Shear flocculation and flotation of hematite using sodium oleate

The separation of ultrafine (< 10 mu m) hematite from quartz using sodium oleate as a selective flocculant has been investigated. The main factors affecting hematite flee size were found to be oleate concentration, pH, shear rate and agitation time. Flocculation was found to occur only when the solubility of oleic acid in solution was exceeded. The flocculation rate and flee size were found to increase if the oleic acid droplets were produced in the presence of the mineral particles. The hematite flocs produced were found to be resistant to breakage over a range of shear rates from 300 to 2200 s(-1). The strength can be attributed to the attractive forces clue to hydrocarbon chain association and hydrophobic interactions, The hydrophobic flocs produced with sodium oleate were found to be readily recoverable by flotation. Rougher flotation recoveries of 94% were achieved to a concentrate grade of 46% Fe from a mixed hematite/quartz feed containing 15% Fe. Shear flocculation of ultrafine minerals prior to flotation therefore offers a possible means of significantly improving mineral recovery. (C) 1997 Elsevier Science B.V.