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A study of the "roast-reaction" of lead sulfide

University of British Columbia

The kinetics and mechanism of the "roast-reaction" of lead sulfide have been examined. The investigation, partitioned by the nature of the problem, included a study of (a) the "roast" which is the several reactions between galena (lead sulfide) and oxygen (or air) yielding oxides, sulfates and basic sulfates of lead, and (b) the reduction "reaction", between lead sulfide and the oxidation products of the roast leading to the production of lead metal. The mechanism of the roasting of lead sulfide does not lead to the formation of distinct PbO and PbSO₄ phases. The products appear to be a mixture of basic sulfates throughout. The rate of the reaction between PbS and PbO or PbSO₄ has been shown to be controlled by the transport of SO₂ from the reacting surface with gas velocities up to 5 cm./min. Under conditions of reduced pressure (<5mm. of Hg) the reduction reactions are shown to be heterogeneous and probably proceed by the adsorption of PbS vapor on the oxidized surface to form a (PbS.xPbO)‡ basic sulfate type activated complex which subsequently decomposes to lead metal. The stoichiometry of this heterogeneous reaction has been checked for the PbS-PbO case with the use of a Pb²¹² tracer. The average value was measured to be 1PbS + 3.4 PbO →4.4Pb + - - - .

Text

2012-01-25

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http://hdl.handle.net/2429/40292

Mining Engineering

University of British Columbia

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