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1、Effect of iron content in sphalerite onflotationAbstractThe effect of 4iron,* substituted in the mineral* lattice, on the froth flotation of sphalerite has been investigated at alkaline pH. It has been found that a critical copper sulphate concentration exists where sphalerite recovery is maximized,
2、 above which the recovery of sphalerite then decreases. The presence of iron* in sphalerite is detrimental to the rate of sphalerite flotation and hence its recovery, with the coarser particles being more affected that the fines. The presence of iron reduces the activation of sphalerite by copper, w
3、hich in turn results in a reduction in collector adsorption.Keywords： Froth flotation; Flotation activators; Flotation kinetics; Particle sizeArticle Outline1. Introduction2. Experimental section3. Results and discussion4. Conclusions References1. IntroductionAs xanthate collectors have a relatively
4、 low affinity for zinc ions, activation of sphalerite by copper ions is generally required to float sphalerite. The activation of sphalerite involves the exchange of zinc for copper ions, thus providing a surface receptive towards collector adsorption (Finkelstein, 1997). One of the main impurities
5、present in sphalerite is 4 iron,* which substitutes for zinc atoms in the sphalerite lattice, thus reducing the number of zinc atoms available for exchange with copper. Previous studies investigating the effect of 4 iron* content in sphalerite on copper activation, collector adsorption and subsequen
6、t sphalerite flotation have produced conflicting results (Pomianowski et al., 1975, Mukherjee and Sen, 1976, Solecki et al., 1979, Nakahiro, 1980, Harris and Richter, 1985 and Gigowski et al., 1991). For example, both an increase and decrease in copper activation, collector adsorption and froth flot
7、ation of sphalerite have been reported with increasing 4 iron content in sphalerite. The loss of sphalerite to tailings in flotation circuits as a result of inadequate particle surface hydrophobicity reduces the economic viability of the 4 processingoperation. Thus an understanding of the effect tha
8、t 4ironA in sphalerite has on the flotation behaviour of thismineral* may allow us to maximise sphalerite recovery. In the present study, we have investigated the effect of 4 ironA content in sphalerite on sphalerite flotation as a function of particle size. These flotation results were correlated w
9、ith the amount and type of copper and collector adsorbed on the sphalerite surface.2. Experimental sectionThe chemical composition of the low 4 iron* content sphalerite sample, ZnS, (Carthage, TN, USA) was 66.7% Zn, 0.3% Fe and 32.7% S (0.06% Cu and 0.07% Pb) while that of the high 4ironA content sp
10、halerite sample, (Zn, Fe)S, (Broken Hill, New South Wales, Australia) was 53.2% Zn, 12.5% Fe and 32.7% S (0.47% Cu and 0.24% Pb). Scanning electron microscopy confirmed that the 4iron* present in the sample was in fact incorporated in the sphalerite particles, and not present as individual pyrite in
11、clusions. The collector, sodium iso-propyl xanthate (SIPX), was re-crystallised from ethanol.ZnS and (Zn, Fe)S (250 g each) were ground in a Galigher mill with stainless steel rods and 0.3 dm3 of demineralised water (pH 12.0) to produce a flotation feed with a d90 of 45 pm. The sample was transferre
12、d to a 3.0 dm3 Agitair flotation cell and conditioned at pH 11.0 with CuSO4, collector and then frother (Aerofroth 65) with each stage having a 2 min conditioning period. The concentrates were then collected for 0.5, 2, 4 and 8 min (for a total of 8 min) of flotation by bubbling air through the 4 mi
13、neral卜 pulp at 4 dm3/min. The -45 pm fraction of each concentrate and tail sample was passed through a pre-cyclone rig. The underflow was sized with a Warman cyclosizer (6 size fractions collected) whilst the overflow constituted the sub 4 pmparticle size fraction. All size fractions were analysed b
14、y ICP-MS (Amdel Pty. Ltd., Australia) for total zinc and 4iron,* and the relative amounts of ZnS and (Zn, Fe)S in each of the size fractions determined.A first order rate equation, R = Rmax(1 e-kt), was used to fit the curves of flotation recovery, R, versus time, t, and to obtain the flotation rate
15、 constant, k, andmaximum flotation recovery, Rmaxat each particle size.3. Results and discussionThe cumulative recoveries of ZnS and (Zn, Fe)S as a function of particle size, flotation time and CuSO4 concentration are shown in Fig. 1. With no copper addition the total recoveries were too low for a s
16、ize analysis of the concentrates. With CuSO4, flotation recovery increases sharply with particle size up to approximately 25 pm, and then levels off or decreases for the coarser particles. This decrease in recoveries of the coarser particles is more pronounced at the higher CuSO4 concentrations and for (Zn, Fe)S.(窜)KL-IIJAOO必100200 0 10 20 30 400 10 20 30 40 0 10 20 30 40 5040208(604()Paj licle diameter (microns)Fig. 1.
