Pyrite surface characterization and control for advanced fine coal desulfurization technologies. Eighth quarterly technical progress report, June 1, 1992--August 31, 1992

The objective of the project is to conduct extensive fundamental studies on the surface reactivity and surface hydrophobicity of coal-pyrites using various surface characterization techniques and to understand how the alteration of the coal-pyrite surface affects the efficiency of pyrite rejection in coal flotation. During this reporting period, the influence of the impurity content, particularly coal/carbon content, on the electrochemical oxidation of pyrite surfaces was investigated. The studies demonstrate that the coal/carbon content in coal-pyrite has a determining effect on the surface reactivity of pyrite. The oxidation behavior of high carbon-content coal-pyrite is completely different from that of purer coal-pyrite and ore-pyrite. The effects of flotation gases on the flotation behavior of coal and the surface hydrophobicity of various coal-pyrite were investigated. It was found from the lab-scale column flotation studies that among the various gases studied (air, oxygen, argon, nitrogen and carbon dioxide), carbon dioxide produced the best results with a combustible recovery of 90% and ash-content of less than 9 percent. Finally, the surface energetic studies revealed that the surfaces of pyrites and coals produced by wet grinding is more heterogenous than that prepared by dry grinding