Influence of important factors on flotation of zinc oxide mineral using cationic, anionic and mixed (cationic/anionic) collectors Majid Ejtemaei a , Mehdi Irannajad a,⇑ , Mahdi Gharabaghi a,b a Department of Mining & Metallurgical Engineering, Amirkabir University of Technology, Hafez Ave., Tehran, Iran b School of Mining Engineering, College of Engineering, University of Tehran, Tehran, Iran article info Article history: Received 3 December 2010 Accepted 31 May 2011 Available online 1 July 2011 Keywords: Cationic collector Flotation Mixed collectors Zinc oxide abstract In this study, the influences of important factors on smithsonite flotation are investigated. Dosages of sul- phidizing agent and collector, desliming prior to flotation and the use of sodium hydroxide instead of sodium carbonate as the pH regulator are essential to the effective recovery of smithsonite in cationic flo- tation. The appropriate temperature for flotation was found to be 30–40 °C. Sodium hexametaphosphate (SH) and sodium silicate had the greatest selectivity between smithsonite–calcite and smithsonite– quartz, respectively. The results of oleic acid flotation showed that the grade and recovery of zinc were relatively low in comparison with the sulphidization-cationic flotation method. Despite using sodium sil- icate and SH as depressants in oleic acid flotation, flotation was not selective. Flotation using mixed col- lectors (Armac C + Potassium Amyl xanthate) showed promising results. The ratio of the mixed collectors and the sequence of addition of mixed collectors were important criteria in attaining true mixed collector flotation. Ó 2011 Elsevier Ltd. All rights reserved. 1. Introduction The most common flotation technique used commercially for the treatment of zinc oxide minerals is sulphidization with Na 2 S, followed by treatment with conventional cationic collectors, namely amine (Mckenna et al., 1949; Rey, 1954; Abramov, 1961; Önal et al., 2005; Pereira and Peres, 2005; Keqing et al., 2005; Hosseini and Forssberg, 2006a; Irannajad et al., 2009). The main flotation characteristics of cationic collectors are lower selectivity and higher reagent consumption. Several amines were tested but a dodecylamine derived from vegetable oil proved to be the most suitable (Billi and Quai, 1963), and several amine salts were also investigated (Armac C, Armac T, Flotigam SA, Flotigam TA and Armeen TD), of which Armac C gave the best results (Irannajad et al., 2009). After sulphidization the mineral surface becomes less hydro- philic due to the presence of the chemisorbed sulfide ion, and in our case, floats more efficiently. Under these conditions, collector consumption may also be reduced significantly (Önal et al., 2005). Excess sodium sulfide acts as a depressant for oxidised lead and zinc minerals because adsorption of divalent sulfide ions on the sur- face of lead oxide minerals increases the negative charge, which prevents the adsorption of collectors (Malghan, 1986; Ozbayoglu et al., 1994; Önal et al., 2005; Pereira and Peres, 2005; Hosseini and Forssberg, 2006a; Irannajad et al., 2009). Flotation using carboxylic acid is applicable for oxide zinc ore if the gangue is silica or clay minerals (Gaudin, 1957). If there are limestone and dolomite as gangue minerals, these are also float- able during smithsonite flotation (Rey, 1979). A process involving the use of mixed anionic and cationic collectors for zinc oxide min- erals has been investigated (Hosseini and Forssberg, 2007). A sys- tem containing two surfactants of different charges is called a catanionic system. The attraction between the differentially charged head groups leads to a decrease in the area per head group (Herrington et al., 1993). The mole ratio of anionic/cationic collectors has a significant effect on smithsonite flotation (Hosseini and Forssberg, 2007). In smithsonite flotation, the optimum ratio of the mixed collec- tors was KAX (Potassium amyl xanthate): DDA (Dodecylamine), 3:1 at pH 11.5 in the presence of 2000 g/t sodium sulfide. The pres- ence of KAX increased the DDA adsorption due to the decrease in the electrostatic head–head repulsion between the surface and ammonium ions and increase in the lateral tail–tail hydrophobic bonds (Hosseini and Forssberg, 2006c). The effect of depressing agents on the flotation of oxidized zinc minerals containing 17% Zn was studied by Marabini et al. (1994). Four classes of reagents, such as guar, starch, celluloses, and acrylic polymers were used. The Zn recovery ranged from 70% to 80%, and the Zn grade from 27% to 29%. Moreover, the compounds having the best separation efficiency were tripoly- phosphate and guar of the methylcarboxylic sodium salt. 0892-6875/$ - see front matter Ó 2011 Elsevier Ltd. All rights reserved. doi:10.1016/j.mineng.2011.05.018 ⇑ Corresponding author. Tel.: +98 21 64542900; fax: +98 21 66405846. E-mail address: iranajad@aut.ac.ir (M. Irannajad). Minerals Engineering 24 (2011) 1402–1408 Contents lists available at ScienceDirect Minerals Engineering journal homepage: www.elsevier.com/locate/mineng