Ash minerals, including pyrite, can be separated from coal by flotation, primarily making use of the natural hydrophobicity of the carbonaceous matter in coal. However, to overcome the deleterious effect of oxygen functional groups on the coal surface, an organic collector is required. The most common industrial coal flotation collector is fuel oil, but the addition of oxygenated functional groups to the collector molecule markedly enhances the flotation of lower rank and oxidized coals. This paper summarizes the results of detailed study of the flotation response of two high-sulfur coals, Illinois No. 6 coal and Pittsburgh No. 8, using different non-ionic oxygenated surfactants as the collector. The performance of these reagents is compared with that of two oily collectors, namely dodecane and nonylbenzene, and mechanisms for the interaction of these compounds with coal are suggested. (C) 2000 Elsevier Science B.V. All rights reserved.