Near-neutral oxidation of pyrite in coal slurry solids. [Quarterly] technical report, September 1--November 30, 1994

In this research project we plan to determine the rate of oxidation of pyrite associated with coaly particles (coal slurry solid) when the pH of the surrounding environment is held at approximately 7.8. Coaly particles that contain pyrite are generated during the preparation of Illinois Basin coal for market. These particles are discharged to an impoundment, which eventually must be reclaimed. The purpose for reclamation is either to prevent the generation of acidic solution as the pyrite in the coal slurry solid reacts with air, or to prevent the migration of the acidic solution to a groundwater aquifer. The reclamation is usually accomplished by covering the impoundment with a four-foot-thick layer of topsoil. One possible alternative method for reclamation of a coal slurry impoundment is to mix in alkaline residue from the fluidized-bed combustion of coal. This codisposal would slow the production of acid and would also neutralize any acid produced. If the codisposal method is found to be environmentally acceptable, it will save the coal mining companies part of their cost of reclamation, and also provide a safe and useful disposal outlet for a portion of the residue that is generated by the fluidized-bed combustion of coal. During this quarter we purchased and set up two automatic titrators, which will be used in determining the rate of pyrite oxidation at nearly neutral pH. The titrators will provide a means for maintaining the pH at the desired level. The rate at which sulfate ion is produced as a result of pyrite oxidation will be used to measure the amount of pyrite oxidized over time