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Lakefield, Canada

Gibson C.E.,Queens University | Kelebek S.,Queens University | Aghamirian M.,SGS Canada Inc.
International Journal of Mineral Processing | Year: 2015

At present, nearly 99% of the world's niobium concentrate is produced by the Catalão and Araxá mines in Brazil and the Niobec mine (St. Honoré) in Canada. In total, Araxá produces approximately 150,000 tonnes of niobium per annum (tpa), while Niobec and Catalão produce 5300 tpa and 4500 tpa, respectively. Niobium recovery at all three operations is near or above 60%, with final concentrates grading 55-65% Nb2O5. The geographic diversification of niobium supply depends on the development of operable beneficiation flowsheets for the upgrading of known niobium deposits worldwide. The beneficiation of niobium oxide ores is predominantly carried out by froth flotation, which generally involves niobium mineral flotation at acid pH using a cationic amine collector. In the case of the Niobec and Catalão mines, there is a reverse gangue mineral flotation step prior to niobium flotation. The main issues associated with currently employed flowsheets are loss of niobium to the gangue mineral concentrate and the slime fraction. Further, there are a number of gaps in understanding with regard to the mechanisms by which amine collectors and auxiliary reagents interact with one another and with niobium minerals. To date, several alternate flotation reagents such as hydroxamates, sulfosuccinates, phosphorous compounds, and hydroxyquinolines have been examined with the aim of improving niobium recovery and concentrate grade in the flotation process. Notably, alkyl hydroxamates were identified in the 1960s as a potential collector for direct niobium mineral flotation eliminating the need to first deslime the ore. Subsequent testwork performed on Niobec ore using this collector has corroborated its effectiveness without desliming. However, due to increased reagent addition requirements when using hydroxamate collectors, the cost benefit of this reagent scheme compared to amine collectors is unclear. Overall, greater understanding of mechanisms at play in currently employed reagent systems is required to effectively improve plant operating conditions and maximize recovery at the industrial scale. Future testwork should also be conducted on real ores using reagents that have been identified as selective collectors at the single mineral flotation level. © 2015 Elsevier B.V. All rights reserved.


Jordens A.,McGill University | Marion C.,McGill University | Langlois R.,McGill University | Grammatikopoulos T.,SGS Canada Inc. | And 2 more authors.
Minerals Engineering | Year: 2016

The beneficiation of rare earth element (REE) minerals may include many different beneficiation unit operations, but the final process choice typically depends on the inherent mineral characteristics. The Nechalacho REE deposit contains multiple low specific gravity, diamagnetic silicate gangue minerals (predominantly feldspars and quartz) and high specific gravity, iron oxide minerals (magnetite and hematite). The valuable REE minerals (REM) in the deposit consist of a variety of relatively high specific gravity, paramagnetic minerals. A process has been proposed to concentrate the value REM through a combination of gravity (rejecting silicate gangue) and magnetic (rejecting iron oxide gangue) separation steps prior to froth flotation.This work employed a laboratory-scale process including two different gravity separation steps (Knelson and Falcon centrifugal concentrators) followed by a series of varying intensity wet drum magnetic separation steps as well as dry induced roll magnetic separation and wet high intensity magnetic separation steps. The resultant fractions have been characterized by XRD, ICP-MS, and QEMSCAN to identify the optimum fraction for downstream flotation separation. The combination of a Knelson Concentrator with low intensity wet drum magnetic separation was found to efficiently concentrate REM while also rejecting high specific gravity iron oxide minerals. A novel finding from this study is the concentration of heavy REE-bearing zircon into coarse size fractions after grinding. © 2016 Elsevier Ltd.


Marion C.,McGill University | Jordens A.,McGill University | McCarthy S.,McGill University | Grammatikopoulos T.,SGS Canada Inc. | Waters K.E.,McGill University
Separation and Purification Technology | Year: 2015

Muscovite mica is a naturally occurring phyllosilicate mineral with a wide range of industrial applications. This work investigated the separation of muscovite from unwanted gangue minerals in a mica ore. Electroacoustic zeta potential measurements and single mineral flotation tests were used to determine the effect of Custamine 8113 (collector) and Norlig-H (depressant) on muscovite. These results were then compared to those of gangue minerals (feldspar and quartz). Muscovite showed an isoelectric point (IEP) at pH 3.5. Feldspar and quartz did not have an IEP, having negative zeta potentials over the pH range investigated (pH 3-10). This suggests that effective separation using a cationic amine collector, which relies on electrostatic attraction as the basic mechanism of adsorption onto mineral surfaces, would not be possible without the use of a depressant. Zeta potential measurements and single mineral flotation tests in the presence of both Custamine 8113 and Norlig-H indicate that reagent adsorption is controlled by Custamine 8113 in the case of muscovite and by Norlig-H in the case of feldspar and quartz. This suggests that effective separation of muscovite from the gangue minerals present in the mica ore is possible. These results were used to determine optimal flotation conditions of the ore. Concentrates from the ore flotation were examined by QEMSCAN analysis, which showed that muscovite was effectively separated from gangue minerals. © 2015 Elsevier B.V. All rights reserved.


Kapsiotis A.,University of Patras | Grammatikopoulos T.A.,University of Patras | Grammatikopoulos T.A.,SGS Canada Inc. | Tsikouras B.,University of Patras | Hatzipanagiotou K.,University of Patras
Resource Geology | Year: 2010

The Pindos ophiolite complex, located in the north-western part of continental Greece, hosts various podiform chromite deposits generally characterized by low platinum-group element (PGE) grades. However, a few locally enriched in PPGE + Au (up to 29.3 ppm) chromitites of refractory type are also present, mainly in the area of Korydallos (south-eastern Pindos). The present data reveal that this enrichment is strongly dependant on chromian spinel chemistry and base metal sulfide and/or base metal alloy (BMS and BMA, respectively) content in chromitites. Consequently, we used super-panning to recover PGM from the Al-rich chromitites of the Korydallos area. The concentrate of the composite chromitite sample contained 159 PGM grains, including, in decreasing order of abundance, the following major PGM phases: Pd-Cu alloys (commonly non-stoichiometric, although a few Pd-Cu alloys respond to the chemical formula PdCu4), Pd-bearing tetra-auricupride [(Au,Pd)Cu], nielsenite (PdCu3), sperrylite (PtAs2), skaergaardite (PdCu), Pd-bearing auricupride [(Au,Pd)Cu3], Pt and Pd oxides, Pt-Fe-Ni alloys, hollingworthite (RhAsS) and Pt-Cu alloys. Isomertieite (Pd11Sb2As2), zvyagintsevite (Pd3Pb), native Au, keithconnite (Pd20Te7), naldrettite (Pd2Sb) and Rh-bearing bismuthotelluride (RhBiTe, probably the Rh analogue of michenerite) constitute minor phases. The bulk of PGE-mineralization is dominated by PGM grains that range in size from 5 to 10 μm. The vast majority of the recovered PPGM are associated with secondary BMS and BMA, thus confirming that a sulphur-bearing melt played a very important role in scavenging the PGE + Au content of the silicate magma from which chromian spinel had already started to crystallize. The implemented technique has led to the recovery of more, as well as noble, PGM grains than the in situ mineralogical examination of single chromitite samples. Although, the majority of the PGM occur as free particles and in situ textural information is lost, single grain textural evidence is observed. In summary, this research provides information on the particles, grain size and associations of PGM, which are critical with respect to the petrogenesis and mineral processing. © 2010 The Authors. Journal compilation © 2010 The Society of Resource Geology.


Melashvili M.,SGS Canada Inc. | Melashvili M.,University of British Columbia | Melashvili M.,Barrick Gold Corporation | Dreisinger D.,University of British Columbia | Choi Y.,Barrick Gold Corporation
Minerals Engineering | Year: 2016

The gold thiosulphate system has been studied for some time due its prospective favourable economics over the gold cyanide system when treating certain ore types. Despite the large amount of work which has been done with gold thiosulphate system, various questions (uncertainties) still remain. For example, the causes for slow gold dissolution kinetics in thiosulphate and the gold losses during leaching observed in some applications. In this study, cyclic voltammetry was used to investigate the oxidation and reduction of gold in magnesium thiosulphate electrolyte. The anodic dissolution of gold is discussed in terms of possible reactions and mechanisms involving catalysts such as thallium and thiourea. The abrupt increase in anodic current in the presence of these catalysts indicates that the passivation of gold anodic dissolution is related to surface phenomenon and not to the depletion of thiosulphate ion at the reaction interface. The Tafel-like plots identified the increase of exchange current for gold oxidation and reduction reactions for catalyst assisted systems. The large anodic to cathodic peak separation ranged between 0.25 V and 0.37 V allowed most of the leached gold to diffuse away from the electrode. This indicates the electrochemically quasi-reversible to irreversible character of this system even in the presence of catalysts. The relationship between reduction peak current and concentration of gold thiosulphate in the bulk electrolyte was estimated based on relevant equation for electrochemically irreversible reaction. © 2016 Elsevier Ltd. All rights reserved.

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