Kinetics of decomposition of tetrathionate, trithionate, and thiosulfate in alkaline media

Abstract

hydrolysis rate constant of 2,4-DOE were observed. These observations are mutually consistent with a rapid, reversible partitioning of 2,4-DOE between water and "dissolved" humic substances. The humic-bound 2,4-DOE is not adsorbed to glass and is protected from alkaline hydrolysis. On the basis of this model, with aquatic humus concentrations expressed as g of C/g of H20, the distribution coefficient of 2,4-DOE between water and aquatic humus (Kb) was calculated from both the glass adsorption data and the alkaline hydrolysis data, yielding log Kb values of 4.4 and 4.8, respectively.From the magnitude of the distribution coefficient of 2,4-DOE between water and "dissolved" humic substances, a significant interaction is generally expected for hydrophobic compounds in natural waters. Rates of alkaline hydrolysis, volatilization, etc., would be expected to be reduced in proportion to the fraction of a hydrophobic solute that is associated with humic substances.If any general acid-base catalysis of the hydrolysis reaction is attributable to humic substances, that contribution is completely masked by the partitioning phenomenon, which strongly decreases the rate of alkaline hydrolysis of 2,4-DOE.

Recovery of Gold from Pregnant Thiosulfate Solutions by the Resin Adsorption Technique

“…In addition, in the thiosulfate leaching system, copper and ammonia are added to accelerate gold dissolution through the formation of copper (II) ammine complexes. However, a problem associated with the use of cupric ammine is that it accelerates the oxidation of thiosulfate to produce tetrathionate, which is also unstable and can be easily degraded into trithionate and thiosulfate [91][92][93][94][95], as presented in Equations (18) and (19 The degradation products of thiosulfate, particularly polythionates including trithionate and tetrathionate, will intensely compete with gold (I) thiosulfate complex for active sites in the resins, and low concentration of them in the leach solution will decrease gold loading capacity of the resins tremendously. Therefore, it is very necessary to minimize the generation of them in the leaching stage to ensure an efficient gold recovery from the pregnant thiosulfate solutions by the resin adsorption technique.…”

An electrochemical study of the dissolution of gold in thiosulfate solutions. Part II. Effect of Copper

“…It has been long known that copper(II) can greatly catalyze the homogeneous oxidation of thiosulfate by a variety of oxidizing agents, including oxygen in aqueous solutions. The oxidation of thiosulfate by oxygen under ambient conditions in the absence of copper ions is known to be extremely slow [18,20]. The catalytic activity of copper is usually explained by assuming that the copper(II) ion rapidly oxidises thiosulfate by the above reaction, followed by re-oxidation of copper(I) to copper(II) by dissolved oxygen.…”

Water-Chemistry and On-Site Sulfur-Speciation Data for Selected Springs in Yellowstone National Park, Wyoming, 1996-1998

“…In the hot springs, high temperature and the presence of oxidation-catalyzing bacteria cause these reactions to proceed at a much faster rate than in cooled and filtered samples stored for later analysis. For example, S 2 O 3 is oxidized rapidly to SO 4 at high temperatures, but this reaction proceeds at a negligible rate (Rolla and Chakrabarti, 1982) under typical sample-storage conditions. Major oxidation products are expected to be SO 4 and S 2 O 3 , with elemental S, polythionates (S n O 6 2-), and polysulfides (S n 2-) as minor products.…”