A facile disposal of Bayer red mud based on selective flocculation desliming with organic humics

Humics flocculant was applied in the disposal of Bayer red mud based on selective flocculation desliming process. The parameters affecting selective flocculation behavior such as flocculant dosage, slurry pH and agitation intensity were studied. For flocculating mechanism analysis, the iron mineral and the flocs product were characterized by zeta-potential testing, settling experiments, optical microscope and SEM imaging. The results show that humics exhibits a good selective flocculation performance in the high alkaline pH range. With an optimal condition of 2% solid density, flocculant dosage 30 mg L-1, Na2SiO3 dosage 200 mg L-1, slurry pH 10.0 and agitation speed 1000 rpm, the recovery of iron minerals of 86.25 +/- 1.31%, the iron grade of concentrate of 61.12 +/- 0.10%, the separation index of 0.69 +/- 0.02 can be obtained in the selective flocculation. It is found that the adsorption bridging of humics polymer dominates the selectively flocculating the iron minerals. Large flocs or aggregates with a better settling capacity are generated because of humics occurring. The maximum settling velocity of 38.23 +/- 1.51 m h(-1) is reached at pH 10. This work brings the easiness in directly recovering fine particle size of iron-bearing minerals from red mud. (C) 2015 Elsevier B.V. All rights reserved.