Different fates of Sb(III) and Sb(V) during the formation of jarosite mediated by Acidithiobacillus ferrooxidans.

Secondary iron-sulfate minerals such as jarosite, which are easily formed in acid mine drainage, play an important role in controlling metal mobility. In this work, the typical iron-oxidizing bacterium Acidithiobacillus ferrooxidans ATCC 23270 was selected to synthesize jarosite in the presence of antimony ions, during which the solution behavior, synthetic product composition, and bacterial metabolism were studied. The results show that in the presence of Sb(V), Fe2+ was rapidly oxidized to Fe3+ by A. ferrooxidans and Sb(V) had no obvious effect on the biooxidation of Fe2+ under the current experimental conditions. The presence of Sb(III) inhibited bacterial growth and Fe2+ oxidation. For the group with Sb(III), products with amorphous phases were formed 72 hr later, which were mainly ferrous sulfate and pentavalent antimony oxide, and the amorphous precursor was finally transformed into a more stable crystal phase. For the group with Sb(V), the morphology and structure of jarosite were changed in comparison with those without Sb. The biomineralization process was accompanied by the removal of 94% Sb(V) to form jarosite containing the Fe-Sb-O complex. Comparative transcriptome analysis shows differential effects of Sb(III) and Sb(V) on bacterial metabolism. The expression levels of functional genes related to cell components were much more downregulated for the group with Sb(III) but much more regulated for that with Sb(V). Notably, cytochrome c and nitrogen fixation-relevant genes for the A.f_Fe2+_Sb(III) group were enhanced significantly, indicating their role in Sb(III) resistance. This study is of great value for the development of antimony pollution control and remediation technology.

Responses of biomarkers, joint effect and drilosphere bacterial communities to antimony (III and/or V) contamination.

Contamination of soils with antimony (Sb) is becoming increasingly severe and widespread, and the associated ecological risks cannot be ignored. To evaluate how different Sb forms affected the earthworm Eisenia fetida in soil, the biomarker response index (BRI), effect addition index (EAI), and microbial diversity were characterized after single and joint application of Sb(III) and Sb(V). The results showed that Sb(III) was better enriched by earthworms than Sb(V). The metallothionein (MT) content in earthworms increased under Sb stress, and the superoxide dismutase (SOD), catalase (CAT), and glutathione S-transferase (GST) activities also showed an increasing trend, suggesting waken-up antioxidant capacity. Severe alterations for health status were observed under combined treatment. Additionally, the EAI indicated that Sb(III) and Sb(V) had synergistic and antagonistic effects at low and high concentrations, respectively. The bacterial populations in the drilosphere (gut and burrow lining) appeared to be more susceptible to Sb contamination than in the non-drilosphere, their specific microecology may be an important factor in soil Sb migration and transformation. The abundance of Actinobacteria exhibited a significant decrease with increasing concentrations of single Sb(III) and Sb(V), while the abundance of Bacteroidia increased. The correlation heatmap showed that Sphingobacterium faecium was highly tolerant to Sb. These results provide not only an important basis for the ecological risk assessment of Sb in the soil environment but also new insights into the altered drilosphere bacterial communities under Sb stress.

Advancing Antimony(III) Adsorption: Impact of Varied Manganese Oxide Modifications on Iron-Graphene Oxide-Chitosan Composites.

Antimony (Sb) is one of the most concerning toxic metals globally, making the study of methods for efficiently removing Sb(III) from water increasingly urgent. This study uses graphene oxide and chitosan as the matrix (GOCS), modifying them with FeCl2 and four MnOx to form iron-manganese oxide (FM/GC) at a Fe/Mn molar ratio of 4:1. FM/GC quaternary composite microspheres are prepared, showing that FM/GC obtained from different MnOx exhibits significant differences in the ability to remove Sb(III) from neutral solutions. The order of Sb(III) removal effectiveness is MnSO4 > KMnO4 > MnCl2 > MnO2. The composite microspheres obtained by modifying GOCS with FeCl2 and MnSO4 are selected for further batch experiments and characterization tests to analyze the factors and mechanisms influencing Sb(III) removal. The results show that the adsorption capacity of Sb(III) decreases with increasing pH and solid-liquid ratio, and gradually increases with the initial concentration and reaction time. The Langmuir model fitting indicates that the maximum adsorption capacity of Sb(III) is 178.89 mg/g. The adsorption mechanism involves the oxidation of the Mn-O group, which converts Sb(III) in water into Sb(V). This is followed by ligand exchange and complex formation with O-H in FeO(OH) groups, and further interactions with C-OH, C-O, O-H, and other functional groups in GOCS.

Novel Insights into Sb(III) Oxidation and Immobilization during Ferrous Iron Oxygenation: The Overlooked Roles of Singlet Oxygen and Fe (oxyhydr)oxides Formation.

Reactive oxygen species (ROS) produced from the oxygenation of reactive Fe(II) species significantly affect the transformation of metalloids such as Sb at anoxic-oxic redox interfaces. However, the main ROS involved in Sb(III) oxidation and Fe (oxyhydr)oxides formation during co-oxidation of Sb(III) and Fe(II) are still poorly understood. Herein, this study comprehensively investigated the Sb(III) oxidation and immobilization process and mechanism during Fe(II) oxygenation. The results indicated that Sb(III) was oxidized to Sb(V) by the ROS produced in the aqueous and solid phases and then immobilized by formed Fe (oxyhydr)oxides via adsorption and coprecipitation. In addition, chemical analysis and extended X-ray absorption fine structure (EXAFS) characterization demonstrated that Sb(V) could be incorporated into the lattice structure of Fe (oxyhydr)oxides via isomorphous substitution, which greatly inhibited the formation of lepidocrocite (γ-FeOOH) and decreased its crystallinity. Notably, goethite (α-FeOOH) formation was favored at pH 6 due to the greater amount of incorporated Sb(V). Moreover, singlet oxygen (1O2) was identified as the dominant ROS responsible for Sb(III) oxidation, followed by surface-adsorbed ·OHads, ·OH, and Fe(IV). Our findings highlight the overlooked roles of 1O2 and Fe (oxyhydr)oxide formation in Sb(III) oxidation and immobilization during Fe(II) oxygenation and shed light on understanding the geochemical cycling of Sb coupled with Fe in redox-fluctuating environments.

Efficient removal of Sb(III) from wastewater using selenium nanoparticles synthesized by Psidium guajava plant extract.

Antimony (Sb) pollution in aquatic ecosystems has emerged as a critical environmental issue on a global scale, emphasizing the urgent need for cost-effective and user-friendly technologies to remove Sb compounds from water sources. In this study, a novel adsorbent, selenium nanoparticles (SeNPs), was synthesized using the aqueous extract of Psidium guajava L. leaves (AEP) for the purpose of eliminating Sb(III) from aqueous solutions. The biosynthesized SeNPs was characterized using scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), X-ray fluorescence spectrometer (XRF), Fourier Transform-Infrared (FT-IR) spectroscopy, X-ray diffraction (XRD), Raman spectroscopy and X-ray photoelectron spectroscopy (XPS) analysis techniques. Additionally, the removal efficiency of the SeNPs for Sb(III) was systematic investigated under the effects of SeNPs dose, temperature, pH and re-usability. The results of this study showed that the adsorption data fitted well into pseudo-second order model, while the Sips modeling demonstrated a high adsorption capacity (62.7 mg/g) of SeNPs for Sb(III) ions at 303.15 K from aqueous solution. The exothermic enthalpy change of - 22.59 kJ/mol and negative Gibbs free energy change assured the viability of the adsorption process under the considered temperature conditions. Surface functional groups on SeNPs like carboxyl, amide, hydroxyl, carbonyl, and methylene significantly facilitate the adsorption processes. Furthermore, the removal efficiencies of Sb in the two actual Sb mine wastewater samples were remarkably high, achieving nearly to 100% with 1.5 g/L SeNPs within 48 h. This outcome underscores the potential of SeNPs as a highly promising solution for efficiently remediating Sb from aquatic environments, owing to their cost-effectiveness, ease of regeneration, and rapid uptake capabilities.

Antimony Isotope Fractionation during Kinetic Sb(III) Oxidation by Antimony-Oxidizing Bacteria Pseudomonas sp. J1.

Antimony (Sb) isotopic fractionation is frequently used as a proxy for biogeochemical processes in nature. However, to date, little is known about Sb isotope fractionation in biologically driven reactions. In this study, Pseudomonas sp. J1 was selected for Sb isotope fractionation experiments with varying initial Sb concentration gradients (50-200 µM) at pH 7.2 and 30 °C. Compared to the initial Sb(III) reservoir (δ123Sb = 0.03 ± 0.01 ∼ 0.06 ± 0.01‰), lighter isotopes were preferentially oxidized to Sb(V). Relatively constant isotope enrichment factors (ε) of -0.62 ± 0.06 and -0.58 ± 0.02‰ were observed for the initial Sb concentrations ranging between 50 and 200 µM during the first 22 days. Therefore, the Sb concentration has a limited influence on Sb isotope fractionation during Sb(III) oxidation that can be described by a kinetically dominated Rayleigh fractionation model. Due to the decrease in the Sb-oxidation rate by Pseudomonas sp. J1, observed for the initial Sb concentration of 200 µM, Sb isotope fractionation shifted toward isotopic equilibrium after 22 days, with slightly heavy Sb(V) after 68 days. These findings provide the prospect of using Sb isotopes as an environmental tracer in the Sb biogeochemical cycle.

Differential Mechanisms of Microbial As(III) and Sb(III) Oxidation and Their Contribution to Tailings Reclamation.

Mine tailings are extremely oligotrophic environments frequently contaminated with elevated As and Sb, making As(III) and Sb(III) oxidation potentially important energy sources for the tailing microbiome. Although they have been proposed to share similar metabolic pathways, a systemic comparison of the As(III) and Sb(III) oxidation mechanisms and energy utilization efficiencies requires further elucidation. In this study, we employed a combination of physicochemical, molecular, and bioinformatic analyses to compare the kinetic and genetic mechanisms of As(III) and Sb(III) oxidation as well as their respective energy efficiencies for fueling the key nutrient acquisition metabolisms. Thiobacillus and Rhizobium spp. were identified as functional populations for both As(III) and Sb(III) oxidation in mine tailings by DNA-stable isotope probing. However, these microorganisms mediated As(III) and Sb(III) oxidation via different metabolic pathways, resulting in preferential oxidation of Sb(III) over As(III). Notably, both As(III) and Sb(III) oxidation can facilitate nitrogen fixation and phosphate solubilization in mine tailings, with Sb(III) oxidation being more efficient in powering these processes. Thus, this study provided novel insights into the microbial As(III) and Sb(III) oxidation mechanisms and their respective nutrient acquisition efficiencies, which may be critical for the reclamation of mine tailings.

Incorporation of Shewanella oneidensis MR-1 and goethite stimulates anaerobic Sb(III) oxidation by the generation of labile Fe(III) intermediate.

Dissimilatory iron-reducing bacteria (DIRB) affect the geochemical cycling of redox-sensitive pollutants in anaerobic environments by controlling the transformation of Fe morphology. The anaerobic oxidation of antimonite (Sb(III)) driven by DIRB and Fe(III) oxyhydroxides interactions has been previously reported. However, the oxidative species and mechanisms involved remain unclear. In this study, both biotic phenomenon and abiotic verification experiments were conducted to explore the formed oxidative intermediates and related processes that lead to anaerobic Sb(III) oxidation accompanied during dissimilatory iron reduction. Sb(V) up to 2.59 µmol L-1 combined with total Fe(II) increased to 188.79 µmol L-1 when both Shewanella oneidensis MR-1 and goethite were present. In contrast, no Sb(III) oxidation or Fe(III) reduction occurred in the presence of MR-1 or goethite alone. Negative open circuit potential (OCP) shifts further demonstrated the generation of interfacial electron transfer (ET) between biogenic Fe(II) and goethite. Based on spectrophotometry, electron spin resonance (ESR) test and quenching experiments, the active ET production labile Fe(III) was confirmed to oxidize 94.12% of the Sb(III), while the contribution of other radicals was elucidated. Accordingly, we proposed that labile Fe(III) was the main oxidative species during anaerobic Sb(III) oxidation in the presence of DIRB and that the toxicity of antimony (Sb) in the environment was reduced. Considering the prevalence of DIRB and Fe(III) oxyhydroxides in natural environments, our findings provide a new perspective on the transformation of redox sensitive substances and build an eco-friendly bioremediation strategy for treating toxic metalloid pollution.

Can Sb(III)-oxidizing prokaryote also oxidize As(III) under aerobic and anaerobic conditions, and vice versa?

Sb(III) and As(III) share similar chemical features and coexist in the environment. However, their oxidase enzymes have completely different sequences and structures. This raises an intriguing question: Could Sb(III)-oxidizing prokaryotes (SOPs) also oxidize As(III), and vice versa? Regarding this issue, previous investigations have yielded unclear, incorrect and even conflicting data. This work aims to address this matter. First, we prepared an enriched population of SOPs that comprises 55 different AnoA genes, lacking AioAB and ArxAB genes. We found that these SOPs can oxidize both Sb(III) and As(III) with comparable capabilities. To further confirm this finding, we isolated three cultivable SOP strains that have AnoA gene, but lack AioAB and ArxAB genes. We observed that they also oxidize both Sb(III) and As(III) under both anaerobic and aerobic conditions. Secondly, we obtained an enriched population of As(III)-oxidizing prokaryotes (AOPs) from As-contaminated soils, which comprises 69 different AioA genes, lacking AnoA gene. We observed that the AOP population has significant As(III)-oxidizing activities, but lack detectable Sb(III)-oxidizing activities under both aerobic and anaerobic conditions. Therefore, we convincingly show that SOPs can oxidize As(III), but AOPs cannot oxidize Sb(III). These findings clarify the previous ambiguities, confusion, errors or contradictions regarding how SOPs and AOPs oxidize each other's substrate.

Formation of Sb2O3 microcrystals by Rhodotorula mucilaginosa.

Antimony (Sb) pollution seriously endangers ecological environment and human health. Microbial induced mineralization can effectively convert metal ions into more stable and less soluble crystalline minerals by extracellular polymeric substance (EPS). In this study, an efficient Sb-resistant Rhodotorula mucilaginosa (R. mucilaginosa) was screened, which can resist 41 mM Sb(III) and directly transform Sb(III) into Sb2O3 microcrystals by EPS. The removal efficiency of R. mucilaginosa for 22 mM Sb(III) reached 70% by converting Sb(III) to Sb2O3. The components of supernatants as well as the effects of supernatants and pH on Sb(III) mineralization verified that inducible and non-inducible extracellular protein/polysaccharide biomacromolecules play important roles in the morphologies and sizes control of Sb2O3 formed by R. mucilaginosa respectively. Sb2O3 microcrystals with different morphologies and sizes can be prepared by the regulation of inducible and non-inducible extracellular biomacromolecules secreted by R. mucilaginosa. This is the first time to identify that R. mucilaginosa can remove Sb(III) by transforming Sb(III) into Sb2O3 microcrystals under the control of EPS. This study contributes to our understanding for Sb(III) biomineralization mechanisms and provides strategies for the remediation of Sb-contaminated environment.

Stibnite dissolution and Sb oxidation by Paraccocus versutus XT0.6 via direct and indirect contact.

In this study Paraccocus versutus XT0.6 was employed to address the mechanism of microbial dissolution and oxidation of stibnite. Results showed that with the growth of XT0.6, pH increased to 9.0 in both microbe-mineral contact (MM) and microbe-mineral non-contact groups (M[M]). Dissolved Sb(III) was released from stibnite, which was subsequently quickly oxidized to Sb(V) completely in MM and partially in M[M] groups. On the contrast, the final pH decreased to 6.5 and 4.9, respectviely, in system amended with extracellular secretion (EM) of XT0.6 and abiotic groups. Dissolution of stibnite and oxidation of Sb(III) were also observed in EM group, suggesting a potential contribution of extracellular enzyme in Sb(III) oxidation. The dissolution and oxidation rates were the highest in MM group, followed by those in M[M], EM and abiotic groups. To be noted, Sb(V) concentration decreased in MM group on the fifth day, which might indicate the formation of Sb(V)-bearing secondary mineral. Genome of XT0.6 consisted of two chromosomes and one plasmid, and most genes responsible for antimony oxidation and antimony resistance were located on the chromosomes. Proteomics analysis of the extracellular secretions indicated the up-regulated proteins were mainly related to electron-transfer, suggesting their potential role in Sb(III) oxidation.

Functional features of a novel Sb(III)- and As(III)-oxidizing bacterium: Implications for the interactions between bacterial Sb(III) and As(III) oxidation pathways.

Antimony (Sb) and arsenic (As) share similar chemical characteristics and commonly coexist in contaminated environments. It has been reported that the biogeochemical cycles of antimony and arsenic affect each other. However, there is limited understanding regarding microbial coupling between the biogeochemical processes of antimony and arsenic. Here, we aimed to solve this issue. We successfully isolated a novel bacterium, Shinella sp. SbAsOP1, which possesses both Sb(III) and As(III) oxidase, and can effectively oxidize both Sb(III) and As(III) under aerobic and anaerobic conditions. SbAsOP1 exhibits greater aerobic oxidation activity for the oxidation of As(III) or Sb(III) compared to its anaerobic activity. SbAsOP1 also significantly catalyzes the oxidative mobilization of solid-phase Sb(III) under aerobic conditions. The activity of SbAsOP1 in oxidizing solid Sb(III) is 3 times lower than its activity in oxidizing soluble form. It is noteworthy that, in the presence of both Sb(III) and As(III) under aerobic conditions, either As(III) or Sb(III) significantly inhibits the oxidation of Sb(III) or As(III), respectively. In comparison, under anaerobic conditions and in the coexistence of Sb(III) and As(III), As(III) significantly inhibits Sb(III) oxidation, whereas Sb(III) almost completely inhibits As(III) oxidation. These findings suggest that under both aerobic and anaerobic conditions, SbAsOP1 demonstrates a partial preference for Sb(III) oxidation. Additionally, bacterial oxidations of Sb(III) and As(III) mutually inhibit each other to varying degrees. These observations gain a novel understanding of the interplay between the biogeochemical processes of antimony and arsenic.

Biological oxidation of As(III) and Sb(III) by a novel bacterium with Sb(III) oxidase rather than As(III) oxidase under anaerobic and aerobic conditions.

Sb and As are chemically similar, but the sequences and structures of Sb(III) and As(III) oxidase are totally distinct. It is thus interesting to explore whether Sb(III) oxidase oxidizes As(III), and if so, how microbial oxidations of Sb(III) and As(III) influence one another. Previous investigations have yielded ambiguous or even erroneous conclusions. This study aimed to clarify this issue. Firstly, we prepared a consortium of Sb(III)-oxidizing prokaryotes (SOPs) by enrichment cultivation. Metagenomic analysis reveals that SOPs with the Sb(III) oxidase gene, but lacking the As(III) oxidase gene are predominant in the SOP community. Despite this, SOPs exhibit comparable Sb(III) and As(III)-oxidizing activities in both aerobic and anaerobic conditions, indicating that at the microbial community level, Sb(III) oxidase can oxidize As(III). Secondly, we isolated a representative cultivable SOP, Ralstonia sp. SbOX with Sb(III) oxidase gene but without As(III) oxidase gene. Genomic analysis of SbOX reveals that this SOP strain has a complete Sb(III) oxidase (AnoA) gene, but lacks As(III) oxidase (AioAB or ArxAB) gene. It is interesting to discover that, besides its Sb(III) oxidation activities, SbOX also exhibits significant capabilities in oxidizing As(III) under both aerobic and anaerobic conditions. Moreover, under aerobic conditions and in the presence of both Sb(III) and As(III), SbOX exhibited a preference for oxidizing Sb(III). Only after the near complete oxidation of Sb(III) did SbOX initiate rapid oxidation of As(III). In contrast, under anaerobic conditions and in the presence of both Sb(III) and As(III), Sb(III) oxidation notably inhibited the As(III) oxidation pathway in SbOX, while As(III) exhibited minimal effects on the Sb(III) oxidation. These findings suggest that SOPs can oxidize As(III) under both aerobic and anaerobic conditions, exhibiting a strong preference for Sb(III) over As(III) oxidation in the presence of both. This study unveils a novel mechanism of interaction within the Sb and As biogeochemical cycles.

Widespread Distribution of the arsO Gene Confers Bacterial Resistance to Environmental Antimony.

Microbial oxidation of environmental antimonite (Sb(III)) to antimonate (Sb(V)) is an antimony (Sb) detoxification mechanism. Ensifer adhaerens ST2, a bacterial isolate from a Sb-contaminated paddy soil, oxidizes Sb(III) to Sb(V) under oxic conditions by an unknown mechanism. Genomic analysis of ST2 reveals a gene of unknown function in an arsenic resistance (ars) operon that we term arsO. The transcription level of arsO was significantly upregulated by the addition of Sb(III). ArsO is predicted to be a flavoprotein monooxygenase but shows low sequence similarity to other flavoprotein monooxygenases. Expression of arsO in the arsenic-hypersensitive Escherichia coli strain AW3110Δars conferred increased resistance to Sb(III) but not arsenite (As(III)) or methylarsenite (MAs(III)). Purified ArsO catalyzes Sb(III) oxidation to Sb(V) with NADPH or NADH as the electron donor but does not oxidize As(III) or MAs(III). The purified enzyme contains flavin adenine dinucleotide (FAD) at a ratio of 0.62 mol of FAD/mol protein, and enzymatic activity was increased by addition of FAD. Bioinformatic analyses show that arsO genes are widely distributed in metagenomes from different environments and are particularly abundant in environments affected by human activities. This study demonstrates that ArsO is an environmental Sb(III) oxidase that plays a significant role in the detoxification of Sb(III).

Oxidation of Sb(III) by Shewanella species with the assistance of extracellular organic matter.

Antimony (Sb) is a toxic substance that poses a serious ecological threat when released into the environment. The species and redox state of Sb determine its environmental toxicity and fate. Understanding the redox transformations and biogeochemical cycling of Sb is crucial for analyzing and predicting its environmental behavior. Dissolved organic matter (DOM) in the environment greatly affects the fate of Sb. Microbially produced DOM is a vital component of environmental DOM; however, its specific role in Sb(III) oxidation has not been experimentally confirmed. In this work, the oxidation capacity of several Shewanella strains and their derived DOM to Sb(III) was confirmed. The oxidation rate of Sb(III) shows a positive correlation with DOM concentration, with higher rates observed under neutral and weak alkaline conditions, regardless of the presence of light. Incubation experiments indicated that extracellular enzymes and common reactive oxygen species were not involved in the oxidation of Sb(III). Characteristics of DOM suggests that microbial humic acid-like and fulvic acid-like substances are the potential contributors to Sb(III) oxidation. These findings not only experimentally validate the role of bacterial-derived DOM in Sb(III) oxidation but also reveal the significance of Shewanella and biogenic DOM in the biogeochemical cycling of Sb.

Mechanistic insights into Sb(III) and Fe(II) co-oxidation by oxygen and hydrogen peroxide: Dominant reactive oxygen species and roles of organic ligands.

Sole O2 or H2O2 oxidant hardly oxidize Sb(III) on a time scale of hours to days, but Sb(III) oxidation can simultaneously occur in Fe(II) oxidation by O2 and H2O2 due to the generation of reactive oxygen species (ROS). However, Sb(III) and Fe(II) co-oxidation mechanisms regarding the dominant ROS and effects of organic ligands require further elucidation. Herein, the co-oxidation of Sb(III) and Fe(II) by O2 and H2O2 was studied in detail. The results indicated that increasing the pH significantly increased Sb(III) and Fe(II) oxidation rates during Fe(II) oxygenation, while the highest Sb(III) oxidation rate and oxidation efficiency was obtained at pH 3 with H2O2 as the oxidant. HCO3- and H2PO4-anions exerted different effects on Sb(III) oxidation in Fe(II) oxidation processes by O2 and H2O2. In addition, Fe(II) complexed with organic ligands could improve Sb(III) oxidation rates by 1 to 4 orders of magnitude mainly due to more ROS production. Moreover, quenching experiments combined with the PMSO probe demonstrated that .OH was the main ROS at acidic pH, whereas Fe(IV) played a key role in Sb(III) oxidation at near-neutral pH. In particular, the steady-state concentration of Fe(IV) ([Fe(IV)]ss) and kFe(IV)/Sb(III) were determined to be 1.66×10-9 M and 2.57×105 M-1 s-1, respectively. Overall, these findings help to better understand the geochemical cycling and fate of Sb in Fe(II)- and DOM-rich subsurface environments undergoing redox fluctuations and are conductive to developing Fenton reactions for the in-situ remediation of Sb(III)-contaminated environments.

Distribution, metabolism, and toxicity of antimony species in wistar rats. A bio-analytical approach.

This work studied the distribution, reactivity, and biological effects of pentavalent or trivalent antimony (Sb(V), Sb(III)) and N-methylglucamine antimonate (NMG-Sb(V)) in Wistar Rats. The expression of fibrosis genes such as α - SMA, PAI-1, and CTGF were determined in Liver, and Kidney tissues. Wistar rats were treated with different concentrations of Sb(V), Sb(III), As(V) and As(III), and MA via intra-peritoneal injections. The results indicated a noteworthy elevation in mRNA levels of plasminogen activator 1 (PAI-1) in the kidneys of rats that were injected. The main accumulation site for Sb(V) was observed to be the liver, from which it is primarily excreted in its reduced form (Sb(III)) through the urine. The generation of Sb(III) in the kidneys has been found to induce damage through the expression of α-SMA and CTGF, and also lead to a higher creatinine clearance compared to As(III).

Influence of Humic Acids on the Removal of Arsenic and Antimony by Potassium Ferrate.

Although the removal ability of potassium ferrate (K2FeO4) on aqueous heavy metals has been confirmed by many researchers, little information focuses on the difference between the individual and simultaneous treatment of elements from the same family of the periodic table. In this project, two heavy metals, arsenic (As) and antimony (Sb) were chosen as the target pollutants to investigate the removal ability of K2FeO4 and the influence of humic acid (HA) in simulated water and spiked lake water samples. The results showed that the removal efficiencies of both pollutants gradually increased along the Fe/As or Sb mass ratios. The maximum removal rate of As(III) reached 99.5% at a pH of 5.6 and a Fe/As mass ratio of 4.6 when the initial As(III) concentration was 0.5 mg/L; while the maximum was 99.61% for Sb(III) at a pH of 4.5 and Fe/Sb of 22.6 when the initial Sb(III) concentration was 0.5 mg/L. It was found that HA inhibited the removal of individual As or Sb slightly and the removal efficiency of Sb was significantly higher than that of As with or without the addition of K2FeO4. For the co-existence system of As and Sb, the removal of As was improved sharply after the addition of K2FeO4, higher than Sb; while the latter was slightly better than that of As without K2FeO4, probably due to the stronger complexing ability of HA and Sb. X-ray energy dispersive spectroscopy (EDS), X-ray diffractometer (XRD), and X-ray photoelectron spectroscopy (XPS) were used to characterize the precipitated products to reveal the potential removal mechanisms based on the experimental results.

Synergistic adsorption and oxidation of trivalent antimony from groundwater using biochar supported magnesium ferrite: Performances and mechanisms.

Antimony (Sb) pollution is considered an environmental problem, since Sb is toxic and carcinogenic to humans. Here, a novel biochar supported magnesium ferrite (BC@MF) was adopted for Sb(III) removal from groundwater. The maximum adsorption capacity was 77.44 mg g-1. Together with characterization, batch experiments, kinetics, isotherms, and thermodynamic analyses suggested that inner-sphere complexation, H-bonding, and electrostatic interactions were the primary mechanisms. C-C/CC, C-O, and O-CO groups and Fe/Mg oxides might have acted as adsorption sites. The adsorbed Sb(III) was oxidized to Sb(V). The generation of reactive oxygen species, iron redox reaction, and oxidizing functional groups all contributed to Sb(III) oxidation. Furthermore, the fixed-bed column system demonstrated a satisfactory Sb removal performance; BC@MF could treat ∼6060 BV of simulated Sb-polluted groundwater. This research provides a promising approach to sufficiently remove Sb(III) from contaminated groundwater, providing new insights for the development of innovative strategies for heavy metal removal.

A Novel Whole-Cell Biosensor for Bioavailable Antimonite in Water and Sediments.

Antimony (Sb) is an emerging contaminant, and its on-site speciation analysis is central to the accurate evaluation of its bioavailability and toxicity. The whole-cell biosensors (WCBs) for Sb(III) are promising but challenging due to the lack of Sb(III)-specific recognition components. Here, we constructed a novel Sb(III)-specific WCB using an Sb(III) transcriptional regulator (antR) and its cognate promoter (Pant). To prevent the promoter leakage of Pant, an additional regulatory gene, antR, was inserted downstream of the Sb(III)-inducible promoter, improving the sensitivity of the WCB by an order of magnitude and reaching the detection limit at 0.009 µM, which is lower than the WHO drinking water standard of Sb. Moreover, the WCB with double antR showed a high specificity toward Sb(III) compared with interfering ions at 3 orders of magnitude higher concentrations. This WCB was capable of measuring Sb(III) bioavailability in natural waters and sediments on-site, and its results were not statistically different from the chemical analysis. The insights gained from this work demonstrate that the addition of regulatory genes prevents promoter leakage and improves the sensitivity of WCBs in field applications. IMPORTANCE Antimony (Sb) is a redox-sensitive pollutant ubiquitous in the environment. Sb(III) is dominant in the subsurface and is readily oxidized to less toxic Sb(V) upon exposure to air, and therefore, on-site Sb speciation analysis is essential to evaluate its bioavailability and toxicity. Dissolved Sb concentration and speciation can be determined accurately using on-site chemical sensors, but chemical sensors have difficulty determining the bioavailable Sb(III) that is taken up by the cells. Here, we constructed an Sb(III)-specific whole-cell biosensor (WCB) using double Sb(III) transcriptional regulators (antR) downstream of its cognate promoter Pant. With an additional antR, the sensitivity of the WCB was improved by approximately 10 times, and the promoter leakage commonly found in WCBs was inhibited. Integrated with a tea-bag design, the WCB is able to measure Sb(III) bioavailability in natural water and sediments on-site. This study demonstrates the importance of inserting one more regulatory gene to improve sensitivity.