Search

Antimony (Sb) is a recognized priority pollutant with toxicity that is influenced by its migration and transformation processes. Oxidation of Fe(II) to Fe(III) oxides, which is a common phenomenon in the environment, is often accompanied by the formation of Mn(III/IV) and might affect the fate of Sb. In this study, incorporated Mn(III) and sorbed/precipitated Mn(III/IV) associated with lepidocrocite were prepared by adding Mn(II) during and after Fe(II) oxidation, respectively, and the effects of these Mn species on Sb fate were investigated. Our results indicated that the association of these Mn species with lepidocrocite obviously enhanced Sb(III) oxidation to Sb(V), while concomitantly inhibiting Sb sorption due to the lower sorption capacity of lepidocrocite for Sb(V) than Sb(III). Additionally, Mn oxide equivalents increased in the presence of Sb, indicating that Sb oxidation by Mn(III/IV) associated with lepidocrocite was a continuous recycling process in which Mn(II) released from Mn(III/IV) reduction by Sb(III) could be oxidized to Mn(III/IV) again. This recycling process was favorable for effective Sb(III) oxidation. Moreover, Sb(V) generated from Sb(III) oxidation by Mn(III/IV) enhanced Mn(II) sorption at the beginning of the process, and thus favored Mn(III/IV) formation, which could further promote Sb(III) oxidation to Sb(V). Overall, this study elucidated the effects of Mn(III/IV) associated with lepidocrocite arisen from Fe(II) oxidation on Sb migration and transformation and revealed the underlying reaction mechanisms, contributing to a better understanding of the geochemical dynamics of Sb., (Copyright © 2021. Published by Elsevier B.V.)

Arsenic (As) and antimony (Sb) are considered as priority environmental pollutants and their accumulation in crop plants particularly in rice has posed a great health risk. This study endeavored to investigate As and Sb contents in paired soil-rice samples obtained from Xikuangshan, the world largest active Sb mining region, situated in China, and to investigate As speciation and location in rice grains. The soil and rice samples were analyzed by coupling the wet chemistry, laser ablation-inductively coupled plasma mass spectrometry (LA-ICP-MS), synchrotron-based micro X-ray fluorescence mapping (μ-XRF) and micro X-ray absorption near-edge structure (μ-XANES) spectroscopy. The results of field survey indicated that the paddy soil in the region was co-polluted by Sb (5.91-322.35 mg kg -1 ) and As (0.01-57.21 mg kg -1 ). Despite the higher Sb concentration in the soil, rice accumulated more As than Sb indicating the higher phytoavailability of As. Dimethylarsinic acid (DMA) was the predominant species (>60% on average) in the rice grains while the percentage of inorganic As species was 19%-63%. The μ-XRF mapping of the grain section revealed that the most of As was distributed and concentrated in rice husk, bran and embryo. Sb was distributed similarly to As but was not in the endosperm of rice grain based on LA-ICP-MS. The present results deepened our understanding of the As/Sb co-pollution and their association with the agricultural-product safety in the vicinity of Sb mining area., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

Birnessites are abundant naturally occurring minerals with high sorption and oxidation capacity that could therefore play an important role in antimony (Sb) migration and transformation. There are various types of birnessites in the environment. However, little is known about the similarities and differences in Sb oxidation and sorption on birnessites with different properties. In this study, the behavior of Sb oxidation and sorption on two contrasting birnessites (δ-MnO 2 and triclinic birnessite (TrBir)) were investigated via batch and kinetic experiments and various spectroscopic techniques. Our results showed that the reaction mechanisms between Sb and the two birnessites were similar. The edge sites of birnessites were responsible for Sb(III) oxidation. Mn(IV) was reduced to Mn(III) and Mn(II), bound with birnessites and released to the solution, respectively. Because of the rapid rate of electron transfer of adsorbed Sb(III) to birnessites, the only Sb species on δ-MnO 2 after the oxidation reaction was Sb(V). Sb(V) was adsorbed at the edge sites of birnessites by replacing the OH group of birnessites, forming corner-sharing complexes with birnessites. However, the Sb sorption and oxidation capacities of the two birnessites were significantly different. Poorly-crystallized δ-MnO 2 exhibited a much higher oxidation and sorption capacity than well-crystallized TrBir because the former had many more edge sites than the latter. This study reveals the general mechanism of the reaction between Sb and birnessite and indicates that birnessite with a high number of edge sites would exhibit a huge capacity in Sb oxidation and sorption., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

Understanding the kinetic reactions of antimony (Sb) at the MnO2-water interface is essential for predicting the dynamic behavior of Sb in soil environments. In this study, we developed a quantitative model for assessing the coupling between Sb(iii) oxidation and Sb(iii)/Sb(v) adsorption/desorption kinetics and the role of each individual reaction process in controlling the overall reaction rates. Based on our modeling results, Sb(iii) oxidation rates were very fast at the early stages of the reactions and may significantly slow down with time, and Sb(iii) and Sb(v) showed different adsorption behavior on δ-MnO2. Our kinetics model is able to account for different adsorption/desorption kinetics of Sb(iii) and Sb(v) and the changes of Sb(iii) oxidation rates during the coupled kinetic processes, which provides a general modeling framework for predicting Sb kinetic behavior at the MnO2-water interface.

Graphical abstract Highlights • Gallic acid significantly mobilized Sb from goethite with increasing pH. • Sb(III) oxidation and the competitive adsorption inhibited Sb adsorption. • Self-generated H 2 O 2 and quinone species accounted for Sb(III) oxidation. • The edge-sharing inner-sphere complexes were formed between Sb and goethite. Abstract Natural organic matter (NOM) profoundly influences the metal(loid)s immobilization by iron (Fe) minerals, which, in turn, are the host phase for Sb that control its mobilization and bioavailability. However, the potential effect of the redox-active phenolic acids derived from NOM on this process has rarely been explored. Therefore, the adsorption of Sb(III) on goethite and Sb(III) oxidation in the presence of a common phenolic acid—gallic acid (GA)—was systematically investigated. The reaction mechanisms were unraveled by the combination of wet chemistry, electron paramagnetic resonance (EPR), X-ray photoelectron spectroscopy (XPS), and X-ray absorption fine structure (XAFS) spectroscopy. Our results showed the addition of GA significantly inhibited Sb adsorption on goethite as the pH increased. Except for the competitive adsorption by GA, the inhibition also resulted from the extensive Sb(III) oxidation in the suspension and the lower Sb(V) sorption capacity of goethite at higher pH. The alkaline condition facilitated the generation of reactive oxygen species (hydrogen peroxide) and quinone species (semiquinone radical (SQ −) and oxidized GA), accounting for the significant Sb(III) oxidation in the solution and on the goethite surface. Besides, the edge-sharing inner-sphere complexes were formed between Sb and goethite regardless of the presence of GA. Our findings demonstrated the remarkable role of the phenolic groups in NOM on the adsorption of Sb(III) on goethite. [ABSTRACT FROM AUTHOR]

Abstract Birnessites are abundant naturally occurring minerals with high sorption and oxidation capacity that could therefore play an important role in antimony (Sb) migration and transformation. There are various types of birnessites in the environment. However, little is known about the similarities and differences in Sb oxidation and sorption on birnessites with different properties. In this study, the behavior of Sb oxidation and sorption on two contrasting birnessites (δ-MnO 2 and triclinic birnessite (TrBir)) were investigated via batch and kinetic experiments and various spectroscopic techniques. Our results showed that the reaction mechanisms between Sb and the two birnessites were similar. The edge sites of birnessites were responsible for Sb(III) oxidation. Mn(IV) was reduced to Mn(III) and Mn(II), bound with birnessites and released to the solution, respectively. Because of the rapid rate of electron transfer of adsorbed Sb(III) to birnessites, the only Sb species on δ-MnO 2 after the oxidation reaction was Sb(V). Sb(V) was adsorbed at the edge sites of birnessites by replacing the OH group of birnessites, forming corner-sharing complexes with birnessites. However, the Sb sorption and oxidation capacities of the two birnessites were significantly different. Poorly-crystallized δ-MnO 2 exhibited a much higher oxidation and sorption capacity than well-crystallized TrBir because the former had many more edge sites than the latter. This study reveals the general mechanism of the reaction between Sb and birnessite and indicates that birnessite with a high number of edge sites would exhibit a huge capacity in Sb oxidation and sorption. Graphical abstract Image 1 Highlights • The reaction mechanisms between Sb and the two birnessite (δ-MnO 2 and TrBir) are similar. • The edge sites of birnessite were responsible for Sb(III) oxidation and Sb(V) sorption. • Sb(V) was adsorbed at the edge sites of birnessite, forming corner-sharing complexes with birnessite. • δ-MnO 2 was much reactive than TrBir in Sb oxidation and adsorption due to the many more edge sites of δ-MnO 2. The general reaction mechanism between Sb and birnessite and the key properties of birnessite affecting the reaction were revealed. [ABSTRACT FROM AUTHOR]

Abstract: The electrochemical behavior of magnetron sputtered Sb2O4 thin film as anode materials for rechargeable sodium ion batteries was investigated for the first time. Sb2O4 thin film electrodes exhibited a large reversible capacity of 896mAhg−1. The reversible conversion reactions involving both alloying/dealloying and oxidation/reduction processes of antimony were revealed during the electrochemical reaction of Sb2O4 film electrode with sodium. The high reversible capacity and good cyclibility of Sb2O4 electrode made it become a promising anode material for future rechargeable sodium ion batteries. [Copyright &y& Elsevier]

Antimony sulfide (Sb 2 S 3) is widely used in photocatalysts and photovoltaic cells because of its abundant reserves, low toxicity, environmental friendliness, narrow band gap, and high light absorption capacity. Sb 2 S 3 shows a quasi-one-dimensional structure composed of [Sb 4 S 6 ] n nanoribbons, a lot of reported studies are focused on preparing Sb 2 S 3 with [hk1] oriented dominant growth to improve the photogenerated carrier transport capacity of Sb 2 S 3. However, there is relatively few research on the preparation of [hk1] oriented rod-like Sb 2 S 3 by vapor transport deposition (VTD) method. In this work, the VTD method was used to prepare Sb 2 S 3 with [hk1] oriented growth on the FTO substrate, and then composite with the ternary solid solution Cd x Zn 1−x S. Finally, a novel Sb 2 S 3 /Cd 0.6 Zn 0.4 S S-scheme heterojunction with rod-like core-shell structure was successfully constructed, which could effectively improve the photoelectrochemical properties. Because the solid solution component x is adjustable, that is, Cd x Zn 1−x S has continuously adjustable band gap width and energy level position, the Sb 2 S 3 /Cd x Zn 1−x S heterojunction type can be regulated from Type-II to S-scheme. Photoelectrochemical (PEC) tests indicated that the composite photoanode Sb 2 S 3 /Cd 0.6 Zn 0.4 S achieved a higher photocurrent density (2.54 mA·cm−2, 1.23 V vs. RHE), which is about 4.31 times that of pure Sb 2 S 3 nanorod photoanode (0.59 mA·cm−2, 1.23 V vs. RHE). • Rod-like Sb 2 S 3 with [hk1] orientation is deposited on FTO substrate by VTD method. • The Sb 2 S 3 /Cd x Zn 1−x S heterojunction type can be regulated from Type-Ⅱ to S-scheme. • The S-scheme heterojunction could effectively promote PEC water splitting. • The photoelectrode exhibits considerable photocurrent 2.54 mA·cm−2 at 1.23 V RHE. [ABSTRACT FROM AUTHOR]

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. [Display omitted] • Continuous soil flooding decreased Sb in porewater with pronounced Sb(V) reduction. • Continuous soil flooding increased phytoavailable Sb and total Sb in root and shoot. • Sb in grain was below acceptable limit and not affected by two water treatments. [ABSTRACT FROM AUTHOR]