Desulfurization of coal.

Coal combustion is the largest single source of sulfur oxide pollution. Treatment of some major representative U.S. coals with aqueous ferric solution removes 40 to 75 percent of the sulfur content through near quantitative oxidation of the pyritic sulfur contained in the coal matrix. Elemental sulfur and iron sulfate are recovered as products of the reaction. Engineering assessment indicates that the system, when fully developed, offers high potential for the economic abatement of sulfur oxide pollution.