Activation of oxidized surface of anthracite waste coal by attrition
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University of Belgrade
Jovica M. Sokolovic   

University of Belgrade, Technical Faculty Bor, Department of Mining, Vojske Jugoslavije 12, 19210, Bor, Serbia
Publication date: 2012-01-01
Physicochem. Probl. Miner. Process. 2012;48(1):5–18
In this paper the activation of oxidized surface of anthracite waste coal was investigated. Coal weathering leads to physical and chemical changes on the coal surfaces and a reduction of its hydrophobicity and floatability. The changes and the presence of oxygen functional groups in the structure and surfaces coal was confirmed by the FTIR study on the raw and waste coal. The groups have remarkable impacts on surface charge and thus flotation kinetics. The floatability of oxidized coal may be improved by the creation of fresh, unoxidized surfaces on coal by attrition at high solid concentration prior to introducing coal to the froth flotation process. This paper presents the results of the effects of attrition on the floatability of the oxidized surface of waste coal, coal pyrite and alumino-silicate minerals through electrokinetics and microflotation experiments. The results show that the attrition, in the viscous pulp with the solid content of 50%, lead to the mechanical cleaning of oxidized surface and activation of the surface of coal particles, which agrees with the change of zeta potential and increasing floatability of coal by 10%. Obviously that the mechanical scrubbing may be able to restore the natural floatability of superficially oxidized coal by removing the thin oxidation layer from the coal surface. The results show that attrition time is an important parameter from the point of view of activating the oxidized coal surface, and positive changes in zeta potential and floatability. The change of zeta potential, as a measure surface charge state of coal particles, from -15 mV to about 0 mV, after attrition for 30 minutes, confirms positive application of attrition. Zeta potential approaching 0 mV resulted in increasing floatability down to the real possibilities of the attrition process prior the coal flotation.