In this work, bio-hydrometallurgy technology was employed and a novel two-stage method based on successive chemical and bio treatments was proposed to collaboratively utilize manganese–silver ore and silver-bearing pyrite. In the optimization research of the chemical leaching stage, the sensitive factors for the Mn leaching efficiency were screened by Plackett–Burman design, and central compound design was performed to settle the optimized parameters. A mixed strain of bacteria containing Sulfobacillus thermosulfidooxidans, At. caldus and Leptospirillum ferrooxidans was applied in the bioleaching stage. A conventional cyanidation process carried out with the Mn leaching residuals suggested an efficient recovery of Ag. Applying a two-stage method with the optimum conditions, the leaching efficiency of 95.3% (Mn) and 96.3% (Ag) were obtained with 284.94 kg/t silver-bearing pyrite addition and 277.44 kg/t sulfuric acid consumption with a temperature at 77.73 °C and stirring speed at 287.76 rpm. Mineral behaviors were investigated with XRD and SEM/EDS analysis, and it was revealed that the oxidation of sulfur is the crux in reducing the usage of reagents, and the presence of leaching bacteria enhanced the oxidation efficiently. Through optimization and mechanism study, this paper provides an opportunity to co-leach the manganese–silver ore and silver-bearing pyrite process in a more economical and environmental way.

The present work investigated the comparison of the effects of Na₂SO₃ and Na₂SiO₃ on thiourea stabilization, and a systematic study was undertaken to establish the effects of these stabilizers on the stability of alkaline thiourea, both qualitatively and quantitatively. The effects of these stabilizers on the activation energy of alkaline thiourea gold leaching was also studied. The results showed that sodium silicate was more suitable as a stabilizer in this system than sodium sulfite because the peak current of gold dissolution with sodium sulfite was higher than that with sodium silicate, but the inhibition of thiourea decomposition by the former was less obvious than that of sodium silicate in the cyclic voltammetry curve. The quartz crystal microbalance results showed that the quality decreased to about 100 ng cm² in the presence of a stabilizer, while it increased to 300 ng cm² in the absence of the stabilizer. It is inferred that gold can be dissolved by alkaline thiourea in the presence of a stabilizer, while it cannot without a stabilizer because of the decomposition of thiourea. This assumption was confirmed by atomic force microscopy measurements. The surface activation energy of Au dissolution decreased from 183.76 to 98.07 kJ/moL with the addition of sodium silicate, indicating that Au dissolution was promoted with the chemical.

In order to improve the thiourea gold leaching rate of a low-grade arsenic–sulfur-containing refractory gold ore in Xinjiang, a microbial pretreatment was used to oxidize pyrite and arsenopyrite to obtain a bio-oxidation residue. The main minerals were quartz, mica, and some sulfides that were not fully oxidized. In this study, the static adsorption method was applied to simulate the thiourea adsorption by typical minerals. The results showed that the amount of thiourea adsorbed by the three minerals could be ordered as follows: pyrite > mica > quartz. Quartz had hardly any adsorption of thiourea. The thiourea adsorption capacities of pyrite and mica were about 8.93 mg g⁻¹ and 2.30 mg g⁻¹, respectively. The adsorption process for pyrite conformed to the Freundlich isotherm equation and pseudo-second-order kinetic model, indicating that the adsorption process was a monolayer chemisorption. The adsorption process for mica conformed to the Langmuir isotherm equation and pseudo-second-order kinetic model, indicating that the adsorption process was a monolayer physical adsorption. Fourier transform infrared spectroscopy showed that the adsorption of thiourea on the surface of mica relied on the formation of hydrogen bonds with Si-OH, whereas a new S-S peak was detected on the surface of pyrite, which further indicated that thiourea was chemically adsorbed on the surface of pyrite.

The co-contamination of manganese ions (Mn²⁺) and ammonia nitrogen (NH₄⁺) caused by the stockpiling of manganese residue poses a serious threat to the ecological environment. In this study, a series of the composite was prepared from red mud, bentonite, and corn straw via oxygen-limited pyrolysis. The effects of pyrolysis temperature and raw material ratio on the material properties were investigated, and the synergistic remediation performance of the composites for Mn²⁺ and NH₄⁺ in manganese residue-contaminated soil was evaluated through a 180-day soil column experiment. The results showed that the composite prepared with a raw material ratio of 1:1:1 at a pyrolysis temperature of 700 °C exhibited the largest specific surface area and the most developed pore structure, achieving a Mn²⁺ removal rate of 92.72% ± 0.85% in aqueous solution. In the soil column experiment, the material prepared at 700 °C gave the highest immobilization rate for soil Mn²⁺ (96.22% ± 0.5%), whereas the combined addition of materials prepared at 700 °C and 500 °C achieved the best removal efficiency for NH₄⁺ (99.33% ± 0.23%). Mechanistic studies revealed that the stabilization of Mn²⁺ is primarily attributable to alkaline precipitation and mineral lattice solid solution induced by the composite, leading to the formation of stable spinel phases (e.g., (Fe,Mn)₃O₄) and insoluble manganese phosphate-carbonate salts. The removal of NH₄⁺ is proposed to proceed via adsorptive enrichment by the porous structure and Fe⁰-mediated Fenton-like catalytic oxidation, ultimately converting NH₄⁺ to N₂ gas. The 180-day monitoring results demonstrated that the remediation effect continuously increased over time, indicating good long-term stability of the composite. This study provides an efficient, low-cost functional material derived from solid waste for the remediation of manganese residue-contaminated soil and offers a theoretical basis for the synergistic resource utilization of multiple solid wastes.

Black shale represents a distinctive and critical mineral resource in China, harboring approximately 90% of the nation’s recoverable vanadium reserves while concurrently containing abundant strategic metal elements such as nickel and molybdenum. However, the complex occurrence states of vanadium, nickel, and molybdenum within black shale pose significant challenges to their efficient extraction. Conventional metallurgical processes—including calcination-leaching and hydrometallurgical leaching—primarily target vanadium recovery, exhibiting limited efficiency for comprehensive utilization of valuable metals. Against the backdrop of green metallurgy and carbon neutrality objectives, bioleaching techniques have garnered extensive research attention. This study developed a specialized consortium of ore-leaching microorganisms, designated WZ-Q, tailored to the mineralogical characteristics of black shale, demonstrating effective leaching capabilities for vanadium, nickel, and molybdenum. Furthermore, the enhancing effects of Fe²⁺, elemental sulfur (S⁰), and pyrite as energy substrates on bioleaching efficiency were investigated. Upon incorporating these energy materials, maximum leaching efficiencies reached 66.5% for vanadium, 82.5% for nickel, and 29.7% for molybdenum. Analysis through leaching process monitoring and multi-characterization of both raw ore and residues revealed that supplemental energy substrates intensify shifts in solution potential and pH, thereby promoting elemental oxidation and mineral decomposition. Nevertheless, critical impediments to leaching efficiency include the encapsulation of target elements within silicate matrices and incomplete dissolution of oxidized species. Subsequent research should prioritize methodologies to intensify silicate mineral dissolution and enhance the release of oxidized compounds during microbial leaching processes.

Tantalum and niobium are critical strategic rare refractory metals; however, most associated tantalum–niobium resources are characterized by ultra-low grade, finely disseminated grains, and severe argillization, which causes pronounced slime coating of gangue mica on valuable mineral surfaces and impedes efficient recovery via gravity separation. In this study, an innovative beneficiation route combining sodium silicate pre-dispersion conditioning with shaking-table gravity separation was proposed to recover a spodumene-dominant pegmatitic lithium ore containing trace associated Nb–Ta minerals, with mica as the major slime-forming gangue. Process mineralogy analysis revealed that the raw ore has a total (Nb,Ta)₂O₅ grade of only 0.019%, with the main valuable minerals being columbite-(Mn), columbite–tantalite, and tantalite, whereas layered mica minerals constitute the primary argillization gangue that readily generates micro-fine slimes smaller than 5 μm. Single-factor tests demonstrated that the optimal grinding fineness was 84.4% passing 200 mesh, and the optimal feed pulp density for gravity separation was 28.6%. Adjusting pulp concentration alone, without a dispersant, yielded a Nb₂O₅ concentrate grade of merely 0.144%, as severe slime coating greatly limited separation selectivity. Following the introduction of sodium silicate for pre-dispersion, the separation performance improved markedly at the optimal dosage of 300 g/t: the concentrate Nb₂O₅ grade reached 1.28% (8-fold higher than the blank test), and the Ta₂O₅ grade increased to 0.47% (85-fold higher than the blank test). Multi-scale characterization, including zeta potential measurements, ultraviolet–visible (UV–vis) diffuse reflectance spectroscopy, Fourier-transform infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS), was employed to elucidate the dispersion mechanism of sodium silicate. The results confirmed that sodium silicate undergoes selective chemisorption on mica surfaces by forming Si–O–Al bonds with surface Al–OH active sites, which substantially increases electrostatic repulsion between mineral particles and eliminates mica slime coating on tantalum–niobium minerals. In contrast, sodium silicate exhibits only weak physical adsorption on tantalum–niobium mineral surfaces, with no evident chemical bonding. This work provides a low-cost, eco-friendly pretreatment–gravity separation coupling technology for the efficient enrichment of argillized ultra-low-grade tantalum–niobium associated ores and offers theoretical guidance for the green utilization of complex tantalum–niobium tailings and low-grade mineral resources.