Selenium aqueous solution chemistry

Aqueous solution chemistry of sulfur, selenium and tellurium... 

A method to circumvent the problem of chalcogen excess in the solid is to employ low oxidation state precursors in solution, so that the above collateral reactions will not be in favor thermodynamically. Complexation strategies have been used for this purpose [1, 2]. The most established procedure utilizes thiosulfate or selenosulfate ions in aqueous alkaline solutions, as sulfur and selenium precursors, respectively (there is no analogue telluro-complex). The mechanism of deposition in such solutions has been demonstrated primarily from the viewpoint of chemical rather than electrochemical processes (see Sect. 3.3.1). Facts about the (electro)chemistry of thiosulfate will be addressed in following sections for sulfide compounds (mainly CdS). Well documented is the specific redox and solution chemistry involved in the formulation of selenosulfate plating baths and related deposition results [11, 12]. It is convenient to consider some elements of this chemistry in the present section. 

Yang, L., Shahrivari, Z., Liu, P.K.T. et al. (2005) Removal of trace levels of arsenic and selenium from aqueous solutions by calcined and uncalcined layered double hydroxides (LDH). Industrial and Engineering Chemistry Research, 44(17), 6804-15. 

The interactions between solid compounds, such as the rock materials, and the aqueous solution and its components are as important as the interactions within the aqueous solution, because the solid materials in the geosphere control the chemistry of the ground water, and they also contribute to the overall solubilities of key elements. The present review therefore also considers the chemical behaviour of solid compounds containing selenium. A list of selenium containing minerals is presented in Appendix D, but no thermodynamic data are available for the minerals. It is, however, difficult to assess the relative importance of the solid phases for performance assessment purposes, particularly since their interactions with the aqueous phase are in many cases known to be subject to quantitatively unknown kinetic constraints. Furthermore, in some circumstances sorption of aqueous ions at mineral water interfaces may be a more important factor in determining migration of selenium than dissolution and precipitation phenomena. 

D.L. Rabenstein (University of California, Riverside) is investigating the biological chemistry of selenium compounds in intact erythrocytes to characterize transport across the erythrocyte membrane and their intracellular metabolism. Reactions will be characterized in erythrocytes, plasma, and aqueous solution by nuclear magnetic resonance (NMR) spectroscopy. Methods will be developed for the determination of selenols, diselenides, and selenosulfides in biological fluids and erythrocytes by high performance liquid chromatography (HPLC) and electrochemical detection. The HPLC methods will be used to determine metabolites formed at trace levels. 

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