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Abstract
Selective flocculation has long been suggested as a method for the treatment of ultra-fine particles typical of which are those produced in a desliming process ahead of coal flotation. Methods reported include the modification of particle surface and/or the modification of the flocculant. The paper describes further investigations into the possible use of a range of commercially available polyacrylamides with a calgon dispersed suspension. Sedimentation tests suggest adsorption mechanisms for individual coal and shale species while funnel separation results reveal preferential adsorption of the polymer onto the coal surface. It is shown that the resulting selectivity and efficiency is dependent upon the polymer and calgon dosages while polymer molecular weight has minimal effect. Subsequent surface modification by oleic acid and creosote promoters improved selectivity but product ash contents below 30% were unobtainable. It is concluded that shale entrapment in the sedimentation and some affinity- of the polymer to the shale surface excludes the use of water soluble polyacrylamides.