Oxidation Of Antimony Research Articles

Simultaneous sorption and catalytic oxidation of trivalent antimony by Canna indica derived biochars

The simultaneous sorption and oxidation of Sb(III) on biochars were investigated using batch experiments. The biochars were derived from Canna indica at different pyrolysis temperatures (300–600 °C, referred as CIB300-CIB600), and characterized by FTIR, BET, XRD, SEM-EDS, EPR and Boehm titration. The Sb(III) sorption data could be well fitted by both the Langmuir and Freundlich models, and the pseudo-second order model is best for describing the kinetic data. The maximum Sb(III) sorption capacity of CIB300 was 16.1 mg g−1, which was greater than that of other biochars. Inner-sphere complexation with oxygen-containing functional groups and coordination with π electrons are the possible sorption mechanisms. It is worthwhile to note that 4.7–32.3% of Sb(III) was oxidized to Sb(V) after sorption equilibration, demonstrating the occurrence of Sb(III) oxidation during the sorption process. Further study of oxidation under anoxic condition confirmed the catalytic role of biochar for Sb(III) oxidation, and free radicals in biochars were crucial for electron transfer. CIB400 exhibited the highest catalytic oxidative ability for Sb(III), which could be ascribe to its reserve of more electroactive polyphenolic macromolecule and less electroinactive cellulose. These results imply that biochars have good potential as a green effective sorbent for remediation of Sb(III) contaminated water, and simultaneously reduce the toxicity of Sb(III) by catalytic oxidation.

Enhancement of oxidation resistance of CoSb3 thermoelectric material by glass coating

Materials based on CoSb3 are ranked among thermoelectrics with the highest conversion rate, however in service they tend to rapidly lose the useful properties as a result of oxidation or sublimation. Glass coatings were designed in this work to protect CoSb3 against degradation in air at elevated temperatures. The coatings were based on borosilicate glass with a high content of titania. Their chemical composition was tailored to match the coefficient of thermal expansion (CTE) of the substrate (9.2·10−6K−1) and to secure thermal stability and low softening point of glass. The coatings deposited by a simple dipping technique were fired in the temperature range 700–740°C. Evaluation of these coatings was based on accelerated oxidation tests at 600°C for 20h. The micro- and nanostructure of the CoSb3/glass coating interface were examined by means of advanced electron microscopy. The coating appeared to have good adherence and to effectively protect the thermoelectric substrate against antimony loss and oxidation up to 600°C.

Reasons for the Discoloration of Postconsumer Poly(ethylene terephthalate) during Reprocessing

Gray and/or yellow discoloration may occur during repeated heating of poly(ethylene terephthalate) (PET). Both phenomena can cause problems in further application. In this work, the reasons for the discoloration of PET during reprocessing are investigated by physical and chemical analysis such as colorimetry, size exclusion chromatography, viscosimetry (ηinh.), inductively coupled plasma mass spectrometry, X‐ray photoelectron spectroscopy, and MALDI‐ToF‐MS analysis. It is found that the antimony content which originates from catalyst residues used in PET synthesis has high influence on the gray discoloration obtained during reprocessing of PET. Antimony ions are reduced to elementary antimony during heating to temperatures above 230 °C as proven by X‐ray photoelectron spectroscopy. The yellow discoloration is partially generated by polyamide contaminants which are used as barrier layers in PET packaging materials such as soft drink bottles. In conclusion, to prevent discoloration of postconsumer PET during reprocessing different methods such as oxidation of gray metallic antimony or sorting out of polyamide contaminants are needed. image

Antimony oxidation and adsorption by in-situ formed biogenic Mn oxide and Fe–Mn oxides

Antimony (Sb), which can be toxic at relatively low concentrations, may co-exist with Mn(II) and/or Fe(II) in some groundwater and surface water bodies. Here we investigated the potential oxidation and adsorption pathways of Sb (III and V) species in the presence of Mn(II) and Mn-oxidizing bacteria, with or without Fe(II). Batch experiments were conducted to determine the oxidation and adsorption characteristics of Sb species in the presence of biogenic Mn oxides (BMOs), which were formed in-situ via the oxidation of Mn(II) by a Mn-oxidizing bacterium (Pseudomonas sp. QJX-1). Results indicated that Sb(III) ions could be oxidized to Sb(V) ions by BMO, but only Sb(V) originating from Sb(III) oxidation was adsorbed effectively by BMO. Introduced Fe(II) was chemically oxidized to FeOOH, the precipitates of which mixed with BMO to form a new compound, biogenic Fe–Mn oxides (BFMO). The BMO part of the BFMO mainly oxidized and the FeOOH of the BFMO mainly adsorbed the Sb species. In aquatic solutions containing both As(III) and Sb(III), the BFMO that formed in-situ preferentially oxidized Sb over As but adsorbed As more efficiently. Chemical analysis and reverse transcription real-time polymerase chain reaction revealed that the presence of Fe(II), As(III) and Sb(III) accelerated the oxidation of Mn(II) but inhibited the activity of Mn-oxidizing bacteria. These results provide significant insights into the biogeochemical pathways of Sb, Mn(II) in aquatic ecosystems, with or without Fe(II).

Kinetic modeling of antimony(III) oxidation and sorption in soils

Kinetic batch and saturated column experiments were performed to study the oxidation, adsorption and transport of Sb(III) in two soils with contrasting properties. Kinetic and column experiment results clearly demonstrated the extensive oxidation of Sb(III) in soils, and this can in return influence the adsorption and transport of Sb. Both sorption capacity and kinetic oxidation rate were much higher in calcareous Huanjiang soil than in acid red Yingtan soil. The results indicate that soil serve as a catalyst in promoting oxidation of Sb(III) even under anaerobic conditions. A PHREEQC model with kinetic formulations was developed to simulate the oxidation, sorption and transport of Sb(III) in soils. The model successfully described Sb(III) oxidation and sorption data in kinetic batch experiment. It was less successful in simulating the reactive transport of Sb(III) in soil columns. Additional processes such as colloid facilitated transport need to be quantified and considered in the model.

Electrochemical formation of SnO2-SbxOy composition-modulated coating

The results of the study of tin and antimony anodic oxidation in complex pyrophosphate-tartrate electrolyte are presented. The conditions of SnO2-SbxOy composition-modulated coating formation are described. Such coatings are formed in three steps. The first step is the deposition of underlayer of tin doped by antimony from the tin pyrophosphate-tartrate strike bath. The second step is the formation of tin-antimony composition-modulated coating that includes the alternating layers of alloy and mixture of metals and metal hydroxides in the pyrophosphate-tartrate electrolyte. The alloy is deposited at the low current density. The mixture of metals and metal hydroxides are deposited at higher current density. The third step is the electrochemical oxidation of composition-modulated coating under anodic polarization in the alkalized strike bath. The SnO2-Sb2O3 coatings may be used in the processes of catalytic oxidation of substances and energy devices.

Redox transformations of triphenylantimony(V) catecholate complexes based on alkyl gallates

The electrochemical transformations of triphenylantimony(V) catecholate complexes containing fragments of alkyl gallates (RO(O)C–(OH)Cat)SbPh3 (R = CH3 (1), C8H17 (2), and C12H25 (3)); (RO(O)C–(OH ∙ NEt3)Cat)SbPh3 (4); and ROC(O)GallH3 (R = CH3 (5), C8H17 (6), and C12H25 (7)) in acetonitrile were studied. The electrochemical oxidation of alkyl gallates 5–7 proceeds in two irreversible stages and leads to formation of o-quinoid products. At the first stage, the oxidation of antimony(V) compounds is electrochemically quasi-reversible and leads to the formation of unstable cationic complexes. The second irreversible redox transfer results in ligand decoordination and destruction of the compounds. Three redox stages were observed for complex 4. The triethylamine-deprotonated hydroxy group is oxidized at the first electrochemical step that leads to a further intramolecular transfer, forming a stable intermediate, whose oxidation occures in quasireversible manner.

Bioleaching of Complex Refractory Gold Ore Concentrate of China: Comparison of Shake Flask and Continuous Bioreactor

The laboratory tests of biooxidation and cyanidation were carried out by using samples of the complex refractory gold ore from China. The elemental composition was 16.8 % iron, 18.6 % sulfur, 4.88 % arsenic，2.30 % carbon and 3.49 % antimony. Gold is assayed at 46 g/t. The arsenic oxidation of 88.11 %，carbon removal rate of 32.34 % and antimony oxidation of 23.92 % over 16d was achieved in shake flasks in the presence of the mixed culture (HQ0211: Thiobacillus ferrooxidans Leptospirillum ferrooxidans and Thiobacillus thiooxidans). The continuous bioreactor tests resulted in greater dissolution rates for arsenic, carbon and antimony, which led to a greater extent of sulphide oxidation within a shorter period of time. The maximum oxidation of arsenic and antimony was 90.72 % and 40.09 % respectively and the removal rate of carbon is 63.48% after 8d in the continuous bioreactor tests. After bioleaching, the gold recovery of the oxidation residue was 98.02 % with the cyanidation method, which was showed the biological pretreatment was applicable to the complex refractory gold ore.

Microbiological oxidation of antimony(III) with oxygen or nitrate by bacteria isolated from contaminated mine sediments.

Bacterial oxidation of arsenite [As(III)] is a well-studied and important biogeochemical pathway that directly influences the mobility and toxicity of arsenic in the environment. In contrast, little is known about microbiological oxidation of the chemically similar anion antimonite [Sb(III)]. In this study, two bacterial strains, designated IDSBO-1 and IDSBO-4, which grow on tartrate compounds and oxidize Sb(III) using either oxygen or nitrate, respectively, as a terminal electron acceptor, were isolated from contaminated mine sediments. Both isolates belonged to the Comamonadaceae family and were 99% similar to previously described species. We identify these novel strains as Hydrogenophaga taeniospiralis strain IDSBO-1 and Variovorax paradoxus strain IDSBO-4. Both strains possess a gene with homology to the aioA gene, which encodes an As(III)-oxidase, and both oxidize As(III) aerobically, but only IDSBO-4 oxidized Sb(III) in the presence of air, while strain IDSBO-1 could achieve this via nitrate respiration. Our results suggest that expression of aioA is not induced by Sb(III) but may be involved in Sb(III) oxidation along with an Sb(III)-specific pathway. Phylogenetic analysis of proteins encoded by the aioA genes revealed a close sequence similarity (90%) among the two isolates and other known As(III)-oxidizing bacteria, particularly Acidovorax sp. strain NO1. Both isolates were capable of chemolithoautotrophic growth using As(III) as a primary electron donor, and strain IDSBO-4 exhibited incorporation of radiolabeled [(14)C]bicarbonate while oxidizing Sb(III) from Sb(III)-tartrate, suggesting possible Sb(III)-dependent autotrophy. Enrichment cultures produced the Sb(V) oxide mineral mopungite and lesser amounts of Sb(III)-bearing senarmontite as precipitates.

Oxidation of tri(o-tolyl)antimony by tert-butyl hydroperoxide. molecular structures of bis[µ2-oxo- tri(O-tolyl)antimony] and µ2-oxo-bis[(tert-butylperoxy)tri(o-tolyl)antimony

Tri(o-tolyl)antimony oxidation by equimolar amount of tert-butyl hydroperoxide in diethylether led to the formation of bis[μ2-oxo-tri(o-tolyl)antimony] (1). At the molar ratio of reactants 1:2 or 1:4 μ2-oxo-bis[(tert-butylperoxy)tri(o-tolyl)antimony] (2) has been formed. According to the X-ray analysis data, antimony atoms are in the trigonal bipyramidal coordination in molecules 1 and 2. The bond lengths SbO vary within the ranges 1.937(2)2.078(2) A (1) and 1.975(17)2.216(15) A (2).

Different mechanisms and electrocatalytic activities of Ce ion or CeO2 modified Ti/Sb–SnO2 electrodes fabricated by one-step pulse electro-codeposition

Nano-CeO2 doping mitigates the surface antimony enrichment and promotes the complete oxidation of antimony, while cerium ion doping aggravates these things.

Isolation and Characterization of Antimony-Reducing Bacteria from Sediments Collected in the Vicinity of an Antimony Factory

To date, there is very little information available on the oxidation and reduction of antimony by bacteria. An antimonate-respiring bacterium was isolated from sediment samples collected in the vicinity of an antimony oxide-producing factory in Korea. This bacterium was isolated by application of the Hungate standard anaerobic culture technique. Temporarily named strain JUK-1, it was found to be a rod-shaped bacterium and occurred individually or in pairs. Antimonate (pentavalent antimony) was reduced to antimonite (trivalent antimony) in the presence of JUK-1 in an anoxic minimal medium containing 5 mM antimonate and 10 mM acetate. The organism grew optimally at an initial pH of 7.7 and a temperature of 30°C. A part of the antimonite which was produced in medium precipitated as a bio-mineral containing approximately 50.0% antimony, 33.5% oxygen, 12.7% carbon, 2.0% sodium and 1.9% magnesium by weight. Based on the phylogenetics of 16S rRNA gene sequence and DNA G+C content, JUK-1 appears to be a new strain of the Sinorhizobium genus. The results suggest that bacteria may play a significant role in changing the redox state of antimony in the environment.

Leaching of pyrite-arsenopyrite concentrate in bioreactors during continuous cultivation of a thermoacidophilic microbial community

A community of thermoacidophilic chemolithotrophic microorganisms was shown to exhibit enhanced efficiency of leaching and biooxidation of the gold-bearing pyrite-arsenopyrite flotation concentrate in continuous mode of cultivation. Under the optimal values of growth parameters, the degree of oxidation of sulfide arsenic, iron, sulfur, and antimony in the line of three laboratory reactors (D = 0.004 h−1) was 99.55, 98.87, 99.65, and 97.08%, respectively, while gold recovery from the solid biooxidation residue was 97.4%.

Optical and structural characterization of antimony doped ZnO single crystal.

We present the optical and structural study of the antimony doped zinc oxide (ZnO) performed by atomic diffusion. Diffusion is carried out at a temperature of 10000C for periods of 1, 2 and 4 hrs from a solid source prepared by partial oxidation of antimony, characterizing each step of the process was performed by photoluminescence (PL) and x-ray diffraction (XRD). The characterization by photoluminescence shows the effect of doping with antimony in radiative transitions caused by the creation of impurity levels. Doped samples were analyzed by high resolution diffraction and reciprocal space mapping which revealed the structural modification of the quality of the single crystal produced by the introduction of antimony. The results indicate that the antimony is introduced fully the volume of ZnO and does not modify the quality of the crystal.

Catalytic production of antimonate through alkaline leaching of stibnite concentrate

A hydrometallurgical treatment based on leaching and oxidation of trivalent antimony in hydroquinone-catalyzed alkaline electrolyte and precipitation of sodium hydroxyantimonate was elucidated. The influences of temperature and hydroquinone concentration on both the leaching and oxidation processes were discussed. Similar trends for recovery curves of antimony were obtained at different temperatures and hydroquinone concentrations in oxygen-rich alkaline electrolyte. The antimony recovery was calculated to be 90% within 1h at 80°C in 0.4g⋅L−1 HQ. The complete trivalent to pentavalent antimony oxidation was achieved within 4h under optimum conditions in a single-stage process. The oxidation rate equation is as follows:rSbIII=−dCSbIIIdt=5.09.CSbIII1.02.CHQ1.05The precipitation product was found to be sodium hydroxyantimonate (mopungite) with pseudo-cubic crystal morphology. It is concluded that O2 was unlikely to be the most powerful oxidant, but rather the HQ is responsible for the rapid oxidation of Sb (III) by the formation of H2O2. The leaching and oxidation reaction mechanism for the formation of pentavalent antimony was proposed, resulting in intermediate species such as SbS33−, SbO2− and Sb2O3.

Oxidation and mobilization of metallic antimony in aqueous systems with simulated groundwater

Antimony (Sb) is a contaminant of concern that can be present in elevated concentrations in shooting range soils due to mobilization from spent lead/antimony bullets. Antimony in shooting range soils has been observed as either metallic Sb(0) or as Sb(V) immobilized by iron (hydr)oxides. The absence of Sb(III) in soils is indicative of rapid Sb(III) oxidation to Sb(V) under surface soil conditions. However, the major controls on antimony oxidation and mobility are poorly understood. To better understand these controls we performed multiple batch experiments under oxic conditions to quantify the oxidation and dissolution of antimony in systems where Sb(0) is oxidized to Sb(III) and further to Sb(V). We also tested how variations in the aqueous matrix composition and the presence of metallic lead (Pb) affect the dissolution, solid phase speciation, and oxidation of antimony. We monitored changes in the aqueous antimony speciation using liquid chromatography inductively coupled plasma mass spectrometry (LC-ICP-MS). To test which solid phases form as a result of Sb(0) oxidation, and therefore potentially limit the mobility of antimony in our studied systems, we characterized the partially oxidized Sb(0) powders by means of extended X-ray absorption fine structure (EXAFS) spectroscopy and powder X-ray diffraction (XRD).The observed oxidation of Sb(0) to Sb(III) and mobilization to solution is rapid: after 5–15min of reaction the aqueous antimony concentration reached 50–600μM. The amount of dissolved antimony and the rate of Sb(III) oxidation to Sb(V) in deionized water is lower than what we measured in the simulated groundwater systems. Sénarmontite (Sb2O3), the primary crystalline oxidation product of Sb(0), was detected after one month from the beginning of Sb(0) oxidation. The maximum aqueous Sb(III) concentration is about 30 times larger than the predicted equilibrium concentration with respect to sénarmontite in the initial stages (<65h) of our experiment. Concentrations reach equilibrium within 146–222days. The maximum concentration of Sb(V) is controlled by cation availability for the precipitation of an antimonate. In the systems where sodium Na(I) exceeded 20mM precipitation of mopungite is observed. No crystalline phases were detected in the systems with added lead, and the dissolved Sb(V) concentration is several orders of magnitude higher than would be expected in equilibrium with bindheimite (Pb2Sb2O7). The observed solubility of Sb(V) in the systems with Ca(II) is several orders of magnitude larger than the solubility reported for roméite (Ca2Sb2O7). The addition of Pb(0) lowered the extent of Sb(0) oxidation due to competitive oxidation or to the coupling of antimony and lead redox reactions. The results from our research can be used to identify substrates that promote precipitation of relatively insoluble antimony compounds in target berm soils and thus prevent the offsite migration of antimony from shooting range target berms.

Control of selective silicate glass coloration by gold metallic nanoparticles: structural investigation, growth mechanisms, and plasmon resonance modelization

Soda lime silicate oxide glasses are studied to perform coloration thanks to gold nanoparticles’ crystallization. This precipitation is conducted by chemical reduction of gold ions with stannous or antimony oxides as reducing agents. A control of the rendered coloration between blank to red shades has been obtained using Sb2O3 agent and appropriate thermal treatments. The glasses remain colorless while heating up to 450 °C. Structural glasses evolution is studied by MAS NMR spectroscopy of 29Si and 23Na nuclei to investigate the silicate network polymerization change and the modification of sodium/oxygen bond length versus nucleation state and growth of Au nanoparticles. A clear decrease of the Q2 species part is observed with nanoparticles growth confirmed by the evolution of chemical shift for 23Na resonance. A slight network polymerization is then showed independently of the only thermal treatment. This structural change could be induced by the antimony oxidation and change towards higher coordinations. Finally, the glasses chemical durability has been studied by leaching tests and shows lower alteration for colored glass. The optical spectroscopy applied to colored glasses has given rise to plasmon resonance phenomena at around 600 nm which is the typical surface plasmon resonance of gold for a refractive medium index of 1.5, with a shift of the resonance towards the higher wavelengths with increasing thermal treatment temperature. This shift is modelized by Drude and MIE approaches and confirms the trend observed by UV-visible measurement with an increasing absorption at the SPR correlated to a typical Ostwald growth mechanism according to the increase of the annealing temperature.

Mobility and chemical fate of antimony and arsenic in historic mining environments of the Kantishna Hills district, Denali National Park and Preserve, Alaska

The Kantishna Hills mining district of interior Alaska, USA, located within Denali National Park and Preserve, contains a number of antimony lode deposits, including Alaska's historically largest antimony producer, the Stampede mine. Oxidative weathering of sulfidic tailings and waste rock associated with historic mining operations has impacted water quality in the region. In the Stampede and Slate Creek watersheds, antimony and arsenic concentrations in stream waters were as high as 720μg/L and 239μg/L, respectively. Antimony in all water samples is predominantly present as Sb(V), whereas arsenic was detected in varying ratios of As(III) and As(V). Based on X-ray absorption spectroscopy (XAS) measurements reduced As(III) and Sb(III) were identified in mine waste materials, whereas predominantly oxidized forms, As(V) and Sb(V), were found in downstream sediments. Elevated antimony concentrations extend for more than 8km downstream from the antimony lodes, whereas arsenic quickly attenuates within 1.5km. The difference between antimony and arsenic aqueous phase speciation suggests that antimony oxidation is more rapid than arsenic within this system. A high correlation is observed between antimony, arsenic, and iron concentrations in fine-fraction streambed sediments downstream of the source lodes. This suggests that sorption and co-precipitation with iron (hydr)oxides are important pathways for the attenuation of antimony and arsenic in these interior Alaska watersheds. Further XAS characterization of the downstream sediments corroborates these observations and indicates that antimony is adsorbed to Fe-oxide phases as inner-sphere bi-dentate edge and corner sharing complexes. The trace element redox states, as well as downstream partitioning, are mainly controlled by iron speciation based on the strong correlation between redox potentials calculated from iron (Fe(II)/Fe(III)) and arsenic (As(III)/As(V)).

Antimony(III) oxidation and antimony(V) adsorption reactions on synthetic manganite

Oxidation and adsorption processes critically affect the mobility of antimony (Sb) in the environment. Minerals such as manganese oxides appear to be important adsorbents or oxidants for Sb in soils and sediments. In this study, Sb oxidation and adsorption onto synthetic manganite (γ-MnOOH) in aqueous suspensions were comprehensively investigated. The oxidation of Sb(III) by manganite occurred on a time scale of minutes and Sb(V) was released into the suspension as soon as the reaction began. X-ray absorption near edge structure (XANES) analyses showed that Sb(V) was the dominant species adsorbed on manganite, suggesting that manganite acts as a strong oxidant of Sb(III). The effects of temperature on the adsorption rates of Sb(V) were investigated. Thermodynamic parameters indicated that adsorption of Sb(V) by manganite is an exothermic process and is spontaneous at the specific temperatures investigated. A change in ionic strength from 0.001 to 0.1M NaNO3 had little effect on the adsorption of Sb(V) onto manganite, indicating that Sb(V) forms inner-sphere complexes at the mineral surface. Anions such as phosphate, sulfate, silicate and carbonate, which may be present in natural waters, were ineffective competitors with Sb(V) for sorption sites.

Characterization of growth of anodic antimony oxide films by ellipsometry and XPS

The processes occurring consecutively during anodic oxidation of antimony in buffered phosphate solutions are followed by in situ ellipsometry. In the first stages of anodization, soluble species formation followed by formation of a highly hydrated film takes place. At higher potentials, the growth of a single layer of Sb 2O 3 anodic film occurs. Oxygen evolution occurring simultaneously with oxide growth is also detected. Surface chemical analysis by XPS allowed obtaining the chemical state and composition of the anodic antimony oxide films. The procedure followed in order to carry out the spectra deconvolution due to overlapping of O1s and Sb3d photoemission lines is discussed. The binding energy values obtained for O1s and Sb3d signals as well as the O/Sb atomic ratio indicates that the anodic film formed at low or high potentials is composed by Sb(III) species only. Hydration as well as phosphate ions incorporation into the film is also demonstrated.