| The goal of this study was to compare the rate of abiotic oxidative pyrite dissolution of pyrite samples from various geological origins, and to evaluate of the feasibility of using electrochemical techniques to study pyrite oxidation mechanisms and kinetics of these samples.; The rate and extent of pyrite dissolution was investigated with five sedimentary and three hydrothermal pyrite samples in a highly controlled batch reactor at pH 3 and 6 with dissolved oxygen ranging from 9 to 12 ppm. The eight pyrite samples exhibited different dissolution rates under identical redox and pH conditions; three sedimentary pyrite samples associated with coal exhibited much faster and greater extent of dissolution than the other five samples. These differences can be attributed to differences in their specific surface area, and in their trace element content.; The feasibility of using the electrochemical techniques to study pyrite dissolution kinetics and relative pyrite dissolution characteristics was assessed. Although cyclic voltammetry and steady-state voltammetry can be used to investigate the pyrite oxidation reaction mechanisms and assess the influence of parameters in kinetic rate expressions, the actual dissolution rate of each pyrite sample cannot be obtained with this approach. However, it was demonstrated in this work that the rate of pyrite dissolution can be controlled by applying a fixed potential on a solid or carbon paste pyrite electrode. The rate of pyrite dissolution associated with different applied potentials was determined by measurement of dissolution products in solution. Only controlled pyrite dissolution conducted under the mixed potential region on the solid electrodes reflected the same pyrite reactivity and dissolution rate order as in the batch dissolution studies. Carbon paste electrodes were not useful for studying the relative dissolution reactivity of pyrite from different environments. |
