Search Results (309)

Direct CO₂ mineralization of carbide slag offers considerable potential for sustainable waste valorization, CO₂ utilization, and high-value CaCO₃ production, although associated Si-, Fe-, and Al-bearing impurities limit product quality. This study comparatively evaluated six process routes to determine how process sequence and separation-stream selection affect impurity partitioning and final product performance. The results suggest that calcination-induced phase reconstruction may improve the separability of impurity-bearing material, while hydrocyclone classification preferentially partitions impurity-rich particles toward the underflow. Relative to the calcined feed, the Si and Fe concentrations in the overflow decreased by 58.4% and 86.9%, respectively, and subsequent magnetic separation further reduced residual Fe. The preferred calcination–hydrocyclone overflow–magnetic separation–mineralization route omitted flotation and produced CaCO₃ with a purity of 98.3%, a whiteness approaching 100%, and a total impurity content of 0.57%. These findings provide a process-sequence framework for balancing impurity removal, product quality, resource recovery, and environmental performance during the sustainable conversion of carbide slag into high-value CaCO₃. Full article

Chrysocolla, a hydrated copper silicate mineral, is notoriously difficult to recover by conventional froth flotation due to its microporous structure, low hydrophobicity, impurity substitutions, and poor response to traditional collectors. This study evaluates the performance and adsorption mechanism of benzohydroxamic acid (BHA) as a collector for chrysocolla flotation under varying pH conditions and collector dosages. Microflotation results showed that chrysocolla recovery increased with BHA concentration, with enhanced flotation occurring at alkaline pH (8–10), consistent with BHA dissociation behavior. Zeta potential measurements indicated selective adsorption of BHA on the chrysocolla surface, while quartz showed minimal interaction, confirming collector selectivity. X-ray photoelectron spectroscopy (XPS) revealed that BHA was chemisorbed through Cu–hydroxamate complex formation. Bench-scale flotation tests on a chrysocolla ore containing 3.7% Cu produced a concentrate grading 26.7% Cu with 35.3% recovery after initial sulfide flotation. Kinetic tests indicated rapid recovery of more floatable copper phases, while scanning electron microscopy (SEM) showed preferential flotation of finer particles. Overall, the results demonstrate that BHA can effectively promote chrysocolla flotation through selective chemisorption, although high collector dosages are required due to the mineral’s high specific surface area and structural complexity. Full article

Microbially induced calcium carbonate precipitation (MICP) is a promising biotechnology for environmental remediation; however, the high cost of conventional chemical-grade calcium sources limits its large-scale scalability. This study evaluated the feasibility of utilizing an aqueous extract of natural attapulgite clay as a sustainable, low-cost calcium source for MICP-mediated arsenic (As) immobilization in both aqueous and soil systems. Among the tested minerals, Baiyin attapulgite (group B) exhibited the highest calcium content (62,808.94 mg kg⁻¹) and minimal toxic metal impurities, providing a favorable chemical matrix for biomineralization. At an optimal solid-to-liquid ratio of 1:10, Lysinibacillus fusiformis LF and Enterococcus LZU-1 successfully induced calcite precipitation driven by the attapulgite extract. In batch aqueous remediation experiments (20 days), the attapulgite extract significantly enhanced As removal efficiency compared to the controls; As removal rates peaked at 66.4% for strain LZU-1 (with LZ1 extract) and 65.8% for strain LF (with group B extract), drastically outperforming the standard CaCl₂ groups (31.2–37.3%) and blank controls (21.8–24.5%). Concurrently, soil incubation experiments (30 days) demonstrated that the combined application of attapulgite and MICP bacteria reduced the highly bioavailable exchangeable As fraction from 0.115 to approximately 0.03 mg kg⁻¹, while effectively driving its transformation into more stable carbonate-bound and organic-bound fractions without causing secondary soil salinization. Morphological and mechanistic analyses revealed that, compared to the well-defined euhedral crystals in the CaCl₂ control, the precipitates mediated by the clay extract exhibited distinctly irregular, defect-rich rhombohedral structures. This structural disruption was governed by the natural matrix effect of attapulgite, which simultaneously supplied dissolved Ca²⁺ and provided an abundance of fine clay fragments, calcite micro-grains, and associated amorphous Fe/Al/Mn-bearing phases. These constituents acted as physical scaffolding and heterogeneous nucleation sites that became embedded in the growing CaCO₃ lattice, driving the formation of highly reactive, defect-rich clay-calcite-arsenic composite precipitates that efficiently encapsulated arsenate. Mantel analysis further revealed that the remediation efficiency was significantly correlated with key environmental variables including Ni, V, Ca. These findings highlight the dual-system potential of natural attapulgite as an inexpensive, eco-friendly calcium alternative for sustainable MICP-based remediation of As-contaminated water and agricultural soils. Full article

This study investigates the potential for recovering valuable minerals from feldspar tailings generated during industrial processing and commonly discarded as waste, causing both economic losses and environmental concerns. A hydrocyclone overflow sample obtained from a feldspar processing plant in the Muğla region of Türkiye was characterized and evaluated for the production of a marketable feldspar concentrate by flotation. Bulk and selective reverse flotation tests were performed using Denver and TK Lab flotation cells incorporating different impeller–stator configurations to evaluate the combined effects of reagent chemistry, flotation cell hydrodynamics, and bubble characteristics on flotation performance. The Sauter mean bubble diameter (d₃₂) was measured under both two-phase and three-phase conditions to characterize bubble size. Compared with the conventional plant reagent scheme (Derna-7 and Der A4), the sequential flotation scheme employing sulfonate collectors (R801–R825) for Fe–Ti-bearing minerals followed by the amine collector DAHC for mica significantly improved impurity rejection. The highest concentrate quality was achieved in the TK Lab Cell, producing a feldspar concentrate containing as low as 0.49% Fe₂O₃ while maintaining a total alkali content of 9.57%, satisfying the Fe₂O₃ requirement for second-grade ceramic applications. Despite producing larger bubbles than the Denver Cell, the TK Lab Cell exhibited superior rejection of Fe–Ti-bearing minerals. The consistently larger bubbles generated by the TK Lab Cell, irrespective of the reagent scheme employed, indicate that the different impeller–stator configurations played a key role in governing bubble generation and gas dispersion, while reagent chemistry primarily modified bubble characteristics within the hydrodynamic environment established by each flotation cell. The results demonstrate that flotation performance is governed by the combined effects of reagent chemistry, flotation cell hydrodynamics, and bubble characteristics, providing new insights into the sustainable valorization of feldspar processing tailings. Full article

Waste-derived fertilising materials, including sewage sludge, compost, digestate, food-waste-derived products and commercial organic or organo-mineral fertilisers, return nutrients to farmland but can also transfer microplastics to agricultural soil. This critical review examines their occurrence across these streams, analytical constraints, fate after application and the EU regulatory framework. Reported abundances span orders of magnitude and cannot be pooled because extraction, polymer identification and reporting are not harmonised, while particle-counting and mass-based methods measure different quantities. Field evidence indicates topsoil retention and accumulation after repeated application, whereas crop transfer and field-scale ecological effects remain poorly quantified. Regulation (EU) 2019/1009 sets no microplastic-specific product limit. For compost qualifying as CMC 3 and digestate other than fresh crop digestate qualifying as CMC 5, it controls plastic impurities above 2 mm by mass, while smaller particles remain outside that criterion. Waste-derived fertilisers can therefore form a recurrent, incompletely regulated pathway for microplastic transfer to soil. Controlled studies demonstrate hazard potential for selected particles and exposure conditions, but the magnitude and likelihood of effects under field conditions remain uncertain. The immediate priority is harmonised monitoring and reporting of the sub-2 mm fraction, including a stated lower size limit, polymer-confirmed particle counts and minimum QA/QC. Full article

China is rich in magnetite mineral resources, but they are generally characterized by low grade, fine dissemination size, and a high content of harmful impurities. Wet low-intensity magnetic separation (WLIMS) is an important method for processing fine-grained magnetite. However, during the separation process, fine magnetite particles are prone to magnetic agglomeration, which makes it difficult for conventional WLIMS separators to achieve high-selectivity separation. To address this issue, a novel WLIMS separator based on a rotating magnetic system was developed in this investigation, and its separation characteristics were systematically investigated through a combined approach comprising CFD–DEM–FEM multiphysics coupling simulations and experimental validation. Simulation results indicate that the rotating magnetic system significantly reduces the chain length and the structural stability of magnetic agglomerates just as magnetite particles enter the magnetic field region. Furthermore, under the rotating action of the magnetic system, the magnetic chains only enclose a portion of the intergrowth minerals, while gangue minerals remain unattached, which positively contributes to improved separation selectivity. Both laboratory-scale experimental results and industrial production data indicate that, compared to the conventional WLIMS separator, the rotating magnetic system WLIMS separator achieves significantly superior separation performance. For a magnetite ore with a grade of 57.68%, the rotating magnetic system WLIMS separator achieved an optimal concentrate grade of 65.43% (with a recovery of 94.78%), whereas the conventional WLIMS separator attained only 60.32% at a similar recovery rate. This investigation provides an important basis for the large-scale industrial application of rotating magnetic system WLIMS separators and the efficient development and utilization of fine-grained magnetite resources. Full article

Phosphorus recovery from wastewater and waste streams has become increasingly critical for addressing phosphate-rock supply insecurity and eutrophication control. Building on previous reviews of phosphorus recovery technologies and product applications, this review presents a product-oriented perspective for evaluating phosphorus recovery, explicitly integrating phosphorus sources, process design, product quality, application requirements, regulatory considerations, and life-cycle assessment (LCA) or techno-economic assessment (TEA). Collectively, the available evidence indicates that phosphorus sources differ substantially in phosphorus concentration, speciation, and impurity profiles, underscoring the importance of source–product matching for effective phosphorus recovery. Different phosphorus sources, therefore, require tailored recovery pathways to produce products that satisfy specific quality and application requirements. Product quality is governed primarily by process design rather than by the recovered mineral itself, with purity, contaminant control, regulatory compliance, and end-use suitability ultimately determining the environmental and economic value of recovered phosphorus. A meaningful comparison of recovery pathways further requires harmonized LCA/TEA, as environmental and economic outcomes are highly sensitive to system boundaries, functional units, and allocation assumptions. In addition, regulatory requirements are emerging as a key determinant of product commercialization and should therefore be incorporated throughout process design and technology development. Overall, this review highlights a shift from removal-oriented phosphorus recovery to product-oriented phosphorus recovery, emphasizing the production of high-quality, application-specific phosphorus products as the foundation for technology selection, product innovation, and the transition toward a circular phosphorus economy. Full article

Anatase-bearing lateritic ores from Qinglong, Guizhou Province, China, are characterized by extremely low TiO₂ grade, high clay content, fine-grained dissemination, and complex intergrowths with iron oxides, which severely hinder efficient beneficiation. In particular, anatase commonly occurs as ultra-fine particles encapsulated by clay minerals or closely associated with iron oxides, and its surface is often covered by nanoscale goethite films, resulting in surface passivation and pseudo-magnetic behavior. These characteristics lead to a pronounced contradiction between mineral liberation and excessive slime generation during conventional grinding processes. To address these challenges, a high-efficiency pre-concentration flowsheet was developed based on selective desliming, stage grinding, intensive scrubbing, flotation, and weak magnetic separation. Selective desliming via hydrocyclones was adopted, which is inferred to preferentially discard true slimes finer than 10 μm while potentially retaining most fine anatase particles within the underflow. Stage grinding was then applied, which may promote the improved liberation of anatase and early rejection of coarse gangue, and may help reduce overgrinding. Intensive scrubbing was introduced, which is expected to weaken or partially remove iron oxide coatings from the anatase surface, thereby potentially restoring surface activity and reducing pseudo-magnetic interference. Subsequent flotation and low-intensity magnetic separation were optimized to increase the concentrate TiO₂ grade and cut iron impurities, which may be associated with improved surface selectivity and weakened pseudo-magnetic responses. Closed-circuit beneficiation tests demonstrated that a TiO₂ concentrate with a grade of 29.62% and a recovery of 65.4% could be obtained from an ore with an initial TiO₂ grade of only 4.39%. Moreover, approximately 40% of the feed mass was rejected at the pre-concentration stage, significantly reducing the load on downstream separation processes. The proposed process demonstrates promising potential as a technical route for the beneficiation of similar refractory anatase-bearing lateritic ores. Full article

The valorization of vegetable-oil biomass into bio-based functional fluids offers a sustainable route for replacing petroleum-derived insulating liquids in power equipment. In this study, soybean and canola oils were used as renewable lipid feedstocks and converted into biomass-derived ester fluids through acid-catalyzed transesterification with methanol, ethanol, 1-propanol, and 1-butanol. The obtained ester-rich products were subjected to a combined physicochemical, dielectric, and thermal screening workflow, including kinematic viscosity at 40 °C (ν₄₀), acid value, breakdown voltage (BDV), differential scanning calorimetry (DSC; 2–8 °C min⁻¹ under N₂), and oxygen bomb calorimetry. Transesterification effectively upgraded the vegetable oils into low-viscosity ester-rich product fluids for most alcohol routes, with soybean methyl ester (SME) reaching 4.41 ± 0.02 mm² s⁻¹ and selected canola-derived esters showing viscosities of 5.81–6.81 mm² s⁻¹. However, the functional performance of the biomass-derived fluids was strongly governed by the alcohol route. SME exhibited the most favorable balance between dielectric and physicochemical properties, delivering the highest BDV of 64.90 ± 9.74 kV, exceeding the IEC 60156 threshold of 30 kV, while maintaining a low acid value of 0.0103 ± 0.0006 mg KOH g⁻¹. In contrast, propyl- and butyl-derived esters showed substantially lower BDV values of ≤14.98 kV, whereas ethanol-derived products retained near-neat-oil viscosities and were unsuitable for BDV testing under the applied conditions. Although propyl- and butyl-derived ester-rich products reduced kinematic viscosity, their markedly lower BDV values were likely associated with route-dependent product heterogeneity, lower alcohol–oil miscibility, possible residual polar impurities, and moisture sensitivity; therefore, they were regarded as non-optimized screening outcomes rather than IEC-compliant transformer-fluid candidates. DSC analysis provided comparative thermal-response descriptors under nitrogen, with methylation producing more coherent endothermic features. The combustion heats of the ester-rich products were concentrated at approximately 39–41 MJ kg⁻¹, lower than that of the mineral-oil reference in this dataset, suggesting combustion heat was used only as a preliminary energy-density descriptor and was not interpreted as direct evidence of improved fire safety. From an engineering-safety perspective, the lower combustion heat of the bio-esters may reduce the potential fire-load contribution during fault-related fire scenarios, although full fire-safety qualification requires additional flash-point, fire-point, and aging evaluations. Overall, this work demonstrates that alcohol route selection is a critical factor in converting vegetable oil biomass into high-value bio-based insulating fluids. Among the tested formulations, soybean methyl ester is the most promising baseline candidate for further development as a biodegradable, sustainable transformer fluid. Full article

Aqueous precipitation and crystallization are central to impurity removal, product formation, and resource recovery in mineral and chemical processing, but robust inline monitoring remains challenging because supersaturation is not measured directly and conductivity signals are affected by temperature, composition drift, bubbles, solids, polarization, and fouling. Electrical conductivity (EC) is attractive as a low-cost, rugged process analytical tool, yet its usefulness depends on mechanistic interpretation: EC reflects charge-carrier concentration and mobility rather than supersaturation itself. This review organizes the literature into a layered framework covering (i) measurement integrity and deployment, (ii) bulk-signal extraction in multiphase media, (iii) estimation of latent variables such as dissolved concentration or supersaturation proxies, and (iv) control readiness based on conductivity-derived targets. Frequency-aware conductivity extraction, event-anchored verification, and observer-based estimation are treated as optional, complementary modules. A Ca-carbonate/CaCO₃ system is used as an illustrative case because its coupling among conductivity, pH/speciation, supersaturation, and precipitation is especially transparent, although the framework is intended for broader processing systems, including complex liquors and slurries. Opportunities are also highlighted for nanomaterials to improve both precipitation control and EC information content. Full article

This study investigated the production of spodumene concentrate and lithium carbonate from a low-grade pegmatite ore containing approximately 0.26 wt.% Li₂O. The ore consisted predominantly of a quartz–feldspar aluminosilicate matrix with dispersed spodumene mineralization, which complicates conventional processing approaches. Preliminary lithium concentration was performed by dense media separation (DMS) using an industrially applicable ferrosilicon-based suspension. The highest separation efficiency was achieved for the −4.0/+2.8 mm fraction, producing a DMS concentrate containing 5.77 wt.% Li₂O with 98% lithium recovery. The obtained spodumene concentrate was subjected to decrepitation at 1000–1100 °C to convert α-spodumene into the more reactive β-modification, followed by sulfation roasting with concentrated sulfuric acid at 250–270 °C. The productive leach solution obtained after water leaching contained up to 12.1 g/L Li₂O. After purification from iron-bearing impurities and precipitation with sodium carbonate, a lithium carbonate product containing at least 98.8 wt.% Li₂CO₃ was obtained. Approximately 53% of the lithium contained in the original ore was recovered into the DMS feed fraction, whereas the overall lithium recovery into lithium carbonate reached about 45% relative to the ore and approximately 70% relative to the concentrate. Full article

Honey has been appreciated for its medicinal properties since ancient times; it is known as a powerful antimicrobial agent, and as a result of the increase in antibiotic resistance of various bacterial strains, honey began to be used in complementary therapies to combat microbial infections. The study aimed to identify the antimicrobial potential of two honey varieties (Acacia honey and polyflora honey) with different botanical and geographical origins on standardized bacterial strains or isolated from patients, some of which showed antibiotic resistance. The physicochemical parameters of the honey varieties analyzed were: water content, impurities, pH of honey, acidity, mineral content, reducing sugar content, total phenol content, and antioxidant capacity (DPPH). The antibacterial potential of the honey varieties was assessed based on tests to determine cell viability and the capacity to inhibit biofilm formation. The Gram-positive strains studied were Staphylococcus aureus (ATCC25923), Staphylococcus aureus MRSA (ATCC43300), Streptococcus pneumoniae (ATCC49619), and the Gram-negative strain was Escherichia coli (ATCC25922). In addition, bacterial strains isolated from the patients were Staphylococcus aureus, Staphylococcus aureus MRSA, Streptococcus pneumoniae, and Escherichia coli. The results of the microbiological tests were correlated with the physicochemical parameters, suggesting that the content of polyphenolic compounds with antioxidant activity and acidic pH may contribute to the antimicrobial potential of honey. Also, statistical analyses indicated significant differences regarding the antimicrobial potential of honey on Gram-positive versus Gram-negative bacteria, standardized versus isolated bacteria from patients, but also for antibiotic-resistant bacteria compared to the other strains studied. Full article

To improve the efficiency, accuracy, and operational stability of postharvest potato tuber sorting in the presence of mineral impurities, mainly soil clods and stones, an intelligent sorting system for potato tubers and mineral impurities was designed and developed. The system employed YOLOv10n as the baseline network and incorporated a PSA module together with a dynamic blur augmentation strategy to establish a task-adapted detection model, termed YOLOv10n-PB. Rather than treating detection accuracy alone as the optimization objective, the proposed system jointly considered detection performance, inference-latency stability, temporal–spatial coordination, and pneumatic rejection reliability. In addition, a programmable logic controller and pneumatic actuators were integrated to enable online target identification and dynamic removal. Comparative experiments involving lightweight YOLO models and $L_{25}\left(5^3\right)$ orthogonal tests were conducted to evaluate the effects of conveyor belt speed, material spacing, and classification threshold on sorting performance. The results showed that YOLOv10n-PB achieved a mAP@0.5 of 98.9% on the test set. Among the investigated factors, conveyor belt speed had the greatest effect on overall sorting accuracy, followed by material spacing and classification threshold. Range analysis identified the optimal parameter combination as a conveyor belt speed of 0.2 m/s, a material spacing of 9 cm, and a classification threshold of 0.4. Validation experiments under these conditions yielded an overall sorting accuracy of 98.3%, a combined mineral-impurity removal accuracy of 98.3%, and a potato tuber false rejection rate of 1.7%. These results demonstrate the feasibility of the proposed system for accurate and stable automatic sorting of potato tubers and mineral impurities under postharvest operating conditions. Full article

Certified reference materials (CRMs) play a pivotal yet frequently overlooked function in mineral exploration. Effective exploration requires CRMs that closely match the geological background. With the full launch of a new round of prospecting strategic breakthrough actions, large-scale regional geochemical surveys will be conducted around the main metallogenic zones in China. Currently, there is a notable shortage of CRMs specifically designed for the arid desert regions of northern China, which have huge mineralization potential. To address this gap and meet analysis and testing needs for stream sediment samples, five stream sediment CRMs have been developed for these arid desert areas. These CRMs represent diverse geological settings: a regional background area, a Ni-polymetallic mining area, a Cu mining area, a Cu-Pb-Zn polymetallic mining area, and a Cu-Fe mining area. The development process strictly followed the requirements outlined in the ISO series of international standards for CRMs. The candidate materials were prepared in accordance with these standards, involving procedures such as impurity removal, drying, multi-stage milling, and homogenization prior to packaging. Homogeneity and stability were evaluated using 30 randomly selected units per candidate, and the results demonstrated excellent performance in both aspects. For characterization, 13 authoritative laboratories collaborated to determine the concentrations of 73 components using validated measurement techniques. Through statistical measurement and rigorous uncertainty assessment, it was confirmed that these materials meet all requirements for CRMs. These new CRMs are recommended for property value assignment, instrument calibration, quality control, and proficiency testing in regional geochemical surveys and mineral exploration. Full article

The lithium battery recycling industry is developing rapidly, and the rapid oxidation and degradation of dimethyl carbonate (DMC) in the wastewater generated by this industry is of crucial importance. In this study, Fe and Cu dopants were controlled and the C-SiO₂ framework with porous structures was constructed to synthesize FeCuC-SiO₂ and C-SiO₂ catalysts. The former could achieve 91.65% of DMC degradation within 60 min through peroxymonosulfate (PMS) activation, and the degradation rate was increased to 4.44 times compared to C-SiO₂ without Fe and Cu doping. And under optimized conditions, a DMC degradation rate of 90.57% can be achieved within 10 min by FeCuC-SiO₂. The catalyst has good stability and the catalytic activity can be maintained during reuse process for five times with over 70% of DMC degradation rate, 58.9% of mineralization rate, and a relatively low amount of metal leaching. Moreover, the degradation rate can still remain above 70% with the existence of impurity anions, demonstrating a strong salt resistance. Hydroxyl radicals (OH^•), sulfate radicals (SO₄^•−), and ¹O₂ were found to dominant the reaction in the FeCuC-SiO₂-PMS system, which were involved in both free radical and non-free radical pathways and led to excellent catalytic oxidation performance and environmental adaptability. In general, a novel design for a Fenton-like catalyst was presented, providing a theoretical basis for the improvement of oxidation efficiency and the regulation of reaction pathways in Fenton-like reactions. Full article