Grinding and flotation experiments on a Pb-Zn ore were carried out to evaluate : 1) wear of the grinding media both in the presence and absence of an inhibitor and 2) effect of the inhibitor on the flotation of Pb-Zn minerals. The percentage reduction in the wear of the grinding media was observed to be between 25-36%, depending on the type of the inhibitor and its critical concentration. The inhibitors used in the investigation were sodium sulphite, sodium nitrite, sodium chromate and sodium silicate. The results indicate that a specific corrosion inhibitor, for example sodium sulphite, may give better recoveries and grades in flotation but is not as efficient as sodium chromate in inhibiting the wear of the grinding media. Pulp solutions (after grinding) analysed for metal ion concentrations showed low Fe. Iron released into the solution as a result of corrosion reactions subsequently forms insoluble hydroxy complexes and may coat the mineral surfaces. Such hydrophilic coatings may adversely affect the floatabilities of minerals. The particle size analysis of the ground product has been carried out and the results are discussed.
The particle surface properties are essential for understanding froth flotation, particularly for the evaluation of various chemical or reagent effects.Dynamic Vapor Sorption (DVS) is used in the pharmaceutical industry for the evaluation of surface properties and has to the knowledge of the authors not been used for applications in mineral processing. This paper describes an evaluation of industrial ore samples using DVS.Four samples (feed, CuPb concentrate, Cu concentrate and Pb concentrate) from each of the Cu - Pb flotation processes in the Boliden and Garpenberg concentrators, Sweden, were analyzed by DVS in order to investigate if this technique could be used to estimate differences in their hydrophilicity. The DVS measures the water uptake as a function of the relative humidity (%RH) at constant temperature.For both series of four samples, it was found that the DVS-data are in precise agreement with the flotation theory on hydrophobicity (indicated by differences in water uptake). The feed material, without any collectors, adsorbed more water compared to the CuPb bulk concentrate, which in turn adsorbed more water than the Cu concentrate. The lead concentrate on the other hand, which had been depressed by dichromate and should be more hydrophilic, showed a higher adsorbance of water than that of the CuPb concentrate.The repeated measurements of three sub samples from one of the ore samples gave a mean value and an estimated standard deviation of 0.13 ± 0.01%. This shows that the method gives highly reproducible results and that the differences between the samples had high significance. This also shows that the DVS method can serve as a useful complement to traditionally used contact angle or capillary absorption-based measurement methods, especially when screening for new flotation reagents on industrial ore samples.
The surface tension and foamability of a series of polypropylene glycols (PPG) with average molecular weights (MW) ranging from 200 to 2000 g mol-1 and hydrophilic-lipophilic balance (HLB) values ranging from 10.4 to 5.8 were compared to methyl isobutyl carbinol (MIBC), 4-methyl-2-pentanol (MW102 g mol-1 and HLB 6.1). Experiments were carried out using a modified Bikermann column in which the foam heights were determined at a range of gas flow rates and retention times were calculated at different foamer concentrations. These studies show the six-carbon polypropylene glycol (PPG400) with HLB value of 9.7 is an unusually strong frother. Since many industrial foamers/frothers commonly contain a mixture of chemical types, we have also studied the foaming behaviour of mixed systems of PPGs and MIBC at a range of concentrations. The foaming data indicated that a synergistic effect occurred for several of the mixed systems with differences in HLB values, which resulted in an increase in foam height compared to the performance of the individual systems. Dynamic surface tension measurements, determined in the short time span range of 0.1–10 s, correlated with the synergistic effect and it was found that the blended systems gave a higher dynamic surface tension gradient compared to the individual PPGs. It could be suggested that the mixed foamer (containing high HLB and low HLB value components) produce closed packed, molecular cohesive films at the air/solution interface giving greater surface elasticity, which appeared to increase foamability
The Kringel Mine (Woxna Graphite AB) in Hälsingland, Sweden is one of the largest graphite flake deposits in the world with over 10 million tons of ore suitable for open cast mining. Concentration of crystalline graphite is carried out through a combination of flotation, gravimetric and magnetic separation. In the present study, several polyethylene oxide type frothers were evaluated as flotation frothers for the graphic ore. From (a) laboratory dynamic and equilibrium surface tension experiments, (b) froth equilibrium height measurements, (c) bench scale flotation tests and (d) plant trials, it was shown that polyoxypropylene glycol butyl ether (MW 300 and HLB 6.5) was the most effective frother for the graphic particles. The frother was found to produce closed packed, molecular cohesive films at the air/solution interface with high elasticity at low concentrations, which prevented bubble coalescence. The plant has been successfully using this frother as a replacement for MIBC since July 1997.
The application of hydrophobic magnetite seeding to concentrate hematite ultrafines (<10 µm) in slimes using a high gradient magnetic separator (HGMS) with coarse expanded metal matrices was investigated. It was shown that the selective aggregation at high shear rate of the seeded hematite particles (produced by surface treatment with sodium oleate and colloidal magnetite) could significantly enhance the HGMS capture of hematite ultrafines. The mechanism of selective aggregation was discussed in terms of the combination of hydrophobic and magnetic interactions.