Computer Science
Scientific paper
May 1988
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1988gecoa..52.1077n&link_type=abstract
Geochimica et Cosmochimica Acta, vol. 52, Issue 5, pp.1077-1085
Computer Science
19
Scientific paper
The kinetic behaviour of pyrite oxidation in carbonate-buffered solution was investigated in the laboratory. Oxygen concentration, surface area and temperature were varied while pH values were limited to the range of 6.7-8.5. The rate experiments were performed on crushed and sieved size-fractions of pyrite that were carefully cleaned and mixed with similar-size silica sand. Oxidation occurred in a moisture-suction device that maintained partially-water-saturated conditions. Dilute NaHCO 3 solution and a CO 2 -O 2 -N 2 gas mixture were passed continuously through the pyritic sand. The reaction rates were monitored by sulphate mass balance in the effluent solutions. The initial rate of oxidation was found to be a linear function of surface area. The rate-dependence on oxygen concentration is non-linear and the data fit a heterogeneous kinetic model in which the surface decomposition reaction, not sorption of oxygen, is the rate-determining step. This decomposition model explains the range of linear to non-linear models reported in the literature when different values of the adsorption constant are applied. The temperature dependence follows Arrhenius behaviour with an equivalent activation energy of about 88 kJ mole -1 in the temperature range of 3 to 25°C, showing that diffusion was not rate limiting. The oxidation rates of five pyrite specimens obtained from various locales exhibited maximum differences of only about 25%.
Gillham Robert W.
Nicholson Ronald V.
Reardon Eric J.
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