Dissolution Of Antimony Research Articles

Bio-oxidation of refractory gold ores containing stibnite and gudmundite

Abstract Arsenic and antimony are environmental pollutants associated with several diseases, including skin cancer. One of the main sources of both elements is the oxidation of sulphide minerals, particularly arsenopyrite and therefore any of both elements is a concern in gold mining operations because arsenic- and antimony-bearing sulphides may contain significant gold contents. Bioleaching is considered more environmentally-friendly than chemical processes to recovery gold, particularly from low-grade ores and residues bearing such sulphides. Thus, the current work has investigated the bio-oxidation of both a gold-bearing sulphide concentrate and a flotation tailing by Acidithiobacillus ferrooxidans, at 32 °C, focusing on the behaviour of both arsenic and antimony. Fe2＋ supplementations were required in order to increase the oxidation efficiency and the optimum pH value was 1.75. The cyanidation tests confirmed the refractory nature of the samples under study (21%). The solid products of the bio-oxidation stage showed gold extractions four times as large (85%) as that of the initial sample. The dissolution of antimony was low with no evidence of the formation antimony precipitates. Unlike arsenic, the latter reported mostly to the solid product of the bioleaching step as inert sulphide particles.

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.

ChemInform Abstract: Electrochemical Behavior of the Antimony Electrode in Sulfuric Acid Solutions. Part 1. Corrosion Processes and Anodic Dissolution of Antimony.

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Electrochemical behaviour of the antimony electrode in sulphuric acid solutions—I. Corrosion processes and anodic dissolution of antimony

The corrosion processes at open circuit conditions and in the active dissolution region of antimony, at low anodic overpotentials, have been studied in sulphuric acid solutions. It was established that antimony dissolution at open circuit is coupled to oxygen reduction, which occurs via the hydrogen peroxide route. The rate of antimony dissolution was found to increase linearly with increasing acid concentration. Based on potentiodynamic, galvanodynamic and steady-state measurements as well as ac impedance data possible mechanisms for the corrosion processes at open circuit as well as for the dissolution of antimony in the active region are proposed and discussed.

Anodic Dissolution of Antimony in Phosphate Solutions

Abstract The anodic dissolution of antimony in alkaline phosphate solutions has been investigated by using a galvanostatic technique. The rate of anodic dissolution was found to depend on pH and showed a Tafel slope of 195 mV/decade. The reaction order with respect to OH− was found to approximately equal to one. The dissolution rate of antimony at constant pH value is increased with solution stirring and dissolution temperature. The activation energy ΔH* for the anodic dissolution process was found to be 20.3 kcal ·mol−1·°K− 1. The anion nature affected the anodic dissolution at pH 7.0, while at pH 12 the same anions have no effect. The dissolution rate of antimony is increased with increasing the phosphate ion concentration up to 1.0 N; higher concentration than this value decreased the dissolution.