A new flowsheet for processing chromite fines by column flotation and the collector adsorption mechanism

Tailings produced from Uckopru Chromite Concentrator are composed of fines mostly below 1 mm of which 52.3 wt. % is below 0.1 mm. A new flow sheet inv olving shaking table for processing -1+0.1 mm size fraction, and High Inten sity Wet Magnetic Separator (HIWMS) and column flotation for treating -0.1 mm size fraction was put forward. According to the new flowsheet, the Uckop ru Concentrator tailings assaying 13.99 wt. % Cr2O3 was upgraded to 47.4 pe rcent Cr2O3 at a recovery of 66.4 wt. % using shaking table followed by a c ombination of magnetic separation and column flotation with a mixture of an ionic collectors at pH 11. The success of such high pH with anionic surfact ants is indeed intriguing. Electrokinetic methods were used to elucidate th e mechanism of collector adsorption and correlate the findings with the opt imum potation conditions. Multivalent constituent ions such as Cr3+, Al3+ F e2+ and Mg2+ were found to adsorb on chromite surface and shift the iep of chromite in the direction of oxide form of the mineral. The anionic collect ors also imparted a negative charge to chromite in the entire pH region. Th e positive sites on the chromite surface, onto which anionic collectors ads orb, are generated through the formation of significant amounts of hydroxy complexes of magnesium ion at pH 11. Complementary infrared data reveals th e absence of a shift in the spectra indicating the possibility of physical adsorption in the system. (C) 1999 Published by Elsevier Science Ltd. All r ights reserved.