au3Cu. This process delivered complete copper and gold leaching from HGCM under laboratory conditions, and provided a more efficient and fast method for chlorination leaching of metals.

Manganese slag production has become a critical problem due to the increasing demand for manganese ore in lithium-ion battery cathode materials, posing serious resource and environmental concerns. The effective recovery of residual Mn/Fe is frequently limited by conventional separation techniques including flotation, magnetic separation, and gravity separation, which have either low extraction rates or high operating costs. To address this issue, herein, this work proposes a unique hydrocyclone separation-leaching collaboration approach via using the Unreacted Shrinking Core Model (USCM) with Computational Fluid Dynamics (CFD) simulations for the first time. According to simulated and experimental results, the procedure can achieve an excellent 99.84% separation efficiency of Fe2O3 to the underflow, while also attaining reaction rates of 78.27% for MnO and 15.44% for Fe2O3. This innovation not only validates the feasibility of simultaneous leaching and separation but also expands the application scope of hydrocyclones from traditional separation to reaction kinetics, offering a sustainable and eco-friendly solution for manganese slag recycling.