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Elemental sulfur (S0) autotrophic reduction is a promising approach for antimonate [Sb(V)] removal from water; however, it is hard to achieve effective removal of total antimony (TSb). This study established internal recirculation in an S0 autotrophic bioreactor (SABIR) to enhance TSb removal from Sb(V)-contaminated water. Complete Sb(V) reduction (10 mg/L) with bare residual Sb(III) (< 0.26 mg/L) was achieved at hydraulic retention time (HRT) = 8 h. Shortening HRT adversely affected the removal efficiencies of Sb(V) and TSb; meanwhile, an increased reflux ratio was conducive to Sb(V) and TSb removal at the same HRT. Sulfur disproportionation occurred in the SABIR and was the primary source for SO42− generation and alkalinity consumption. The alkalinity consumption decreased with the shortening HRT and increased with an increased reflux ratio at the same HRT. The generated SO42− was significantly higher (50–100 times) than the theoretical value for Sb(V) reduction. Coefficient of variation (CV), first-order kinetic models, and osmolality analyses showed that internal recirculation did not significantly affect the stability of SABIR but contributed to enhancing TSb removal by increasing mass transfer and reflowing generated sulfide back to the SABIR. SEM–EDS, Raman spectroscopy, XRD and XPS analyses identified that the precipitates in the SABIR were Sb2S3 and Sb-S compounds. In addition, high-throughput sequencing analysis revealed the microbial community structure's temporal and spatial distribution in the SABIR. Dominant genera, including unclassified-Proteobacteria (18.72–38.99%), Thiomonas (0.94–4.87%) and Desulfitobacterium (1.18–2.75%) might be responsible for Sb(V) bio-reduction and removal. This study provides a strategy to remove Sb from water effectively and supports the theoretical basis for the practical application of the SABIR in Sb(V)-contaminated wastewater. [ABSTRACT FROM AUTHOR]

Antimony, extensively used in energy applications, poses toxicity and contamination concerns, especially in anaerobic environments where its impact on microbial activity is poorly understood. Emerging remedies, like biochar, show promise in soil and water treatment. This study investigates biochar's influence on methanogenic activity under Sb(V) and Sb(III) stress using anaerobic sludge as inoculum and lactate as the carbon source. Sb(III) and Sb(V) were introduced at varied concentrations (5–80 mg/L), with or without biochar, monitoring changes in biogas production, pH, Sb, and lactate levels over time. Experiments with Sb(V) also involved calculating mass balance and electron distribution. Results showcased the following significant enhancements: biochar notably improved COD removal and biogas production in Sb(III) spiked conditions, up to 5-fold and 2-fold increases, respectively. Sb(III) removal reached up to 99% with biochar, while in high Sb(V) concentrations, biochar reduced the adverse effect on biogas production by 96%. Adsorption capacities favored biomass (60.96 mg Sb(III)/gVSS, and 22.4 mg Sb(V)/gVSS) over biochar (3.33 mg Sb(III)/g, and 1.61 mg Sb(V)/g) for both Sb species. This study underscores biochar's potential to mitigate metalloid impact on methanogenic activity while aiding Sb removal from liquid phase, suggesting promising implications for remediation and methane production enhancement strategies. HIGHLIGHTS Antimony negatively affects methanogenic activity.; Biochar notably improves COD removal and biogas production in presence of Sb(III).; Biochar demonstrates potential enhancing the biogas production even at high Sb(V) concentrations.; Biochar improves the effectiveness in aiding Sb removal from anaerobic digestion process.; Biochar mitigates adverse effect of Sb toxicity.;

Geobacter sp. strain SVR uses antimonate [Sb(V)] as a terminal electron acceptor for anaerobic respiration. Here, we visualized a possible key enzyme, periplasmic Sb(V) reductase (Anr), via active staining and non-denaturing gel electrophoresis. Liquid chromatography-tandem mass spectrometry analysis revealed that a novel dimethyl sulfoxide (DMSO) reductase family protein, WP_173201954.1, is involved in Anr. This protein was closely related with AnrA, a protein suggested to be the catalytic subunit of a respiratory Sb(V) reductase in Desulfuribacillus stibiiarsenatis. The anr genes of strain SVR (anrXSRBAD) formed an operon-like structure, and their transcription was upregulated under Sb(V)-respiring conditions. The expression of anrA gene was induced by more than 1 μM of antimonite [Sb(III)]; however, arsenite [As(III)] did not induce the expression of anrA gene. Tandem mass tag-based proteomic analysis revealed that, in addition to Anr proteins, proteins in the following categories were upregulated under Sb(V)-respiring conditions: (i) Sb(III) efflux systems such as Ant and Ars; (ii) antioxidizing proteins such as ferritin, rubredoxin, and thioredoxin; (iii) protein quality control systems such as HspA, HslO, and DnaK; and (iv) DNA repair proteins such as UspA and UvrB. These results suggest that strain SVR copes with antimony stress by modulating pleiotropic processes to resist and actively metabolize antimony. To the best of our knowledge, this is the first report to demonstrate the involvement of AnrA in Sb(V) respiration at the protein level. Furthermore, this is the first example to show high expression of the Ant system proteins in the Sb(V)-respiring bacterium. IMPORTANCE Antimony (Sb) exists mainly as antimonite [Sb(III)] or antimonate [Sb(V)] in the environment, and Sb(III) is more toxic than Sb(V). Recently, microbial involvement in Sb redox reactions has received attention. Although more than 90 Sb(III)-oxidizing bacteria have been reported, information on Sb(V)-reducing bacteria is limited. Especially, the enzyme involved in dissimilatory Sb(V) reduction, or Sb(V) respiration, is unclear, despite this pathway being very important for the circulation of Sb in nature. In this study, we demonstrated that the Sb(V) reductase (Anr) of an Sb(V)-respiring bacterium (Geobacter sp. SVR) is a novel member of the dimethyl sulfoxide (DMSO) reductase family. In addition, we found that strain SVR copes with Sb stress by modulating pleiotropic processes, including the Ant and Ars systems, and upregulating the antioxidant and quality control protein levels. Considering the abundance and diversity of putative anr genes in the environment, Anr may play a significant role in global Sb cycling in both marine and terrestrial environments. [ABSTRACT FROM AUTHOR]

This study evaluated the effects of post-calcination on the charge properties and active sites of Mg/Al layered double hydroxide-decorated spent coffee ground biochars (LDH MgAl @SCGB) governing adsorption behaviors and mechanisms of arsenic (AsV) and antimony (SbV) anions from aqueous phases. Post-calcinated LDH MgAl @SCGB (PLDH MgAl @SCGB) exhibited higher adsorption capacities for AsV and SbV compared to spent coffee ground biochars (SCGB) and LDH MgAl @SCGB as post-calcination of LDH MgAl @SCGB enhanced the charge properties (surface zeta potential at pH 7.0: SCGB = −21.8 mV, LDH MgAl @SCGB = 28.5 mV, and PLDH MgAl @SCGB = 34.4 mV) and increased active sites by eliminating the anions (i.e., Cl− ions) and water molecules at its interlayers. The calculated kinetic, intra-particle diffusion, and isotherm parameters indicated that the chemisorption and intra-particle diffusion were mainly responsible for the adsorption of AsV and SbV by SCGB, LDH MgAl @SCGB, and PLDH MgAl @SCGB. Moreover, post-calcination of LDH MgAl @SCGB enhanced its selectivity toward AsV and SbV by reinforcing the electrostatic surface complexation via its improvement of charge properties. Since PLDH MgAl @SCGB exhibited the excellent reusability for the adsorption of AsV (reuse efficiency >63.6%) and SbV (reuse efficiency >52.1%), it can be concluded that post-calcination of LDH MgAl @SCGB is a promising method for improving the adsorption capacities for AsV and SbV in real water matrices. [Display omitted] • Post-calcination effectively removes interlayer anions of LDH MgAl @SCGB. • Increased active sites of PLDH MgAl @SCGB enhance electrostatic surface complexation. • PLDH MgAl @SCGB exhibits highest adsorption capacities of AsV and SbV. • PLDH MgAl @SCGB has excellent reusability for the adsorption of AsV and SbV. [ABSTRACT FROM AUTHOR]

Excess antimony (Sb) has been shown to damage plant growth. Rice plants readily absorb a large amount of Sb after a long period of flooding, yet the mechanisms underlying Sb toxicity in plants have not been solved. This study was conducted to explore the effects of Sb on the uptake of N and S, and monitor the concentrations of reduced glutathione (GSH) and enzymes associated with these processes. In addition, we analyzed differentially expressed metabolites (DEMs) correlated with amino acids (AAs) and oligopeptides, specifically DEMs containing sulfur (S), GSH and indole–3–acetic acid (IAA). The results showed that antimonite [Sb(III)] inhibited shoot growth whereas antimonate [Sb(V)] stimulated shoot growth. Interestingly, Sb(III) 5/10 enhanced shoot concentrations of total nitrogen (N), NH 4 +–N [only at Sb(III) 10 ] and S; but reduced the shoot concentrations of NO 3 –N and soluble protein. Sb(III) 5/10 addition significantly increased oxidized glutathione (GSSG) concentration and activities of glutathione peroxidase (GSH–Px) and glutathione S-transferase (GST) but non–significantly affected concentration of reduced glutathione (GSH) and activities of γ-glutamylcysteine synthetase (GCL) and glutathione reductase (GR), suggesting Sb(III) restricted GSH recycling. Addition of Sb (1) increased the abundance of DEMs associated with lignins, Ca uptake, toxicity/detoxification, and branched chain AAs; (2) decreased the abundance of AAs inclcuding isoleucine (Ile), leucine (Leu), tryptophan (Trp), tyrosine (Tyr) and histidine (His); (3) increased the abundance of arginine (Arg), putrescine (Put) and spermidine (Spd); and (4) affected methylation and acetylation of many AAs, especially acetylation. [Display omitted] • Sb(III) enhanced total N, NH 4 +–N and S but reduced NO 3 −–N and soluble protein in shoots. • Sb(III) enhanced GSSG concentration and activities of GSH-Px and GST in shoots. • Sb affected DEMs associated with lignins, Ca uptake, and branched chain amino acids in shoots. • Sb inhibited shoot abundances of Ile, Leu, Ser, Trp, Tyr, and His but stimulated that of Arg, Put, Gln, and Spd. • Sb may affect methylation and acetylation of many amino acids, especially for acetylation. [ABSTRACT FROM AUTHOR]

Long-persistent luminescence (LPL) materials have attracted intensive attention due to their fascinating emission after excitation. However, current LPL materials typically depend on external doping to introduce traps or emitting centers, resulting in a complex synthesis and controllability. For the first time, we develop another category of undoped LPL materials based on antimonate CaSb 2 O 6 , which exhibits blue LPL for over 8000 s. Both experimental and theoretical evidence indicate that excitons are trapped by intrinsic oxygen vacancies. Then, they are detrapped and recombine through singlet and triplet emission of Sb 3+ to form LPL. Moreover, CaSb 2 O 6 maintains approximately 100% of its initial LPL performance and structural integrity even after being treated under 1000 °C, UV irradiation, and extreme conditions (pH = 1 or 13). This study highlights the significant potential of antimonates as robust and versatile luminescent materials.

Schwertmannite is a poorly-crystalline Fe(III) oxyhydroxysulfate mineral that may control Sb(V) mobility in acid sulfate environments, including acid mine drainage and acid sulfate soils. However, the mechanisms that govern uptake of aqueous Sb(V) by schwertmannite in such environments are poorly understood. To address this issue, we examined Sb(V) sorption to schwertmannite across a range of environmentally-relevant Sb(V) loadings at pH 3 in sulfate-rich solutions. Antimony K-edge extended X-ray absorption fine structure (EXAFS) spectroscopy revealed that Sb(V) sorption (at all loadings) involved edge and double-corner sharing linkages between SbVO 6 and FeIIIO 6 octahedra. The coordination numbers for these linkages indicate that sorption occurred by Sb(V) incorporation into the schwertmannite structure via heterovalent Sb(V)-for-Fe(III) substitution. As such, Sb(V) sorption to schwertmannite was not limited by the abundance of surface complexation sites and was strongly resistant to desorption when exposed to 0.1 M PO 4 3-. Sorption of Sb(V) also conferred increased stability to schwertmannite, based on changes in the schwertmannite dissolution rate during extraction with an acidic ammonium oxalate solution. This study provides new insights into Sb(V) sorption to schwertmannite in acid sulfate environments, and highlights the role that schwertmannite can play in immobilizing Sb(V) within its crystal structure. [Display omitted] • Sb(V) sorption by schwertmannite was investigated under acid sulfate conditions. • Sorption involved incorporation of Sb(V) into the schwertmannite structure. • Sb(V)-sorbed schwertmannite showed resistance to desorption and dissolution. • Schwertmannite may be a secure host-phase for Sb(V) in acid sulfate environments. [ABSTRACT FROM AUTHOR]

Novel antimonate Ca 3 LiSbO 6 : x Eu3+ red phosphor was synthesised using a high-temperature solid-phase reaction. The effect of Eu3+ doping concentration on its crystal structure and luminescence performance was investigated. It was found that Eu3+ was at the inversion symmetry site in the lattice of Ca 3 LiSbO 6. To improve the luminescence performance of Ca 3 LiSbO 6 : 0.05Eu3+ red phosphor, Ca 3 LiSbO 6 : 0.05Eu3+, x Li + red phosphor was synthesised. The doping of Li + can correct the charge difference generated by the substitution of Ca2+ by Eu3+, reduce the generation of defects, enhance the local symmetry of the luminescence centre of Eu3+, improve the structural rigidity, and thus enhance the luminous intensity of the phosphor. At 423 K, the luminous intensity of this phosphor was 68 % of the initial temperature, which was higher than that of the phosphor without the charge compensator Li+ (60 %), indicating that Li+ improved the thermal stability of the phosphor. Changes in luminescence properties of Ca 3 LiSbO 6 doped Eu3+ and co-doped Eu3+ and Li+ and applications in white light-emitting diodes. [Display omitted] • Ca 3 LiSbO 6 :Eu3+ and Ca 3 LiSbO 6 :Eu3+,Li+ phosphors have high color purity. • Co-doping with Li+ improves color purity and thermal stability of the phosphor. • W-LED made of Ca 3 LiSbO 6 :Eu3+,Li+ have better color rendering indices than commercially W-LED. [ABSTRACT FROM AUTHOR]

[Display omitted] • Eu3+-activated LiSbO 3 phosphor was synthesized by a solid-state reaction. • LiSbO 3 :Eu3+ demonstrates efficient pure red luminescence. • The lattice always provides two positions of Li+ and Sb5+ for Eu3+ doping. • Eu3+ ions mainly occupy Li sites, and only a few are doped in Sb5+ positions. It is a challenge to accurately determine the exact location of the rare earth ion (RE) in the lattice when there are significant differences in radius, electronegativity and valence between the lattice cation and the corresponding RE activator in a host material. This study presents the findings on the luminescence and site occupancy of Eu3+ emission centers in the lithium antimonate LiSbO 3 lattice. The phase-formation, structures, elemental composition, band transition characteristics, luminescence properties, and lifetimes of the Eu3+-doped phosphors were investigated. Eu3+-doped LiSbO 3 exhibits a typical 5D 0 →7F 2 red luminescence transition at 613 nm. Site-selective excitation, luminescence, and decay properties at the 7F 0 →5D 0 transition wavelength were measured using a tunable pulsed narrow-band dye laser. Two Eu3+ luminescence centers in LiSbO 3 were identified across the temperature range from 10 K to 300 K. The doping of RE(Eu3+) in LiSbO 3 consistently occupies two crystallographic positions of Li+ and Sb5+. Furthermore, the probability of RE(Eu3+) ions preferentially occupying the Li+ (M) sites is notably high. The decay curves and luminescence lifetimes of the two Eu3+ centers were determined. Drawing from the experimental data, we discuss the potential defects induced by Eu3+ doping in LiSbO 3 and the mechanism of charge compensation. These results could be instrumental in the advancement of new RE-activated luminescent materials or serve as a reference for investigating the specific positioning of RE ions within a phosphor lattice. [ABSTRACT FROM AUTHOR]

BACKGROUND Chemical phase analysis of antimony ores involves three mineral phases:valentinite, stibnite and insoluble antimonate. Solvents used for extracting various antimony mineral phases are different. In addition, coexisting ions are complex and concentration gradients vary greatly. These factors affect the accurate determination of antimony chemical phases by inductively coupled plasma-optical emission spectrometry (ICP-OES). OBJECTIVES To solve the problem during rapid and accurate measurement of chemical phases of antimony ore. METHODS The effects of hydrochloric acid, nitric acid and potassium sulfate-nitric acid-sulfuric acid on the determination of antimony by ICP-OES were studied with valentinite, stibnite and antimonate as selective separation solvents. RESULTS The same concentration of hydrochloric acid and nitric acid medium had no effect on the determination of antimony. The same standard solution series can be used to determine antimony in valentinite and stibnite. Hydrolysis of antimony can be avoided by using 15%-20% hydrochloric acid or nitric acid of. Mixed acid medium (4g/L potassium sulfate-15% nitric acid-3% sulfuric acid) had an effect on the determination of antimony. The matrix matching method can be used to solve the problem. In determining the amount of antimony in antimonate, the calibrated solution was formulated to add the same amount of mixed acid as the antimonate leaching agent. The detection limits of antimony in valentinite, stibnite and antimonate mineral phases by ICP-OES were 0.0006%, 0.0012% and 0.0021%, respectively, by choosing the 206.833nm line as the analytical line, under optimized analytical method flow and measurement parameters. The relative standard deviations (n=12) of the method were 0.16%-5.76%, and the absolute relative deviations of phase addition and total amount were 0.07%-7.38%. CONCLUSIONS The precision and accuracy of the method meet the quality control requirements of antimony ore chemical phase analysis, and provide fast and accurate measurement of antimony ore chemical phase.

In this study, novel deep-red-emitting Mg 2 InSbO 6 :Mn4+ phosphors were prepared through a high-temperature solid-state reaction. The as-prepared phosphors belong to the perovskite structure with the space group of R 3 ‾ (No.148). The calculated energy gap value of Mg 2 InSbO 6 is ~1.788 eV. Emission spectrum of the Mg 2 InSbO 6 :0.3%Mn4+ was obtained under 301 nm excitation, which centered 665 nm due to the 2E g →4A 2g transition. The optimum concentration of Mg 2 InSbO 6 : x Mn4+ is confirmed to 0.3% mol, and the concentration quenching effect is ascribed to the dipole–dipole interaction. The relative temperature-dependent PL spectra demonstrate that phosphors possess commendable repeatability and high activation energy. The chromaticity shift diagram shows the phosphors have good resistance of color drifting. The Mg 2 InSbO 6 :0.3%Mn4+ phosphor has a high color purity of 99.8%. Furthermore, a red light-emitting diode is fabricated with Mg 2 InSbO 6 :0.3%Mn4+ phosphor and a 365 nm near-ultraviolet chip. The emission spectrum of the red LED is perfectly overlapped with plant pigments (chlorophyll a and chlorophyll b) absorption spectrum. Thus, Mn4+-activated Mg 2 InSbO 6 :Mn4+ phosphors have the potential to apply in plant-cultivation LEDs. [ABSTRACT FROM AUTHOR]

The new lanthanum chalcoantimonate TlLa2Sb3Se9 has been synthesized and its crystal structure determined. TlLa2Sb3Se9 crystallizes in an ordered variant of the KLa2Sb3S9 type, space group P212121 with the lattice parameters a=4.2621(2) Å, b=15.155(5) Å, c=25.505(9) Å. The band gap of TlLa2Sb3Se9 was calculated to be 0.47 eV, and experimentally determined to be 0.68 eV. Its thermoelectric properties were optimized via doping with Ca2+; samples with the compositions TlLa2‐xCaxSb3Se9 (x=0.01, 0.03, 0.05) were synthesized. Despite ultralow thermal conductivity, the maximum thermoelectric figure‐of‐merit of the undoped sample was only zT=0.031 at 623 K, which was increased to 0.078 for the sample with the nominal composition of TlLa1.95Ca0.05Sb3Se9. These low values are a consequence of the uncompetitively low electrical conductivity. [ABSTRACT FROM AUTHOR]

The new lanthanum chalcoantimonate TlLa2Sb3Se9 has been synthesized and its crystal structure determined. TlLa2Sb3Se9 crystallizes in an ordered variant of the KLa2Sb3S9 type, space group P212121 with the lattice parameters a=4.2621(2) Å, b=15.155(5) Å, c=25.505(9) Å. The band gap of TlLa2Sb3Se9 was calculated to be 0.47 eV, and experimentally determined to be 0.68 eV. Its thermoelectric properties were optimized via doping with Ca2+; samples with the compositions TlLa2‐xCaxSb3Se9 (x=0.01, 0.03, 0.05) were synthesized. Despite ultralow thermal conductivity, the maximum thermoelectric figure‐of‐merit of the undoped sample was only zT=0.031 at 623 K, which was increased to 0.078 for the sample with the nominal composition of TlLa1.95Ca0.05Sb3Se9. These low values are a consequence of the uncompetitively low electrical conductivity. [ABSTRACT FROM AUTHOR]

Ramie (Boehmeria nivea L.) is a promising phytoremediation candidate due to its high tolerance and enrichment capacity for antimony (Sb). However, challenges arise as Sb accumulated mainly in roots, complicating soil extraction. Under severe Sb contamination, the growth of ramie may be inhibited. Strategies are needed to enhance Sb accumulation in ramie's aboveground parts and improve tolerance to Sb stress. Considering the beneficial effects of selenium (Se) on plant growth and enhancing resistance to abiotic stresses, this study aimed to investigate the potential use of Se in enhancing Sb uptake by ramie. We investigated the effects of Se (0.5, 1, 2, 5, or 10 μM) on ramie growth, Sb uptake and speciation, antioxidant responses, and ionomic profiling in ramie under 10 mg/L of SbIII or antimonate (SbV) stresses. Results revealed that the addition of 0.5 μM Se significantly increased shoot biomass by 75.73% under SbIII stress but showed minimal effects on shoot and root length in both SbIII and SbV treatments. Under SbIII stress, 2 μM Se significantly enhanced Sb concentrations by 48.42% in roots and 62.88% in leaves. In the case of SbV exposure, 10 μM Se increased Sb content in roots by 42.57%, and 1 μM Se led to a 91.74% increase in leaves. The speciation analysis suggested that Se promoted the oxidation of SbIII to less toxic SbV to mitigate Sb toxicity. Additionally, Se addition effectively minimized the excess reactive oxygen species produced by Sb exposure, with the lowest malondialdehyde (MDA) content at 0.5 μM Se under SbIII and 2 μM Se under SbV, by activating antioxidant enzymes including superoxide dismutase, catalase, peroxidase, and glutathione peroxidase. Ionomic analysis revealed that Se helped in maintaining the homeostasis of certain nutrient elements, including magnesium, potassium (K), calcium (Ca), iron (Fe), and copper (Cu) in the SbIII-treated roots and K and manganese (Mg) in the SbV-treated roots. The results suggest that low concentrations of Se can be employed to enhance the phytoremediation of Sb-contaminated soils using ramie. [Display omitted] • Se effectively mitigated Sb-induced ramie biomass inhibition. • Se enhanced Sb uptake in ramie and facilitated the conversion of SbIII to less toxic SbV. • Se upregulated SOD, CAT, POD, and GPX to counteract excessive ROS generated by Sb. • Se contributed to maintaining the homeostasis of Mg, K, Ca, Fe, Cu, and Mn. • Se dosage should be optimized for maximum effect as it is dose-dependent. [ABSTRACT FROM AUTHOR]

It is unclear to what extent sorption of antimony (Sb) in soils occurs over long time scales. This study was set up to monitor slow reactions (7 days to 6 months) of Sb in Sb(V)‐spiked soil samples during aerobic incubation. The solid–liquid distribution coefficients (KD) increased by factors of 3 to 6 between 7 and 190 days after spiking, depending on the soil. This increase in the KD value, hereafter named the Sb ageing factor, increased with increasing amorphous iron and aluminium hydroxide concentration and decreasing pH of the soil samples. Finally, ageing factors were highest in topsoils and could be important in preventing Sb from migrating downwards into groundwater bodies. Highlights: Quantification of antimonate ageing in soils.Topsoils could prevent downward leaching of Sb in the long‐term.Ageing of Sb increased in soils with increasing amorphous iron and aluminium hydroxide concentration and decreasing pH.Slow sorption reactions reduce Sb mobility in soils. [ABSTRACT FROM AUTHOR]

Background and aims: Antimony is an analogue of arsenic (As), but its uptake mechanisms are not as well understood as As. Antimonite [Sb(III)] probably enters into plant roots via aquaporins but antimonate [Sb(V)] not through the phosphate [P(V)] uptake system as with arsenate [As(V)]. However, previous studies observed a dose−dependent interaction between As(V) and P(V) in some plants. This study was conducted mainly to identify that 1) whether the uptake of Sb(III) by plants will be via aquaporin channels; 2) whether the interaction effects between Sb(V) and P(V) might be dose−dependent; 3) whether the uptake of Sb(III) or Sb(V) is at the cost of energy. Methods: Two hydroponic culture systems were set up using a rice plant (YeXiangYou No.3) to investigate the effects of different chemicals on the uptake of Sb in the rice plants subjected to Sb(III) and Sb(V). These chemicals included malonic acid (C3H4O4), Na3PO4 [P(V)] and HgCl2. Results: Sb was mainly sequestrated in the roots of the rice plants, suggesting a low transport capacity of Sb from roots to shoots. The plants took up Sb more easily under Sb(III) exposure than under Sb(V) exposure. 10 mg L−1 Sb(III) increased the Sb concentration in the bleeding sap rather than the weight of the bleeding sap; but the situation reversed when rice plants were exposed to Sb(V), suggesting different transport mechanisms of Sb from roots to shoots between Sb(III) and Sb(V). The addition of C3H4O4 generally reduced the Sb concentrations in the shoots and roots subjected to Sb(V), suggesting the uptake of Sb(V) to be energy dependent. The addition of Na3PO4 also significantly reduced the concentrations of Sb in the shoots and roots when plants were exposed to Sb(V). Interestingly, the addition of HgCl2 significantly reduced the concentrations of Sb in the shoots and roots when rice plants were exposed to both Sb(III) or Sb(V), possibly implying that uptake of Sb(III) might be via aquaporins and Cl− played a role in affecting the uptake of Sb(V). Conclusions: The results of this study suggested that uptake of Sb(III) is via aquaporins, and Cl− as well as PO43− may compete with Sb(V) for uptake pathway. [ABSTRACT FROM AUTHOR]

We investigated the adsorption performance of five Fe-based MOFs (Fe-BTC, MIL-100(Fe), MIL-101(Fe), MIL-53(Fe) and MIL-88C(Fe)) for removal of antimonite (Sb(III)) and antimonate (Sb(V)) from water. Among these MOFs, MIL-101(Fe) exhibited the best adsorption capacities for both Sb(III) and Sb(V) (151.8 and 472.8 mg/g, respectively) which were higher than those of most adsorbents previously reported. The effect of steric hindrance was evident during Sb removal using the Fe-based MOFs, and the proper diameter of the smallest cage windows/channels should be considered an important parameter during the evaluation and selection of MOFs. Additionally, the adsorption capacities of MIL-101(Fe) for Sb(V) decreased with increasing initial pH values (from 3.0 to 8.0), while the opposite trend was observed for Sb(III). Chloride, nitrate and sulfate ions had a negligible influence on Sb(V) adsorption, while NO 3 − and SO 4 2− improved Sb(III) adsorption. This result implies that inner sphere complexes might form during both Sb(III) and Sb(V) adsorption. Unlabelled Image [ABSTRACT FROM AUTHOR]

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In this study, the importance of Sb behavior under different pH conditions has been addressed with respect to its stabilization in aqueous solutions using Mg-Fe layered double hydroxides (LDHs). The Sb(V) adsorption onto Mg-Fe LDHs was performed at different initial Sb(V) concentrations and pH values (pH 5.5, 6.5 and 7.5). The removal rate and the maximal adsorbed amount increased with decreasing pH values. Moreover, the surface complexation modeling (SCM) predicted preferable formation of monodentate mononuclear and bidentate binuclear complexes on the Mg-Fe LDH surface. Spectroscopic (X-ray diffraction analysis, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy) and microscopic (scanning electron microscopy and energy-dispersive X-ray spectroscopy) techniques were used to further specify the adsorption mechanisms. The influence of chemical adsorption, surface-induced precipitation of brandholzite Mg[Sb(OH) 6 ] 2 ·6H 2 O, formation of brandholzite-like phases and/or anion exchange was observed. Moreover, Sb(V) was nonhomogeneously distributed on the Mg-Fe LDH surface at all pH values. The surface complexation modeling supported by solid-state analyses provided a strong tool to investigate the binding arrangements of Sb(V) on the Mg-Fe LDH surface. Such a complex mechanistic/modeling approach has not previously been presented and enables prediction of the Sb(V) adsorption behavior onto Mg-Fe LDHs under different conditions, evaluating their possible use in actual applications. Image 1 • The adsorbed amount of Sb(V) onto Mg-Fe LDHs increased by decreasing pH values. • Monodentate/bidentate complexes were predominantly formed on the Mg-Fe LDH surface. • Formation of brandholzite-like phases influenced Sb(V) removal using Mg-Fe LDHs. • Adsorption modeling was supported by spectroscopic and microscopic techniques. • Nonhomogeneous distribution of Sb(V) was observed on the Mg-Fe LDH surface. [ABSTRACT FROM AUTHOR]

The ternary copper antimony oxide Cu3‐xSb1+xO5.5+3x/2 (x=0.23) has been synthesized under 0.8–1.3 MPa pO2 at 1022–1082 °C. Rietveld refinements of X‐ray and neutron powder diffraction patterns concluded that the oxide adopts a bixbyite type structure, crystallising in the cubic space group Ia‐3 with the unit cell parameter a=9.61164(4) Å at room temperature from powder neutron diffraction data. The cationic 8b and 24d sites were found to be occupationally disordered where both Cu and Sb could be found on both sites. This is supported by X‐ray absorption spectroscopy experiments showing more than one possible Cu environment. There was a significant net deficiency of oxygen in the compound which was first inferred from observations of a thermochromic‐like phenomena and also seen from in situ high temperature neutron diffraction experiments. Magnetic susceptibility and magnetization measurements show paramagnetic behaviour with spin‐glass like transition below 6 K. [ABSTRACT FROM AUTHOR]

Abstract Far red-emitting Mn4+ activated oxide phosphors based on the substitution of Mn4+ for Sb5+ in the lattice of Sr 3 LiSbO 6 (SLSO) was prepared via solid state reaction process. The phases and micrographs of powders were analyzed by X-ray diffraction (XRD) and field emission scanning electron microscopy (FE-SEM). The luminescent properties of the samples with varying Mn4+ concentrations were investigated, and the result indicates that prepared phosphor SLSO:Mn4+ can be excited by (UV) light and exhibit intense far red emission at 698 nm. This emission band is well matched with the absorption band of phytochrome P FR. The mechanism of quenching concentration has been investigated. The thermal stability and thermal quenching concentration of SLSO:Mn4+ were discussed. In addition, the internal quantum efficiency (IQE) has been tested and calculated. All the above results suggest that the SLSO:Mn4+ phosphors have great potential applications in plant growth n-UV LEDs. Highlights • A novel far red-emitting Mn4+ activated oxide phosphors based on the substitution of Mn4+ for Sb5+ in the lattice of Sr 3 LiSbO 6 was prepared via solid state reaction process. • The results show that Sr 3 LiSbO 6 :Mn4+ has excellent thermal stability (I 423K /I 298K = 66.2%). • The phosphors can absorb UV, NUV and blue light between 250 nm and 500 nm and exhibit strong far-red emission at 698 nm (2E g →4A 2g transition of Mn4+), which can be absorbed by P FR effectively. • This emission band is well matched with the absorption band of phytochrome P FR. The internal quantum efficiency has been tested and calculated (η = 52.3%). [ABSTRACT FROM AUTHOR]

Used as a hardening agent in lead bullets, antimony (Sb) has become a major contaminant in shooting range soils of some countries including Switzerland. Soil contamination by Sb is also an environmental problem in countries with Sb-mining activities such as China and Bolivia. Because of its toxicity and relatively high mobility, there is concern over the risk of Sb transfer from contaminated soils into plants, and thus into the food chain. In particular there is very little information on the environmental behavior of methylated antimony, which can be produced by microbial biomethylation of inorganic Sb in contaminated soils. Using a new extraction and high-performance liquid chromatography inductively coupled plasma mass spectrometry (HPLC-ICP-MS) method, we investigated antimony speciation in roots and shoots of wheat, fescue, rye, and ryegrass plants exposed to trimethyl antimony(V) (TMSb), antimonite (Sb(III)), and antimonate (Sb(V)) in hydroponics. The total root Sb concentrations followed the order Sb(III) treatment > Sb(V) treatment > TMSb treatment, except for fescue. Shoot Sb concentrations, however, did not differ among the three treatments. In the Sb(V) treatment small quantities of TMSb were found in the roots, whereas no TMSb was detected in the roots of Sb(III)-treated plants. In contrast, similar concentrations of TMSb were found in the shoots in both inorganic Sb treatments. The results indicate that biomethylation of Sb may occur in plants. In the TMSb treatment TMSb was the major Sb species, but the two inorganic Sb species were also found both in shoots and roots along with some unknown Sb species, suggesting that also TMSb demethylation may occur within plant tissues. The results furthermore indicate that methylated Sb is more mobile in plants than inorganic Sb species. Knowledge about this is important in risk assessments of Sb-contaminated sites, as methylation may render Sb more toxic than inorganic Sb, as it is known for arsenic (As).

Abstract Antimony is an environmental contaminant, whose mobility in soils, sediments and groundwater systems is strongly influenced by interactions with Fe(III) oxide minerals. When exposed to reducing conditions, these minerals can undergo reductive dissolution via the activity of Fe(III)-reducing microorganisms, thereby potentially liberating previously retained Sb. In addition, microbial Fe(III)-reduction and the consequent production of Fe(II) can induce the formation of secondary Fe(III)- and Fe(II)-bearing minerals, which may alter the speciation and partitioning of Sb. In this study, we examined Sb behaviour during (1) the microbially-mediated reduction and transformation of Sb(V)-bearing ferrihydrite by the dissimilatory Fe(III)-reducing bacterium, Shewanella putrefaciens (strain CN32), and (2) during the associated abiotic Fe(II)-catalyzed transformation of Sb(V)-bearing ferrihydrite. Antimony K-edge XANES spectroscopy showed negligible reduction of Sb(V) to Sb(III) in both experiments, reflecting the redox stability of Sb(V) under these conditions. X-ray diffraction and Fe K-edge EXAFS spectroscopy revealed that both microbially-mediated Fe(II) production as well as the experimental addition of aqueous Fe(II) under abiotic conditions triggered rapid transformation of the initial ferrihydrite to feroxyhyte (δ′-FeOOH) and goethite (α-FeOOH). Goethite has been widely observed as a product of the Fe(II)-catalyzed transformation of ferrihydrite. However, the present study is the first to document the formation of feroxyhyte via this pathway, with feroxyhyte formation appearing to be favored by the presence of Sb(V). The formation of these secondary Fe(III) oxides was associated with substantial decreases in aqueous Sb concentrations and in the amount of surface-bound Sb (as defined via extractions with 1 M PO 4 3−). This is consistent with the incorporation of Sb(V) into the newly formed feroxyhyte and goethite via substitution for Fe(III). The results of this study provide new perspectives on coupling between Sb geochemistry and Fe mineralogy by showing that microbial Fe(III)-reduction and associated secondary Fe(III)-oxide formation can help to immobilize Sb(V) in reducing environments. [ABSTRACT FROM AUTHOR]

Antimonate (Sb(V)) and arsenate (As(V)) pollution frequently occur in aqueous environment and can be absorbed by poorly crystalline Fe minerals (i.e., ferrihydrite). In this study, the adsorption capacity and rate of Sb(V) and As(V) from water with fresh ferrihydrite were compared by establishing adsorption isotherms and kinetics, and the effects of ferrihydrite dosage, solution pH and humic substances on Sb(V) and As(V) adsorption were also investigated. The adsorption isotherms results showed that the equilibrium and maximum adsorption capacities of Sb(V) on ferrihydrite were approximately equal to those of As(V) under different temperatures. The results of adsorption kinetics showed that the adsorption rate of Sb(V) derived from the pseudo-second-order equation was much lower than that of As(V). In addition, the adsorption capacity and rate of Sb(V) and As(V) were greatly affected by various ferrihydrite dosage and solution pHs. The presence of humic acid and fulvic acid (FA) significantly affected the adsorption process of Sb(V) due to competition adsorption, whereas the adsorption properties of As(V) were little affected by FA under this experimental conditions. [ABSTRACT FROM AUTHOR]

Abstract In the current context, it is imperative to seek for a sustainable management and an efficient use of natural resources. Pinus pinaster bark is a forest and industrial waste whose chemical richness is commonly ignored. In this work, tannins were extracted from P. pinaster bark and converted into adsorbents through polymerization. Aqueous (alkaline) extraction yielded more formaldehyde-condensable phenols than an organic extraction using ethanol (Soxhlet) (53 ± 8 vs. 13 ± 4 mg of gallic acid equivalents per g of bark). The polymerization reaction was optimized and higher amounts of adsorbent were produced using 6.0 mL of 0.25 mol L−1 sodium hydroxide solution and 0.40 mL of formaldehyde (36 % wt) per g of extract. The performance of the produced adsorbent was assessed on the sequestration of Sb(III) and Sb(V) species from water. The adsorbent was effective for both species, in diluted and heavily-contaminated waters, providing maximum adsorption capacities (Langmuir model) of 24 ± 3 mg g−1 (pH 6) and 27 ± 7 mg g−1 (pH 2), respectively for Sb(III) and Sb(V). No significant effect was observed due to the presence of arsenic, chloride, nitrate, sulfate or phosphate and little influence was obtained when a tailings water from a mine site was used as aqueous matrix. Electrostatic attraction and Sb(III) and Sb(V) complexation with polyol groups of tannin-adsorbents were the suggested adsorption mechanisms. Moreover, tannin-adsorbents were stable at different pH (no color leaching; total dissolved carbon ≤16 mg L−1) and their production does not require high energy or expensive chemicals. Highlights • Tannins were extracted from maritime pine bark. • The production of tannin-based adsorbents was optimized. • The tannin-adsorbents successfully removed Sb(III,V) from water. [ABSTRACT FROM AUTHOR]

The removal of As, Sb, and Bi impurities from copper electrolyte is a primary objective of copper electrorefineries. The present experimental work demonstrates that the presence of Sb2O3 facilitates efficient and fast removal these impurities (with removal rates of 38.50, 98.50, and 99.00% for As, Sb, and Bi) through the formation of antimonate (AsSbO4/Sb2O4/BiSbO4), which plays a critical role in the self-purification of copper electrolyte. However, the antimonate which is a valuable metallurgical by-product contained high contents of As and Sb. The thermal decomposition of the antimonate was characterized by TG/DTA, a new method was proposed for recovering the target components, As, Sb, Bi, and to regenerate Sb2O3 with a two-stage roasting process under argon atmosphere. According to the results of XRD, SEM-EDS and ICP-MS, AsSbO4 decomposed during the first stage roasting at 800°C over 2 h, affording As with a recovery rate of 98.80%. During the second stage, decomposition of BiSbO4 and Sb2O4 at 1200°C over 2 h resulted in 99.01, 95.14% recovery rates for Sb, Bi. [ABSTRACT FROM AUTHOR]

Antimony (Sb) contamination of soils is of concern due to human activities such as recycling of Sb containing Pb acid batteries, shooting and mining. However Sb uptake by plants is poorly documented, especially when plants are growing on waterlogged soils and iron plaques form on their roots. The effect of iron plaques on Sb uptake has been investigated in rice, but not so far in other plants. Here, rye, ryegrass, wheat and meadow fescue were induced to form iron plaques and then exposed to antimonite (Sb(III)) or antimonate (Sb(V)) under hydroponic conditions. In the Sb(III) treatment, although iron plaques adsorbed Sb(III), this did not affect root and shoot Sb concentrations of plants. In the Sb(V) treatment, iron plaques adsorbed Sb(V) to a lesser extent than for Sb(III), although it was still significant in all plants but wheat. Iron treatments also significantly increased root Sb concentrations of fescue while they significantly decreased shoot Sb concentrations in rye, ryegrass and fescue. This may be due to other factors as well as antimony adsorption to iron plaques. [ABSTRACT FROM AUTHOR]

Used as a hardening agent in lead bullets, antimony (Sb) has become a major contaminant in shooting range soils of some countries including Switzerland. Soil contamination by Sb is also an environmental problem in countries with Sb-mining activities such as China and Bolivia. Because of its toxicity and relatively high mobility, there is concern over the risk of Sb transfer from contaminated soils into plants, and thus into the food chain. In particular there is very little information on the environmental behavior of methylated antimony, which can be produced by microbial biomethylation of inorganic Sb in contaminated soils. Using a new extraction and high-performance liquid chromatography inductively coupled plasma mass spectrometry (HPLC-ICP-MS) method, we investigated antimony speciation in roots and shoots of wheat, fescue, rye, and ryegrass plants exposed to trimethyl antimony(V) (TMSb), antimonite (Sb(III)), and antimonate (Sb(V)) in hydroponics. The total root Sb concentrations followed the order Sb(III) treatment > Sb(V) treatment > TMSb treatment, except for fescue. Shoot Sb concentrations, however, did not differ among the three treatments. In the Sb(V) treatment small quantities of TMSb were found in the roots, whereas no TMSb was detected in the roots of Sb(III)-treated plants. In contrast, similar concentrations of TMSb were found in the shoots in both inorganic Sb treatments. The results indicate that biomethylation of Sb may occur in plants. In the TMSb treatment TMSb was the major Sb species, but the two inorganic Sb species were also found both in shoots and roots along with some unknown Sb species, suggesting that also TMSb demethylation may occur within plant tissues. The results furthermore indicate that methylated Sb is more mobile in plants than inorganic Sb species. Knowledge about this is important in risk assessments of Sb-contaminated sites, as methylation may render Sb more toxic than inorganic Sb, as it is known for arsenic (As). [ABSTRACT FROM AUTHOR]

The influence of weak magnetic field (WMF) and tartrate on the oxidation and sequestration of Sb(III) by zerovalent iron (ZVI) was investigated with batch and semi-continuous reactors. The species analysis of antinomy in aqueous solution and solid precipitates implied that both Sb(III) adsorption preceding its conversion to Sb(V) in solid phase and Sb(III) oxidation to Sb(V) preceding its adsorption in aqueous phase occurred in the process of Sb(III) sequestration by ZVI. The application of WMF greatly increased the rate constants of Sb tot (total Sb) and Sb(III) disappearance during Sb(III)-tartrate and uncomplexed-Sb(III) sequestration by ZVI. The enhancing effect of WMF was primarily due to the accelerated ZVI corrosion in the presence of WMF, as evidenced by the influence of WMF on the change of solution and solid properties with reaction. However, tartrate greatly retarded Sb removal by ZVI. It was because tartrate inhibited ZVI corrosion, competed with Sb(III) and Sb(V) for the active surface sites, increased the negative surface charge of the generated iron (hydr)oxides due to its adsorption, and formed soluble complexes with Fe(III). The positive effect of WMF on Sb(III)-tartrate and uncomplexed-Sb(III) removal by ZVI was also verified with a magnetic semi-continuous reactor. [ABSTRACT FROM AUTHOR]

This study gives a contribution to assess the efficacy of some LDHs (layered double hydroxides) in Sb(V) uptake and understand the mechanisms involved in the removal process. Uncalcined nitrate Mg/Al LDHs and the mixed Mg-Al oxides derived from calcined carbonate Mg/Al LDHs mainly remove Sb(OH) from aqueous solution through the formation of a brandholzite-like phase (a non-LDH compound with general formula Mg[Sb(OH)]·6HO), although with a different efficiency (< 50 and 90-100% of Sb(V) removed, respectively). The formation of a brandholzite-like compound highlights the fundamental role of Mg in the removal process. The Sb(OH) removal capacity of uncalcined nitrate Mg/Al LDHs increases from 22 to 46% as the Mg/Al molar ratio decreases from 4 to 2 thanks to the increasing excess of positive charge of brucite-like sheets and the expanding interlayer thickness due to the different spatial orientations of nitrate groups (flat for Mg/Al = 4, perpendicular for Mg/Al = 2). The presence of Fe in the trivalent cationic site of carbonate LDHs (Mg/(Al + Fe) = 3/(0.5 + 0.5)) improves the Sb(OH) removal capacity of their calcined products. When Mg is replaced by Zn in the divalent cationic site of carbonate LDHs and the sorption experiments are performed using the mixed Zn-Al oxides derived from calcination, Sb(OH) is mainly removed from the solution through the reconstruction of an antimonate LDH structure (i.e., a zincalstibite-like compound with general formula ZnAl(OH)[Sb(OH)]). The removal efficiency of calcined carbonate Zn/Al LDHs is high and comparable to that of calcined carbonate Mg/Al LDHs; however, the mechanisms involved in the removal process are substantially different: entrance of Sb(OH) in the interlayer in the first case, adsorption of Sb(OH) onto the surface and formation of a new phase (a brandholzite-like compound) in the second case. In both cases, the removal processes are described with the pseudo-second-order kinetic model; the theoretical maximum adsorption capacity determined with the Langmuir isotherm results to be 4.54 and 4.37 mmol g for calcined carbonate Mg/AlFe and Zn/Al LDHs, respectively. [ABSTRACT FROM AUTHOR]

The environmental behavior of antimony (Sb) in soils is often considered to be similar to th a t of arsenic (As). Comparing the adsorption behavior of these two elements on soil minerals is important because both elements coexist in contamination areas. In this study, the differences in antimonate (Sb(V)) and arsenate (As(V)) adsorption reaction kinetics and isotherm characteristics on a poorly crystalline phyllomanganate (δ-Mn02) were studied. The potential mechanisms were identified using zeta potential, Fourier transform infrared spectrometry (FTIR), and X-ray photoelectron spectroscopy (XPS) analyses. The adsorption isotherm results indicated th a t the maximum adsorption capacity for As(V) was 1.5 times higher than th a t for Sb(V). The adsorption kinetics of Sb(V) and As(V) were well fitted using pseudo-first-order model, and the adsorption rate of Sb(V) and As(V) significantly depended on δ-Mn02 dosage and pH. At all tested pH values (3.0-9.0), the adsorption rate of As(V) was 4.0-7.7 times faster than th a t of Sb(V) at the same δ-Mn02 dosage and pH conditions. FTIR and XPS analysis confirmed that M (metal)-O was bonded w ith Sb(V) and As(V). The adsorption capacity and rate of As(V) were significantly higher than those of Sb(V), suggesting that δ-Mn02 had higher affinity toward As(V). The different adsorption behaviors of Sb(V) and As(V) onto δ-Mn02 should be considered in soils. [ABSTRACT FROM AUTHOR]

Antimony (Sb) is a contaminant of increased prevalence in the environment, but there is little knowledge about the mechanisms of its uptake and translocation within plants. Here, we applied for the synchrotron based X-ray absorption near-edge structure (XANES) spectroscopy to analyze the speciation of Sb in roots and shoots of rye grass ( Lolium perenne L. Calibra). Seedlings were grown in nutrient solutions to which either antimonite (Sb(III)), antimonate (Sb(V)) or trimethyl-Sb(V) (TMSb) were added. While exposure to Sb(III) led to around 100 times higher Sb accumulation in the roots than the other two treatments, there was no difference in total Sb in the shoots. Antimony taken up in the Sb(III) treatment was mainly found as Sb-thiol complexes (roots: >76% and shoots: 60%), suggesting detoxification reactions with compounds such as glutathione and phytochelatins. No reduction of accumulated Sb(V) was found in the roots, but half of the translocated Sb was reduced to Sb(III) in the Sb(V) treatment. Antimony accumulated in the TMSb treatment remained in the methylated form in the roots. By synchrotron based XANES spectroscopy, we were able to distinguish the major Sb compounds in plant tissue under different Sb treatments. The results help to understand the translocation and transformation of different Sb species in plants after uptake and provide information for risk assessment of plant growth in Sb contaminated soils. [ABSTRACT FROM AUTHOR]

Kyawthuite, Bi3+Sb5+O4, is a new gem mineral found as a waterworn crystal in alluvium at Chaung-gyiah- le-ywa in the Chaung-gyi valley, near Mogok, Burma (Myanmar). Its description is based upon a single sample, which was faceted into a 1.61-carat gem. The composition suggests that the mineral formed in a pegmatite. Kyawthuite is monoclinic, space group I2/c, with unit cell dimensions a = 5.4624(4), b = 4.88519(17), c = 11.8520(8) Å, β = 101.195(7)°, V = 310.25(3) Å3 and Z = 4. The colour is reddish orange and the streak is white. It is transparent with adamantine lustre. The Mohs hardness is 5½. Kyawthuite is brittle with a conchoidal fracture and three cleavages: {001} perfect, {110} and {1̄10} good. The measured density is 8.256(5) g cm-3 and the calculated density is 8.127 g cm-3. The mineral is optically biaxial with 2V = 90(2)°. The predicted indices of refraction are α = 2.194, β = 2.268, γ = 2.350. Pleochroism is imperceptible and the optical orientation is X = b; Y ≈ c; Z ≈ a. Electron microprobe analyses, provided the empirical formula (Bi3+0.82Sb3+0.18)Σ1.00(Sb5+0.99Ta5+0.01)Σ1.00O4. The Raman spectrum is similar to that of synthetic Bi3+Sb5+O4. The infrared spectrum shows a trace amount of OH/H2O. The eight strongest powder X-ray diffraction lines are [dobs in Å(I)(hkl)]: 3.266(100)(1̄12), 2.900(66)(112), 2.678(24) (200), 2.437(22)(020,1̄14), 1.8663(21)(024), 1.8026(43)(1̄16,220,204), 1.6264(23)(2̄24,116) and 1.5288(28)(312,1̄32). In the crystal structure of kyawthuite (R1 = 0.0269 for 593 reflections with Fo > 4σF), Sb5+O6 octahedra share corners to form chequerboard-like sheets parallel to {001}. Atoms of Bi3+, located above and below the open squares in the sheets, form bonds to the O atoms in the sheets, thereby linking adjacent sheets into a framework. The Bi3+ atom is in lopsided 8 coordination, typical of a cation with stereoactive lone electron pairs. Kyawthuite is isostructural with synthetic β-Sb2O4 and clinocervantite (natural β-Sb2O4). [ABSTRACT FROM AUTHOR]