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Keywords = pH/Eh control

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26 pages, 7253 KB  
Article
Effects of Total Calcium and Iron(II) Concentrations on Heterogeneous Nucleation and Crystal Growth of Struvite
by Pengcheng Wei, Kaiyu Deng, Yang Huang, Jiayu Yang, Fujiang Hui, Dunqiu Wang and Kun Dong
Crystals 2026, 16(2), 80; https://doi.org/10.3390/cryst16020080 (registering DOI) - 23 Jan 2026
Viewed by 26
Abstract
This study investigated the effects of calcium (Ca2+) and iron (II) Fe2+ concentrations (0–500 mg/L) on the heterogeneous nucleation and crystallization behavior of struvite (MgNH4PO4·6H2O) through controlled batch precipitation experiments. Struvite formed under different [...] Read more.
This study investigated the effects of calcium (Ca2+) and iron (II) Fe2+ concentrations (0–500 mg/L) on the heterogeneous nucleation and crystallization behavior of struvite (MgNH4PO4·6H2O) through controlled batch precipitation experiments. Struvite formed under different Ca2+ and Fe2+ concentrations were systematically characterized using XRD, SEM, FTIR, and XPS, while real-time pH and redox potential (Eh) monitoring was employed to elucidate reaction dynamics and thermodynamic speciation and saturation indices were calculated, and classical nucleation theory (CNT) was applied to interpret nucleation behavior. The results show that Ca2+ primarily suppresses struvite formation through bulk-phase competition with Mg2+ for phosphate, diverting phosphate into Ca–P phases and progressively reducing struvite supersaturation, which leads to decreased crystallinity and distorted Crystal habit. In contrast, Fe2+ does not form detectable crystalline Fe-P phases but inhibits struvite crystallization mainly through surface-mediated processes. Surface analyses indicate that Fe-bearing species adsorb onto struvite surfaces and promote amorphous Fe-P deposition, increasing interfacial resistance to nucleation and growth. CNT analysis further reveals that Ca2+ inhibition is governed by reduced thermodynamic driving force, whereas Fe2+ inhibition is dominated by surface-related kinetic barriers. This study provides mechanistic insight into ion-specific interference during struvite crystallization and offers guidance for optimizing phosphorus recovery in ion-rich wastewater systems. Full article
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16 pages, 1139 KB  
Article
Study on the Bioavailability of Arsenic in the Rice–Crayfish Farming System
by Kelei Zhang, Shoudong Zhang, Longjun Deng, Tiancai Li, Li Liu, Wei Luo, Yibo Zhang, Yongyao Guo, Dan Liu, Shiyong Yang, Jun Wang, Dongjie Wang and Zongjun Du
Fishes 2025, 10(12), 645; https://doi.org/10.3390/fishes10120645 - 15 Dec 2025
Viewed by 318
Abstract
Rice–fishery integrated farming has expanded rapidly in China, yet its implications for arsenic (As) accumulation remain insufficiently understood. This study evaluated As bioavailability and enrichment in a rice–crayfish farming system (RCFS) by establishing controlled field plots with soil As concentrations ranging from 5 [...] Read more.
Rice–fishery integrated farming has expanded rapidly in China, yet its implications for arsenic (As) accumulation remain insufficiently understood. This study evaluated As bioavailability and enrichment in a rice–crayfish farming system (RCFS) by establishing controlled field plots with soil As concentrations ranging from 5 to 40 mg/kg under three water-management regimes: alternating wetting and drying (AWD), continuously flooded (CF), and RCFS. Soil–water physicochemical variables and As accumulation in both rice organs and crayfish tissues were systematically analyzed, followed by human health risk assessment. Inorganic As in brown rice increased linearly with soil As, following Y = 0.0117X + 0.0598 (R2 = 0.96), and the estimated soil safety thresholds were 26.48 mg/kg for AWD, 11.98 mg/kg for RCFS, and 9.24 mg/kg for CF. AWD consistently exhibited the lowest As risk due to its ability to elevate soil Eh and maintain a more favorable pH, thereby suppressing As mobilization. Compared with CF, RCFS reduced As bioavailability through crayfish-induced bioturbation, which increased Eh, enhanced SOM and CEC, and improved soil aeration. As accumulation in crayfish tissues also rose with soil As, with abdominal muscle As fitting Y = 0.0085X + 0.0553 (R2 = 0.8588). Although abdominal muscle met safety limits, the hepatopancreas accumulated substantially higher As and exceeded carcinogenic risk thresholds, even at 5 mg/kg of soil As, indicating a potential health concern for consumers. This work elucidates As dynamics and enrichment mechanisms in RCFS, providing guidance for safer rice–crayfish production in As-impacted areas. Full article
(This article belongs to the Special Issue Advances in Integrated Rice-Fish Farming)
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12 pages, 1901 KB  
Article
Hepatic Arterial Infusion Chemotherapy in the Treatment of Unresectable Hepatocellular Carcinoma with and Without Extrahepatic Spread: A Propensity Score Matching Study
by Chao-Ting Chen, Huei-Lung Liang, Chia-Ling Chiang, Wei-Lun Tsai and Yu-Chia Chen
J. Pers. Med. 2025, 15(11), 561; https://doi.org/10.3390/jpm15110561 - 19 Nov 2025
Viewed by 539
Abstract
Purpose: We aimed to study the efficacy and safety of hepatic artery infusion chemotherapy (HAIC) in the treatment of unresectable hepatocellular carcinoma (HCC) with extrahepatic spread (EHS). Materials and Methods: A total of 323 patients with unresectable HCC received HAIC plus lipiodol microvascular [...] Read more.
Purpose: We aimed to study the efficacy and safety of hepatic artery infusion chemotherapy (HAIC) in the treatment of unresectable hepatocellular carcinoma (HCC) with extrahepatic spread (EHS). Materials and Methods: A total of 323 patients with unresectable HCC received HAIC plus lipiodol microvascular embolization. HAIC was performed via puncture of the left subclavian artery with a temporary 4-French angio-catheter placed in the common/proper hepatic artery. The HAIC regimen consisted of a daily infusion of cisplatin (10 mg/m2), mitomycin-C (2 mg/m2), and leucovorin (15 mg/m2), administered over a period of 20–30 min, and then a 5-fluorouracil (5-FU, 100 mg/m2) infusion for the remaining of 22 h of each day, for five consecutive days. Before the temporary catheter was removed, 10 mL of ethiodized oil (Lipiodol, Guerbet, France) was injected to obtain a synergistic effect of chemoinfusion and lipiodol microvascular embolization. Treatment responses were evaluated based on mRECIST criteria. The objective response rate (ORR), progression-free survival (PFS), and overall survival (OS) of patients with EHS were compared to those without. Subgroup analyses of patients with and without major portal vein tumor thrombosis (PVTT) were performed both before and after propensity score matching (PSM). The survival analyses were conducted with the Kaplan–Meier method and compared using the log-rank test. All the statistical analyses were performed by SPSS (version 26.0). Result: The overall ORR was 59.1%. The median OS of the initial cohort and patients positive and negative for EHS were 16.3, 12.0, and 18.0 months, respectively (p = 0.002). In the subgroup analysis, there was no statistical difference in survival in patients with major PVTT between the with-EHS and without-EHS groups (13.0 vs. 15.0 months, p = 0.407). However, the median OS in patients with EHS was significantly shorter than those without EHS (11.4 vs. 19.4 months, p < 0.001) in the subgroup of non-major PVTT patients. After PSM, there were no significant survival differences between the EHS and non-EHS groups in any patient cohort or sub-cohort analysis. Conclusions: For unresectable HCC, controlling intrahepatic tumor progression through HAIC is more important than controlling extrahepatic tumor growth, especially in patients with major PVTT. Personalized locoregional HAIC can be performed in patients with EHS. Full article
(This article belongs to the Special Issue Current Trends and Future Challenges in Hepatocellular Carcinoma)
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21 pages, 4239 KB  
Article
Melatonin-Producing Bacillus aerius EH2-5 Enhances Glycine max Plants Salinity Tolerance Through Physiological, Biochemical, and Molecular Modulation
by Eun-Hae Kwon, Suhaib Ahmad and In-Jung Lee
Int. J. Mol. Sci. 2025, 26(16), 7834; https://doi.org/10.3390/ijms26167834 - 13 Aug 2025
Cited by 1 | Viewed by 1501
Abstract
Climate change has intensified extreme weather events and accelerated soil salinization, posing serious threats to crop yield and quality. Salinity stress, now affecting about 20% of irrigated lands, is expected to worsen due to rising temperatures and sea levels. At the same time, [...] Read more.
Climate change has intensified extreme weather events and accelerated soil salinization, posing serious threats to crop yield and quality. Salinity stress, now affecting about 20% of irrigated lands, is expected to worsen due to rising temperatures and sea levels. At the same time, the global population is projected to exceed 9 billion by 2050, demanding a 70% increase in food production (UN, 2019; FAO). Agriculture, responsible for 34% of global greenhouse gas emissions, urgently needs sustainable solutions. Microbial inoculants, known as “plant probiotics,” offer a promising eco-friendly alternative by enhancing crop resilience and reducing environmental impact. In this study, we evaluated the plant growth-promoting (PGP) traits and melatonin-producing capacity of Bacillus aerius EH2-5. To assess its efficacy under salt stress, soybean seedlings at the VC stage were inoculated with EH2-5 and subsequently subjected to salinity stress using 150 mM and 100 mM NaCl treatments. Plant growth parameters, the expression levels of salinity-related genes, and the activities of antioxidant enzymes were measured to determine the microbe’s role in promoting plant growth and mitigating salt-induced oxidative stress. Here, our study shows that the melatonin-synthesizing Bacillus aerius EH2-5 (7.48 ng/mL at 24 h after inoculation in Trp spiked LB media) significantly improved host plant (Glycine max L.) growth, biomass, and photosynthesis and reduced oxidative stress during salinity stress conditions than the non-inculcated control. Whole genome sequencing of Bacillus aerius EH2-5 identified key plant growth-promoting and salinity stress-related genes, including znuA, znuB, znuC, and zur (zinc uptake); ptsN, aspA, and nrgB (nitrogen metabolism); and phoH and pstS (phosphate transport). Genes involved in tryptophan biosynthesis and transport, such as trpA, trpB, trpP, and tspO, along with siderophore-related genes yusV, yfhA, and yfiY, were also detected. The presence of multiple stress-responsive genes, including dnaK, dps, treA, cspB, srkA, and copZ, suggests EH2-5′s genomic potential to enhance plant tolerance to salinity and other abiotic stresses. Inoculation with Bacillus aerius EH2-5 significantly enhanced soybean growth and reduced salt-induced damage, as evidenced by increased shoot biomass (29%, 41%), leaf numbers (12% and 13%), and chlorophyll content (40%, 21%) under 100 mM and 150 mM NaCl compared to non-inoculated plants. These results indicate EH2-5′s strong potential as a plant growth-promoting and salinity stress-alleviating rhizobacterium. The EH2-5 symbiosis significantly enhanced a key ABA biosynthesis enzyme-related gene NCED3, dehydration responsive transcription factors DREB2A and NAC29 salinity stresses (100 mM and 150 mM). Moreover, the reduced expression of peroxidase (POD), superoxide dismutase (SOD), and catalase (CAT) by 16%, 29%, and 24%, respectively, and decreased levels of malondialdehyde (MDA) and hydroxy peroxidase (H2O2) by 12% and 23% were observed under 100 mM NaCl compared to non-inoculated plants. This study demonstrated that Bacillus aerius EH2-5, a melatonin-producing strain, not only functions effectively as a biofertilizer but also alleviates plant stress in a manner comparable to the application of exogenous melatonin. These findings highlight the potential of utilizing melatonin-producing microbes as a viable alternative to chemical treatments. Therefore, further research should focus on enhancing the melatonin biosynthetic capacity of EH2-5, improving its colonization efficiency in plants, and developing synergistic microbial consortia (SynComs) with melatonin-producing capabilities. Such efforts will contribute to the development and field application of EH2-5 as a promising plant biostimulant for sustainable agriculture. Full article
(This article belongs to the Special Issue Genetics and Novel Techniques for Soybean Pivotal Characters)
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43 pages, 2907 KB  
Systematic Review
A Systematic Review of Copper Heap Leaching: Key Operational Variables, Green Reagents, and Sustainable Engineering Strategies
by Fabian León, Luis Rojas, Vanesa Bazán, Yuniel Martínez, Alvaro Peña and José Garcia
Processes 2025, 13(5), 1513; https://doi.org/10.3390/pr13051513 - 15 May 2025
Cited by 3 | Viewed by 7722
Abstract
Heap leaching of copper is faced with a complex set of challenges, including mineral heterogeneity, the formation of passivating species, and the need to regulate critical variables such as pH, redox potential (Eh), oxidant concentration, and irrigation rate. If these factors are not [...] Read more.
Heap leaching of copper is faced with a complex set of challenges, including mineral heterogeneity, the formation of passivating species, and the need to regulate critical variables such as pH, redox potential (Eh), oxidant concentration, and irrigation rate. If these factors are not properly managed, copper recovery is reduced, and significant environmental impacts may be generated, highlighting the urgency for systematic and sustainable approaches. To address this challenge, a systematic literature review (SLR) was conducted, screening 2344 documents and selecting 106 primary sources to analyze operational drivers and environmental considerations. Statistical methodologies (factorial designs, response surface methodology), multiscale modeling, and laboratory column tests were used to validate key variables, including pH (1.5–2.0), Eh (600–750 mV), temperature (25–55 °C), irrigation rate (5–15 L/(h·m2)), acid concentration (0.5–2.0 M), and emerging “green” reagents (e.g., glycine, organic surfactants). Precise control of these factors was found to reduce passivation, minimize fine-particle migration, and improve copper extraction up to 90%. The incorporation of oxidizing agents (e.g., Fe3+, H2O2) further accelerated mineral dissolution while preventing unwanted precipitates. In parallel, bioleaching strategies maintained high recoveries with lower chemical demand. Reviews of pilot studies confirmed the scalability of these optimized conditions, emphasizing both sustainability and cost-effectiveness. Full article
(This article belongs to the Special Issue Green Separation and Purification Processes)
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18 pages, 6291 KB  
Article
A Study on the Oxidation Performance of Soil Chromium with Acid Birnessite and Cryptomelane
by Wei Zhang, Huan Yang, Shaohong You, Xia Zhong, Pingping Jiang, Xudong Lan and Rui Ma
Toxics 2025, 13(4), 262; https://doi.org/10.3390/toxics13040262 - 31 Mar 2025
Cited by 3 | Viewed by 1296
Abstract
Current research focuses more on redox of toxic Cr(VI), with less attention to Cr(III) changes in flooded soil. First, the structure of acid birnessite and cryptomelane was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and other test [...] Read more.
Current research focuses more on redox of toxic Cr(VI), with less attention to Cr(III) changes in flooded soil. First, the structure of acid birnessite and cryptomelane was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and other test methods. This study investigated farmland soil in Yuxi, Yunnan Province, under flooding stress induced by the addition of two distinct concentrations of manganese oxides. Throughout the experiment, key physicochemical properties of the soil—including pH, redox potential (Eh), Cr(VI) concentration, and chromium speciation—were systematically measured and analyzed. Structural characterization demonstrated distinct morphological and surface area properties. Specifically, acid birnessite, with petal-like stacked spheres, has a specific surface area of 103.76 m2/g, while cryptomelane, strip-shaped, has an area of 95.92 m2/g. The submergence experiment yielded the following phenomena: (1) During the 60-day flooding experiment, soil amended with 0.5% or 1% acid birnessite or cryptomelane exhibited an increase in Eh compared to the control group. (2) At the end of the 60-day submergence period, the Cr(VI) concentration in the soil treated with 1% acid birnessite increased by 2.4 times compared to the control group. In addition, after 60 days, Cr(VI) concentrations in the soil exceeded 5 mg/L in soils with manganese oxide added to them. This study evaluates how manganese oxides oxidize Cr(III), aiding in assessing their environmental risks and long-term impacts on metal transformation. The findings help predict chromium behavior in farm soils and guide remediation strategies. Full article
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20 pages, 1936 KB  
Article
Utilizing Invasive Pterygoplichthys pardalis as a Sustainable Fish Meal Substitute and Euphorbia hirta Extract Supplement: Effects on Growth Performance, Organosomatic Indices, Hematological Profiles, and Serum Biochemistry in Chinese Bullfrogs (Hoplobatrachus chinensis)
by Sontaya Sookying, Phanit Srisuttha, Vipada Rodprasert, Chanthima Chaodon, Wikit Phinrub, Nantaporn Sutthi and Paiboon Panase
Life 2025, 15(1), 115; https://doi.org/10.3390/life15010115 - 16 Jan 2025
Cited by 4 | Viewed by 2679
Abstract
This research examined the efficacy of substituting commercial fish meal (CFM) with Pterygoplichthys pardalis meal (PPM) in Hoplobatrachus chinensis diets, with and without Euphorbia hirta extract (EHE) supplementation. The study utilized six dietary treatments: a control diet (0% PPM, no EHE) and five [...] Read more.
This research examined the efficacy of substituting commercial fish meal (CFM) with Pterygoplichthys pardalis meal (PPM) in Hoplobatrachus chinensis diets, with and without Euphorbia hirta extract (EHE) supplementation. The study utilized six dietary treatments: a control diet (0% PPM, no EHE) and five experimental diets with varying PPM levels (0%+, 25%+, 50%+, 75%+, and 100%+), each fortified with 300 mg/kg EHE. The experiment spanned 90 days. The analysis revealed that PPM exhibited superior amino acid profiles compared to CFM, both in quality and quantity, while CFM demonstrated higher fatty acid content. The growth metrics showed a significant decline only in the group receiving 100% PPM replacement with EHE supplementation. Most organosomatic indices remained consistent across the treatments, with the exception of intraperitoneal fat, which decreased in all EHE-supplemented groups. Blood parameters, including white blood cells, red blood cells, and hematocrit, along with serum proteins (total protein, globulin, and albumin), displayed an upward trend in all EHE-supplemented groups. The 50%+ and 75%+ PPM replacement groups exhibited significantly elevated serum glucose levels (p < 0.05). Liver enzymes (alanine transaminase and aspartate transaminase) showed no significant variations among the treatments. The results indicate that PPM can serve as an effective replacement for up to 75% of CFM in H. chinensis feed, without compromising their growth performance. Moreover, supplementing with EHE helps to enhance essential biochemical indices in the body, without adversely affecting liver function. This investigation offers valuable perspectives on the development of sustainable aquaculture feed and the potential application of invasive fish species in aquatic animal nutrition. Full article
(This article belongs to the Special Issue Fish Nutrition, Production, and Welfare)
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12 pages, 4518 KB  
Article
Recovery of Samarium from Waste SmCo Magnets via Selective Precipitation with Ammonium Bicarbonate: Optimization of Process Efficiency
by Emircan Uysal, Elif Emil-Kaya, Halide Nur Dursun, Merve Papakci, Sebahattin Gürmen and Bernd Friedrich
Metals 2024, 14(12), 1363; https://doi.org/10.3390/met14121363 - 29 Nov 2024
Cited by 2 | Viewed by 2082
Abstract
SmCo magnets are a common material utilized in advanced technological applications. These magnets contain elevated concentrations of Sm and Co within their structural compositions. Given that both Sm and Co are classified as critical metals, the recycling of these magnets after their operational [...] Read more.
SmCo magnets are a common material utilized in advanced technological applications. These magnets contain elevated concentrations of Sm and Co within their structural compositions. Given that both Sm and Co are classified as critical metals, the recycling of these magnets after their operational lifespan is of significant economic and environmental importance. Hydrometallurgical recycling processes represent an effective method for the recycling of these magnets. In this study, a pH-controlled selective precipitation method was developed using two HNO3 solutions with distinct oxidizing properties for the recovery of Sm and Co from end-of-life (EoL) SmCo magnets. In the initial stage of the process, the magnets were leached in a low-oxidizing 2M HNO3 solution, with a 1:30 (w/v) solid-to-liquid ratio at 20 °C. This step was undertaken to ensure the dissolution of Fe, thereby creating an environment conducive to its removal from the solution. The leaching experiments resulted in dissolution efficiencies of 95%, 96%, and 96% for Sm, Co, and Fe, respectively. In the second stage, a leaching experiment was performed using 3M HNO3 with a 1:10 solid-to-liquid ratio at 60 °C. Under these conditions, Sm and Co achieved dissolution efficiencies of 99%, while Fe remained undissolved in the solid phase due to hydrolysis at the high temperature, thus increasing the solution purity. In the precipitation process, the pH of both leachates was initially adjusted to 4 to precipitate impurities such as Fe ions. As a result of precipitation at pH 4 in the 2M HNO3 leachate, Fe ions were almost completely removed. This was followed by selective Sm precipitation in the pH range of 5–6.5 using NH4HCO3. The highest purity of Sm precipitation was achieved when the pH reached 6.5. An increase in Sm precipitation efficiency was observed with increasing pH, with an efficiency of 12.75% at pH 5, which rose to 82.37% at pH 6.5. Furthermore, although the precipitation efficiency of Co increased from 6.25% to 10% within this pH range, no significant difference in the extent of this increase was observed. In the case of the 3M HNO3 leachate, the Sm precipitation efficiency at pH 5 was 44.28%, while at pH 6.5, nearly all of the Sm ions were precipitated. The co-precipitation efficiency at pH 5 was 1.89%, increasing to 36.43% at pH 6.5. This increase in co-precipitation was attributed to the system’s Eh value, which reflects the enhanced oxidizing properties of the 3M HNO3 leach solution. The results of the study indicate that as the oxidizing strength of the solution increased, the co-precipitation rate also increased with rising pH. Full article
(This article belongs to the Special Issue Feature Papers in Extractive Metallurgy)
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26 pages, 1615 KB  
Review
Behavior of Silver Species in Soil: Ag Nanoparticles vs. Ionic Ag
by Joanna Kyziol-Komosinska, Agnieszka Dzieniszewska and Justyna Czupioł
Molecules 2024, 29(23), 5531; https://doi.org/10.3390/molecules29235531 - 22 Nov 2024
Cited by 12 | Viewed by 2649
Abstract
Silver nanoparticles are one of the most commonly used forms of silver (Ag) in nanotechnology applications due to their antibacterial properties and electrical and thermal resistance. The increasing production and use of products containing nanoparticles has led to their release into and contamination [...] Read more.
Silver nanoparticles are one of the most commonly used forms of silver (Ag) in nanotechnology applications due to their antibacterial properties and electrical and thermal resistance. The increasing production and use of products containing nanoparticles has led to their release into and contamination of soil and water. This review summarizes the literature on the fate, behavior (adsorption/desorption, precipitation/oxidative dissolution, transformation), and transport/mobility of Ag forms in soils (Ag+ ions and Ag nanoparticles—AgNPs). The behavior of Ag+/AgNPs in soil is a complex process. It depends on many factors, including the characteristics of the Ag forms (ions, nanoparticle size, ligand type used for coating, surface charge, initial Ag concentration), the soil properties (organic matter and clay mineral content, textural properties, point of zero charge, cation exchange capacity, surface functional groups), and the solute properties (pH–Eh, ionic strength, cation type, oxygen content). The binding of Ag+ and AgNPs is significantly positively correlated with Al/Fe/Mn oxide and SOM content and depends on the surface charge of the minerals and CEC, which controls adsorption processes. Very important parameters to consider are the pH and Eh of the solution, which determine the durability of the ligands, the aggregation rate and the oxidation process of AgNPs, as well as the presence of sulfide and chloride and the Cl/Ag ratio, which determine the stability/mobility of Ag. Since AgNPs can be oxidized to Ag+ ions during their life cycle, it is necessary to consider the behavior of both forms of Ag in soils. Understanding the transport and behavior of Ag in soil is essential for the environmental risk assessment and management of wastes containing Ag. Full article
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21 pages, 10722 KB  
Article
The Mechanism of Arsenic Release in Contaminated Paddy Soil with Added Biochar: The Role of Dissolved Organic Matter, Fe, and Bacteria
by Jianxin Fan, Maoyu Liao, Ting Duan, Ying Hu and Jiaoxia Sun
Toxics 2024, 12(9), 661; https://doi.org/10.3390/toxics12090661 - 10 Sep 2024
Cited by 3 | Viewed by 2144
Abstract
The addition of biochar inevitably modifies the acidity (pH), redox potential (Eh), and dissolved organic matter (DOM) level in the soil. These alterations also have coupled effects on the cycling of iron (Fe) and the composition of bacterial communities, thereby impacting the speciation [...] Read more.
The addition of biochar inevitably modifies the acidity (pH), redox potential (Eh), and dissolved organic matter (DOM) level in the soil. These alterations also have coupled effects on the cycling of iron (Fe) and the composition of bacterial communities, thereby impacting the speciation and availability of arsenic (As) in the soil. This study explored the potential mechanisms through which biochar affects As in paddy soil during flooded cultivation with different pyrolysis temperature biochars (300 °C, 400 °C, and 500 °C) added. The results revealed that the TAs concentration increased in the initial 15 days of soil cultivation with SBC300 or SBC400 addition because increasing the concentration of DOM induced the mobility of As though the formation of As-DOM complexes. Meanwhile, biochar addition elevated the pH, decreased the Eh, and promoted the transformation of specific adsorbed As (A-As) and amorphous iron oxide-bound As (Amo-Fe-As) to supernatant As through enhancing the reductive dissolution of Fe(oxy)(hydr)oxides. Moreover, the biochar altered the relative abundance of As (V)-reducing bacteria (such as Firmicutes) and As (III)-oxidizing bacteria (such as Chloroflex), thereby affecting As speciation. However, these mechanistic effects varied depending on the pyrolysis temperature of the biochar. The microbial composition of SBC300 and SBC400 were similar, with both containing larger populations of Enterobacteriaceae (AsRB) and pseudomonas (FeRB) compared to CK and SBC500. It was proposed that lower pyrolysis temperatures (300 °C and 400 °C) are more favorable for the dissolution of Fe(oxy)(hydr)oxides and the reduction of As (V). However, the biochar from the higher pyrolysis temperature (500 °C) showed environmental impacts akin to the control group (CK). This study demonstrated potential mechanisms of biochar’s effect on As and the role of pyrolysis temperature. Full article
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23 pages, 8461 KB  
Review
Regolith-Hosted Rare Earth Element Mineralization in the Esperance Region, Western Australia: Major Characteristics and Potential Controls
by Nikita Sergeev and Tiffany Collins
Minerals 2024, 14(8), 847; https://doi.org/10.3390/min14080847 - 22 Aug 2024
Cited by 5 | Viewed by 3580
Abstract
A number of regolith-hosted REE occurrences have recently been discovered in the Esperance region in southern Western Australia. This paper summarizes major characteristics of REE mineralization and discusses contributing factors and potential controls. The main aim is to explain why there is a [...] Read more.
A number of regolith-hosted REE occurrences have recently been discovered in the Esperance region in southern Western Australia. This paper summarizes major characteristics of REE mineralization and discusses contributing factors and potential controls. The main aim is to explain why there is a lack of highly sought-after ion-adsorption-clay-type REE deposits across the region despite the presence of the regolith-hosted REE mineralization on a regional scale. Local mineralization mostly occurs as continuous flat-lying enrichment “blankets” within the residual regolith developed over Archaean–Proterozoic granite gneisses and granitoids with elevated REE content. The enriched horizon is commonly located in the lower saprolite and saprock and is accompanied by an overlying REE-depleted zone. This distribution pattern, together with the data on HREE fractionation and the presence of the supergene REE minerals, indicates chemogenic type enrichment formed by supergene REE mobilization into groundwater, downward transport, and accumulation in the lower part of the weathering profile. Residual REE accumulation processes due to bulk rock volume and mass reduction during weathering also contribute to mineralization. It is proposed that climate and groundwater chemistry are the critical regional controls on the distribution of REEs in the weathering profile and on their speciation in the enrichment zone. Cenozoic aridification of climate in southwest Australia heavily overprinted pre-existing REE distributions in the weathering profile. Acidic (pH < 4), highly saline groundwaters intensely leached away any relatively weakly bound, adsorbed or colloidal REE forms, moving them downward. Dissolved REEs precipitated as secondary phosphates in neutral to alkaline environment at lower Eh near the base of the weathering profile forming the supergene enrichment zone. Low denudation rates, characteristic of areas of low relief under the arid climate, are favourable for the preservation of the existing weathering profiles with REE mineralization. Full article
(This article belongs to the Special Issue Chemical Weathering Studies)
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15 pages, 938 KB  
Article
Remediation of Sulfides in Produced Waters of the Oil and Gas Industry Using Hydrogen Peroxide
by Samantha Schovan, Grant McEachern, Alexandria Seeger, Victor V. Nguyen, Bobby Burkes, Amitava Adhikary and Linda E. Schweitzer
Water 2024, 16(14), 1987; https://doi.org/10.3390/w16141987 - 13 Jul 2024
Cited by 2 | Viewed by 3864
Abstract
Produced waters are often treated in open lagoons where hydrogen sulfide (H2S) can off gas, posing a risk to human health and the environment. The aim of this study was to optimize a treatment process using hydrogen peroxide (H2O [...] Read more.
Produced waters are often treated in open lagoons where hydrogen sulfide (H2S) can off gas, posing a risk to human health and the environment. The aim of this study was to optimize a treatment process using hydrogen peroxide (H2O2) to oxidize H2S while minimizing off gassing. Samples of produced water from West Texas and laboratory-prepared waters utilizing sodium sulfide (Na2S) or biogenic polysulfides were oxidized with H2O2 alone or in combination with copper or iron catalysts, sodium hydroxide (NaOH), or a commercial sulfide oxidizer, HydroPower Green™. Sulfur speciation was measured using Hach test kits for sulfide/sulfate/sulfite and Dräger tubes for headspace H2S. HydroPower Green™ (HPG) helped to reduce H2S in the headspace of water samples; some of this was pH related as NaOH also worked, but not as well as HPG. The dose of peroxide necessary to oxidize sulfides to sulfate is a function of the oxidation-reduction potential (Eh) of the water and total sulfide concentration as well as pH; approximately a 1–4:1 ratio of peroxide to sulfide concentration was needed to oxidize sulfidic waters of pH 7–10 with half-lives under 30 min. Both copper and iron catalysts reduce H2O2 demand and the half-life of H2S. Peracetic acid (PAA) and copper (II) sulfate pentahydrate (CuSO4, 5H2O) were explored as biocides for controlling sulfate-reducing bacteria (SRBs) that produce H2S. An AquaSnap (Hygenia) test kit was employed to monitor relative microbial activity in a wetland porewater containing H2S. Microbial regrowth occurred after a few days using the highest dose of PAA; these results showed that PAA was being used by bacteria as a carbon source even after the initial substantial reduction in the microbial activity. CuSO4, 5H2O at a dose of 1 ppm prevented microbial regrowth. The recommended treatment process from this research is determined by jar testing with H2O2, a base for pH control, a biocide, and possibly a metal catalyst or other co-oxidants in order to achieve oxidation of sulfides without H2S release or the precipitation of metal carbonates or oxides. Full article
(This article belongs to the Section Wastewater Treatment and Reuse)
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21 pages, 11761 KB  
Article
Study on the Hydrothermal Superposition Period: Mineralization–Alteration Zoning Model and Zoning Mechanism of the Dahongshan Fe-Cu Deposit in Yunnan Province
by Xing Mao, Runsheng Han, Dong Zhao, Liuqing Meng, Wenlong Qiu, Hongsheng Gong, Long Sun, Xuhao Kang and Yinkang Zhou
Minerals 2024, 14(1), 96; https://doi.org/10.3390/min14010096 - 15 Jan 2024
Cited by 2 | Viewed by 2483
Abstract
The Dahongshan large-scale iron (Fe)–copper (Cu) polymetallic deposit is in the Proterozoic metallogenic domain on the western margin of the Yangtze Block. It is a typical representative of Fe-Cu polymetallic composite mineralization in the Kangdian area. The deposit comprises a group of layered [...] Read more.
The Dahongshan large-scale iron (Fe)–copper (Cu) polymetallic deposit is in the Proterozoic metallogenic domain on the western margin of the Yangtze Block. It is a typical representative of Fe-Cu polymetallic composite mineralization in the Kangdian area. The deposit comprises a group of layered orebodies formed by volcanic exhalation sedimentation and metamorphism, and a group of vein-like orebodies formed by hydrothermal superposition. The large-scale mapping of altered lithofacies in the deposit has resolved issues of weak links and unclear mineralization and alteration zoning of hydrothermal superimposed deposits within the study area. The mineralization type, hydrothermal alteration type and intensity, mineral assemblage, and mineral structure of the vein-type Cu polymetallic deposits during the hydrothermal superposition period are meticulously analyzed and studied. Finally, the zoning relationships of vein orebodies (mineralization) are summarized. On the basis of the results of the study of the distribution pattern of this mineral body, a mineralization alteration zoning model of the hydrothermal superposition period is constructed. The results show that the alteration is primarily silicification, carbonation, and chloritization, and the mineralization is chalcopyrite, bornite, chalcocite, and pyrite. The Dibadu anticline and the cutting layer faults and fractures strictly control the hydrothermal alteration zoning. The mineralization alteration zoning from the core to the flank is divided into coarse vein zone (I) → stockwork zone (II) → veinlet zone (III). The corresponding mineral assemblages are quartz–calcite–chalcocite–bornite–(native copper) (I) → calcite–dolomite–quartz–bornite–chalcopyrite–chlorite (II) → dolomite–quartz–chalcopyrite–(pyrite) (III), where the stockwork zone has the most substantial mineralization. The mineral assemblages of each alteration zone, the characteristics of rare earth elements of typical samples, and the test results on the fluid inclusions confirm that pH and Eh primarily control the zoning mechanism. This study has significance for deepening the understanding of the composite metallogenic system, guiding deep and peripheral prospecting, and providing significant enlightenment for the study of this type of deposit. Full article
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22 pages, 5556 KB  
Article
Impact of Reperfusion on Plasma Oxylipins in ST-Segment Elevation Myocardial Infarction
by Zahra Solati, Arun Surendran, Harold M. Aukema and Amir Ravandi
Metabolites 2024, 14(1), 19; https://doi.org/10.3390/metabo14010019 - 27 Dec 2023
Cited by 5 | Viewed by 2422
Abstract
ST-segment elevation myocardial infarction (STEMI) occurs as a result of acute occlusion of the coronary artery. Despite successful reperfusion using primary percutaneous coronary intervention (PPCI), a large percentage of myocardial cells die after reperfusion, which is recognized as ischemia/reperfusion injury (I/R). There are [...] Read more.
ST-segment elevation myocardial infarction (STEMI) occurs as a result of acute occlusion of the coronary artery. Despite successful reperfusion using primary percutaneous coronary intervention (PPCI), a large percentage of myocardial cells die after reperfusion, which is recognized as ischemia/reperfusion injury (I/R). There are rapid changes in plasma lipidome during myocardial reperfusion injury. However, the impact of coronary artery reperfusion on plasma oxylipins is unknown. This study aimed to investigate alterations in the oxylipin profiles of STEMI patients during ischemia and at various reperfusion time points following PPCI. Blood samples were collected from patients presenting with STEMI prior to PPCI (Isch, n = 45) and subsequently 2 h following successful reperfusion by PPCI (R-2 h, n = 42), after 24 h (R-24 h, n = 44), after 48 h (R-48 h, n = 43), and then 30 days post PPCI (R-30 d, n = 29). As controls, blood samples were collected from age- and sex-matched patients with non-obstructive coronary artery disease after diagnostic coronary angiography. High-performance liquid chromatography–mass spectrometry (HPLC-MS/MS) using deuterated standards was used to identify and quantify oxylipins. In patients presenting with STEMI prior to reperfusion (Isch group), the levels of docosahexaenoic acid (DHA)-derived oxylipins were significantly higher when compared with controls. Their levels were also significantly correlated with the peak levels of creatine kinase (CK) and troponin T(TnT) before reperfusion (CK: r = 0.33, p = 0.046, TnT: r = 0.50, p = 1.00 × 10−3). The total concentrations of oxylipins directly produced by 5-lipoxygenase (5-LOX) were also significantly elevated in the Isch group compared with controls. The ratio of epoxides (generated through epoxygenase) to diols (generated by soluble epoxide hydrolysis (sEH)) was significantly lower in the Isch group compared with the controls. Following reperfusion, there was an overall reduction in plasma oxylipins in STEMI patients starting at 24 h post PPCI until 30 days. Univariate receiver operating characteristic (ROC) curve analysis also showed that an elevated ratio of epoxides to diols during ischemia is a predictor of smaller infarct size in patients with STEMI. This study revealed a large alteration in plasma oxylipins in patients presenting with STEMI when compared with controls. Total oxylipin levels rapidly reduced post reperfusion with stable levels reached 24 h post reperfusion and maintained for up to 30 days post infarct. Given the shifts in plasma oxylipins following coronary artery reperfusion, further research is needed to delineate their clinical impact in STEMI patients. Full article
(This article belongs to the Special Issue Inflammatory Biomarkers in Critical Patients)
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44 pages, 3332 KB  
Review
Control of Non-Ferrous Metal-Sulfide Minerals’ Flotation via Pulp Potential
by Marinela Panayotova
Minerals 2023, 13(12), 1512; https://doi.org/10.3390/min13121512 - 1 Dec 2023
Cited by 12 | Viewed by 4787
Abstract
Studies on the dependence of the technological results of non-ferrous sulfide ore (copper—arsenic-bearing and non-arsenic-bearing—lead–zinc, and polymetallic) flotation on the pulp potential Eh are reviewed. Findings on the relation of Eh and collectorless flotation are presented. Changes in the pulp potential due to [...] Read more.
Studies on the dependence of the technological results of non-ferrous sulfide ore (copper—arsenic-bearing and non-arsenic-bearing—lead–zinc, and polymetallic) flotation on the pulp potential Eh are reviewed. Findings on the relation of Eh and collectorless flotation are presented. Changes in the pulp potential due to different gas applications and various reagent additions are considered. The influence of the grinding medium on the pulp Eh and hence on the flotation results is presented through various examples. The relation between the oxidation–reduction potential and reagent effects is exhibited and explained. pH–Eh ranges of different minerals’ flotation, as recorded in various studies, are summarized and visualized jointly for all mentioned ores. It is concluded that the pulp Eh value, considered together with the pH value, is a useful means for flotation selection controlling and deserves further research, especially under industrial conditions. Some problems and difficulties in using pulp Eh for flotation control are discussed. Full article
(This article belongs to the Special Issue Valuable Metals Recovery by Mineral Processing and Hydrometallurgy)
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