Oxidation of Coal Mine Pyrite

Abstract

The process of pyrite and marcasite decomposition as it occurs in coal mining regions is described as an electrochemical process analogous to the corrosion of iron. The polymorphic minerals, pyrite and marcasite, conduct electricity and as electrodes exhibit electromotive forces. On thermodynamic grounds the reduction of ferric ion and the reduction of dissolved oxygen can each serve as oxidizing agents to the iron disulfides. Contrary to recent published reports the reduction of water cannot serve as such. The kinetics of the aqueous oxidation of ground coal mine pyrite have been studied in a series of vessels each having a particular partial pressure of oxygen in the atmosphere over the solution. The dissolved oxygen concentration in the solution was maintained constant by rapid stirring of the pyrite suspension. The results of these experiments show that the concentration of dissolved oxygen raised to a power of about two-thirds is a rate-controlling factor. Acid pollution abatement practices which have the reduction of the dissolved oxygen concentration in waters overlying mine pyrite as their objective are therefore based on a sound principle.