Trivalent Sb Research Articles

Weathering of Sb-rich mining and smelting residues: Insight in solid speciation and soil bacteria toxicity

Tailings and slag residues from the most important antimony mine of the French Massif Central were analysed for their mineralogical and chemical contents by conventional X-ray powder diffraction and synchrotron-based X-ray microdiffraction (μ-XRD). Results show that ∼2000 metric tons of Sb are still present at the abandoned mining site. Mean concentrations of Sb in slags and tailings are 1700 and 5000mgkg−1, respectively. In addition, smaller quantities of As were also measured (∼800mgkg−1 in tailings). Toxicity tests of As and Sb indicate that the growth of bacteria is severely affected at these concentrations. In particular, Sb was observed to cause negative effects for several types of bacteria. Almost all primary minerals carrying trivalent Sb disappeared during weathering at the expense of phases in which Sb5+ is the most abundant form. Instead of sulphides, Sb-bearing Fe hydroxides (goethite and lepidocrocite) are now present in the residues together with Sb-bearing jarosite and Sb(-Fe) oxides and hydroxides such as tripuhyite, senarmontite, romeite, cervantite, and valentinite. Water analyses of the main local stream indicate little remobilization of Sb downstream the site and despite the acidic pH of the surface tailings, pH values show neutral or near-neutral values on all locations of the site.

Antimony Resistance and Trypanothione in Experimentally Selected and Clinical Strains of Leishmania panamensis

The participation of trypanothione in clinical and experimental antimony (Sb) resistance in Leishmania panamensis was examined by using specific inhibitors. Buthionine sulfoximine (BSO) significantly reversed the resistance to trivalent Sb (Sb(III)) of promastigotes of experimentally derived Sb-resistant lines, supporting the participation of a trypanothione-mediated mechanism of resistance. In contrast, promastigotes of strains isolated at the time of clinical treatment failure and resistant to pentavalent Sb (Sb(V)) as intracellular amastigotes were not cross resistant to Sb(III), and BSO had little or no effect on susceptibility. Difluoromethylornithine did not alter the Sb(III) susceptibilities of experimentally selected lines or clinical strains. The mechanisms of acquired resistance emerging in clinical settings may differ from those selected by in vitro exposure to Sb.

Determination of antimony(iii) and total antimony by hydride generation atomic absorption spectrometry in samples of injectable drugs used for leishmaniasis treatment

A procedure for the determination of Sb(III) and total Sb in commercial samples of injectable drugs based on pentavalent antimony was proposed. The drugs studied in this work are currently used for leishmaniasis treatment in many countries. Determination of Sb was performed by hydride generation atomic absorption spectrometry under controlled conditions for the reaction medium. The following parameters were investigated: type and concentration of acid, sodium tetrahydroborate concentration and purge time. The chosen conditions for Sb(III) were: 4% (m/v) citric acid, 1% (m/v) sodium tetrahydroborate and 10 s (a pre-reduction step was performed using 10% m/v KI in 0.2% m/v ascorbic acid solution). The same parameters for total Sb determination were: 0.5 mol l−1 sulfuric acid, 4% (m/v) sodium tetrahydroborate and 10 s. Interference from As, Ni, Cu and Pb on the analytical signal for Sb(III) was also investigated. Two kinds of commercial drugs were analyzed. The trivalent Sb concentration varied from 1.7 to 3.1 mg l−1, corresponding to 1.6 to 2.8% for the total Sb. Recovery tests for Sb(III) showed values varying from 98.9 to 101.9%. The characteristic mass for Sb(III) was 0.22 ng and the detection limit (3s) was about 1.5 ng (absolute). The main advantage of the proposed procedure is to allow the determination of Sb(III) in the presence of a large excess of pentavalent Sb (about 2000 ng).

Correlated Atomic Resolution Microscopy and Spectroscopy Studies of Sn(Sb)O2 Nanophase Catalysts

A series of antimony-doped tin oxide (ATO), Sn(Sb)O2, nanophase catalysts (containing 43 mol% Sb calcined at temperatures of 250, 600, and 1000°C, respectively) have been studied by correlated electron energy-loss spectroscopy (EELS) and Z-contrast imaging in a scanning transmission electron microscope (STEM) and by high-resolution electron microscopy (HREM). As reference materials, pure SnO2, Sb2O3, and Sb2O5 are also analyzed. Results show that the particle size of these ATO catalysts increases with the calcination temperature. At low calcination temperatures, the catalyst contains crystalline nanoparticles surrounded by amorphous material, while the nanoparticles become well crystallized when calcined at higher temperatures. EEL spectra acquired from these ATO catalysts are qualitatively interpreted using ‘fingerprints’ from the reference materials. Results suggest that at low calcination temperatures (250°C), Sb exists in the pentavalent state Sb (V) either incorporated into the SnO2 lattice or as an amorphous layer surrounding the SnO2 crystals. At higher temperatures (≥600°C), Sb segregation occurs as trivalent Sb (III) at the surface and Sb (V) in the core of the majority of the nanoparticles. However, it should be noted that nearly no Sb was detected in some particles. The surface Sb (III) ions are proposed as active sites in the ATO catalysts.

121Sb Mössbauer and X-ray Photoelectron Spectroscopy Studies of the Electronic Structure of Some Antimony Misfit Layer Compounds

The chemical environment of Sb atoms in misfit layer sulfides (SbS)pTS2 (T = Nb, Ti and Ta) was examined by using 121Sb Mossbauer spectroscopy (MS) and X-ray photoelectron spectroscopy (XPS). 121Sb Mossbauer spectra exhibited an asymmetric profile that can be interpreted by assuming two different coordination numbers for trivalent Sb ions. However, these data do not give evidence for the presence of a significant Sb atom fraction of valence similar to metallic antimony as reported by X-ray single-crystal structure calculations. Sb 3d peak profiles were found to be highly symmetric and to suggest the presence of a single electronic state for Sb atoms within the SbS lattice. Although the binding energy of Sb 3d electrons in Sb-containing misfit layer sulfides was found to coincide with that in Sb2S3, the Wagner−Auger parameter values are intermediate between those reported for Sb2S3 and metallic Sb.

Sb-rich titanite in the manganese concentrations at St. Marcel-Praborna, Aosta Valley, Italy: petrography and crystal-chemistry

AbstractTitanites rich in antimony (up to 12.59 wt.% Sb2O5; equal to 0.165 Sb5+ per Si4+ = 1.000) arc described for the first time. They coexist with various greenschist-facies minerals in three different petrographical environments in the manganese concentrations at St. Marcel-Praborna in the Aosta Valley, Italy. These titanites are chemically zoned, the Sb-richest parts generally occurring alongside grain boundaries, microfractures, pores or inclusions. Moderately-good positive correlations exist between the Sb, Al and Fe contents, with negative correlations of each of these elements with Ti. Cr has perturbed the Al and Fe contents since a better negative correlation with Ti is obtained with [Al + Cr + Mn + Fe]. The Sr, Ba, Mn and F contents are rather small and vary irregularly. Several crystal-chemical hypotheses are presented concerning the method of structural formula calculation and the valencies and site distributions of Sb and the companion additional minor elements. The favoured interpretation is to place: Sr2+, Ba2+, Mn2+, Fe2+ and possibly also Sb3+ in the viiCa2+ site; Sb5+, Cr3+, Al3+, Sb3+, Fe3+ and possibly also Mn3+ in the viTi4+ site; and Al3+ in the ivSi4+ site; this indicates the existence of a natural silicate containing not only both trivalent and pentavalent Sb, but also both valencies in the same site. The principal ionic substitution is believed to be: 2 viTi4+ = vi[Al3+ + Cr3+ + Mn3+ + Fe3+] + viSb5+ accompanied by a substantial minor proportion of: 2 viTi4+ = viSb3+ + viSb5, or possibly = 2 viSb4+ The data indicate a very late stage penetration of pre-existing titanites by mobilized Sb, Al, Cr, Mn, Fe, F and presumably also (OH) at this locality, whereas Sr and Ba were mobile at an earlier stage. Manganese, which existed in the sedimentary protoliths, did not enter the titanite structure in very significant quantities.

The Chemistry of Anionic Antimony Selenides

Abstract The reaction of [HFe(CO)4]− with various binary antimony selenides was investigated. In the presence of Sb2Se3 the organometallic anion acts as a reducing agent leading to formation of [Sb4Se6]2- which has a crown shaped geometry with a transannular Sb-Sb bond. Reaction with Sb2Se5 leads to incorporation of iron carbonyl with formation of a dimer of formula [Fe2(CO)4(SbSe4)2]2-. The cluster contains two Fe(CO)2 fragments bridged by SbSe4 3- units. The main group anions are not tetrathiometallates, but rather a trivalent Sb bound to two selenides and a diselenide. Both compounds were structurally characterized as their [PPh4]+ salts. Crystal data for [PPh4]2[Sb4Se6], triclinic, P-1, a = 10.124(2)A, b = 14.670(2)A, c = 17.352(2)A, α = 96.42(2)˚, β = 95.78(2)˚, γ = 97.09(2)˚, V = 2524.2(7)A3, Z = 2, R = 0.0377, Rw = 0.0465; crystal data for [PPh4]2[Fe2(CO)4(SbSe4)2], monoclinic, P21/n, a = 15.552(5)A, b = 110.279(3)A, c = 18.159(6)A, β = 101.72(3)˚, V = 2819(1)A3, Z = 2, R = 0.0372, Rw = 0.0395.

Pharmacokinetics of antimony during treatment of visceral leishmaniasis with sodium stibogluconate or meglumine antimoniate

5 patients with visceral leishmaniasis were treated with sodium stibogluconate (2 patients) or meglumine antimoniate (3 patients) given intramuscularly at a dose of 10 mg antimony (Sb) per kg body weight daily for 30 d. Blood samples were obtained at intervals during treatment and blood Sb concentrations measured by anodic stripping voltametry. The pharmacokinetics of both drugs were remarkably similar, with peak concentrations of approximately 10 mg/litre occurring 2 h after the initial dose. Most of the Sb was eliminated rapidly, but nadir Sb concentrations increased gradually during treatment from 0·04-0·08 mg/litre 24 h after the first dose to 0·19-0·33 mg/litre 24 h after the 30th dose. For both drugs, the data were best described by a two compartment, three term pharmacokinetic model representing an initial absorption phase with a mean half-life of 0·85 h, a rapid elimination phase with a mean half-life of 2·02 h, and a slow elimination phase with a mean half-life of 76 h. The slow terminal elimination phase may be related to in vivo conversion of pentavalent Sb to trivalent Sb, which could contribute to the toxicity associated with long-term, high dose therapy.

A quick and direct micro-heterometric determination of traces of copper with rubeanic acid in metals and alloys

About 0.2 mg copper in 20 ml aqueous acetic acid, containing in addition 99.9–99.98% of foreign mono-, bi- ou trivalent metals, were determined heterometrically at 20° C with ~ 0.001M rubeanic acid. The monovalent cation present was Tl, the bivalent cations: Ca, Ba, Mg, Zn, Mn, Ni, Co, Cd and Pb and the trivalent cations: Fe, Cr and Al, In the presence of trivalent Sb or Bi an ammoniacal citrate or tartrate solution was used. In most cases the error was close to zero.