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Search Results (235)

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Keywords = mineral acid neutralization

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18 pages, 3967 KiB  
Article
A Thorough Investigation of the Mechanism of theAntagonistic Effect Between Phosphorus and Basic Oxide-Forming Minerals as Flame Retardants of PolymericComposite Coatings
by Evangelia Mitropoulou, Georgios N. Mathioudakis, Amaia Soto Beobide, Athanasios Porfyris, Vassilios Dracopoulos, Kerim Kılınç, Theodosios Chatzinikolaou, Deniz Savci, Cem Gunesoglu, Joannis Kallitsis and George A. Voyiatzis
Coatings 2025, 15(8), 886; https://doi.org/10.3390/coatings15080886 - 30 Jul 2025
Viewed by 274
Abstract
Halogenated flame retardants have been amongst the most widely used and effective solutions for enhancing fire resistance. However, their use is currently strictly regulated due to serious health and environmental concerns. In this context, phosphorus-based and mineral flame retardants have emerged as promising [...] Read more.
Halogenated flame retardants have been amongst the most widely used and effective solutions for enhancing fire resistance. However, their use is currently strictly regulated due to serious health and environmental concerns. In this context, phosphorus-based and mineral flame retardants have emerged as promising alternatives. Despite this, their combined use is neither straightforward nor guaranteed to be effective. This study scrutinizes the interactions between these two classes of flame retardants (FR) through a systematic analysis aimed at elucidating the antagonistic pathways that arise from their coexistence. Specifically, this study focuses on two inorganic fillers, mineral huntite and chemically precipitated magnesium hydroxide, both of which produce basic oxides upon thermal decomposition. These fillers were incorporated into a poly(butylene terephthalate) (PBT) matrix to be utilized as advanced-mattress FR coating fabric and were subjected to a series of flammability tests. The pyrolysis products of the prepared polymeric composite compounds were isolated and thoroughly characterized using a combination of analytical techniques. Thermogravimetric analysis (TGA) and differential thermogravimetric analysis (dTGA) were employed to monitor decomposition behavior, while the char residues collected at different pyrolysis stages were examined spectroscopically, using FTIR-ATR and Raman spectroscopy, to identify their structure and the chemical reactions that led to their formation. X-ray diffraction (XRD) experiments were also conducted to complement the spectroscopic findings in the chemical composition of the resulting char residues and to pinpoint the different species that constitute them. The morphological changes of the char’s structure were monitored by scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDS). Finally, the Limited Oxygen Index (LOI) and UL94 (vertical sample mode) methods were used to assess the relative flammability of the samples, revealing a significant drop in flame retardancy when both types of flame retardants are present. This reduction is attributed to the neutralization of acidic phosphorus species by the basic oxides generated during the decomposition of the basic inorganic fillers, as confirmed by the characterization techniques employed. These findings underscore the challenge of combining organophosphorus with popular flame-retardant classes such as mineral or basic metal flame retardants, offering insight into a key difficulty in formulating next-generation halogen-free flame-retardant composite coatings. Full article
(This article belongs to the Special Issue Innovative Flame-Retardant Coatings for High-Performance Materials)
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19 pages, 15843 KiB  
Article
Hydrochemical Characteristics and Formation Mechanisms of Groundwater in the Nanmiao Emergency Groundwater Source Area, Yichun, Western Jiangxi, China
by Shengpin Yu, Tianye Wang, Ximin Bai, Gongxin Chen, Pingqiang Wan, Shifeng Chen, Qianqian Chen, Haohui Wan and Fei Deng
Water 2025, 17(14), 2063; https://doi.org/10.3390/w17142063 - 10 Jul 2025
Viewed by 298
Abstract
The Nanmiao Emergency Groundwater Source Area, rich in H2SiO3, serves as a strategic freshwater reserve zone in western Jiangxi Province. However, the mechanisms underlying groundwater formation in this area remain unclear. This study applied a combination of statistical analysis, [...] Read more.
The Nanmiao Emergency Groundwater Source Area, rich in H2SiO3, serves as a strategic freshwater reserve zone in western Jiangxi Province. However, the mechanisms underlying groundwater formation in this area remain unclear. This study applied a combination of statistical analysis, isotopic tracing, and hydrochemical modeling to reveal the hydrochemical characteristics and origins of groundwater in the region. The results indicate that Na+ and Ca2+ dominate the cations, while HCO3 and Cl dominate the anions. Groundwater from descending springs is characterized by low mineralization and weak acidity, with hydrochemical types of primarily HCO3–Na·Mg and HCO3–Mg·Na·Ca. Groundwater from boreholes is weakly mineralized and neutral, with dominant hydrochemical types of HCO3–Ca·Na and HCO3–Ca·Na·Mg, suggesting a deep circulation hydrogeochemical process. Hydrogen and oxygen isotope analysis indicates that atmospheric precipitation is the primary recharge source. The chemical composition of groundwater is mainly controlled by rock weathering, silicate mineral dissolution, and cation exchange processes. During groundwater flowing, water and rock interactions, such as leaching, cation exchange, and mixing, occur. This study identifies the recharge sources and circulation mechanisms of regional groundwater, offering valuable insights for the sustainable development and protection of the emergency water source area. Full article
(This article belongs to the Special Issue Advances in Surface Water and Groundwater Simulation in River Basin)
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15 pages, 270 KiB  
Article
Performance, Metabolism, and Economic Implications of Replacing Soybean Meal with Dried Distillers Grains with Solubles in Feedlot Cattle Diets
by Andrei L. R. Brunetto, Guilherme L. Deolindo, Ana Luiza de F. dos Santos, Luisa Nora, Maksuel Gatto de Vitt, Renato S. de Jesus, Bruna Klein, Luiz Eduardo Lobo e Silva, Roger Wagner, Gilberto V. Kozloski and Aleksandro S. da Silva
Fermentation 2025, 11(7), 363; https://doi.org/10.3390/fermentation11070363 - 23 Jun 2025
Viewed by 617
Abstract
The growing demand for biofuels, especially ethanol produced from corn, has driven the production of co-products such as dried distillers grains with solubles (DDGS). With a high protein content (around 30%), fiber, and minerals, DDGS presents an economical alternative for animal nutrition, replacing [...] Read more.
The growing demand for biofuels, especially ethanol produced from corn, has driven the production of co-products such as dried distillers grains with solubles (DDGS). With a high protein content (around 30%), fiber, and minerals, DDGS presents an economical alternative for animal nutrition, replacing traditional sources like soybean meal while maintaining productive performance and reducing costs. This study evaluated the total replacement of soybean meal with DDGS in the diet of confined Holstein cattle, focusing on weight gain, feed intake, digestibility, feed efficiency, animal health, meat quality, and economic viability. The 24 animals received diets with 80% concentrate, containing either DDGS or soybean meal, and no significant differences were observed in terms of body weight (p = 0.92), feed intake (p = 0.98), or feed efficiency (p = 0.97) between the two treatments. The average daily gain was 1.25 and 1.28 kg for cattle in the DDGS and soybean meal groups, respectively (p = 0.92). Regarding metabolic and digestive parameters, no relevant changes were found in blood levels, except for higher serum cholesterol (p = 0.03) levels in animals fed DDGS. The digestibility of neutral detergent fiber (NDF) (p = 0.03) and acid detergent fiber (ADF) (p = 0.05) was lower in the DDGS group, while the digestibility of ether extract was higher (p = 0.02). Rumen fluid analysis revealed an increase in the production of short-chain fatty acids (p = 0.01), such as acetic and butyric acids (p = 0.01), in the DDG-fed animals. In terms of meat quality, animals fed DDGS produced meat with lower levels of saturated fatty acids (SFA) (p = 0.05) and higher levels of unsaturated fatty acids (UFA) (p = 0.02), especially oleic acid (p = 0.05). This resulted in a healthier lipid profile, with a higher UFA/SFA ratio (p = 0.01). In terms of economic viability, DDGS-based diets were 10.5% cheaper, reducing the cost of production per animal by 7.67%. Profitability increased by 110% with DDGS compared to soybean meal, despite the high transportation costs. Therefore, replacing soybean meal with DDGS is an efficient and economical alternative for feeding confined cattle, maintaining zootechnical performance, increasing meat lipid content and improving fatty acid profile, and promoting higher profitability. This alternative is particularly advantageous in regions with easy access to the product. Full article
17 pages, 1437 KiB  
Article
pH-Dependent Ozonation of Diclofenac: Molecular Insights and Implications for Water Quality and Nature-Based Water Reuse Systems
by Natalia Villota, Unai Duoandicoechea and Enzo Valentin Tosi-Zarate
Clean Technol. 2025, 7(2), 47; https://doi.org/10.3390/cleantechnol7020047 - 5 Jun 2025
Viewed by 553
Abstract
Diclofenac (DCF), a widely consumed non-steroidal anti-inflammatory drug, presents significant environmental challenges due to its persistence and toxicity in aquatic ecosystems. This study investigates the pH-dependent ozonation of DCF in aqueous media, focusing on degradation kinetics, transformation pathways, and effects on key water [...] Read more.
Diclofenac (DCF), a widely consumed non-steroidal anti-inflammatory drug, presents significant environmental challenges due to its persistence and toxicity in aquatic ecosystems. This study investigates the pH-dependent ozonation of DCF in aqueous media, focusing on degradation kinetics, transformation pathways, and effects on key water quality indicators. Ozonation experiments were conducted across a broad pH range (2.0–13.0), using a multi-scale analytical approach combining UV/Vis spectroscopy, colorimetry, turbidity, and aromaticity measurements. The results show that pH strongly influences DCF degradation efficiency: acidic conditions favor selective reactions with molecular ozone, while an alkaline pH enhances non-selective oxidation via hydroxyl radicals. Spectroscopic analyses revealed the progressive breakdown of aromatic structures, the transient formation of quinonoid and phenolic intermediates, and eventual mineralization to inorganic by-products such as nitrate. Low-pH conditions also induced turbidity due to precipitation of neutral DCF species. These findings underline the importance of pH control in optimizing ozonation performance and minimizing toxic by-products. Furthermore, this study proposes ozonation as a viable pre-treatment step within Nature-Based Solutions (NBSs), potentially improving the performance of downstream biological systems such as constructed wetlands. The results contribute to the development of integrated and sustainable water treatment strategies for pharmaceutical contaminant removal and water reuse. Full article
(This article belongs to the Special Issue Nature-Based Solutions for Water Reuse and Contaminant Reduction)
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21 pages, 3035 KiB  
Article
Study on the Unblocking Fluid System for Complex Blockages in Weiyuan Shale Gas Wellbores
by Yadong Yang, Yixuan Wang, Longqing Zou, Jianfeng Xiao, Qiyue He, Teng Zhang, Bangkun Qiu and Jingyi Zhu
Processes 2025, 13(6), 1684; https://doi.org/10.3390/pr13061684 - 27 May 2025
Cited by 1 | Viewed by 370
Abstract
During the early stages of drilling and completion in the Weiyuan shale gas wells, a large number of downhole materials were introduced, some of which inevitably remained in the wellbore or migrated into the reservoir. Over time, these residual materials underwent physicochemical reactions [...] Read more.
During the early stages of drilling and completion in the Weiyuan shale gas wells, a large number of downhole materials were introduced, some of which inevitably remained in the wellbore or migrated into the reservoir. Over time, these residual materials underwent physicochemical reactions with reservoir minerals and fluids, gradually forming dense composite blockages that severely restricted the production efficiency of shale gas wells. The effectiveness of single-component unblocking agents in removing such blockages is limited. This study systematically analyzed the physicochemical properties of wellbore blockages in Weiyuan shale gas wells using refined chemical techniques. The results revealed that the main inorganic components of the blockages were Fe3O4 and SiO2, while the organic components were primarily related to polymer materials from drilling and fracturing fluids. Based on the physicochemical characteristics of the blockages, a novel “organic dispersion and inorganic decomposition” unblocking strategy was proposed. Furthermore, an innovative approach that combined molecular simulation with laboratory experiments was employed to develop three unblocking fluid systems tailored to different blockage conditions: neutral, acidic, and composite. Performance evaluation showed that the composite unblocking fluid exhibited the best efficacy in treating these dense composite blockages, achieving a scale dissolution and dispersion efficiency of over 90%. Compared to the other two systems, the composite fluid demonstrated the longest penetration distance in simulated composite blockages, improving penetration by over 30%. In field applications, unblocking strategies were optimized based on whether the oil and casing were interconnected. For blocked wells without connectivity, a circulating wash method was used, while for interconnected wells, a dragging wash method was employed, ensuring efficient blockage removal. Full article
(This article belongs to the Section Energy Systems)
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35 pages, 8311 KiB  
Review
Efficient Exploitation of Lepidolite Resources: A Review on Beneficiation Techniques, Extraction Methods, and Synergistic Optimization
by Jiangang Ku, Xiao Shi, Qian Wang, Hanyu Lin, Hongliang Shang and Zhengchang Shen
Separations 2025, 12(5), 130; https://doi.org/10.3390/separations12050130 - 16 May 2025
Cited by 2 | Viewed by 983
Abstract
Lithium is a critical mineral resource. With the development of high-end manufacturing industry, the demand for high-performance lithium-containing chemical raw materials continues to grow. At present, lithium needs to be acquired from a large amount of lepidolite ore, constrained by the existing lithium [...] Read more.
Lithium is a critical mineral resource. With the development of high-end manufacturing industry, the demand for high-performance lithium-containing chemical raw materials continues to grow. At present, lithium needs to be acquired from a large amount of lepidolite ore, constrained by the existing lithium resource supply limitation quandary, and the industry urgently needs to develop more efficient beneficiation and extraction methods for lepidolite. Findings have suggested mixed collectors (e.g., DDA/SDBS) achieve a 4.99% Li2O grade and 98% recovery at neutral pH, reducing reagent use by 20–30%. Microwave-assisted roasting boosts Li recovery to 95.9% and cuts energy use by 26.9%. Bioleaching with Acidithiobacillus ferrooxidans (A.F.) and rhamnolipid releases 6.8 mg/L Li with a lower environmental impact. Sulfuric acid baking recovers Li (97.1%), Rb (96.0%), and Cs (95.1%) efficiently. Despite challenges in fine-particle recovery and reagent costs, integrated strategies like nanobubble flotation, green collectors, and AI optimization offer sustainable, high-efficiency extraction. This work provides insights for advancing lepidolite processing, balancing economics and environmental stewardship. Full article
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24 pages, 4411 KiB  
Article
Characterization of Historical Tailings Dam Materials for Li-Sn Recovery and Potential Use in Silicate Products—A Case Study of the Bielatal Tailings Dam, Eastern Erzgebirge, Saxony, Germany
by Kofi Moro, Nils Hoth, Marco Roscher, Fabian Kaulfuss, Johanes Maria Vianney and Carsten Drebenstedt
Sustainability 2025, 17(10), 4469; https://doi.org/10.3390/su17104469 - 14 May 2025
Cited by 1 | Viewed by 644
Abstract
The characterization of historical tailings bodies is crucial for optimizing environmental management and resource recovery efforts. This study investigated the Bielatal tailings dam (Altenberg, Germany), examining its internal structure, material distribution influenced by historical flushing technology, and the spatial distribution of valuable elements. [...] Read more.
The characterization of historical tailings bodies is crucial for optimizing environmental management and resource recovery efforts. This study investigated the Bielatal tailings dam (Altenberg, Germany), examining its internal structure, material distribution influenced by historical flushing technology, and the spatial distribution of valuable elements. To evaluate the tailings resource potential, drill core sampling was conducted at multiple points at a depth of 7 m. Subsequent analyses included geochemical characterization using sodium peroxide fusion, lithium borate fusion, X-ray fluorescence (XRF), and a scanning electron microscope with energy dispersive X-ray spectroscopy (SEM-EDX). Particle size distribution analysis via a laser particle size analyzer and wet sieving was conducted alongside milieu parameter (pH, Eh, EC) analysis. A theoretical assessment of the tailings’ potential for geopolymer applications was conducted by comparing them with other tailings used in geopolymer research and relevant European standards. The results indicated average concentrations of lithium (Li) of 0.1 wt%, primarily hosted in Li-mica phases, and concentrations of tin (Sn) of 0.12 wt%, predominantly occurring in cassiterite. Particle size analysis revealed that the tailings material is generally fine-grained, comprising approximately 60% silt, 32% fine sand, and 8% clay. These textural characteristics influenced the spatial distribution of elements, with Li and Sn enriched in fine-grained fractions predominantly concentrated in the dam’s central and western sections, while coarser material accumulated near injection points. Historical advancements in mineral processing, particularly flotation, had significantly influenced Sn distribution, with deeper layers showing higher Sn enrichment, except for the final operational years, which also exhibited elevated Sn concentrations. Due to the limitations of X-ray fluorescence (XRF) in detecting Li, a strong correlation between rubidium (Rb) and Li was established, allowing Li quantification via Rb measurements across varying particle sizes, redox conditions, and geological settings. This demonstrated that Rb can serve as a reliable proxy for Li quantification in diverse contexts. Geochemical and mineralogical analyses revealed a composition dominated by quartz, mica, topaz, and alkali feldspars. The weakly acidic to neutral conditions (pH 5.9–7.7) and reducing redox potential (Eh, 570 to 45 mV) of the tailings material indicated a minimal risk of acid mine drainage. Preliminary investigations into using Altenberg tailings as geopolymer materials suggested that their silicon-rich composition could serve as a substitute for coal fly ash in construction; however, pre-treatment would be needed to enhance reactivity. This study underscores the dual potential of tailings for element recovery and sustainable construction, emphasizing the importance of understanding historical processing techniques for informed resource utilization. Full article
(This article belongs to the Special Issue Geological Engineering and Sustainable Environment)
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15 pages, 6357 KiB  
Article
Study on Floatation Separation of Molybdenite and Talc Based on Crystal Surface Anisotropy
by Qidong Zhang, Xiaoli Li, Zhifang Hu, Bowen Gao and Chen Liu
Separations 2025, 12(5), 123; https://doi.org/10.3390/separations12050123 - 13 May 2025
Viewed by 337
Abstract
Talcose molybdenite resources are abundant but resource utilization is low. The floatation separation of molybdenite (MoS2) and talc is challenging due to their similar natural hydrophobicity and layered structures. This study investigates the surface properties and interaction mechanisms between these minerals [...] Read more.
Talcose molybdenite resources are abundant but resource utilization is low. The floatation separation of molybdenite (MoS2) and talc is challenging due to their similar natural hydrophobicity and layered structures. This study investigates the surface properties and interaction mechanisms between these minerals to improve their separation efficiency. Density functional theory (DFT) calculations confirm that the basal planes of both minerals are hydrophobic, while their edge surfaces are hydrophilic. Atomic force microscopy (AFM) and DLVO theory reveal that molybdenite and talc particles aggregate in neutral/acidic conditions but disperse in alkaline solutions due to altered surface forces. Floatation experiments demonstrate that pulp pH is the key controlling factor—alkaline conditions (pH > 10) effectively reduce hetero-aggregation, enabling selective molybdenite recovery. These findings provide critical insights into optimizing floatation processes for talcose molybdenite ores, enhancing resource utilization. Full article
(This article belongs to the Special Issue Advances in Novel Beneficiation Technology of Critical Minerals)
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19 pages, 3436 KiB  
Article
Carbon Dioxide Capture by Alkaline Water with a Semi-Batch Column and Ultra-Fine Microbubble Generator
by Samiya A. Almamari, Salam K. Al-Dawery, Saima Farooq, Dalal H. Al Aisri, Sumaya S. Alrahbi, Aisha A. Al Fazari, Hamed N. Harharah, Ramzi H. Harharah, Salim S. Al Alawi and Gasim Hayder
Processes 2025, 13(4), 1259; https://doi.org/10.3390/pr13041259 - 21 Apr 2025
Viewed by 718
Abstract
Increased emissions of carbon dioxide (CO2) from industrial activities are the main cause of the growing problem of global warming and climate change, highlighting the needs for efficient CO2 capture and storage (CCS) techniques. The present work aims to investigate [...] Read more.
Increased emissions of carbon dioxide (CO2) from industrial activities are the main cause of the growing problem of global warming and climate change, highlighting the needs for efficient CO2 capture and storage (CCS) techniques. The present work aims to investigate the possibility of CO2 sequestration using sodium hydroxide (NaOH) in a semi-batch column with an integrated gas lift tower and an ultra-micro bubbles generator, a novel setup designed to enhance mass transfer rates and capture efficiency. Unlike the previously reported setups, our system achieves a 50% faster capture rate with improved mass transfer, enhanced gas-liquid interaction and higher removal efficiency due to finer bubble dispersion, as confirmed by experimental findings. Preliminary tests to ascertain the effectiveness of CO2 removal were carried out across various CO2 gas flow rates (3, 5, 7 L/min), NaOH volumes (2, 3, 4 L) and concentrations (0.1, 0.2, 0.3 M). The results indicated that both gas flow rate and NaOH concentration have profound impacts on the CO2 capture rate. Increasing either of these parameters, or using low concentrations of NaOH, leads to a rapid drop in pH due to a faster rate of neutralization and the formation of carbonic acid (H2CO3), a weak acidic solution. For instance, with 0.1 M NaOH and 2 L volume, the pH decreased from 13.07 to 7.02 within 1.5 min at gas flow rate of 7 L/min, while with 0.3 M NaOH, pH reduced to 7.3 after 6 min. Higher volumes and concentrations of NaOH caused a decrease in the capture rate of CO2 due to reversed reaction with formed sodium carbonate. For instance, with 0.3 M NaOH and 4 L volume, the pH reduced from 13.58 to 8 after 5 min at 7 L/min gas flow rate. Scaling up to a 100 L semi-batch column with an ultra-fine micro bubble generator, as a new approach, reduced the time taken by half in the capture of CO2. Additionally, the study also investigated the comparison of tap versus deionized water in CO2 capture reaction. The results demonstrated that dissolved minerals in tap water, particularly Ca2+ and Mg2+ ions, affected precipitate formation and capture efficiency differently than deionized water, offering practical insights for CCS in varied water sources. Full article
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15 pages, 2841 KiB  
Article
A Bio-Based Collector Derived from Vitamin E for Hematite Flotation
by Rocky Mensah, Tammitage Danesh S. Perera, Tina Hsia, Pouria Amani, San H. Thang and Mahshid Firouzi
Colloids Interfaces 2025, 9(2), 24; https://doi.org/10.3390/colloids9020024 - 11 Apr 2025
Viewed by 735
Abstract
The increasing demand for sustainable mining practices has driven the development of environmentally friendly reagents for mineral processing. This study investigates vitamin E sodium succinate (VE_SS), a novel bio-based collector, for its potential in hematite flotation. The performance of VE_SS was benchmarked against [...] Read more.
The increasing demand for sustainable mining practices has driven the development of environmentally friendly reagents for mineral processing. This study investigates vitamin E sodium succinate (VE_SS), a novel bio-based collector, for its potential in hematite flotation. The performance of VE_SS was benchmarked against sodium oleate (NaOL), a widely used conventional collector in mineral processing. To assess the flotation performance of VE_SS, micro-flotation experiments were conducted using hematite, sourced from a mine, and silica, a common associated gangue mineral. These tests were complemented by comprehensive surface characterizations, including contact angle measurements, zeta potential analysis, Fourier-transform infrared (FTIR) spectroscopy, and X-ray photoelectron spectroscopy (XPS), to investigate the adsorption mechanisms of VE_SS in comparison to NaOL. The results demonstrate that VE_SS effectively enhances hematite recovery, achieving levels comparable to NaOL. Furthermore, VE_SS exhibited reduced sensitivity to pH, addressing a key limitation of NaOL, which performs well in neutral to alkaline conditions but shows significantly lower recovery under acidic pH. These findings highlight the potential of VE_SS as a bio-based alternative to conventional collectors, contributing to the advancement of more sustainable mineral processing practices. Full article
(This article belongs to the Special Issue Colloids and Interfaces in Mineral Processing)
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19 pages, 4826 KiB  
Article
Mechanisms and Implications of Phosphate Retention in Soils: Insights from Batch Adsorption Experiments and Geochemical Modeling
by Zhi Tang, Zeyong Chi, Fengcheng Jiang, Mingzhe Zhao, Shengbo Fu, Lingqiao Wei, Qingsheng Feng, Yongming Wu and Nuchao Xu
Water 2025, 17(7), 998; https://doi.org/10.3390/w17070998 - 28 Mar 2025
Viewed by 890
Abstract
Soil plays a critical role as a natural barrier in mitigating the infiltration of industrial-derived phosphate pollution into groundwater, with its phosphate retention capacity governed mainly by its mineralogical composition. In this study, three soil samples were collected from the Huangmailing phosphate mine [...] Read more.
Soil plays a critical role as a natural barrier in mitigating the infiltration of industrial-derived phosphate pollution into groundwater, with its phosphate retention capacity governed mainly by its mineralogical composition. In this study, three soil samples were collected from the Huangmailing phosphate mine area, and the minerals responsible for phosphate retention were identified through batch adsorption experiments, chemical extraction, and spectroscopy analyses. The distribution of phosphate retention within soil samples was further quantified using a geochemical model. The results indicate that the adsorption capacity of soils to phosphate ranges from 0.193 to 0.217 mg/g. Adsorption equilibrium was reached at 750 min, conforming to the intra-particle diffusion kinetic model. Elevated temperatures facilitate phosphate adsorption. Under acidic and neutral conditions, approximately 80–90% of the phosphate is adsorbed onto iron oxides, primarily through inner-sphere surface complexation, thus unaffected by ionic strength. Under alkaline conditions, the retention mechanism was dominated by the release of exchangeable Ca2+ from vermiculite and biotite, as well as the precipitation of hydroxyapatite. Notably, the critical pH at which the retention mechanism shifts decreased with increasing content of layered silicate minerals and the concentration of cations in the solution. Our study underscores the distinct roles of effective minerals in phosphate retention under different pH conditions and highlights the significance of exchangeable Ca2+ in layered silicate minerals under alkaline conditions. Based on these findings, it is recommended that sites with favorable mineralogical characteristics tailored to the pH of phosphate-containing wastewater be prioritized for phosphorus chemical industries. This study also assesses the cost-effectiveness of adding vermiculite to soil in industrial and agricultural applications. The findings can provide a scientific basis for preventing groundwater phosphorus pollution in critical areas. Full article
(This article belongs to the Section Soil and Water)
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20 pages, 18130 KiB  
Article
Lab-Scale Experimental Study of Microbial Enhanced Oil Recovery on Low-Permeability Cores Using the Silicate Bacterium Paenibacillus mucilaginosus
by Lei Li, Chunhui Zhang, Peidong Su and Hongmei Mu
Microorganisms 2025, 13(4), 738; https://doi.org/10.3390/microorganisms13040738 - 25 Mar 2025
Viewed by 463
Abstract
Silicate bacteria, capable of decomposing silicate minerals that are widely distributed in oil reservoirs, have never been applied in microbial enhanced oil recovery (MEOR). This study investigated a typical silicate bacterium (Paenibacillus mucilaginosus) for the first time in a simulation experiment [...] Read more.
Silicate bacteria, capable of decomposing silicate minerals that are widely distributed in oil reservoirs, have never been applied in microbial enhanced oil recovery (MEOR). This study investigated a typical silicate bacterium (Paenibacillus mucilaginosus) for the first time in a simulation experiment on low-permeability cores. Meanwhile, a biosurfactant-producing bacterium (Pseudomonas aeruginosa) and an acid-producing bacterium (Bacillus licheniformis) that have been widely studied and applied in MEOR were used for comparison. The results show that although P. mucilaginosus is inferior to P. aeruginosa and B. licheniformis in terms of enhancement of oil recovery at the microbial flooding stage, it can maintain efficient dissolution of minerals over extended periods during the subsequent water flooding stage. This is different from the other two bacteria and ultimately leads to a 6.9% enhancement in oil recovery (7.9% for P. aeruginosa and 4.8% for B. licheniformis). P. mucilaginosus improves oil recovery by increasing the porosity (1.4%) and permeability (12.3 mD) of low-permeability cores through biological weathering. The μCT results show that the pore quantity and pore volume across varying pore radii in low-permeability cores are altered after the MEOR simulation experiment by reducing the quantity and volume of pores with radii less than 10 μm and increasing the quantity and volume of pores with radii between 10 and 25 μm. Under MEOR simulation experimental conditions, P. mucilaginosus slightly degrade saturated hydrocarbons (1.9%), mainly the n-alkanes of C11–C20, but cannot degrade aromatic hydrocarbons, resins, and asphaltenes. The enhanced oil recovery by P. mucilaginosus is attributed to its bio-dissolution under neutral pH conditions, which prevents acid sensitivity damage to low-permeability cores. Thus, its MEOR characteristics are significantly different from the biosurfactant-producing bacterium P. aeruginosa and acid-producing bacterium B. licheniformis. Injecting P. mucilaginosus at the early stages of reservoir development or using it together with other microorganisms should maximize its MEOR effect. This study advances the MEOR framework by extending silicate-dissolving bacteria from agricultural microbial fertilizer systems to MEOR in low-permeability reservoirs, revealing the broad prospects of mineral-targeting microbes for both research and industrial applications in MEOR. Full article
(This article belongs to the Section Environmental Microbiology)
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25 pages, 5539 KiB  
Article
Hydrogeochemical Signatures and Processes Influencing Mineral Waters at Furnas Volcano (São Miguel, Azores)
by Letícia Ferreira, José Virgílio Cruz, Fátima Viveiros, Nuno Durães, César Andrade, Carlos Almeida, Nuno Cabral, Rui Coutinho and José Francisco Santos
Water 2025, 17(6), 898; https://doi.org/10.3390/w17060898 - 20 Mar 2025
Viewed by 617
Abstract
Furnas volcano, one of the three active central volcanoes of São Miguel (the Azores archipelago), hosts mineral waters with significant special variations, divided into hyperthermal (89.4–95.4 °C), thermal (29.9–70.0 °C), and cold (14.2–21.4 °C) waters. Groundwaters are classified as Na-HCO3, with [...] Read more.
Furnas volcano, one of the three active central volcanoes of São Miguel (the Azores archipelago), hosts mineral waters with significant special variations, divided into hyperthermal (89.4–95.4 °C), thermal (29.9–70.0 °C), and cold (14.2–21.4 °C) waters. Groundwaters are classified as Na-HCO3, with a neutral to slightly acidic pH, except one SO4-Na acidic sample. The major elements are primarily influenced by rock leaching and volcanic input, patterns also reflected in the trace elements, including the rare earth elements. The major cations, along with lithium, iron, aluminum, rubidium, and strontium, indicate the influence of water–rock interactions. Some samples depict a higher influence in this input, shown by the similar REE behavior between them and the local rock behavior. The volcanic input is distinguished into two environments: an acid sulfate boiling pool, formed by steam heating, and neutral HCO3-Cl waters, where bicarbonate-rich waters mix with a neutral chloride fluid from a deep reservoir. The deeper reservoir also provides boron, arsenic, antimony, and tungsten, also seemingly associated with a positive spike in europium due to rock dissolution at temperatures above 250 °C or a reducing environment. This interpretation is corroborated by the stability of the strontium isotopes between samples. Full article
(This article belongs to the Section Hydrogeology)
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28 pages, 16980 KiB  
Article
Genesis of the Gongjuelong Sn Polymetallic Deposit in the Yidun Terrane, China: Constraints from the In Situ Geochemistry of Garnet, Cassiterite, and Quartz
by Yuchang Zhou, Yiwei Peng, Chang Liu, Jianji Tian, Zhi Wang, Mingwei Song and Yan Zhang
Minerals 2025, 15(3), 314; https://doi.org/10.3390/min15030314 - 18 Mar 2025
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Abstract
Numerous skarn-type Sn and hydrothermal vein-type Pb–Zn–Ag deposits occur in the northern Yidun Terrane, China. The Gongjuelong skarn Sn polymetallic deposit, adjacent to the Haizishan granite, is situated in the central region of Yidun Terrane. The genesis of the Gongjuelong Sn deposit and [...] Read more.
Numerous skarn-type Sn and hydrothermal vein-type Pb–Zn–Ag deposits occur in the northern Yidun Terrane, China. The Gongjuelong skarn Sn polymetallic deposit, adjacent to the Haizishan granite, is situated in the central region of Yidun Terrane. The genesis of the Gongjuelong Sn deposit and its relationship with the adjacent Pb–Zn–Ag deposits remains controversial. The ore-forming process can be divided into three stages: the prograde stage (I), marked by the formation of garnet and pyroxene; the retrograde stage (II), which includes the epidote–actinolite sub-stage (II-1) and the quartz-cassiterite sub-stage (II-2); and the sulfide stage (III), consisting of the chalcopyrite–pyrrhotite sub-stage (III-1) and the arsenopyrite–sphalerite sub-stage (III-2). Two types of garnet (Grt-I and Grt-II) have been identified in stage I and both belong to the grossular–andradite solid solution. Grt-II (Gro52-73And25-45Spe+Pyr+Alm2-3) contains slightly more Fe than Grt-I (Gro64-76And20-28Spe+Pyr+Alm2-10). Grt-I is enriched in heavy rare-earth elements (HREEs) and depleted in light rare-earth elements (LREEs), whereas Grt-II is enriched in LREEs and depleted in HREEs. Grt-I has higher U contents and lower Th/U ratios than those of Grt II, indicating a lower oxygen fugacity for the earlier skarn alteration. In contrast to Grt-I, Grt-II shows a more significant negative Eu anomaly along with lower LREEs/HREEs. Therefore, Grt-I and Grt-II likely formed under mildly acidic and near-neutral conditions, respectively. The W (350–3015 ppm) and Fe (235–3740 ppm) contents and Zr/Hf ratios (18.7–49.4) of cassiterite from Gongjuelong are similar to those of cassiterite from the granite-related Sn deposits, as well as the Xiasai hydrothermal vein-type Pb–Zn–Ag deposit in the northern Yidun Terrane. The Ti/Ge ratio (0.06–1.13) and P contents (13.9–173 ppm) of quartz are also similar to those from the Xiasai Pb–Zn–Ag deposit, both of which resemble those of skarn-type deposits and Sn-associated quartz. Furthermore, the Ti/Zr ratio (average 33.2) of cassiterite at Gongjuelong are much higher than that of cassiterite at Xiasai (average 3.7), indicating that the Pb–Zn–Ag veins could represent the distal product of the “parent” granite. On the basis of combined evidence from geology, geochemistry, and published geochronology data, we propose that the proximal skarn-type Sn deposits and distal hydrothermal vein-type Pb–Zn–Ag±Sn deposits in the northern Yidun Terrane constitute an integrated ore system, which is genetically related to the late Cretaceous highly fractionated granites. This proposed hypothesis highlights the potential prospecting of Sn mineralization beneath the hydrothermal Pb–Zn–Ag veins, as well as the hydrothermal Pb–Zn–Ag veins controlled by faults/fractures within the strata around the Sn deposits and highly fractionated granites. Full article
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19 pages, 17888 KiB  
Article
Carbon Dioxide and Methane Emission into the Atmosphere and Its Relationship with Chemogenic Sedimentation in the Hypersaline Lake Baskunchak (Russia)
by Dmitry Gar’kusha, Yury Fedorov, Asya Ovsepyan, Yury Popov, Yury Andreev, Boris Talpa, Natalya Tambieva and Igor’ Myakinnikov
Water 2025, 17(5), 738; https://doi.org/10.3390/w17050738 - 3 Mar 2025
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Abstract
Baskunchak is a large drainless, highly saline lake located in the Caspian lowland. The chemical and gas composition of water (brine) and bottom sediments lying under a 10 cm layer of salt in the lake has been studied; specific fluxes of CH4 [...] Read more.
Baskunchak is a large drainless, highly saline lake located in the Caspian lowland. The chemical and gas composition of water (brine) and bottom sediments lying under a 10 cm layer of salt in the lake has been studied; specific fluxes of CH4 and CO2 at the water–atmosphere interface have been measured. The lake’s sodium chloride brine is characterized by high mineralization (313.5–334.7 g/L) and a slightly acidic–neutral pH (5.75–6.80). Bottom sediments are characterized by a slightly acid–neutral pH (6.27–6.64) and a reducing condition (Eh from −104.7 to +22.0 mV). Specific fluxes of CH4 into the atmosphere were low (0.11–0.12 mg CH4/(m2 h)) due to its low concentrations in the brine of the lake (0.91–2.66 µL/L). The appearance of an excess of HCO3 during the anaerobic oxidation of CH4 in the bottom sediments of the lake contributes to the formation of autigenic gypsum and calcite. Specific CO2 fluxes into the atmosphere ranged from 12.2 to 73.1 mg CO2/(m2 h). The probable source of CO2 in the brine of the lake and its emission into the atmosphere, in addition to the process of organic matter cycling and uptake by microorganisms, is the chemogenic precipitation of sulfates and calcium carbonates. Full article
(This article belongs to the Section Water and Climate Change)
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