Diethylenetriamine depression of Cu-activated pyrite hydrophobised by xanthate Eric A. Agorhom ⇑ , W. Skinner, M. Zanin Ian Wark Research Institute, The ARC Special Research Centre for Particle and Interfaces, University of South Australia, Mawson Lakes Campus, Adelaide, SA 5095, Australia article info Article history: Received 24 August 2013 Accepted 6 December 2013 Available online 28 December 2013 Keywords: Flotation Depression Diethylenetriamine Surface analysis Pyrite abstract In copper sulphide flotation, copper adsorbs on pyrite through superficial oxidation of the copper miner- als (e.g. chalcopyrite) which promotes pyrite flotation in the presence of xanthate. This ‘‘inadvertent’’ activation of pyrite by copper ions is undesirable in copper sulphide flotation. In order to minimise this effect, depressants are used to suppress the effect of the activating ions. The effect of diethylenetriamine (DETA) in different combinations (under aerated and non-aerated conditions) on Cu-activated pyrite hydrophobised by xanthate was examined using flotation, spectroscopic and solution analyses, at pH 10. The results showed that DETA affects the flotation behaviour and surface chemistry of pyrite. How- ever, high dosages are required. The depression action of DETA on Cu-activated pyrite was attributed to both the removal of surface copper to form soluble Cu–DETA complex in solution and competition for Cu sites on the activated pyrite surface. The significant depression of pyrite in the presence of DETA under the aerated condition was due to increased amount of iron oxy–hydroxides (Fe–O/OH), copper oxides and Cu(I)–DETA hydrophilic species. Ó 2013 Elsevier Ltd. All rights reserved. 1. Introduction Chalcopyrite and gold are the main valuable mineral phases in most polymetallic sulphide ores, with pyrite being the main sulphide gangue mineral. Chalcopyrite and gold are mostly associ- ated with pyrite in these ores; therefore, their economical extrac- tion requires a selective depression of pyrite. The major problem associated with chalcopyrite and pyrite selectivity is due to accidental activation of pyrite by dissolved Cu 2+ or Pb 2+ ions from complex sulphide minerals through oxida- tion/dissolution reactions, which may be enhanced by galvanic interactions. This enhances pyrite interaction with thiol collectors and hence promotes its floatability. In most processing plants, so- dium cyanide is employed to depress pyrite (by removing Cu 2+ ions from its surfaces) under alkaline conditions. The environmental and health hazards associated with cyanide usage make it an un- safe approach to depress sulphides in selective flotation. As an alternative to cyanide, sulphur–oxy depressants, in the form of sul- phite (SO 2 3 ), bisulphite (HSO 2 3 ), metabisulphite (S 2 O 2 5 ) or sulphur dioxide (SO 2 2 ) have been used in depressing pyrite, sphalerite and galena (Grano et al., 1997a, 1997b; Khmeleva et al., 2002, 2003; Shen et al., 2001; Chander and Khan, 2000; Bulut et al., 2011). The general mechanism of sulphide mineral depression using sul- phite ions involves the formation of metal sulphite hydrophilic species, decomposition of xanthate and consumption of oxygen (reduction in Eh) (Misra et al., 1985; Yamamoto, 1980; Miller, 1970). Despite numerous studies on the mechanism of sulphite ions in pyrite depression, little effort has been made to understand the effect of diethylenetriamine (DETA) in selective depression of pyrite in sulphide minerals. DETA is a polyamine and soluble in water and alcohol (Weast, 1985). Generally, polyamines are excellent complexing or chelat- ing agents. The application of DETA in flotation is to depress sul- phide minerals and has been used extensively in pyrrhotite rejection in Ni–Cu ore flotation. It has been observed by Falcon- bridge Ltd., that DETA was only effective in rejecting pyrrhotite in the presence of SO 2 (Kelebek et al., 1995). The mechanism of DETA in the rejection of pyrrhotite was linked to the removal of activating ions (e.g. Cu 2+ and Ni 2+ ). The removal of activating ions from pyrrhotite surfaces in the presence of DETA resulted in a de- creased xanthate adsorption and hence reduced its floatability (Yoon et al., 1995). In another related operation (Inco operations), it was observed that DETA was only effective when pyrrhotite was extensively oxidised. This is because the activation product on the pyrrhotite surface (CuS species) is insoluble in the reducing condi- tion which is not soluble in DETA (Yoon et al., 1995). However, when pyrrhotite is oxidised, the activation product is converted to oxide/hydroxides of copper and nickel, which are more soluble in DETA. The effective role of DETA in depressing pyrrhotite has led to an investigation into its applicability in depressing other sul- phide minerals like pyrite. Sui et al. (1998) have shown that DETA 0892-6875/$ - see front matter Ó 2013 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.mineng.2013.12.010 ⇑ Corresponding author. Tel.: +61 883023692. E-mail address: Aminartey.Agorhom@mymail.unisa.edu.au (E.A. Agorhom). Minerals Engineering 57 (2014) 36–42 Contents lists available at ScienceDirect Minerals Engineering journal homepage: www.elsevier.com/locate/mineng