An instrumented leach column for the study of sulphide oxidation in waste heaps.

The construction commissioning and first year of operation of a large scale instrumented leach column are described. The column material was sulphidic mine overburden. Monitored parameters included matrix potential temperature redox potential dissolved oxygen pore space gas water addition and drainage together with pH, Cd, Cu, Fe, Ni, Zn, Cl, F, SO42 and PO43 in the effluent

Alpha decay radioisotopes

A detailed review is made of the experimental techniques that are available or are in the process of development for the determination of 238U, 235U, 234U, 231Pa, 232Th, 230Th, 228Th, 228Ra, 226Ra, 223Ra, 210Po and 210Pb. These products of the uranium and thorium decay chains are found in uranium mine tailings. Reference is also made to a procedure for the selective phase extraction of mineral phases from uranium mine tailings

Bacterial leaching of uranium ores - a review.

The bacterial leaching of uranium ores involves the bacterially catalysed oxidation of associated pyrite to sulphuric acid and Pe3+ by autotrophic bacteria and the leaching of the uranium by the resulting acidic, oxidising solution. Industrial application has been limited to Thiobacillus thiooxidans and Thiobacillus ferrooxidans at pH 2 to 3, and examples of these are described. The bacterial catalysis can be improved with nutrients or prevented with poisons. The kinetics of leaching are controlled by the bed depth, particle size, percolation rate, mineralogy and temperature. Current work is aimed at quantitatively defining the parameters controlling the kinetics and extending the method to alkaline conditions with other autotrophic bacteria

A vibrational spectroscopic ¹⁸O tracer study of pyrite oxidation

Pyrite was oxidised under 18O2 gas in H216O solutions, with and without added ferric ion, and the sulfate produced was analysed by vibrational spectroscopy to determine the relative amounts of sulfate isotopomers (S16On18O4-n2-) formed. At 70°C and pH 1, with no added Fe3+, the majority of the sulfate formed was that which derived all four oxygen atoms from water (i.e., S16O42-), but significant amounts of two other isotopomers, S16O318O2- and S16O218O22-, which derive one or two oxygen atoms from molecular oxygen were observed. When Fe3+ was added at the start under identical conditions, no S16O218O22- was observed. The major isotopomer formed was still S16O42-, with S16O318O2- present as a minor product. Experiments which were performed at initial pH 7 yielded similar results, as did others performed at 20°C, although the amounts of the minor isotopomers formed vary with temperature. All of the results were confirmed by performing identical experiments with the source of the oxygen isotopes reversed, that is, by oxidising pyrite under air in H218O solutions and obtaining the same products in isotopic reverse. © 1991