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http://nopr.niscpr.res.in/handle/123456789/16092| Title: | Role of manganese dioxide in the oxidation of aqueous sulphur(IV) in oxic and anoxic suspensions |
| Authors: | Gupta, Krishna S Singh, Rajeshwar Saxena, Deepa S V, Manoj Sharma, Madhu |
| Issue Date: | Nov-1999 |
| Publisher: | NISCAIR-CSIR, India |
| Abstract: | The kinetics of direct oxidation of Sulphur(IV) by MnO2 has been
studied in stirred suspensions in nitrogen atmosphere and that of autoxidation reaction in stirred suspensions in equilibrium with atmospheric oxygen. Sulphate has been detected to be the only oxidation product of sulphur(IV) in both the cases. In the pH range 4.6-5.8, the kinetics of direct oxidation of sulphur (IV) in anoxic suspensions agreed with the rate law (I). On
the other hand at pH 7.9 for the same reaction a much simpler rate law (II)
is obeyed.
-d[S(IV)]/dt = {(A[H+]-1+B)[MnO2]0 [S(IV)]0 }/ { 1 +C[S(IV)]0[H+]-1} ... (I) -d[S(IV)]/dt = {k3K3[MnO2]0 [S(IV)]0}/{1 +K3[S(IV)]0} ... (II) At 30°C, the values of empirical constants are: A = 4.8×10-10 mol g-1 s-1; B = 2.8×10-5 L g-1 s-1; C = 1.1 × 10-3; k3 = 9.3 ×10-7 s-1 and K3 = 34. For MnO2 catalysed autoxidation in oxic suspensions the rate data pertaining to pH range 4.6-5.8 fitted Eq. (III) and those -d[S(IV)]/dt = k3[MnO2]0 [S(IV)]0[H+]-0.34 ... (III) -d[S(IV)]/dt = k8[MnO2]0 [S(IV)]0[H+]-0.4 ... (IV) in the pH range 6.5-7.0 fitted Eq. (IV). At 30°C, k5 and k8 have values of 1.4 × 10-4 L0.66 g-1 mol-0.34 s-1 and 3.2 L1.4 g-1 mol-0.4 s-1. The rate of autoxidation is independent of oxygen partial pressure. The atmospheric conversion rates at 30°C have been calculated. |
| Page(s): | 1129-1138 |
| Appears in Collections: | IJC-A Vol.38A(11) [November 1999] |
Files in This Item:
| File | Description | Size | Format | |
|---|---|---|---|---|
| IJCA 38A(11) 1129-1138.pdf | 2.39 MB | Adobe PDF | View/Open |
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