Search Results (8,282)

The decline in the injectivity of injection wells is a serious problem in geothermal systems. In this article, we analyse the mechanisms responsible for the reduction in permeability in Lower Jurassic sandstones during the injection of cooled formation brine. Flow experiments were conducted on rock cores using three types of brines with varying degrees of contamination. The studies included microscopic analysis, scanning electron microscopy (SEM) and mercury intrusion capillary pressure (MICP) before and after the experiments. The results showed that the main factor in the decrease in permeability is the formation of a filter cake from secondary iron minerals on the front surface of the core. Filter cake formation was observed in all samples, with ferrous sediment penetrating to a maximum depth of 1.5 cm from the core front. In addition, the mobilisation of clay particles was observed, which accumulate in pore constrictions, causing additional flow restriction. Mercury porosimetry revealed significant increases in hysteresis values in the front zone (from 16.5 to 42%), indicating complex pore connectivity changes without substantial porosity reduction. The rate of injectivity decline correlates strongly with the fluid flow velocity. The results of the study provide a scientific basis for optimising reinjection processes in geothermal systems and developing strategies to prevent formation damage. Full article

The presence of arsenic-bearing minerals in ores, notably enargite (Cu₃AsS₄), remains an unresolved issue for copper beneficiation processes, including those for porphyry copper deposits. In particular, several operational challenges remain for the selective flotation of enargite from copper–sulphide ores, as well as the selective leaching of arsenic from enargite in copper concentrates. This study addresses these challenges from the standpoint of mediator science, where structures with specific elemental compositions observed by several authors at the surface of enargite and chalcopyrite, under different conditions and analytical techniques, are compiled and analysed. Most probable surface species, observed using technologies measuring the outmost surface layer and occurring onto the mentioned minerals, are identified and compared to species predicted by classic thermodynamic calculations. The results indicate that for chalcopyrite the major species formed in acidic conditions is elemental sulphur, while copper oxide and iron oxides and oxy-hydroxides species predominate with increasing pH. For the case of enargite, a similar situation is observed at low pH values, although slightly acidic conditions appear as a less examined condition for this mineral. Some of the observed species were found to be consistent with thermodynamic predictions, while others are notably absent. Particularly, for the case of enargite researchers have reported the formation of arsenic (III) oxide at pH values as high as 13, and observation not predicted by Pourbaix diagrams. Thus As₂O₃ could be considered a metastable species at highly alkaline conditions, which opens an option to beneficiation from froth flotation. Interestingly, at the same pH condition, iron oxide and oxyhydroxides species predominate at the surface of chalcopyrite. Therefore, applying the mediator concept, the initial alkaline flotation of sulphide ores turns into an oxide flotation case. Full article

Seawater desalination has emerged as a crucial solution for addressing global freshwater scarcity. However, it generates significant volumes of concentrated brine waste. This brine is rich in dissolved salts and minerals, primarily, chloride (55%), sodium (30%), sulfate (8%), magnesium (4%), calcium (1%), potassium (1%), bicarbonate (0.4%), and bromide (0.2%), which are often discharged into marine environments, posing ecological challenges. This study presents a comprehensive global review of innovative technologies for recovering these constituents as valuable products, thereby enhancing the sustainability and economic viability of desalination. The paper evaluates a range of proven and emerging recovery methods, including membrane separation, nanofiltration, electrodialysis, thermal crystallization, solar evaporation, chemical precipitation, and electrochemical extraction. Each technique is analyzed for its effectiveness in isolating salts (NaCl, KCl, and CaSO₄) and minerals (Mg(OH)₂ and Br₂), with a discussion of process-specific constraints, recovery efficiencies, and product purities. Furthermore, the study incorporates a detailed techno-economic assessment, highlighting revenue potential, capital and operational expenditures, and breakeven timelines. Simulated case studies of a 100,000 m³/day seawater reverse osmosis (SWRO) facility demonstrates that a sequential brine recovery process and associated energy balances, supported by pilot-scale data from ongoing global initiatives, can achieve over 90% total salt recovery while producing marketable products such as NaCl, Mg(OH)₂, and Br₂. The estimated revenue from recovered materials ranges between USD 4.5 and 6.8 million per year, offsetting 65–90% of annual desalination operating costs. The analysis indicates a payback period of 3–5 years, depending on recovery efficiency and product pricing, underscoring the economic viability of large-scale brine valorization alongside its environmental benefits. By transforming waste brine into a source of commercial commodities, desalination facilities can move toward circular economy models and achieve greater sustainability. A practical integration framework is proposed for both new and existing SWRO plants, with a focus on aligning with the principles of a circular economy. By transforming waste brine into a resource stream for commercial products, desalination facilities can reduce environmental discharge and generate additional revenue. The study concludes with actionable recommendations and insights to guide policymakers, engineers, and investors in advancing brine mining toward full-scale implementation. Full article

Goji berry is a rich source of polyphenols, carotenoids and polysaccharides, contributing to its diverse biological activities. Due to their high water content and perishability, the berries are often processed into dried forms or juices. This study hypothesized that juice obtained from Serbian-grown goji berries would exhibit a distinctive phytochemical composition and significant in vitro antioxidant and hypoglycemic potential. Antioxidant activity was assessed using DPPH, ABTS, CUPRAC, FRAP and β-carotene bleaching assays, while hypoglycemic potential was evaluated via α-amylase and α-glucosidase inhibition. The analyzed goji juice exhibited mild acidity and moderate sweetness. In terms of bioactive composition, the juice contained high levels of polyphenols (194.50 ± 3.88 mg GAE/100 mL) exceeding the values reported for most commercial fruit juices, as well as notable levels of flavonoids (70.30 ± 5.11 mg CE/100 mL), carotenoids (289.53 ± 0.65 µg/100 mL) and polysaccharides (375.20 ± 12.46 mg Glu/100 mL), along with minerals, particularly potassium and copper. It also showed strong antioxidant capacity and concentration-dependent inhibition of α-amylase (IC₅₀ = 5.28 ± 0.26 mg/mL) and α-glucosidase (IC₅₀ = 10.12 ± 0.23 mg/mL). This study provides the first comprehensive characterization of Serbian-grown goji berry juice, confirming its potential as a functional ingredient. Full article

Hyperspectral unmixing aims to extract pure spectral signatures (endmembers) and estimate their corresponding abundance fractions from mixed pixels, enabling quantitative analysis of surface material composition. However, in geological mineral exploration, existing unmixing methods often fail to explicitly identify informative spectral bands, lack inter-layer information transfer mechanisms, and overlook the physical constraints intrinsic to the unmixing process. These issues result in limited directionality, sparsity, and interpretability. To address these limitations, this paper proposes a novel model, CResDAE, based on a deep autoencoder architecture. The encoder integrates a channel attention mechanism and deep residual modules to enhance its ability to assign adaptive weights to spectral bands in geological hyperspectral unmixing tasks. The model is evaluated by comparing its performance with traditional and deep learning-based unmixing methods on synthetic datasets, and through a comparative analysis with a nonlinear autoencoder on the Urban hyperspectral scene. Experimental results show that CResDAE consistently outperforms both conventional and deep learning counterparts. Finally, CResDAE is applied to GF-5 hyperspectral imagery from Yunnan Province, China, where it effectively distinguishes surface materials such as Forest, Grassland, Silicate, Carbonate, and Sulfate, offering reliable data support for geological surveys and mineral exploration in covered regions. Full article

While sweet cherries (Prunus avium L.) are globally recognized for their numerous potential health benefits, yet limited data exist on New Zealand-grown cultivars. This study examined the nutritional and bioactive profiles of six commercial cultivars—Kordia^®, ‘Lapins’, Sweetheart^®, Staccato^®, ‘Bing’, and ‘Rainier’—in both fresh and processed (washed and packaged) forms. All cultivars contained notable levels of minerals, phenolics, and essential nutrients. Fresh cherries had higher mineral content (0.3–0.5 g/100 g) than processed ones (0.2–0.3 g/100 g). Carbohydrates ranged from 16.8 to 18.6 g/100 g in fresh and 15.1–17.5 g/100 g in processed cherries. Dietary fiber was slightly higher in processed samples (0.5–0.6 g/100 g) than fresh (0.2–0.5 g/100 g). Potassium, calcium, and phosphorus were more concentrated in fresh cherries. Major phenolic metabolites included neochlorogenic acid (up to 44.26 mg/100 g), (-)-epicatechin (7.89 mg/100 g), quercetin 3-rutinoside (4.34 mg/100 g), and cyanidin 3-rutinoside (80.42 mg/100 g). Processed ‘Lapins’ and ‘Bing’ retained high levels of neochlorogenic acid (40.98 and 44.26 mg/100 g), indicating minimal loss during processing. This study offers insights into the nutritional and bioactive composition of New Zealand-grown cherries, emphasizing their dietary value and health-promoting compounds such as polyphenols. Full article

The application of efficient optical-electrical sorting technology for the automatic separation of copper mine waste rocks not only enables the recovery of valuable copper metals and promotes the resource utilization of non-ferrous mine waste, but also conserves large areas of land otherwise used for waste disposal and alleviates associated environmental issues. However, the process is challenged by the low copper content, fine dissemination of copper-bearing minerals, and complex mineral composition and associated relationships. To address these challenges, this study leverages dual-energy X-ray imaging and multi-modal learning, proposing a lightweight twin-tower convolutional neural network (CNN) designed to fuse high- and low-energy spectral information for the automated sorting of copper mine waste rocks. Additionally, the study integrates an emerging Kolmogorov-Arnold network as a classifier to enhance the sorting performance. To validate the efficacy of our approach, a dataset comprising 31,057 pairs of copper mine waste rock images with corresponding high- and low-energy spectra was meticulously compiled. The experimental results demonstrate that the proposed lightweight method achieves competitive, if not superior, performance compared to contemporary mainstream deep learning networks, yet it requires merely 1.32 million parameters (only 6.2% of ResNet-34), thereby indicating extensive potential for practical deployment. Full article

The Central Asian Orogenic Belt (CAOB) represents one of the largest Phanerozoic accretionary orogenic systems globally, with its easternmost segment located in Northeast China. This study integrated broadband magnetotelluric (MT) surveys, geochemical analyses, and high-pressure, high-temperature electrical conductivity experiments to elucidate the deep structural characteristics and tectonic evolution of the Heihe-Hegenshan Suture (HHS) within the CAOB. A dense MT profile survey comprising 15 stations was deployed across the HHS, revealing distinct high-conductivity anomalies interpreted as the suture zone and associated tectonic features. Geochemical and petrophysical analyses of representative andesite and granite samples under simulated crustal conditions (573–973 K, 1.0 GPa) provided critical constraints for MT data interpretation. The integration of MT inversion results with aeromagnetic and Bouguer gravity anomaly data delineates the strike and spatial extent of the HHS, confirming its continuity and northward extension beyond previously recognized limits. Numerical modeling of geothermal gradients and electrical conductivity–depth relationships highlights the dominant role of hydrothermal fluids and alteration minerals in controlling shallow high-conductivity anomalies (<5 km), while deeper structures (>5 km) reflect temperature-controlled rock conductivity. These findings offer novel insights into the lithospheric-scale architecture and geodynamic processes governing the HHS, advancing our understanding of complex accretionary orogenesis in the CAOB. Full article

Research on the Mesozoic–Cenozoic magmatism and the tectonic framework within the Lhasa Terrane is voluminous. However, the sparse documentation of Early Cretaceous magmatism in this region fuels ongoing debate over the prevailing tectonic regime during this time period (i.e., normal subduction vs. flat subduction). The present study investigates the Luerma pyroxenite and Boyun granitoid in the Western Lhasa Terrane through zircon U-Pb dating, whole-rock geochemistry, mineral chemistry, and Sr-Nd-Hf isotopes. The findings date the formation of Luerma pyroxenite at 115 Ma and Boyun granites at 113 Ma to the Early Cretaceous period (115–113 Ma). SiO₂ content of pyroxenite is relatively low (34.27–44.16 wt.%), characterized by an enrichment in large ion lithophile elements (LILEs), light rare earth elements (LREEs), and a depletion in heavy field strength elements (HSFEs), indicative of a metasomatic origin. The εNd (t) and εHf (t) values of the Early Cretaceous ultrabasic rocks range from +2.1 to +2.7 and −0.8 to +10.1, respectively, suggesting their derivation from an enriched mantle source with asthenospheric material incorporation. The Early Cretaceous granodiorites and their mafic enclaves belong to the high-K calc-alkaline series, and show enrichment in LILEs (e.g., Rb, Ba, U, and Th) and depletion in HFSEs (e.g., Nb, Ta, Ti, and Zr). The acidic rocks and their developed mafic enclaves exhibit the geochemical characteristics of trace elements found in island arc magmas. Their εNd (t) values are (−6.0–−5.0), while their εHf (t) values are (−11.7–−1.8); the MMEs εHf (t) values are (−4.1–+0.9). In summary, the Early Cretaceous pyroxenite in the Gangdese Belt originated from a combination of asthenospheric and enriched lithospheric mantle melts, while the granitoids were generated by partial melting of the mantle wedge, a process driven by metasomatism resulting from the slab-derived fluids. At the same time, heat from upwelling mantle-derived melts induced the partial melting of lower crustal materials, leading to the formation of acidic magmas through varying degrees of mixing with basic magmas. This study suggests that Early Cretaceous magmatic activity occurred within a northward subduction setting, characterized by the rotation and fragmentation of the Neo-Tethys oceanic crust. Full article

The effectiveness of periodate-assisted photocatalysis in removing the cationic dye Safranin O (SO) was evaluated using a UV/TiO₂/IO₄⁻ process operated at room temperature under near-neutral pH conditions. Under base conditions ([IO₄⁻] = 0.15 mM, [TiO₂] = 0.4 g/L, [SO] = 10 mg/L), the ternary system achieved a pseudo-first-order rate constant of 0.6212 min⁻¹, outperforming the UV/TiO₂ and UV/IO₄⁻ processes by approximately 21- and 29-fold, respectively. This yielded a synergy ratio of about 12 compared to the sum of the binary processes. Targeted quenching experiments revealed the operative pathways. Strong inhibition by ascorbic acid and phenol indicates that interfacial holes and ^•OH are key oxidants. Methanol caused a moderate slowdown, consistent with ^•OH and hole scavenging. Benzoquinone and oxalate suppressed removal by intercepting the electron and O₂^•− pathways, respectively. Dichromate markedly inhibited the process via optical screening and competition for electrons. Azide had little effect, suggesting a minor role for singlet oxygen. Matrix studies showed progressively slower kinetics from deionized water to mineral water to seawater. This was due to halides, sulfate, alkalinity, and TiO₂ aggregation driven by ionic strength. Additional tests confirmed that the dominant modulators of performance were humic acid (site fouling and light screening), chloride and sulfate (radical speciation and surface effects), nitrite (near-diffusion radical quenching), and bicarbonate at pH 8.3 (conversion of ^•OH to CO₃^•−). Nonionic surfactants (Tween 80, Triton X-100) also depressed SO removal through micellar sequestration and competitive adsorption on TiO₂. The study confirms the potential of UV/TiO₂/IO₄⁻ as a tunable AOP capable of delivering rapid and reliable dye degradation under a wide range of water quality conditions. The mechanistic mapping unifies two roles for IO₄⁻, an electron acceptor that inhibits recombination and a photochemical precursor of iodine centered and ^•OH radicals and connect these roles to the observed synergy and to the trend across deionized water, mineral water, and seawater. The scavenger outcomes assign the main oxidant flux to holes and ^•OH radicals with a contributory electron or O₂^•− branch from IO₄⁻ reduction. Full article

Pegmatite ores, the primary and technologically advanced lithium (Li)-bearing minerals, comprise various rare metal-based elements, including niobium (Nb), tantalum (Ta), tin (Sn), and beryllium. With increasing Li demand, global exploitation of pegmatite ores has generated vast tailings, mainly comprising quartz and feldspar. However, the process for comprehensively utilizing valuable minerals from pegmatite ores remains undeveloped, and the persistent gap between laboratory studies and industrial practice hinders the sustainable advancement of the pegmatite mineral processing industry. Herein, a comprehensive utilization beneficiation process was designed and validated at both laboratory- and pilot-scale levels. Locked-circuit flotation tests at the laboratory-scale on spodumene and feldspar yielded (i) an Li concentrate with an Li₂O grade of 5.80% and recovery of 88.62%, and (ii) a feldspar concentrate with a (K₂O + Na₂O) grade of 11.41% and good recoveries of K₂O (81.30%) and Na₂O (84.81%). In a 72 h continuous pilot-scale test, an Li flotation concentrate with an Li₂O grade of 5.72% and recovery of 86.78%, and a final Li concentrate with an Li₂O grade of 5.89% and recovery of 86.56% were obtained. Using Li flotation tailings as feed, a feldspar concentrate with a (K₂O + Na₂O) grade of 11.41% was obtained, achieving K₂O and Na₂O recoveries of >75%. The proposed process realizes nearly overall mineral recovery from the pegmatite ores, producing qualified concentrates of Li, Nb–Ta, Sn, feldspar, and quartz. In water reuse feasibility tests, ferrous sulfate (FeSO₄) was identified as the optimum flocculant at a dosage of 1000 g m⁻³. In the locked-circuit test with returned water, the consumption of sodium hydroxide (NaOH), sodium carbonate (Na₂CO₃), and EMT-12 (collector) was reduced by 18.75%, 3.33%, and 3.45%, respectively, while the flotation indices of the Li concentrate (Li₂O grade of 5.77% and recovery of 86.47%) were slightly lower than those in freshwater. In addition to increasing economic benefits, the process offers considerable reductions in tailings disposal, full utilization of multiple elements, and a potential decrease in water and reagent consumption. This study provides important guidelines for the mineral processing of Li pegmatite and other associated multimetallic ores. Full article

This study investigates the viability of industrial hempseed oil as a sustainable extender oil in rubber compounding, addressing the urgent demand for alternatives to petroleum-based oils due to regulatory pressures on polycyclic aromatic hydrocarbons (PAH). We employed automated neural networks to analyze the physical and mechanical properties of rubber composites containing industrial hempseed oil, comparing them with six vegetable oils and three petroleum-based oils at extender oil concentrations from 0 to 30 phr. The results revealed that compounds with 20 phr of industrial hempseed oil and raw soybean oil exhibited the highest cure rate index values of 64.32 1/min. Rubber samples with industrial hempseed oil showed a significant 18% reduction in hardness compared to conventional oils, with the softest rubber measuring 40.5 Shore A hardness at 30 phr. Additionally, energy consumption during mixing was decreased by up to 12% for vegetable oil samples compared to mineral oils, enhancing processing efficiency. The neural network approach yielded more accurate predictions of the cure rate index, Shore A hardness, and power consumption during rubber mixing, with a validation performance exceeding 99.2%. Sensitivity analysis identified key factors, including oil content and surface tension, influencing rubber hardness. Overall, this study underscores the potential of industrial hempseed oil as an effective, eco-friendly substitute for conventional mineral oils, contributing to more sustainable practices in the rubber industry. Full article

Gold deposits of the Iron Quadrangle are highly heterogeneous, requiring integrated studies to optimize processing. This study presents a geometallurgical assessment of the Lamego orogenic gold deposit, located in the Iron Quadrangle, Brazil. Eleven composite samples representing four lithotypes, namely metandesite, banded iron formation (BIF), smoky quartz, and carbonaceous phyllite, were analyzed through QEMSCAN, fire assay, and Leco methods. Samples underwent gravity separation and flotation tests to evaluate mineralogical variability and its metallurgical implications. The results show that sulfide-rich lithotypes, particularly those containing pyrite and arsenopyrite, achieved higher gold and sulfur recoveries, especially in flotation. In contrast, samples with high concentrations of muscovite or reactive carbonates such as ankerite and dolomite showed reduced selectivity due to reagent competition and flotation interference. Grinding behavior varied among lithologies, with smoky quartz requiring the highest energy input (10.32 kWh/t) and displaying the lowest breakage parameter (K = 0.120), reflecting its high hardness and fine mineral intergrowths. Strong correlations were established between ore mineralogy and process performance; for instance, sulfide abundance directly predicted flotation recovery, while quartz content correlated with higher grinding energy consumption. These findings underscore the importance of incorporating detailed mineralogical characterization into process design. Geometallurgical tools enable more accurate prediction of metallurgical performance and support the development of lithotype-specific flowsheets for improved recovery, reduced energy consumption, and more efficient gold processing in complex ore systems such as Lamego. Full article

The limestone quarrying and processing industry generates huge amounts of waste, with limestone sludge being one of the most prevalent and challenging by-products. This study aims to evaluate the potential of limestone sludge as a sustainable secondary raw material for the mechanochemical synthesis of bioceramics, specifically hydroxyapatite (HA), for high-added-value applications in bone tissue engineering. High-energy milling is innovatively used as the processing route: dry sludge (functioning as the calcium source), a phosphate source, and water were milled with the aim of producing calcium phosphates (in particular, hydroxyapatite) via mechanosynthesis. The industrial sludge was thoroughly analyzed for chemical composition, heavy metals, and mineral phases to ensure suitability for biomedical applications. The mixture of reagents was tailored to comply with Ca/P = 1.67 molar ratio. Milling was carried out at room temperature; the milling velocity was 600 rpm, and milling time ranged from 5 to 650 min. Characterization by XRD, Raman spectroscopy, and SEM confirmed the progressive transformation of calcite into hydroxyapatite through a metastable DCPD intermediate, following logarithmic reaction kinetics. The resulting powders are fine, homogeneous, and phase-pure, demonstrating that mechanosynthesis provides a low-cost and environmentally friendly pathway to convert limestone waste into functional bioceramic materials. This suggests that Moleanos sludge is a viable and sustainable source to produce tailored calcium phosphates and confirms mechanosynthesis as a cost-effective and reliable technology to activate the low-kinetics chemical reactions in the CaCO₃-H₃PO₄–H₂O system. This work highlights a novel circular economy approach for the valorization of industrial limestone sludge, turning a difficult waste stream into a high-value, sustainable resource. Full article

In this study, we investigate the effects of adding varying proportions of fulvic acid during the digestion of pyrite on the iron concentration in both dissolved and diluted sodium aluminate solutions. Based on the occurrence characteristics of iron in the solutions, oxygen was introduced into the diluted solution to examine its iron removal efficiency, and the influence of organic compounds in the solution on iron removal through oxidation was investigated. The results indicate that, during high-pressure digestion, organic compounds forms complexes with iron, disrupting the hydrophilic iron (or ferrous) hydroxide film formed on the pyrite surface, thereby accelerating its dissolution and leading to a sharp increase in sulfur and iron content in the leachate. After cooling and dilution (100 °C, Na₂O_k 170 g/L), the iron content in the sodium aluminate solution continued to be influenced by organic compounds, showing a significant positive correlation. Oxygenation experiments for iron removal were performed using the diluted solution. Under conditions of an oxygen flow rate of 60 mL/min and an oxidation duration of 2 h (95 °C, oxygen partial pressure was 0.05 Mpa), the iron content (calculated as Fe₂O₃) decreased from 0.078 g/L to 0.021 g/L. Characterization and analysis of the iron removal precipitates revealed that the iron-containing minerals were primarily trivalent iron phases, such as goethite and hematite, with minimal ferrous iron content. Additionally, organic carbon also precipitated together with iron, which confirms the synergistic removal of iron and organic compounds. These findings demonstrate that the oxidation of reducing sodium aluminate solutions containing organic compounds, sulfur, and iron with atmospheric oxygen during the Bayer process sedimentation stage can effectively oxidize predominantly ferrous iron into less soluble ferric iron, thereby achieving iron removal. Full article