Search

he efficiency of mineral flotation relies on the ability to selectively recover different value minerals into their respective concentrates at optimum grades and recoveries based on the differing hydrophobicities. Many of the common hydrophobizing reagents (collectors) currently used in flotation have significant occupational and environmental implications, and hence there is a quest for environmentally benign chemical additives that give similar or better performance than the more toxic conventional reagents. In this paper, we provide substantial experimental evidence that the use of edible, fatty acid-based oils (canola and palm) can foster the flotation recovery of chalcopyrite and molybdenite minerals more selectively against pyrite than the conventional collectors, sodium isopropyl, potassium amyl xanthates and diesel oil. Single and mixed chalcopyrite/pyrite minerals and plant sulphide ores’ flotation studies using canola and palm oils, in contrast with conventional collectors, are reported herein. The results indicate greater efficacy of the canola and palm oils in comparison with the conventional collectors for chalcopyrite and molybdenite recoveries and product upgrades. This is believed to be due to the edible oils’ specific interactions with iron oxides sites preferentially formed in situ on the surfaces of the chalcopyrite or molybdenite in the pulp rather than on the pyrite surfaces, causing limited recovery of the pyrite. Complementary contact angle results confirmed that more canola oil is adsorbed onto chalcopyrite surfaces than onto pyrite surfaces. For the mineral mixtures tested, the edible oil's degree of unsaturation had a noticeable effect on its performance as a collector. A higher pyrite recovery and slightly lower chalcopyrite grade was obtained with palm oil than with canola oil. These findings suggest that the use of canola oil has a potential to add to the existing array of flotation collectors and would represent a combined opportunity for both the mining and agricultural sectors, with concomitant health, environmental and economic benefits. Refereed/Peer-reviewed

The aim of this paper was to review how the use of zeta potential measurements on suspensions of selected non-sulphide minerals in the presence of oleate could provide additional information on these interactions. From this literature review it was found that the presence of oleate causes a reduction in both the zeta potential and isoelectric point of these minerals compared to their values in the absence of oleate. There have been a number of suggested mechanisms including the precipitation of undissociated oleic acid, adsorption of soluble oleate solution species (monomers, acid-soap complex or dimers) and precipitation of oleate salts and/or oleate colloids or micelles, depending on the pH and the concentration of oleate in solution. Physical adsorption of oleic acid droplets at acidic pH values has also been postulated. These phenomena are investigated in this review in order to consolidate the results of a significant number of systems leading to a better understanding of the interactions of oleates with non-sulphide minerals. Where appropriate, results of oleate interactions on these minerals using other techniques have been included as supporting evidence. This combination of information should lead to an enhancement of subsequent oleate flotation of these minerals which will have significant industrial benefits. Refereed/Peer-reviewed

The aim of this paper was to investigate how the use of zeta potential measurements on the hematite-oleate system as a function of pH could provide additional information on this system. From the literature survey it was found that the presence of oleate causes a reduction in both the zeta potential and isoelectric point of hematite compared to their values in the absence of oleate. There have been a number of suggested mechanisms including the adsorption of soluble oleate solution species and precipitation of oleate salts and/or oleate colloids or micelles, depending on the pH and the concentration of oleate in solution. These phenomena were investigated using two hematite samples containing differing amounts of silica. The results for oleate addition to the hematite sample containing the lower amount of silica followed the anticipated trends indicating lower values of zeta potential and isoelectric point with increasing oleate addition. The situation for the hematite sample containing the higher amount of silica, even though it only contained 2.5% silica, was more complex. Although the increased addition of silica reduced the values of the zeta potential, there appeared to be a major influence of the silica driving the values of the zeta potential below those of the oleate at acid values of pH. It was proposed that this was due to a combination of the presence of silica and oleate, suggesting that the mechanism was the physical adsorption or heterocoagulation of colloidal hematite on fine silica followed by the adsorption of oleate species onto the hematite. An attempt was made to correct the equilibrium oleate concentration to account for the adsorption of oleate onto the surface of the hematite, but this was only significant at the very low addition rate of the oleate. Refereed/Peer-reviewed

Laboratory flotation tests were conducted to investigate the role of pH, zinc sulphate and potassium metabisulphite in the flotation of galena and marmatite in the Broken Hill orebody. Marmatite was depressed under alkaline conditions alone, however the addition of the two depressants, either individually or combined, resulted in the greatest selectivity. The use of zinc sulphate under alkaline conditions resulted in good selectivity whilst maintaining a high lead recovery. The addition of potassium metabisulphite under alkaline conditions reduced zinc recovery, but high additions reduced lead recovery. The addition of both depressants at alkaline pH produced the best result, with a lead concentrate of 72.6% at 98% recovery with less than 4% zinc recovery. The overall aim of the study was to minimise the flotation of marmatite into the galena rougher concentrate, which was achieved under the conditions given above.