Contents lists available at ScienceDirect Minerals Engineering journal homepage: www.elsevier.com/locate/mineng The effect of saline water on copper activation of pyrite in chalcopyrite flotation Yufan Mu, Yongjun Peng ⁎ School of Chemical Engineering, The University of Queensland, St. Lucia, Brisbane, QLD 4072, Australia ARTICLE INFO Keywords: Flotation Chalcopyrite Pyrite Fresh water Seawater Copper activation ABSTRACT Saline water has been widely used in the flotation of copper sulfide minerals against pyrite where pyrite may be activated by copper ions emanating from copper sulfide minerals. The effect of saline water on copper activation on pyrite surface has not been studied before. In this study, the effect of seawater with a high ionic strength on the flotation of chalcopyrite against pyrite was investigated. Compared to fresh water, seawater significantly increased pyrite recovery in flotation and made the separation of chalcopyrite from pyrite more difficult. The significant increase in pyrite recovery in flotation using seawater mainly resulted from the increased copper activation on pyrite surface. Polarization analysis and EDTA extraction show that the use of seawater enhanced chalcopyrite oxidation and dissolution leading to the formation of a larger amount of copper ions available for copper activation. The flotation of pyrite in the presence of copper ions together with cyclic voltammetry (CV) measurements indicates that the copper activation process on pyrite surface was facilitated in seawater owning to the lower potential of seawater. 1. Introduction Chalcopyrite, the major mineral for copper production, is often found finely interlocked with iron sulfide minerals, particularly pyrite (Owusu et al., 2014). Pyrite is usually perceived as a gangue mineral and removed by flotation to minimize its contamination in copper concentrates (Wang and Forssberg, 1991). In froth flotation, hydro- phobic particles are supposed to attach to the rising bubbles, float to the pulp surface and are recovered as a froth product (Hirajima et al., 2016). However, the separation of pyrite from chalcopyrite in flotation is difficult due to the galvanic interaction between chalcopyrite and pyrite which facilitates the oxidation and dissolution of chalcopyrite and subsequent copper activation on pyrite surface (Finkelstein, 1997; Peng et al., 2003). On the other hand, flotation is a water-intensive process and the flotation efficiency is highly dependent on water quality (Castro and Laskowski, 2011). Fresh water is an ideal water resource for froth flo- tation (Qiu et al., 2016). However, the scarcity of fresh water resources and the increasingly stringent environment regulations on water usage and discharge have led to the reuse of water with a high ionic strength (Liu et al., 2013). For mining operations located near the seashore or in highly arid regions, the use of saline water becomes a sustainable so- lution to alleviate the pressure of water shortage (Laskowski et al., 2014). Today, a great number of base metal sulfide flotation plants in Australia, Canada, Chile and Indonesia are operated in seawater or underground water with a high ionic strength (Kurniawan et al., 2011; Jeldres et al., 2016). The flotation process using saline water is highly complex due to the presence of salts. Compared to fresh water, saline water has a high concentration of inorganic electrolytes including the primary ions of Na + and Cl - , and the secondary ions of Ca 2+ , Mg 2+ , SO 4 2- and HCO 3 - , etc. (Kester et al., 1967), which may have a positive or nega- tive effect on the flotation of chalcopyrite and pyrite. It is well known that the presence of some inorganic salts (e.g., KCl, NaCl, Na 2 SO 4 , MaCl 2 and CaCl 2 ) in water inhibits bubble coalescence thus increasing froth stability while reducing bubble size (Craig et al., 1993a, 1993b; Quinn et al., 2007; Del Castillo et al., 2011). Froth stability and bubble size are important parameters in flotation influencing both true flota- tion and mechanical entrainment (Wang et al., 2013). In addition, saline water often has a high conductivity and a low dissolved oxygen (DO) concentration (Fondriest, 2013, 2014). The high conductivity may promote the galvanic interaction between chalcopyrite and pyrite, while the low DO concentration may be accompanied by the low po- tential which favors copper activation of pyrite (Peng et al., 2012). In the present work, the effect of saline water on the separation of pyrite from chalcopyrite in flotation and the underpinning mechanism https://doi.org/10.1016/j.mineng.2018.11.032 Received 2 August 2018; Received in revised form 16 November 2018; Accepted 19 November 2018 ⁎ Corresponding author. E-mail address: yongjun.peng@uq.edu.au (Y. Peng). Minerals Engineering 131 (2019) 336–341 0892-6875/ © 2018 Elsevier Ltd. All rights reserved. T