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PGM Recovery from Mine Waste
Published in Hossain Md Anawar, Vladimir Strezov, Abhilash, Sustainable and Economic Waste Management, 2019
PGMs are principally extracted from two types of deposits, namely the platinum rich layered mafic intrusion (e.g. Bushveld in South Africa and the great Dyke in Zimbabwe) and palladium-rich nickel sulfide deposits (e.g. Norilssk-Talnakh in Russia). In both types of deposits, there is a strong association between the PGMs. Natural PGM deposits are almost always related to basic igneous rocks and are closely associated with copper, nickel and iron sulphides. The concentration of PGM in these ores differs quite markedly depending on the origin and this has a significant bearing on the manner in which they are refined (Bernardis et al., 2005).The average concentration of these metals in the earth crust is estimated to be in the range of 0.001–0.005mg/kg for Pt., 0.015mg/kg for Pd, 0.0001mg/kg for Rh, 0.0001mg/kg for Ru, 0.005mg/kg for Os and 0.001mg/kg for Ir (Mack, 2005). Considerable treatment of the original PGM bearing ore is required before a product suitable for final refining is obtained.
Flotation of Platinum Group Elements Ores: A Review
Published in Mineral Processing and Extractive Metallurgy Review, 2023
P. Sahu, P. Dash, M. S. Jena, N. R. Mandre
Vermaak, Pistorius and Venter (2005) investigated the PGE ores of Mimosa mine, Great Dyke, and confirmed the presence of an appreciable amount of PGE through different characterization studies. PGEs are present in the form of Pd-Bi-Te. Electrochemical and Raman spectroscopy studies were carried out to know the interaction of xanthate with Pd-Bi-Te. The presence of xanthate and dixanthogen on the surface is confirmed using Raman spectroscopy, and dixanthogen is found in the anodically polarized surface of the mineral. Generally, in South African ore (except UG2), PGE minerals are primarily associated with BMS. Hence, assuming that the PGE minerals will behave similar to BMS, the same reagent regimes were used in PGE flotation, which is suitable for sulfide flotation. The study shows that PGE minerals which are associated with tellurides and arsenides being reported in flotation tailings. The arsenide has poor floatability characteristics, which lead to a significant loss of PGE minerals during flotation (Shackleton, Malysick and O’Connor 2007). When the ore is treated with sodium isobutyl xanthate (SIBX), it increases the recovery of Pt and Pd minerals, but adding CuSO4 as an activator decreases the rate of flotation (O’Connor and Shackleton 2013; Shackleton, Malysick and O’Connor 2007). It is found that dixanthogen is the active species for flotation and the presence of CuSO4 hinders the flotation rate. In the case of PtAs2 relatively small number of Pt blebs and their high arsenic concentrations reduced the extent of xanthate conversion to dixanthogen. The negative effect of Cu on the recovery may be due to Cu(OH)2 precipitation on the mineral surface. When xanthate ions are added, the hydrophilic Cu(OH)2 group already occupies most of the active sites and reduces the xanthate adsorption directly on the Pt, Pd mineral surface sites. The hydrophilic species coat the outer surface of the targeted minerals (Corin et al. 2021). As the surface gets covered by colloidal Cu(OH)2 species, thus inhibiting the adsorption of xanthate or to makes slow conversion of the hydrophilic Cu(OH)2 mineral surface to hydrophobic Cu(I)X species (O’Connor and Shackleton 2013; Shackleton, Malysick and O’Connor 2007). A study is carried out to evaluate the performance of the reagent suite on the PGE ore of Mimosa mine, Zimbabwe (Nashwa 2007). The synergistic effect of SIBX (Tri-thiocarbamate) TTC, and DTP was investigated. It is observed that SIBX in combination with DTP improves both sulfide and PGE+Au recovery each by 10% as compared to SIBX treated on its own. It may be because of DTP as a co-collector helps to recover the fine particles (<25µ) and stabilizes the froth life. The SIBX at a dosage of 530 g/t gives a good grade and recovery for PGE ore of Mimosa mine, Great Dyke, Zimbabwe. DTP mixed with SIBX at a 1: 1.3 mole ratio gives the best result in terms of sulfur and PGE+Au recovery (Nashwa 2007).