This study investigates the ultrasound-assisted leaching of Li and Co from spent batteries using a deep eutectic solvent (DES) composed of polyethylene glycol and thiourea. The synergistic effect of ultrasound and DESs was explored to enhance the efficiency of Li and Co recovery. The experimental results demonstrated that ultrasound significantly accelerates the leaching process, achieving up to four times higher recovery rates compared to traditional methods. Optimal leaching conditions were identified at a solid-to-liquid ratio of 0.02 g/g, a temperature of 160 °C, and periodic ultrasound exposure. Under these conditions, the leaching efficiency reached 74% for Li and 71% for Co within 24 h. A kinetic analysis revealed that the ultrasound application shifts the rate-limiting step from a mixed control of mass transfer and chemical reactions to predominantly chemical reaction control, reducing the activation energy by approximately 27%.

The study investigates the application of high-voltage electrical pulses (HVEP) as a pretreatment to enhance the leaching efficiency of rare earth elements (REE) from coal ash (CA) produced from the combustion of Ekibastuz Basin coal in Almaty, Kazakhstan. HVEP treatment was applied to the finest (<40 µm) non-magnetic fraction of CA under controlled conditions, optimizing discharge current, voltage, and treatment duration. Leaching experiments with 1 M citric acid at various solid-to-liquid ratios, temperatures, and durations were conducted on both treated and untreated samples. Results indicated that HVEP-treated CA significantly improved REE recovery rates compared to untreated samples, with optimal conditions achieving 74% cerium, 79% yttrium, and 77% lanthanum recovery. The leaching of untreated CA under the specified conditions allowed no more than 28% REE to be extracted into the solution. The leaching process was found to follow first-order kinetics, with the chemical reaction of metal dissolution being the rate-limiting step.

Copper smelting flue dust (CFD) is a byproduct of pyrometallurgical copper production, containing valuable metals like lead, zinc, and copper, but also hazardous arsenic, which complicates its handling and recycling. Traditional methods for arsenic removal from CFD, such as pyrometallurgical and hydrometallurgical processes, are often inefficient or result in the loss of valuable metals. This study explores the efficacy of ultrasound-assisted leaching for selective arsenic extraction from CFD, offering a potentially more efficient and environmentally friendly alternative. We employed a combination of sodium hydroxide and sodium sulfide in an aqueous solution, enhanced by ultrasonic waves, to selectively recover arsenic into solution. The optimal leaching conditions were determined to be 0.4 M NaOH, 0.2 M Na₂S, a liquid-to-solid ratio of 50 mL/g, a temperature of 80 °C, an ultrasound power of 150 W, and an ultrasound frequency of 100 kHz, under which up to 99% of arsenic was extracted within 45 min. The kinetic analysis conducted suggests that the leaching process is controlled by the chemical reactions occurring at the surface of the particles.

This study investigates the optimization of an ammonia-based leaching process for the recovery of lithium and cobalt from spent LiCoO₂ cathodes, coupled with an energy-efficient ammonia stripping approach. Kinetic analysis revealed that both lithium and cobalt extraction follow pseudo-first-order kinetics, with activation energies of 76.54 kJ/mol and 97.22 kJ/mol, respectively, indicating a chemically controlled process. Optimal leaching conditions were established at 6 M NH₃, 1.5 M (NH₄)₂CO₃, liquid-to-solid ratio of 10:1, and 70 °C for 5 h, achieving 82.5% lithium and 96.1% cobalt recovery. The ammonia stripping process was optimized for energy efficiency, with operations at 95–98 °C providing the best balance between rapid NH₃ removal and energy consumption. At 98 °C, energy demand was reduced to ~282 kJ/mol, a sevenfold improvement over lower temperature operations. A stepwise separation strategy was developed, involving selective lithium precipitation at pH 10.7–10.8, followed by controlled ammonia stripping to precipitate cobalt at pH 8.8–9.0. This integrated approach offers a promising alternative to conventional acid-based recycling methods, combining high metal recovery with improved energy efficiency and reagent recyclability.

Background: Being by-products of non-ferrous metallurgy, slags contain fayalite (Fe₂SiO₄) as the major component. Since hydrometallurgical methods are considered as the most promising for processing such material to obtain valuable metals, increasing the leachability of fayalite in sulfuric acid as a widely used leaching agent is an important task. Objective: The present work was devoted to increasing the reactivity of fayalite by using mechanical activation. Methods: Fayalite, synthesized with the use of powders of metallic Fe, Fe₂O₃, and SiO₂, was subjected to mechanical activation in the planetary ball mill for at 400 rpm with a ball/powder ratio of 5 for 45 minutes. Then, activated and non-activated fayalite samples were subjected to sulfuric acid leaching. Before leaching, solid samples were characterized by XRD and dynamic light scattering (DLS). Quantitative analysis of Fe and Si in the leachate was determined by Inductively Coupled Plasma-Atomic Emission Spectroscopy. Results: Mechanical activation led to partial amorphization of the initial fayalite sample. It was found that the leaching rate constants of the treated samples in sulfuric acid solution (50-80 g×L-1) at 298, 338, and 368 K increased and the activation energy of the leaching process decreased, i.e. mechanical activation enhances the reactivity of fayalite in H₂SO₄ solution. Conclusion: Mechanical activation can be applied to improve fayalite leachability in sulfuric acid solution. The results obtained can be used in the development of methods for leaching slag of non-ferrous metallurgy, in particular, copper smelter slags, the major component of which is fayalite.