Fraction Of Sb Research Articles

Remediation of As, Sb, and Pb co-contaminated mining soils by using Fe/C based solid wastes: Synergistic effects and field applications

Existing passivators for mining soil remediation suffer from high-costs and detriment to soil health. Here we reported the iron-carbon (Fe/C) based passivators (high-Fe/C, mid-Fe/C, and low-Fe/C) prepared by composing of high-Fe steel slag, high-C coal fly ash and FeSO4 for the remediation of As, Sb, and Pb co-contaminated mining soil. High-Fe/C, and mid-Fe/C addition (5 % dosage) for 30 days decreased soil available As, Sb, and Pb content by 85.5–87.3 %, 58.3–71.2 %, and 55.3–65.7 %, respectively, with only slight degradation of stabilization efficiency with 210 days. Moreover, the labile fractions of As, Sb and Pb were transformed to residual state. After high-Fe/C and mid-Fe/C amendment, the relative abundance of microbial community (bacteria and fungi) and soil fertility were enhanced. Facilitated by the Fe/C micro-electrolysis effect, As, Sb and Pb species were well passivated via adsorption with C-containing functional groups, and precipitation (Fe-As/Sb and Ca-Sb) mechanisms. Noteworthy, the increased soil organic matter (OM), cation exchange capacity (CEC) and microbial activity also enhanced the stabilization of As, Sb, and Pb. Field application results demonstrated that the stabilization efficiency of available As and TCLP-As/Sb/Pb was over 80 % after mid-Fe/C amendment. Fe/C based solid wastes hold the potential for being cost-effective in the remediation of mining soil while achieving large-scale utilization of solid wastes.

Characterising the effect of commercial wheat grain milling methods on wheat bran characteristics

SummaryTo assess the effect of wheat milling or bran separation method, five wheat bran fractions, one from stone milling (SB), two from roller flour milling (coarse: RB1, fine: RB2), and two from grain pearling (0–3%: PB1, 3–6%: PB2) were analysed. Physiological properties provided good physical and flow characteristics of SB fraction; however, it was the darkest. Particle size was in the order of RB1 > SB > RB2 > PB1 > PB2. The fibre analysis showed the highest insoluble fibre components for RB1, PB1, and exceptionally higher soluble fibre for PB1. The protein, fat, ash, and starch content were highest for RB2 and PB2. Antioxidant properties followed the order PB2 > RB2 > PB1 > RB1 > SB. Pearled fractions (PB1 and PB2) showed better functional properties than others. SEM, XRD, and FT‐IR verified the changes in the properties of bran fractions. The characterisation data will find applications to help increase the usage of bran fractions in specific food products.

Weathering-induced Sb isotope fractionation during leaching of stibnite and formation of secondary Sb minerals

In this work, we investigated the extent of antimony (Sb) isotopic fractionation during weathering of stibnite at supergene conditions. Antimony isotope data have been obtained from secondary Sb minerals collected from Pezinok, Dobšiná (both Slovakia) and Allchar (North Macedonia) deposits and mine tailings. The Sb isotope compositions of sulfides and secondary Sb minerals formed on the primary stibnite [Sb2S3] or in mine tailings grains were compared with each other. Furthermore, we experimentally investigated Sb isotope fractionation during stibnite leaching with different acids. Our study reveals a large isotopic range for δ123Sb (from −0.50 to +0.69 ‰) for secondary Sb minerals. They are either isotopically indistinguishable or isotopically lighter than the primary stibnite. Isotopically indistinguishable weathering products likely formed by quantitative Sb transfer from stibnite to the secondary minerals, such as brandholzite [Mg(H2O)6[Sb(OH)6]2] from Pezinok. Isotopic fractionation towards lighter δ123Sb was observed for adsorption of Sb onto iron oxides. Distinctly isotopically lighter δ123Sb was observed in secondary Sb minerals tripuhyite [FeSbO4], chapmanite [Fe3+2Sb3+(Si2O5)O3(OH)], hydroxyferroromeite [Fe2Sb2O6(OH)], and stibiconite [Sb3O6OH] that either replace stibnite or formed in mine tailings from the pore solutions. These secondary minerals were likely generated by partial precipitation of Sb from aqueous solutions produced by dissolution of stibnite. In the leaching experiments with HCl and oxalic acid, Sb was leached without significant isotope effects during the first 2–3 days, followed by a drop of the dissolved Sb concentration associated with Sb isotope fractionation towards high δ123Sb in the leachate (by up to 0.5 ‰) after 4–7 days. We interpret these observations to be related to the precipitation of secondary Sb oxides with low δ123Sb, resulting in an isotopically heavy dissolved Sb pool. These findings are in agreement with previous results of isotopically heavy groundwater and mine drainage water with δ123Sb > +0.36 ‰ that may suggest that the ‘truly’ dissolved (operationally defined as <0.45 μm) Sb fraction in general may be isotopically heavy.

Nonequivalent Antiferromagnetically Coupled Sublattices Induce Two-Step Spin-Crossover Transitions: Equilibrium and Nonequilibrium Aspects

As a continuation to the previously published work (Yalçın et al. (2022)), we investigate the equilibrium and nonequilibrium properties of the spin-crossover systems, with a specific focus on the nonequivalent sublattice, and compare these properties with those of the equivalent sublattices. We used the lowest approximation of the cluster variation method (LACVM) to derive the static equations for the order parameters of the two sublattices and determine high-spin fraction in relation to temperature and external magnetic field in a spin-crossover system. At a low temperature, the transition from stable high-spin (HS) state where nHS=1 occurs in the plateau region, where nHS=0.5 for nonequivalent sublattices. The order parameters for non-equivalent sublattices exhibit different states at the transition temperature. Also, we study the nonequilibrium properties of the order parameters and high-spin fraction using the path probability method (PPM). With the current model, we obtain and analyze the relaxation curves for the order parameters Sa, Sb, and high-spin fraction. These curves demonstrate the existence of bistability at low temperatures. At the end of this study, we present the flow diagram that shows the order parameters for different temperature values. The diagram exhibits states that are stable, metastable, and unstable.

Sb/As immobilization and soil function improvement under the combined remediation strategy of modified biochar and Sb-oxidizing bacteria at a smelting site

Antimony (Sb) and arsenic (As) lead to soil pollution and structural degradation at Sb smelting sites. However, most sites focus solely on Sb/As immobilization, neglecting the restoration of soil functionality. Here, we investigated the effectiveness of Fe/H2O2 modified biochar (Fe@H2O2-BC) and Sb-oxidizing bacteria (Bacillus sp. S3) in immobilizing Sb/As and enhancing soil functional resilience at an Sb smelting site. Over a twelve-month period, the leaching toxicity of As and Sb was reduced to 0.05 and 0.005 mg L−1 (GB3838–2002) respectively, with 1% (w/w) Fe@H2O2-BC and 2% (v/v) Bacillus sp. S3 solution. Compared to CK, the combination of Fe@H2O2-BC and Bacillus sp. S3 significantly reduced the bioavailable As/Sb by 98.00%/93.52%, whilst increasing residual As and reducible Sb fractions by 210.31% and 96.51%, respectively. The combined application generally improved soil aggregate structure, pore characteristics, and water-holding capacity. Fe@H2O2-BC served as a pH buffer and long-term reservoir of organic carbon, changing the availability of carbon substrates to bacteria. The inoculation of Bacillus sp. S3 facilitated the transformation of Sb(III)/As(III) to Sb(V)/As(V) and differentiated the composition and functional roles of bacterial communities in soils. The combination increased the abundance of soil saprotrophs by 164.20%, whilst improving the relative abundance of N- and S-cycling bacteria according to FUNGuild and FAPROTAX analysis. These results revealed that the integrated application was instrumental in As/Sb detoxification/immobilization and soil function restoration, which demonstrating a promising microbially-driven ecological restoration strategy at Sb smelting sites.

Investigation of the migration of natural organic matter-iron-antimony nano-colloids in acid mine drainage

Colloids can potentially affect the efficacy of traditional acid mine drainage (AMD) treatment methods such as precipitation and filtration. However, it is unclear how colloids affect antimony (Sb) migration in AMD, especially when natural organic matter (NOM) is present. To conduct an in-depth investigation on the formation and migration behavior of NOM, iron (Fe), Sb and NOM-Fe-Sb colloids in AMD, experiments were performed under simulated AMD conditions. The results demonstrate significant variations in the formation of NOM-Fe-Sb colloids (1–3–450 nm) as the molar ratio of carbon to iron (C/Fe) increases within acidic conditions (pH = 3). Increasing the C/Fe molar ratio from 0.1 to 1.2 resulted in a decrease in colloid formation but an increase in particulate fraction. The distribution of colloidal Sb, Sb(III), and Fe(III) within the NOM-Fe-Sb colloids decreased from 68 % to 55 %, 72 % to 57 %, and 68 % to 55 %, respectively. Their distribution in the particulate fraction increased from 28 % to 42 %, 21 % to 34 %, and 8 % to 27 %. XRD, FTIR, and SEM-EDS analyses demonstrated that NOM facilitates the formation and crystallization of Fe3O4 and FeSbO4 crystalline phases. The formation of the colloids depended on pH. Our results indicate that NOM-Fe-Sb colloids can form when the pH ≤ 4, and the proportion of colloidal Sb fraction within the NOM-Fe-Sb colloids increased from 9 % to a maximum of 73 %. Column experiments show that the concentration of NOM-Fe-Sb colloids reaches its peak and remains stable at approximately 3.5 pore volumes (PVs), facilitating the migration of Sb in the porous media. At pH ≥ 5, stable NOM-Fe-Sb colloids do not form, and the proportion of colloidal Sb fraction decreases from 7 % to 0 %. This implies that as pH increases, the electrostatic repulsion between colloidal particles weakens, resulting in a reduction in the colloidal fraction and an increase in the particulate fraction. At higher pH values (pH ≥ 5), the repulsive forces between colloidal particles nearly disappear, promoting particle aggregation. The findings of this study provide important scientific evidence for understanding the migration behavior of NOM-Fe-Sb colloids in AMD. As the pH gradually shifts from acidic to near-neutral pH during the remediation process of AMD, these results could be applied to develop new strategies for this purpose.

Biogeochemical cycling in paddy soils controls antimony transformation: Roles of iron (oxyhydr)oxides, organic matter and sulfate

In paddy fields, periodic flooding and drainage phases can significantly affect the availability of antimony (Sb), but the underlying mechanisms remain unclear. In this study, Sb-contaminated paddy soil was incubated under anaerobic (40 day) and subsequently aerobic (40–55 day) conditions. The Sb fractions was investigated and a kinetic model was established to quantitatively evaluate the main processes controlling Sb transformation. Under anaerobic conditions, the reductive dissolution of iron (Fe) (oxyhydr)oxides, the release of soil colloids, and dissolved organic carbon (DOC) could facilitate the release of Sb(V), while newly released Sb(V) were synchronously reduced to Sb(III) that could be incorporated into the solid phase (34.1%, 40 day) or precipitated as Sb2S3 (9.7%, 40 day). After soil aeration, a significant increase in dissolved and extracted Sb(V) (34.7%, 45 day) was observed due to the Sb(III) oxidization by the reactive oxygen species (ROS) generated from Fe(II) oxidization. The dissolved and extracted Sb(V) were simultaneously incorporated into the solid phase as the re-aggregation of soil colloids and DOC, and only contributed to 17.1% of the total Sb content at the end of aerobic phase (55 day). Our results elucidated the mechanisms about how biogeochemical Fe/S/C cycling jointly controlled Sb transformation in paddy systems.

Simultaneous stabilization of arsenic and antimony co-contaminated mining soil by Fe(Ⅱ) activated-Fenton sludge: Behavior and mechanisms

Fenton sludge (FS) with high iron contents that discharged from the Fenton process was rarely studied for soil remediation. Herein, a novel Fe(Ⅱ) activated-Fenton sludge (FS–FeSO4) was proposed to stabilize arsenic (As) and antimony (Sb) co-contaminated soil meanwhile disposing FS. Multiple characteristic analyses revealed that the porous structures and rich functional groups of FS-FeSO4 involved in As and Sb adsorption. Meanwhile, Fe (hydro)oxides played a key role in As and Sb stabilization. Under the optimal application parameters (stabilizers dosage: 5%, incubation time: 60 days), the available As and Sb content decreased by 88.6% and 83.3%, respectively, and the leachability of As and Sb was reduced by 100% and 72.6% for FS-FeSO4 stabilized soil. Moreover, the mobile As and Sb fractions (F1 and F2) were transformed into the most stable fraction (F5). The adsorption of As and Sb on FS-FeSO4 was well fitted by pseudo-second-order kinetic and Langmuir models, while FS-FeSO4 exhibited a better affinity for As than Sb under competition conditions. Poorly crystalline α-FeOOH and amorphous Fe (hydro)oxides provided sufficient active sites for As and Sb, and the generation of Fe–As/Sb and Ca–Sb chemical bonds promoted the stability of As and Sb. This study demonstrated that FS-FeSO4 was a potentially effective stabilizer for As and Sb co-contaminated soil remediation.

Improved Method of Background Value Determination for Sb and Cd in Freshwater Sediment—Insights from Controlling Factors on Spatial Variability

Variability in the distribution of natural total Sb and Cd in freshwater sediments leads to difficulties in background value (BV) determination. This study aimed to establish a method to determine BV more accurately by investigating the vertical distribution of Sb and Cd in sediment cores collected from a typical river in alluvial plain in China and revealed the factors that control the variation of Sb and Cd BV, which has not been studied in alluvial freshwater sediment. The results suggested that uncontaminated samples for BV calculation should be determined by statistical analysis as human and natural disturbance led to high variation in contamination depth, from <5 cm to >55 cm. The sequential chemical extraction method showed a considerable amount of non-residual fractions of Sb and Cd, which accounted for 48% and 43% of the total, respectively. Acid extractable Cd (16%) was associated to the limestone geology in the area. Fine particles which governed by sedimentary environment contained more natural Sb and Cd, as strong positive correlation was found between clay content and Sb concentration (r = 0.89, p < 0.01), as well as Cd concentration (r = 0.54, p < 0.01). Based on these findings, a method combined with standard deviation and geochemical method was established to calculate the BV of Sb and Cd, and counter maps were made to cover the variation of BV in the Taipu river sediment. The pollution level has been evaluated by the geoaccumulation index more accurately.

Novel InGaSb/AlP Quantum Dots for Non-Volatile Memories.

Non-volatile memories based on the flash architecture with self-assembled III-V quantum dots (SAQDs) used as a floating gate are one of the prospective directions for universal memories. The central goal of this field is the search for a novel SAQD with hole localization energy (Eloc) sufficient for a long charge storage (10 years). In the present work, the hole states' energy spectrum in novel InGaSb/AlP SAQDs was analyzed theoretically with a focus on its possible application in non-volatile memories. Material intermixing and formation of strained SAQDs from a GaxAl1-xSbyP1-y, InxAl1-xSbyP1-y or an InxGa1-xSbyP1-y alloy were taken into account. Critical sizes of SAQDs, with respect to the introduction of misfit dislocation as a function of alloy composition, were estimated using the force-balancing model. A variation in SAQDs' composition together with dot sizes allowed us to find that the optimal configuration for the non-volatile memory application is GaSbP/AlP SAQDs with the 0.55-0.65 Sb fraction and a height of 4-4.5 nm, providing the Eloc value of 1.35-1.50 eV. Additionally, the hole energy spectra in unstrained InSb/AlP and GaSb/AlP SAQDs were calculated. Eloc values up to 1.65-1.70 eV were predicted, and that makes unstrained InGaSb/AlP SAQDs a prospective object for the non-volatile memory application.

Immobilization and phytoavailability of antimony (Sb) in contaminated agricultural soils amended with composted manure

A pot experiment was conducted to assess the Sb phytoavailability and its accumulation in the wheat before and after remediation, using the composted manure of poultry and sheep, and a chemical amendment (limestone). The present study evaluates the effects of amendments on Sb bioavailability in different soils and investigates the relationship between bioaccumulated Sb and its availability in spiked soils using two different single extraction methods. Furthermore, a sequential extraction procedure was used to measure different fractions of Sb in soil, in order to assess the effect of remediation. The results revealed that bioavailability of Sb were highly affected by the three soil amendments on plant height, uptake of Sb by wheat. Poultry compost (Pc) and Sheep compost (Sc) increased the residual fraction of Sb in soils, and decreased the Sb uptake by wheat, enhanced the height, biomass and dry yield of the wheat crop. While the residual fraction of Sb in soils didn't obviously increased by adding Chemical (limestone) in the four soils. It is concluded that uptake of Sb in the soils significantly decreased with the addition of amended materials in the Sb spiked soils, and poultry compost is the most effective. In the lower level of Sb contaminated soils remediated by poultry compost (Pc), the uptake of Sb in wheat decreased 63.1–74.4 %, 68.7–79.0 %, 68.9–76.9 % and 66.3–82.6 % in S1, S2, S3, S4, compared to the contaminated soils without amendments, respectively.

Remediation of antimony-contaminated soil with composite materials of Fe/Fe2+-fly ash-concrete additive in seasonal freezing regions

Antimony (Sb) finds its wide application in industries, however, the research on Sb solidification/stabilization (S/S) in the Sb-contaminated soil is currently insufficient, particularly in seasonal freezing regions. Here six composite materials of Fe/Fe2+-fly ash-concrete additive (Fe-FA-CA) were employed and optimized to remediate the Sb-contaminated soil subject to 40 freezing-thawing (F-T) cycles. After remediation, FeSO4-fly ash-calcium lignosulfonate (FFC) exhibited the best resistance performance to F-T. The stabilization efficiency was evaluated with TCLP at 92.92%. Meanwhile, Sb concentration met the criteria of landfill for inert waste assessed with the compliance test for leaching (CT) of European Standard. The S/S efficiency of Sb dropped slightly from 92.68% to 88.22% (TCLP) and from 97.18% to 93.37% (CT), respectively, after aging 40 F-T cycles. The fraction of residual Sb in the soil treated by FFC was increased by 10.41%, and the strength of the S/S soil was much higher than 350 kPa, the requirement of landfills in the U.S. during F-T cycles. Additionally, the poorly crystalline Fe in the soil remediated by FFC was increased by 4.54 g/kg, suppressing Sb migration. The feasibility and effectiveness of FFC in S/S of Sb demonstrated its potential to remediate Sb-contaminated soil in seasonal freezing regions.

Impact of Biochars on the Iron Plaque Formation and the Antimony Accumulation in Rice Seedings.

Biochar was a kind of restoration material for soil pollution. Investigation about biochar amendment on the Sb transformation in rice plants is scarce. The pot experiment was conducted to evaluate the impact of biochar on the iron plaque formation in Sb-contaminated soil, and the translocation and accumulation of Sb in rice seedings. After thestraw and husk biochar amendments (5% by weight), the levels increased on average by 20.0% and 16.0% for exchangeable Sb in soil, and by 233.3% and 74.8% for soluble Sb in pore water, respectively; but the residual fractions of Sb decreased by 18.5% and 15.1%. The iron plaque formation on rice root surface was enhanced, but its sequestration capacity for Sb decreased due to increasing competition for binding sites led by the elevated phosphorus and silicon levels in pore water after biochar application. The shoot Sb content sharply increased by 215.8% upon straw biochar application.

Evaluation of the effectiveness of ex-situ stabilization for arsenic and antimony contaminated soil: Short-term and long-term leaching characteristics

Ex-situ stabilization for As and Sb co-contaminated soil was conducted through an iron-based stabilizer, PFSC (a mixture of polymerized ferric sulfate (PFS) and hydrated lime (Ca(OH2)) with a dry mass ratio of 2:1). After field aging for one week, the stabilized contaminated soil was subjected to a horizontal vibration leaching test (HJ 557), Wenzel's sequential extraction, and a semi-dynamic leaching test (ANS 16.1). By assessing the cumulative fractions of As and Sb, the observed diffusion coefficients (Dobs) and leachability indices (LX) of metalloids released from the soil specimens were calculated. The PFSC ex-situ stabilization was effective to immobilize metalloids, and the As and Sb leached concentrations of stabilized contaminated soil samples were lower than remediation targets. Nonspecifically bound As and Sb in the stabilized contaminated soil samples decreased from 4.5 – 9.2 % to 1.5–2.5 % and from 2.2 – 5.8 % to 1.1–1.5 %, respectively. The mechanisms controlling the leaching behaviors of As and Sb included wash-off and diffusion and they were changed with the leaching interval. The mean Dobs of As and Sb released from stabilized contaminated soil specimen were 3.46 × 10−12 and 2.99 × 10−13 cm2 s−1, in the which were two orders of magnitude lower than that of untreated contaminated soil specimen. The mean LX of stabilized contaminated soil specimen for As and Sb releases were 11.40 and 12.83, respectively, indicating that the stabilized contaminated soil was acceptable for “controlled utilization”.

Airborne and Dermal Collection Methods of Gunshot Residue for Toxicity Studies

Gunshot residue (GSR) has potential negative health effects on humans as a result of inhalation and dermal exposure to the chemical and physical characteristics of GSR such as Pb, Sb, Ba, nitrocellulose, nitroglycerine, and particulate size fraction. Filter (size selective) and double-sided tape (non-size selective) samples collected airborne GSR during single and triple firing of a 0.22 caliber revolver. Dermal exposures were considered using hand swabs and de-leading wipes, designed to remove the heavy metals. The samples underwent analysis to investigate physical (morphology, size distribution, zeta potential), chemical (black carbon and element concentrations), and potential to induce oxidative stress (oxidative potential via the dithiothreitol (DTT) assay). All sample types detected Pb concentrations higher than national ambient air standards. The de-leading wipes reduced the metal content on the hands of the shooter for Pb (15.57 ± 12.99 ppb and 3.13 ± 4.95 ppb). Filter samples provided health relevant data for airborne PM2.5 for all of the analysis methods except for GSR morphology. This work identified collection and analysis methods for GSR in an outdoor setting, providing protocols and considerations for future toxicological studies related to inhalation and dermal exposures to particulate GSR. Future studies should investigate the influence of meteorological factors on GSR exposure in an outdoor setting.

Stabilization of arsenic and antimony Co-contaminated soil with an iron-based stabilizer: Assessment of strength, leaching and hydraulic properties and immobilization mechanisms

Soils with relatively high concentrations of arsenic (As) and antimony (Sb) in mining areas would impose significant risks to human health and ecosystem. A new stabilizer PFSC composed of polymerized ferric sulfate (PFS) and calcium hydroxide (Ca(OH)2) is proposed to stabilize the soil with co-existed As and Sb sampled at an abandoned arsenic factory site. The effects of stabilizer dosage on the properties of the stabilized soil including leached concentrations of As and Sb, unconfined compressive strength (UCS), and hydraulic conductivity (kw) were investigated. The mechanisms of As and Sb immobilization in the soils were interpreted by Tessier's sequential extraction procedure (SEP), scanning electron microscope (SEM), and X-ray diffraction (XRD) results. The results showed increasing PFSC dosage was effective for reducing leached concentrations of As and Sb. When the PFSC dosage increased from 2% to 10%, the UCS and kw increased from 84 to 206 kPa and decreased from 6.48 × 10−8 to 6.33 × 10−9 m s−1, respectively. Tessier's SEP results showed that the leachable As and Sb fractions decreased from 12% to 5.6% and 7.5% to 3.8%, while the Fe–Mn oxides bound fractions increased from 22.3% to 29.4% and 13.2% to 19.5%. The SEM images and XRD patterns of untreated and PFSC stabilized contaminated soils indicated that hematite and calcite (CaCO3) were the main products of PFSC stabilization processes. Adsorption on ferrihydrite, entrapment in hematite lattices, and co-precipitate with calcite might were the main mechanisms of As and Sb immobilization.

Simultaneous stabilization of Sb and As co-contaminated soil by Fe[sbnd]Mg modified biochar

Currently, metalloid co-contamination, such as antimony and arsenic in soil, poses a serious threat to ecological stability and human health. Stabilization, a low-cost, effective, environmentally mild remediation strategy, shows enormous potential for mitigating environmental concerns. In this study, a novel FeMg modified porous biochar with different Fe/Mg proportions was prepared using the co-precipitation method to investigate the stabilizing efficiency in aqueous solutions and real soils. The optimal removal performance for Sb(V) and As(V) was the 1/3 mol ratio of Fe/Mg (3FMKBC), in which the maximum adsorption capacities of Sb(V) and As(V) were 296.9 and 195.4 mg/g, respectively. Detailed morphological and BET analyses suggested that BC effectively reduced Fe and Mg oxide agglomeration and endowed more interfacial active sites. Meanwhile, detailed adsorption behavior and surface analysis of 3FMKBC indicated that electrostatic interactions, hydrogen bonds, surface hydroxyl complexation, and ligand exchange induced by ≡C-O-Fe/Mg-OH dominated the stabilization process. Moreover, according to a 40-day incubation study in soil, 3FMKBC (1 wt. ml) decreased the available Sb (28.5% and 23.0%) and As (83.1% and 31.1%) extracted by toxicity characteristic leaching procedure (TCLP) and 0.1 M Na2HPO4, respectively. The above results indicated that 3FMKBC was an optimal amendment for limiting the migration and bioavailability of Sb and As. In addition, the sequential extraction and soil properties confirmed that 3FMKBC could realize the redistribution of resolved Sb and As between the soil solution and solid particles effectively, thereby converting the bioavailable/labile fraction of Sb and As to a more stabilized fraction. All results demonstrated that 3FMKBC could be a prospective material for Sb and As co-contamination stabilization.

The impact of alternate wetting and drying and continuous flooding on antimony speciation and uptake in a soil-rice system

The accumulation of trace elements in rice, such as antimony (Sb), has drawn special attention owing to the potential increased risk to human health. However, the effects of two common irrigation methods, alternate wetting and drying and continuous flooding, on Sb behaviors and subsequent accumulation in rice is unclear. In this study a pot experiment with various Sb additions (0, 50, 200, 1000 mg Sb kg−1) was carried out with these two irrigation methods in two contrasting paddy soils (an Anthrosol and a Ferralic Cambisol). The dynamics of Sb in soil porewater indicated that continuous flooding generally immobilized more Sb than alternate wetting and drying, concomitant with a pronounced reduction of Sb(V) in porewater. However, a higher phytoavailable fraction of Sb was observed under continuous flooding. The content of Sb in the rice plant decreased in the order of root > shoot > husk > grain, and continuous flooding facilitated Sb accumulation in rice root and shoot as compared with alternate wetting and drying. The differences of Sb content in root, shoot, and husk between the two irrigation methods was smaller in aboveground parts, and almost no difference in Sb was observed in grain between the two methods. The findings of this study facilitates the understanding of Sb speciation and behavior in soils with these common yet different water management regimes.

Valency distributions and geochemical fractions of arsenic and antimony in non-ferrous smelting soils with varying particle sizes

Arsenic and antimony are common toxic metalloids found in associated minerals. These metalloids generally cause high-concentration pollution in non-ferrous metal smelting soils; however, few studies have investigated the pollution characteristics of these two metalloids at non-ferrous smelting sites using varying soil particle sizes. In this study, the valency distributions and geochemical fractions were investigated with varying soil particle sizes (≤ 0.05, 0.05–0.25, 0.25–1, and 1–2 mm). Soils were mainly concentrated in ≤ 0.05 and 0.05–0.25 mm with mass percentages of 32.97% and 29.02%, respectively. The highest total As and Sb concentrations in ≤ 0.05 mm were found to be 20,350 and 3655 mg/kg, respectively. In addition, As(Ⅲ), As(Ⅴ), Sb(Ⅲ), and Sb(Ⅴ) concentrations in this soil particle size were found to be 224, 19,813, 1036, and 24 mg/kg, respectively. The geochemical fractions of As and Sb in varying soil particle sizes were mainly residual, accounting for 50% and 90% in the ≤ 0.05 mm. Soil may bind ≤ 0.25 mm due to the disparity found in the geochemical compositions and valency distributions of arsenic and antimony. X-ray diffraction and scanning electron microscopy/energy dispersive system analysis confirmed that arsenolite accumulated in particle sizes of ≤ 0.05 and 0.05–0.25 mm. The results of this study may provide a scientific reference for risk assessment and restoration strategies for non-ferrous metal smelting soils.

The leaching of antimony and arsenic by simulated acid rain in three soil types from the world's largest antimony mine area.

A simulated acid rain (SAR) experiment on leaching of antimony (Sb) and arsenic (As) in three soil types including paddy soils (PS), vegetable soils (VS) and slag based soils (SS) from Xikuangshan (XKS) Sb mine area was conducted. The SAR at pH 2.5, 3.5, 4.5 and 5.6 were sprayed to soil columns with intermittent pattern in a period of 50days. Through the spraying duration, leaching Sb in PS, VS and SS showed decreasing trends regardless of pH values in SAR and were in the ranges of 0.026-0.064mg L-1, 0.19-2.18mg L-1 and 11.8-32.4mg L-1, respectively. By contrast, leaching As in these three soil types continuously increased at the initial five spraying times and then deeply decreased afterward, with ranges being 0-0.007mg L-1, 0.001-0.071mg L-1 and 0.17-1.07mg L-1, respectively. The leaching Sb in all the three soil types were extremely higher than the reference value in grade IV (0.01mg L-1) for groundwater quality of China (GB/T 14,848-2017). For leaching As, peck values in VS and all the values in SS were also greater than the corresponding reference value (0.05mg L-1). This indicated that leaching Sb and As could pollute the groundwater in XKS Sb mine area, especially those in slag based soils. The total leaching losses of Sb and As were affected by pH ambiguously, such as SAR at pH 2.5, 5.6 and 2.5 induced the greatest losses of Sb in PS, VS and SS, and pH 3.5, 5.6 and 2.5 resulted in the greatest leaching losses of As in these soils. After SAR treatment, the specific sorbed and Fe/Mn oxide-associated Sb and As significantly decreased. It demonstrated that these two fractions of both Sb and As were involved in leaching losses. The present study also found that the SAR treatment resulted in soil acidification in all the three soil types. In addition, available N, P and K in all the SAR treatments decreased regardless of pH values, except for available N and P in PS.