Sorption of Sb(III) on carbon steel surface in presence of molybdate and selenite in citric acid medium

Sorption of Sb(III) on carbon steel surface in aqueous medium (pH 2.8) in presence of different oxyanions like molybdate and selenite has been studied. It is observed that the presence of molybdate or selenite in solution reduced Sb(III) adsorption and surface precipitation to a great extent. The solution at different stages of the adsorption experiment has been analyzed by inductively coupled plasma-atomic emission spectroscopy technique. X-ray diffraction and X-ray photoelectron spectroscopy (XPS) techniques have been used to characterize the precipitate layer and the adsorbed layer. A detailed analysis of the XPS data reveals the mechanism involved in the two cases.     

Urea and thiourea based efficient colorimetric sensors for oxyanions

Urea and thiourea based receptors 1 and 2 bind H₂PO₄⁻, OH⁻, CH₃CO₂⁻, and PhCO₂⁻ ions in an acetonitrile/DMSO (9:1, v/v) medium. Binding of these anions causes an appreciable change in the visible region of the spectrum, which can be detected by the naked eye. The affinity constant for H₂PO₄⁻ is higher by about an order of magnitude as compared to the other oxyanions mentioned above. Ab initio calculations predicted tweezer-like binding modes for receptors 1 and 2 with these anions and a higher affinity toward H₂PO₄⁻ was predicted in acetonitrile.     

含氧酸盐熔盐Raman光谱V1峰位移的解释

若干含氧酸盐熔盐Raman光谱表明:含氧酸根离子的v₁峰(对称伸缩振动散射)位置随阳离子不同而异,James在解释NO₃^-在熔盐中的Raman光谱时,认为正电场较强的阳离子可能使NO₃^-中N-O键电子云密度增加,从而使力常数增大,v₁峰频率上升。为了探讨这一观点是否正确以及它对其它含氧酸根离子是否适用,我们用EHMO方法计算了若干由碱金属离子Me⁺和含氧酸根离子XO_m^m-(包括NO₃^-、NO₂^-、IO₃^-等)组成的原子簇(Me⁺)_x(XO_n^m-)中的X-O键的重叠集居数和原子净电荷,并考察其与相应的熔盐的Raman光谱v₁峰位置的关系。以探讨v₁峰位移的物理实质。     

Optimization of an anion-exchange high performance liquid chromatography-inductively coupled plasma-mass spectrometric method for the speciation analysis of oxyanion-forming metals and metalloids in leachates from cement-based materials

A method was developed for the speciation analysis of the oxyanions of As(III), As(V), Cr(VI), Mo(VI), Sb(III), Sb(V), Se(IV), Se(VI) and V(V) in leachates from cement-based materials, based on anion-exchange HPLC coupled with ICP-MS. The method was optimized in a two-step multivariate approach: the effect of sample pH and mobile phase composition on resolution, peak symmetry and analysis time was studied. Optimum conditions were then identified for the significant experimental factors by studying their interdependence. A mobile phase composition of 20 mM ammonium nitrate, 50 mM ammonium tartrate and pH 9.5 was found to be a compromise optimum for the separation of the target analytes using isocratic elution. The optimum condition provided separation of the analytes in less than 6 min, at a mobile phase flow rate of 1.0 mL/min. The signal intensities of the analytes were improved by adding 1% methanol to the mobile phase. The limit of detection of the method was in the range 0.2–2.2 μg/L for the various species. The effect of sample constituents was studied using spiked concrete leachates. The method was used to determine the target oxyanionic species in leachates generated from a concrete material in the pH range 3.5–12.4; CrO₄²⁻, MoO₄²⁻ and VO₄³⁻ were detected in most of the leachates.     

Fractionation analysis of oxyanion-forming metals and metalloids in leachates of cement-based materials using ion exchange solid phase extraction

A simple and versatile solid phase extraction (SPE) method has been developed to determine the anionic species of As, Cr, Mo, Sb, Se and V in leachates of cement mortar and concrete materials in the pH range 3-13. The anionic fractions of these elements were extracted using a strong anion exchanger (SAX) and their concentrations were determined as the difference in element concentration between the sample and the SAX effluent. Inductively coupled plasma mass spectrometry (ICP-MS) was used off-line to analyse solutions before and after passing through the SAX. The extraction method has been developed by optimizing sorbent type, sorbent conditioning and sample percolation rate. Breakthrough volumes and effect of matrix constituents were also studied. It was found that a polymer-based SAX conditioned with a buffer close to the sample pH or in some cases deionised water gave the best retention of the analytes. Optimal conditions were also determined for the quantitative elution of analytes retained on the SAX. Extraction of the cement mortar and concrete leachates showed that most of the elements had similar distribution of anions in both leachate types, and that the distribution was strongly pH dependent. Cr, Mo and V exist in anionic forms in strongly basic leachates (pH > 12), and significant fractions of anionic Se were also detected in these solutions. Cr, Mo, Se and V were not determined as anions by the present method in the leachates of pH < 12. Anionic As and Sb were found in small fractions in most of the leachates.     

Noble gas compounds and chemistry: a brief review of interrelations and interactions with fluorine-containing species

This review is composed of six vignettes. They deal with respectively: the reaction of Xe and PtF₆; the reaction of O₂ and O₃ with PtF₆; salts of O⁺, the covalent OF, and noble gas-containing cations; synthesis, reactions and structure of [XeO₂]⁺ en route to [XeF]⁺ salts; [Xe₂]⁺, green and related species; neutral xenon oxides, nonmetal oxyanions, and a nonmetal fluoride “mid-valence” crisis. Interrelations and interactions are emphasized.     

Disparities between experimental and environmental conditions: Research steps toward making electrochemical water treatment a reality

Electrochemical water treatment is one of the key topics of environmental electrochemistry. Identifying electrocatalytic materials capable of electrogenerating high oxidant species in situ seems to have catalyzed researchers’ interest in these processes. While most studies have focused on ideal lab-made solutions, translation to higher technology readiness levels and commercialization requires reframing research questions in context of real water matrices. In this current opinion, we discuss disconnects that may occur when focusing on synthetic solution treatment rather than on real waters. Future research can fill the gaps identified herein, thus facilitating application of electrochemical water treatment technologies.     

Resolution and Trace Determination of Selected Oxyanions in Binary and Ternary Mixtures by Differential Pulse Polarography

Abstract

Resolution and trace determination of selected oxyanions in binary and ternary mixtures were studied by differential pulse polarography (DPP) at the dropping mercury electrode. The applicability of DPP for the simultaneous determination of the investigated oxyanions (TeO^{2- 4}, VO^? ₃, IO^? ₃, IO^? ₄, and BrO^? ₃) in the binary and ternary mixtures was also examined with regard to the dependence of the DP current on various parameters such as pH, pulse amplitude, scan rate and drop time. Statistical analysis is included on t h e observed concentrations for each of the oxyanions in the mixture and compared with that obtained by the calibration curves. Limits of detection and quantitat - ion have been calculated for the DPP determination of binary and ternary mixtures of these lected oxyanions.