Decomposition of aqueous dithionite. Part II. A reaction mechanism for the decomposition of aqueous sodium dithionite

Wayman, Morris; Lem, Winnie

doi:10.1139/v70-127

Cited by 53 publications

(26 citation statements)

References 7 publications

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“…The pH of the solutions was found to be 5.8, 6.5, 7.1 and 7.6, respectively without adjusting the pH level externally. This is in agreement with the earlier report [22]. The samples were stirred continuously and analyzed for Cr(VI) after 15, 30, 45 and 60 min.…”

Section: Resultssupporting

confidence: 92%

Complete Reduction of Hazardous Cr(VI) in Chromium Ore Processing Residue Dump Site

Murugaiyan¹,

Sehar²,

Selvaraj³

et al. 2018

Asian J. Chem.

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Section: Resultssupporting

confidence: 92%

Complete Reduction of Hazardous Cr(VI) in Chromium Ore Processing Residue Dump Site

Murugaiyan¹,

Sehar²,

Selvaraj³

et al. 2018

Asian J. Chem.

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“…The more rapid reaction, represented as [4] HSz04-+ HS02--t S~0 3~-+ HSO3-+ H + is catalyzed by election acceptors such as sulfide or sulfur which result in free radical formation (3, 6) The shapes of the decomposition curves and the data, such as those of Table 3, suggest that the function of the stabilizing cations is anti-catalytic.…”

Section: Discussionmentioning

confidence: 99%

The decomposition of aqueous dithionite III. Stabilization of dithionite by cations

Lem¹,

Wayman²

1970

Can. J. Chem.

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At the same conditions of pH (3.5 to 5.0), temperature (23 "C), and concentration (1 to 10 x M), ZnSZO4 is more stable in aqueous solution than Na2SZ04, and the rate of decomposition is much less sensitive to [H+]. At pH 4.5 and 5.0, the decomposition of the Zn salt is essentially linear, whereas the Na2S20, decomposes slowly at first, during an induction period, and then rapidly by an autocatalytic reaction. The rate of decomposition of dilute aqueous Na2S204 at pH about 4 is slowed greatly by the addition of small quantities of In3+, CdZ+, or ZnZ+. The effect of the stabilizing ions is attributed to anti-catalytic action.Canadian Journal of Chemistry, 48, 2778Chemistry, 48, (1970 IntroductionExperiments and Results ZnS204 is used industrially as a reducing agent or for bleaching, especially by the pulp and paper industry. It is unstable in aqueous solution, especially under acidic conditions, but the kinetics and mechanism of its decomposition have not been investigated. Qualitatively it is known to be more stable than Na2S,04 under similar conditions of pH (1). Following our studies of the kinetics and mechanism of the decomposition of Na2S20, (2, 3), aqueous ZnS204 was studied in the same manner. The dependence of its rate of decomposition on p H was determined. Methods of stabilizing dithionite by cations such as Zn2+ were tried since, if successful, they could be of commercial significance.'Present address: Imperial Oil Enterprises Ltd., Sarnia, Ontario. (a) Decomposition of ZnS204Several concentrations of ZnS204 from 0.8 to 8.0 x M were studied, some at fixed p H values in the same way as aqueous buffered Na2S204 described in Part 1 (2), and some in unbuffered solution, with p H measurement (3). The continuous polarographic method previously described (4) was used to determine the concentration of ZnS204 against time continuously; the experimental arrangements are shown in Fig. 2 48, 1970 solution in this range of p H is characterized by a slow "induction" period followed by a much more rgpid autocatalytic reaction. The decomposition of ZnS204 in the same p H region does not follow the same course. Figure 1 shows the decomposition of4 x MZnS204 at pH4.0. It is seen that there is a gradual increase in the rate of decomposition, but the division into an induction period and an autocatalytic period is by no means obvious. This figure may be compared with Fig. 5 of ref. 2 showing the decomposition of 5 x M Na2S204 at p H 4.0. In the case of the sodium salt the curve is sharply S-shaped: an induction period of about 10 min is followed by a sharp decrease in concentration, decomposition is half complete at 14 min and essentially complete at 17 min. The initial rate of decomposition of the zinc salt is in fact somewhat more rapid, but the change in slope is less sharp, although there appears to be a distinct change at about 25 min, and decomposition, which is half complete at 30 min, is essentially complete at 60 min. At higher p H the rate of decomposition is slower and nearly linear; decomposition is h...

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“…In the experiments in more acidic media, dithionite is rapidly consumed by its decomposition. For example, it has been reported (Wayman and Lem, 1970) that at pH 4 and 296 K, dithionite concentration falls rapidly to zero after an induction period of around 5 min. The same autoacceleratory behavior has been reported at higher pH values, but with a longer time scale (e.g., 20 min at pH 6 and 333 K) (Rinker et al, 1965).…”

Section: The Outer Sphere Pathwaymentioning

confidence: 98%

Dithionite as a Dissolving Reagent for Goethite in the Presence of Edta and Citrate. Application to Soil Analysis

Rueda

1992

Clays and clay miner.

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Abstract--A synergistic effect of reductant and complexant is observed in the dissolution of goethite by dithionite and citrate or EDTA. The rate data are interpreted using the surface complexation approach to describe the interface of the reacting oxide. Adsorption of both $202 (D) and complexant (L) generates =-Fe D three surface complexes that define the dissolution behavior: ~Fe-D, -~Fe-L, and dimeric -Fe L surface complexes. The initial rate increases at lower pH values because of increased surface complexation conditional formation constants. At pH values below 4, however, the fast decomposition of $20,~ gives rise to a rapid depletion of reductant, and total dissolution is not observed. It is shown that for best analytical results in soil analysis, EDTA is a better complexant than citrate; the iron extracted in one dithionite-EDTA treatment at pH 5-6, under N2 at 315 K is not increased by increasing the number of extractions, and is equivalent to the total extractable iron found by previous procedures.

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Decomposition of aqueous dithionite. Part II. A reaction mechanism for the decomposition of aqueous sodium dithionite

Cited by 53 publications

References 7 publications

Complete Reduction of Hazardous Cr(VI) in Chromium Ore Processing Residue Dump Site

Complete Reduction of Hazardous Cr(VI) in Chromium Ore Processing Residue Dump Site

The decomposition of aqueous dithionite III. Stabilization of dithionite by cations

Dithionite as a Dissolving Reagent for Goethite in the Presence of Edta and Citrate. Application to Soil Analysis

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