Characterization and dewatering of fine coal tailings by dual-flocculant systems

Characterization of fine coal tailings using a variety of techniques reveal that it is composed of 30% clay minerals (kaolinite and illite), 23% muscovite, 26% quartz and 20% coal with little amount of carbonate minerals. Various flocculant combinations and their order of additions are utilized to understand the ability of dual flocculant systems on dewatering of these fine coal tailings. Settling rate and turbidity are used as criteria for screening and measuring the performance of anionic, cationic and nonionic flocculants. Dual flocculation of tailings has been tested with the aim of identifying if the synergy reported for mono-disperse systems is also valid for multicomponent systems. While the nonionic-cationic combination leads to the highest settling rates, the lowest turbidity values were obtained when using the anionic-nonionic combinations. The mechanism of interaction of dual polymers with particle surfaces and their synergy are discussed with the help of settling and turbidity data. The turbidity values obtained in mono-flocculation tests using nonionic and cationic flocculants and those made with dual flocculation combinations reveal that this kind of flocculant combinations play an unfavorable role in the flocculation of coal preparation plant tailings though there are contrary systems reported in the literature.