The Oxidation of Sulphur Dioxide and the Formation of Sulphuric Acid in Situ at Atmospheric Pressure in the Leaching of a Uranium Ore

Abstract

The oxidation of SO2 to form H2SO4 in situ, at atmospheric pressure and temperatures from 25 to 80°C, was examined by passing a mixture of SO2 dioxide and air for 7 hrs through a reaction vessel containing quartz- or uranium-bearing solids moistened with H2O to 85% solids. At the end of the contact period the solution was analyzed for free acid and other constituents of SO2 and extraction of Uranium.In tests with quartz at 80°C, the addition of Fe2(SO4)3 or Fe2O3 increased the amount of SO2 converted to H2SO4. E.g. without Fe2(SO4)3 added the conversion obtained was 2% with 0.7 and 2.3 1b/ton quartz of Fe2(SO4)3 the conversions were 18 and 24% respectively.Tests were conducted on a mixture of flotation tailings, and a residue, which contained 24.3 per cent Fe+++ as oxide, derived from the roasting of a sulphide concentrate at 500°C. The tailings and sulphide concentrate were obtained from the flotation of a uranium ore containing brannerite and about 9 per cent pyrite Roasting of the sulphide concentrate yielded "160 to 180 lb per ton of ore of sulphur dioxide of which 80,to, 100 lb was introduced into the conversion system over a 7-hour period. At 80°C, 40 per cent of the sulphuric dioxide introduced was converted to sulphuric acid which dissolved 93 per cent of the uranium in the mixturet of solids.