Search Results (56)

Lithium is an essential material for lightweight batteries. Traditional mining of soluble salts expanded to include the extraction of hard rocks, which requires their solubilization through roasting. Among hard lithium rocks, spodumene has recently received attention from the scientific community. Its metallurgical processing can be classified according to the type of reagents, as well as the operating temperature and pressure. The use of calcium carbonate as a natural alkali avoids aggressive chemicals such as sulfuric acid or caustic soda. In this article, 0.5 g of jewelry-grade spodumene was loaded into a ceramic crucible with 2.5 g of reducing agent in a tandem of roasting at 1050 °C-1 bar-30 min and leaching with neutral water at 90 °C-1 bar-20 min at a water/clinker mass ratio of 25. Measurements by XRD, ICP-OES, and SEM-EDX suggest a pathway of spodumene cracking because of poor contact with the reductant. Potassium present in the crucible acts as a flux and encapsulates spodumene crystals, causing lithium to end up bound to silica. While lithium metasilicate is barely soluble in water, leaching potassium aluminate hoards in the liquid. The empirical observations were supported with thermodynamic spontaneity studies, which required compiling the mineral properties based on open reference tabulations. Full article

Ochratoxins (OTs) pose a major food safety threat, yet analytical methodologies and regulations focus almost exclusively on ochratoxin A (OTA), overlooking the toxic analogues OTB and OTC, especially in complex coffee and spice matrices. The present study addressed this gap by first systematically confirming the high cross-reactivity (>85%) of commercial OTA immunoaffinity columns (IACs) toward OTB and OTC. It was identified that conventional alkaline methanol extraction caused OTC degradation, and subsequently a stable and unified acetonitrile-water (8/2, v/v) extraction protocol was developed. To overcome severe matrix interference endemic to these foods, a novel 0.5% Tween-20-PBS IAC load and wash procedure was optimized. The resulting method was fully validated in representative roasted coffee and pepper matrices on both HPLC-FLD and UHPLC-MS/MS platforms, demonstrating excellent linearity (r > 0.999), accuracy (mean recovery 82.00–112.51%), and precision (RSD% ≤ 8.81%) across three spiked levels (0.3, 5, 10 µg/kg). While UHPLC-MS/MS achieved higher sensitivity (LOQs 0.1 µg/kg) than that of HPLC-FLD (LOQs 0.3 µg/kg), with isotope internal standards essential for correcting significant matrix effects. Application to forty commercial coffee and spice samples (19 coffee, 21 spice) revealed OTA contamination in 47.5% of products (up to 3.46 µg/kg) and co-occurrence of OTA/OTB in 3 of 8 cumin samples. This work establishes the first comprehensively validated IAC-based method for multi-OTs in complex foods, facilitating an urgently needed, robust tool for comprehensive risk assessment. Full article

Refractory gold and silver ores present significant challenges because precious metals are encapsulated within sulfide matrices, severely limiting extraction by conventional cyanidation. In this study, a pyritic concentrate from the Bacis Mine (Durango, Mexico) was characterized and subjected to two oxidative pretreatments—roasting and alkaline pressure oxidation—before cyanidation. X-ray diffraction confirmed pyrite to be the dominant phase, with quartz and minor carbonates contributing to the material’s refractory character. Roasting at 550 °C achieved gold and silver extraction of 80% and 70%, respectively, which improved to 89% Au and 74% Ag with the addition of hydrogen peroxide. In contrast, alkaline pressure oxidation at 150 °C and 1 MPa O₂ yielded the highest extraction of 92% for Au and 76% for Ag at 1 h. Thermodynamic analysis using the Fe–S Pourbaix diagram at 80 °C supported these experimental results, showing the destabilization of FeS₂ under oxidizing and moderately alkaline conditions. Overall, this study demonstrates that alkaline pressure oxidation is a technically efficient and environmentally favorable pretreatment for refractory gold ores. Full article

This study evaluates four physicochemical pretreatments—ultra-fine grinding, roasting, alkaline pressure oxidation (POX), and oxidative ammoniacal pre-leaching—for improving gold extraction from a refractory sulfide concentrate produced trough flotation. The gold extraction by direct cyanidation is only ~48.6%, mainly due to the encapsulation of gold by associated minerals. Ultra-fine grinding increased the BET surface area eight-fold but depressed gold dissolution from 74% to 18% due to accelerated thiosulfate decomposition and copper (I) passivation in the presence of a bigger surface area. Oxidative roasting at 750 °C converted pyrite–pyrrhotite to hematite without liberating additional gold, indicating limited benefit from thermal treatment. POX was conducted at 190 °C and 10 bar O₂ dissolved 33% of the solids and yielded only 26% of gold in a thiosulfate leaching step with 50% of the thiosulfate consumption. In contrast, a two-step oxidative ammoniacal conditioning (0.4 M NH₃ + 10 mM Cu²⁺ for 42 h) followed by thiosulfate leaching boosted gold extraction from 71% to 85% while cutting thiosulfate consumption from 48.4 to 29.0 kg t⁻¹. The results demonstrate that among the pretreatments investigated, oxidative ammoniacal pre-leaching provides the most effective and environmentally benign route to unlock encapsulated gold and enhance reagent efficiency for thiosulfate processing of refractory gold ore. Full article

Based on the physicochemical properties of waste phosphate-based rare earth phosphors containing glass, this paper proposes a novel recovery method for rare earth elements (REEs) that integrates pre-enrichment, alkali roasting, and enhanced leaching. Initially, preliminary enrichment of REEs was achieved through sieving to remove silicon (from glass components) and pickling to reduce calcium content (originating from calcium phosphate compounds). The enriched material was then subjected to alkaline roasting, followed by washing for impurity removal, hydrochloric acid leaching, and finally oxalic acid precipitation to extract the rare earth elements. Experimental results demonstrate that the overall recovery rate of rare earth oxides (REO) reached 96.6%, indicating highly efficient extraction and separation of REEs from the waste phosphors. Furthermore, the mechanism of the alkali roasting process was investigated via differential thermal analysis (TG-DSC). Microstructural and phase changes in the waste phosphors before and after roasting were systematically characterized using X-ray diffraction (XRD) and scanning electron microscopy (SEM). The results indicate that green phosphor (REPO₄) was converted into rare earth oxides and water-soluble sodium phosphate under alkaline roasting conditions. The Na₃PO₄ could be effectively removed through washing, while the rare earth elements were retained in the form of oxides within the washed residue. This study provides an important theoretical foundation and technical approach for the efficient recovery of rare earth resources from waste phosphate-based phosphors. Full article

Aflatoxin (AF) contamination in pistachios remains a critical food safety and trade challenge, given the potent carcinogenicity of AF-B₁ and the nut’s high susceptibility to Aspergillus infection throughout production and storage. Traditional decontamination methods such as roasting, irradiation, ozonation, and acid/alkaline treatments can reduce AF levels but often degrade sensory and nutritional quality, implying the need for more sustainable approaches. In recent years, innovative nonthermal interventions, including pulsed light, cold plasma, nanomaterial-based adsorbents, and bioactive coatings, have demonstrated significant potential to decrease fungal growth and AF accumulation while preserving product quality. Biosensing technologies such as electrochemical immunosensors, aptamer-based systems, and optical or imaging tools are advancing rapid, portable, and sensitive detection capabilities. Combining these experimental strategies with artificial intelligence (AI) and machine learning (ML) models can increasingly be applied to integrate spectral, sensor, and imaging data for predicting fungal development and AF risk in real time. This review brings together progress in nonthermal reduction strategies, biosensing innovations, and data-driven approaches, presenting a comprehensive perspective on emerging tools that could transform pistachio safety management and strengthen compliance with global regulatory standards. Full article

The article presents the material composition of the titanium- and iron-rich ilmenite concentrate from the Satpayev deposit in Eastern Kazakhstan, which is unacceptable for processing by commercial hydro- and pyrometallurgical enrichment methods due to the presence of rutile, soluble only in hydrofluoric acid, and many refractory aluminosilicate associations: kaolinite, kyanite, pyrophyllite and mullite, cementing titanium minerals. The solution to the problem of reducing the cost of titanium sponge production was developed by developing an economically efficient and environmentally safe technology for the conversion of clayey ilmenite sand concentrate, including thermal activation of particularly resistant raw materials in an air atmosphere, soda-carbothermic smelting of cinder, hydrothermal refining of titanium slag with water, then hydrochloric acid and regeneration of reagents. Oxidative roasting ensures disintegration of intergrowths and destruction of mineral grains of the concentrate. The addition of soda ash to the concentrate cinder batch accelerates the reduction and agglomeration of over 98% of the iron, prevents the formation of lower refractory titanium oxides, facilitates the stratification of the thin-flowing titanium slag melt and cast iron and significantly reduces energy costs and the duration of the carbothermic smelting process. Refining primary titanium slag with water provides the production of modified slag with a mass fraction of TiO₂ of at least 83% and FeO of no more than 0.4%, suitable for the production of high-quality titanium sponge. Subsequent refining of modified titanium slag with 20% hydrochloric acid yields synthetic rutile of 96% purity, surpassing in the content of the main substance the branded titanium pigments of the American company DuPont. The resource-saving and environmental significance of this innovative technology is increased by the possibility of recycling easily regenerated soda, hydrochloric acid and recyclable carbon dioxide released during the decomposition of the alkaline reagent during the carbothermic smelting of the concentrate. Full article

Coffee silverskin (CS), a by-product generated during coffee roasting, contains high levels of xylan hemicellulose and protein, making it a promising substrate for functional ingredient production. This study developed an integrated bioprocess to simultaneously produce bioactive peptides and xylooligosaccharides (CS-XOS) from CS. Conventional alkaline extraction (CAE) under optimized conditions (1.0 M NaOH, 90 °C, 30 min) yielded 80.64 mg of protein per gram of CS and rendered the solid residue suitable for XOS production. Enzymatic hydrolysis of the extracted protein using protease_SE5 generated low-molecular-weight peptides (0.302 ± 0.01 mg/mL), including FLGY, FYDTYY, and FDYGKY. These peptides were non-toxic, exhibited in vitro antioxidant activity (0–50%), and showed ACE-inhibitory activities of 60%, 26%, and 79%, and DPP-IV-inhibitory activities of 19%, 18%, and 0%, respectively. Concurrently, the alkaline-treated CS solid residue (ACSS) was hydrolyzed using recombinant endo-xylanase, yielding 52.5 ± 0.08 mg of CS-XOS per gram of ACSS. The CS-XOS exhibited prebiotic effects by enhancing the growth of probiotic lactic acid bacteria (μ_max 0.100–0.122 h⁻¹), comparable to commercial XOS. This integrated bioprocess eliminates the need for separate processing lines, enhances resource efficiency, and provides a sustainable strategy for valorizing agro-industrial waste. The co-produced peptides and CS-XOS offer significant potential as functional food ingredients and nutraceuticals. Full article

Among the strategic materials considered by the EU, tungsten is included; thus, investigations about the recovery of this metal both from natural and recyclable sources are of interest. In this work, we presented an investigation about the recovery of tungsten based on the treatment of three tungsten-bearing concentrates: scheelite (29% W), wolframite (50% W), and mixed scheelite–wolframite (29% W). All of these come from a cassiterite ore of Spanish origin. The characteristics of each concentrate pave the procedure to be followed in each case. In the case of the wolframite concentrate, the best results were derived from the leaching of the ore with NaOH solutions, whereas the treatment of the scheelite concentrate benefits from an acidic (HCl) leaching. The attack of the mixed concentrate is only possible by a previous roasting step (sodium carbonate and 700–800 °C) followed by a leaching step with water. In the acidic leaching, tungstic acid (H₂WO₄) was obtained, and the alkaline–water leaching produces Na₂WO₄ solutions from which pure synthesized scheelite is precipitated. Full article

In the wake of global energy transition and the “dual-carbon” goal, the rapid growth of electric vehicles has posed challenges for large-scale lithium-ion battery decommissioning. Retired batteries exhibit dual attributes of strategic resources (cobalt/lithium concentrations several times higher than natural ores) and environmental risks (heavy metal pollution, electrolyte toxicity). This paper systematically reviews pyrometallurgical and hydrometallurgical recovery technologies, identifying bottlenecks: high energy/lithium loss in pyrometallurgy, and corrosion/cost/solvent regeneration issues in hydrometallurgy. To address these, an integrated recycling process is proposed: low-temperature physical separation (liquid nitrogen embrittlement grinding + froth flotation) for cathode–anode separation, mild roasting to convert lithium into water-soluble compounds for efficient metal oxide separation, stepwise alkaline precipitation for high-purity lithium salts, and co-precipitation synthesis of spherical hydroxide precursors followed by segmented sintering to regenerate LiNi_1/3Co_1/3Mn_1/3O₂ cathodes with morphology/electrochemical performance comparable to virgin materials. This low-temperature, precision-controlled methodology effectively addresses the energy-intensive, pollutive, and inefficient limitations inherent in conventional recycling processes. By offering an engineered solution for sustainable large-scale recycling and high-value regeneration of spent ternary lithium ion batteries (LIBs), this approach proves pivotal in advancing circular economy development within the renewable energy sector. Full article

Industrial technologies for processing tungsten concentrates using soda roasting or autoclave leaching are based on the production of alkaline sodium tungstate solutions that contain impurities such as silicon, phosphorus, arsenic, and others. The purification of these solutions from impurities requires the neutralization of excess soda or alkali with inorganic acids, which leads to the formation of chloride and sulfate effluents that are subsequently discharged into waste repositories. An analysis was carried out on existing methods for the production and processing of sodium tungstate solutions using HNO₃ and NH₃, as well as extraction and sorption techniques involving anion exchange resins. Currently, processes such as nanofiltration, reverse osmosis, and electrodialysis are being applied for water purification and the treatment of sulfate and chloride effluents. These processes employ various types of industrially manufactured membranes. For the purpose of electrodialysis, a two-compartment electrodialyzer setup was employed using cation-exchange membranes of the MK-40 (Russia) and EDC1R (China) types. The composition and structure of sodium tungstate, used as the starting reagents, were analyzed. Based on experiments conducted on a laboratory-scale unit with continuous circulation of the catholyte and anolyte, dependencies of various parameters on current density and process duration were established. Stepwise changes in the anolyte pH were recorded, indirectly confirming changes in the composition of the Na₂WO₄ solution, including the formation of polytungstates of variable composition and the production of H₂WO₄ via electrodialysis at pH < 2. The resulting tungstic acid solutions were also analyzed. The conducted studies on the processing of sodium tungstate solutions using electrodialysis made it possible to obtain alkaline solutions and tungstic acid at a current density of 500–1500 A/m², without the use of acid for neutralization. Yellow tungstic acid was obtained from the tungstic acid solution by evaporation. Full article

Conventional lithium extraction from spodumene via sulfuric acid roasting can achieve up to 98% recovery but suffers from high energy use, acidic residues, and purification complexity. This review evaluates alternative methods for both α- and β-spodumene, aiming for improved sustainability. For α-spodumene, Na₂SO₄–CaO salt roasting achieved >95% recovery at 900 °C via water leaching. Sodium carbonate roasting–NaOH leaching and mechanical activation–Na₂SO₄ roasting reached 95.9% and ~92%, respectively. High-pressure NaOH leaching reached 95.8%, while alkaline decomposition–acid leaching yielded 53.2–84.1%. Microwave-assisted calcination achieved up to 97% recovery, and fluoride-based roasting gave 93–98% but raised environmental concerns. Bioleaching is eco-friendly but slow, with <3.5% recovery. For β-spodumene, high-pressure leaching using sodium carbonate (>94%), sodium sulfate (90.7%–93.3%), sodium chloride (~93%), and nitric acid (~95%) provided high recoveries. Atmospheric leaching with HF and H₃PO₄ yielded ~90% and ~40%, respectively, while carbonic acid leaching reached 75% after multiple stages. Chlorination roasting achieved near-complete recovery. The Metso-Outotec high-pressure sodium carbonate leaching process is set for industrial-scale implementation at the Keliber project in 2025, confirming its scalability. Overall, these emerging processes have the potential to reduce energy input, reagent demand, and waste generation, offering practical pathways toward more sustainable lithium production from spodumene. Full article

The geopolitical and economic situation impacts raw materials demand. As principal ore deposits reach exhaustion, the study of new sources of raw materials becomes essential. Therefore, mining wastes emerge as alternative sources of raw materials. Their physicochemical properties, such as small particle size or concentration of some metals of interest, enhance reprocessing. A number of critical raw materials (As, Co, Cu, Sb) and base metals (Pb, Zn), as well as precious metals (Ag), were found present in an abandoned tailing deposit composed by finely grounded washed roasted pyrites within the Iberian Pyrite Belt. Copper leaching from a sample of this deposit was investigated. Two hydrometallurgical approaches were studied: acidic leaching with and without activated carbon; and alkaline leaching with glycine solutions. Leaching tests were carried out during 24 h at ambient and moderate temperatures (60 °C). In acidic medium, the maximum copper extraction varied from 88 to 92.5%, while in alkaline medium, the maximum copper extraction was in the range of 71%–76%. Using activated carbon and H₂O₂ seemed to slightly promote the copper extraction with the maximum extraction (92.5%) after 2 h of leaching at 60 °C. Complementarily, above 50% of the zinc and cobalt contained were extracted. In contrast, temperature in alkaline conditions played a key role in reaction speed, but also in precipitation of copper insoluble compounds. In addition, the glycine solution at pH 10–10.5 showed high selectivity for copper over zinc, iron, lead, arsenic, and antimony. Two extra tests at pH above 12 showed arsenic dissolution (up to 51% at pH 12.5). Full article

The lithium market has been expanding due to the high demand for lithium-ion batteries, which are essential for electric and hybrid vehicles as well as portable devices. This has driven the search for new lithium ore deposits and the development of more efficient extraction and processing technologies. The main methods used for lithium extraction from hard rock ores include the acid process, the alkaline process, and chlorination roasting. This study investigated a chlorination process applied to α-spodumene extracted in Brazil for lithium chloride (LiCl) production. The ore underwent thermal treatment in the presence of calcium chloride (CaCl₂) and magnesium chloride (MgCl₂), followed by water leaching at 90 °C. The thermodynamics of the α-Li₂O·Al₂O₃·SiO₂ system, combined with calcium and magnesium chlorides, was analyzed using HSC 5.1 software. The main objective of this study was to produce lithium chloride from alpha spodumene and avoid decrepitation of the ore to the beta phase before mixing with the reagents, making the process faster and less expensive compared to traditional extraction methods. Pyrometallurgical tests were conducted in a muffle furnace, varying the molar ratio between chlorides (MgCl₂:CaCl₂) at 1:0, 0:1, 1:1, 2:1, and 1:2 and the mass ratio of spodumene to chlorides at 1:4, 1:6, and 1:8. The best lithium extraction result was approximately 95%, the conditions for obtaining the result were a spodumene:chloride ratio of 1:6 and a molar ratio between chlorides of 2:1. The results provide a better understanding of the chlorination roasting process and demonstrate the potential of the chlorination technique as a viable alternative to conventional lithium extraction methods. Full article

The difficulty of separating iron and manganese is a bottleneck issue in the traditional utilization process of iron manganese ore (Fe-Mn ore). In this work, ammonium polyvanadate (APV), an intermediate product in the vanadium industry, was introduced innovatively to convert the manganese-containing phase in Fe-Mn ore into manganese pyrovanadate (Mn₂V₂O₇) and iron and manganese were then separated efficiently through the acid leaching process. The migration of manganese, iron, and vanadium were systematically studied through XRD, SEM, and leaching experiments. Results show that during the mixed roasting process of Fe-Mn ore and APV, V₂O₅, the decomposition product of APV, reacts with the decomposition product of manganese minerals in Fe-Mn ore, Mn₂O₃, to produce the target product, acid-soluble Mn₂V₂O₇. Iron and silicon exist in the form of Fe₂O₃ and SiO₂ like in Fe-Mn ore. After the two-step leaching process of the sample roasted at 850 °C with n(MnO₂)/n(V₂O₅) of 2.25, the leaching ratios of manganese, iron and vanadium are 84.57%, 0.046%, and 4.68%, respectively, achieving the efficient separation of manganese with iron and vanadium. MnCO₃ obtained by carbonization and precipitation from the manganese-containing leaching solution can be used as an intermediate product of manganese metallurgy or manganese chemical industry. APV obtained by alkaline leaching and precipitation from the vanadium- and iron-containing tailing can be recycled into the roasting system as the roasting additive. The TFe content in the iron-containing tailing reaches 57.21 wt.%, which meets the requirement of iron concentrate. More than 99 wt.% of vanadium from the additive APV can be recovered and recycled back into the Fe-Mn ore utilization process by APV recycling and wastewater recycling, making the Fe-Mn ore utilization with APV roasting a green process. Full article