Physicochemical studies of oxide zinc mineral flotation

University dissertation from Luleå : Luleå tekniska universitet

Abstract: At the present, zinc is produced mostly from zinc sulphide ores because the sulphides are easy to separate from the gangue and to concentrate by conventional flotation techniques but in the case of oxide zinc ores, the recovery of zinc is not enough high. The objective of the present study is to investigate the influence of different cationic, anionic and mixed collectors on the flotation of smithsonite mineral and an oxide zinc ore at various concentrations and pH values. The present thesis consists of three studies parts. First, characterization of smithsonite mineral and oxide zinc ore from the Angooran ore deposit, Iran, second, physicochemical studies on smithsonite sample include zeta- potential, contact angle, microflotation tests and adsorption studies using diffuse reflectance FTIR (DRIFT) and X-ray photoelectron spectroscopy (XPS) techniques in the presence of cationic, anionic and mixed collectors (cationic/anionic) and third, flotation behavior of oxide zinc ore from the Angooran ore in the presence of cationic, anionic and mixed collectors. According to the characterization studies of samples, the size fraction of - 125 +75 µm is selected as the liberation degree and the result of heavy liquid tests (HLS) confirms it. The results of XPS and EDX on ore samples in different size fractions showed no significant variations in zinc percentage on bulk and surface of samples. The smithsonite flotation results in the presence of dodecylamine after sulphidization using sodium sulphide show a maximum recovery (94 %) at around pH 11.5. These results are in agreement with obtained zeta-potential and contact angle measurements. Among the used anionic collectors i.e. oleic acid, hexylmercaptan, KAX alone and KAX in the presence of sodium sulphide and copper sulphate, oleic acid indicates a maximum flotation recovery (93 %) at around pH 10. Regarding the mixed collector flotation, the recovery increases with the increasing KAX concentration i.e. the flotation recovery is enhanced to 97 %. Also the recoveries and contact angles are much higher when KAX and DDA alone are used. The spectroscopic data is compared to flotation, zeta potential and contact angle results. The qualitative and quantitative evaluation of the adsorbed layer which causes the surface hydrophobicity or hydrophilicity, are performed using spectroscopic methods (FTIR and XPS). The DRIFT and XPS spectra confirm the adsorption of dodecylamine, oleic acid, hexylmercaptan, KAX and mixed collector (KAX+DDA) on the smithsonite surface. These results are in consistence with obtained zeta-potential, contact angle and also microflotation results. The studies on oxide zinc ore indicate a maximum bench scale flotation recovery of 84.5% with zinc grade 24.5% in the presence of dodecylamine at pH 11.5. There are no significant variations in recovery between cationic and anionic and mixed collectors, however, amine and mixed collector flotation are more selective than anionic collectors. The recoveries with mixed collectors show that increasing KAX, the flotation recovery enhances.