Oxidation of aqueous sulfide solutions by dioxygen Part I: Autoxidation reaction

Abstract

The autoxidation of aqueous sulfide solutions by dioxygen is studied at pH 9 and 14 and at initial sulfide concentrations between 1 and 100 mM. Disulfide as a primary intermediate is proposed to enhance the sulfide oxidation by autocatalytically forming polysulfides. The postulate is supported by the observed acceleration of the process at increasing pH favoring the presence of disulfide rather than that of sulfur. The final reaction products thiosulfate and sulfate are proposed to result from the hydrolysis of the highly instable intermediate polythiosulfite in parallel reaction pathways, assuming probabilities for breaking the sulfur chain at the a (sulfate) and / 3 (thiosulfate) positions to be responsible for the selectivity.A reaction scheme is proposed, considering all experimental observations.

Photooxidation of sulfide, thiol, phenols, and cyclopentadiene by artificial light and solar light irradiation

“…In the dark and in the presence of a catalyst like CoPcTS catalytic oxidations of sulfide to thiosulfate [20], 2-mercaptoethanol to the disulfide [21] occur; phenol and cyclopentadiene are stable under these conditions (see equations (9), (11) and plots 1, 2 in Figure 1). …”

“…In the dark and in the absence of a catalyst or photocatalyst sulfide is slowly oxidized to thiosulfate [20], and 2-mercaptoethanol, phenols and cyclopentadiene are relatively stable.…”

“…Sulfide and thiols can be oxidized in the dark in presence of a catalyst (e.g., cobalt(II) phthalocyanine, CoPcTS) to yield thiosulfate [20], and disulfides [21], respectively (important processes in the petroleum industry for sweetening of gasoline fractions) (equations (9), (11)). …”

Microwave-assisted synthesis of WS2nanowires through tetrathiotungstate precursors

“…S dissolved ) was also validated through UV-vis spectroscopy. The absorbance bands at 232, 360 and 305 nm in the UV-vis spectra may be respectively assigned to HS − , S 2− ions [37,38] and zero-oxidation sulfur (S 0 ) in soluble state [36,39]. The band at 232 nm can be ascribed to S 2 O 2− 3 ions.…”

Hydrosulphide oxidation pathways in oxic alkaline media containing iron/cerium oxide‐hydroxide

“…Although the homogeneous oxidation of H 2 S by DO2 has been the subject of several studies (Chen and Morris, 1972;O'Brien and Birkner, 1977;Hoffmann and Lim, 1979;Steudel, 1996;Fischer et al, 1997), Herszage and dos Santos Afonso (2000) were the first who studied the heterogeneously-mediated reactions between an Fe-based oxide, hydrosulphide, and oxygen in the pH range [5][6][7]. They concluded that the reaction conducted in oxic conditions (with oxygen) is a fast surface-controlled process and that depending on the O 2 /HS À ratio, either sulphate or thiosulphate were the major products of hydrosulphide oxidation.…”