The influence of water quality on the flotation performance of complex sulphide ores: Case study at Hajar Mine, Morocco

the most intensive water-consuming processes. To reduce fresh water consumption, numerous research works have focused on the use of recycled process water. However, in flotation, recycling water can have adverse effects on the mineral separation. The content of organic reagents (frothers, collectors, depressants) as well as inorganic constituents (suspended matter, base metals, calcium, magnesium, sodium, sulphite, sulphate etc.) (Leavay et al., 2001; Johnson, 2003; Slatter et al., 2009) builds up and consequently affects the flotation performance (Lui et al., 1993; Leavay et al., 2001; Seke et al.,2006; Kelebek and Nanthakumar, 2007; Haran et al., 2008; Bıçak et al., 2012; Ikumapayi et al., 2012). Generally, the hydrolyzed metallic ions in the alkaline recycled water form a hydrophilic precipitate (metal hydroxides, sulphates, or carbonates) on the mineral surfaces, resulting in the formation of a hydrophilic barrier that prevents adsorption of the collector (Senior and Trahar, 1991; Fornasiero and Ralston, 2006). Cu2+ in copper sulphate form is known as a sphalerite activator, and Zn recovery by flotation is enhanced by increasing concentrations of Cu2+ ions in synthetic water (Bıçak et al., 2012). Cu2+ can also enhance the recovery of galena, chalcopyrite, and pyrite (Coetzer et al., 2003). However, the effect of increasing copper concentration on flotation is not evident above pH 12 and below pH 5, where Cu(OH)3 and Cu2+ are respectively the stable copper species (Fornasiero and Ralston, 2006). The hydrophobicity of the sphalerite surface is controlled by the Zn(OH)2 formed (Prestidge et al., 1997; Fornasiero and Raston, 2006). For sphalerite in alkaline media, the surface Cu(OH)2 directly interacts with the xanthate (Leppinen,1990). Cyanide ions used as depressant in a polymetallic ore can produce cupric ions by reaction with copper minerals and cause inadvertent activation of sphalerite. The activation process is enhanced at higher pH values (Seke et al., 2006; Rao et al., 2011). The presence of Zn2+ in recycled water strongly depresses the recovery of sphalerite, and slightly depresses chalcopyrite and pyrite, but favours the recovery of galena (Coetzer et al., 2003). The use of zinc sulphate at alkaline pH decreases the recovery of galena due to coating by hydrophilic Zn(OH)2 (Trahar et al., 1997; Seke, 2005). The influence of water quality on the flotation performance of complex sulphide ores: case study at Hajar Mine, Morocco

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