To complement the data, on the aqueous oxidation
of sulphide minerals, that is, treatment of sulphides in
aqueous solution at elevated temperatures under oxygen
pressure, a study was undertaken of the aqueous oxidation
of galena in sodium hydroxide solution. It was hoped by
the study of the kinetics of the reaction to learn something
of the mechanism involved.
The reaction was followed by means of a cathoderay
polarograph. A crystal of galena was mounted in a small
autoclave equipped with suitable electrodes, and during
the course of the reaction photographs were taken at intervals
of the current-voltage curves. From the height of
the lead wave relative concentrations could be recorded,
and after a suitable time the run was stopped and the solution assayed to give absolute values to the wave heights.
The variables of oxygen partial pressure agitation,
sodium hydroxide concentration, temperature, silicate-ion,
and electrical potential were investigated. It was found
that the polarograph under these conditions gave reproducible
results.
On the basis of the experimental results three
alternative mechanisms for the reaction were proposed. One
of these was too indefinite to treat quantitatively, but
the other two were examined by calculations using the theory of absolute reaction rates. One was found to give agreement
in rate with experiment, a model in which desorption
accompanied by hydration and ionization was the rate controlling step.
The experimental results were reviewed in the
light of this mechanism and appeared to show no serious
contradictions, so this model is put forward as a postulate
of the reaction of galena with oxygen in sodium hydroxide
solution. / Applied Science, Faculty of / Materials Engineering, Department of / Graduate
| Identifer | oai:union.ndltd.org:UBC/oai:circle.library.ubc.ca:2429/41490 |
| Date | January 1951 |
| Creators | Andersen, John Enevold |
| Publisher | University of British Columbia |
| Source Sets | University of British Columbia |
| Language | English |
| Detected Language | English |
| Type | Text, Thesis/Dissertation |
| Rights | For non-commercial purposes only, such as research, private study and education. Additional conditions apply, see Terms of Use https://open.library.ubc.ca/terms_of_use. |
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