The effect of grinding conditions on the flotation of a sulphide copper ore

The challenge of process development for the beneficiation of Salobo’s copper ore started in 1978 and the studies still go on. Copper is predominantly present as secondary minerals, such as chalcocite, bornite, and digenite, and liberation requires very fine grinding. These minerals may undergo rapid oxidation at the alkaline pH range and under mildly oxidising conditions. The oxidation products may adsorb onto the minerals altering their surface characteristics, flotation behaviour, and may also significantly modify the mechanisms of interaction between the minerals and the collector. These facts impair the flotation process performance and increase the reagents consumption, the required flotation cells volume, and the overall processing costs. This paper describes the effect of grinding conditions on the flotation performance. Different media and mill construction materials were tested at bench scale aiming at evaluating the effects of the pulp electrochemical potential and the availability of iron oxide and hydroxide compounds on the flotation response. The results indicated that the grinding process affects significantly the flotation metallurgical performance of Salobo’s ore. The conditions that yielded the highest levels of copper recovery and the fastest flotation kinetics were rubber lined steel mill and stainless steel media.     

The effect of non-sulphide gangue minerals on the flotation of sulphide minerals from Carlin-type gold ores

Flotation pre-concentration of sulphide and gold values from certain Carlin-type deposits characterised as double-refractory gold ores is quite challenging. Numerous studies conducted on these ores in many laboratories globally (including the present study) under a variety of chemical and physical conditions have merely confirmed low recovery (and poor concentrate grades) for sulphide minerals and gold, and poor separation between sulphide minerals and carbonaceous matter, even when the valuable minerals are adequately liberated. None of the traditional reasons based on liberation or the choice of chemical and physical conditions and separation strategies could provide satisfactory explanation for the observed poor separation.In this study, the focus was on the role of non-sulphide gangue (NSG) minerals. It was hypothesised that specific NSG minerals have a detrimental effect on flotation recovery of gold bearing minerals and their separation selectivity. In order to test this hypothesis and delineate the effect of the various gangue minerals, a new approach was taken. This involved first isolating the various mineral components of a double-refractory gold ore from one of the Carlin-type deposits using a gravity separation technique. Then flotation experiments were performed using a mixture design on various mixtures of these isolated components under controlled conditions. The results of these mixture experiments supported the hypothesis and demonstrated, for the first time for these types of ores, that even small amounts of NSG minerals, especially carbonaceous matter and clays, had a large adverse effect on the flotation of sulphides and selectivity of separation. While it is tempting to attribute the observed effects solely to slime coating, there is no basis to do so at this stage; it is more reasonable to propose that multiple contributions exist. The results of this study provide the much-needed context and direction for further fundamental studies and for developing processing strategies.     

Effect of Leptospirillum ferrooxidans on the flotation kinetics of sulphide ores

The objective of this work was to determine the effect of Leptospirillum ferrooxidans on the floatability of chalcopyrite, sphalerite, and pyrrhotite by using xanthate as a collector. The tests were carried out in the absence and presence of bacteria in relation to the type of ore and contact time with bacteria. The results indicate that the chalcopyrite flotation rate significantly increased in the presence of L. ferrooxidans due to the formation of hydrophobic species. The bacteria function as a weak depressant for pyrrhotite after a conditioning time ?60 min. The behaviour of sphalerite remains without changes due to its low susceptibility to oxidation. It was concluded that L. ferrooxidans brings about superficial changes mainly due to the oxidation of minerals.     

Effect of particle size on flotation performance of complex sulphide ores

Flotation processes occurring in the bulk and froth phases have a characteristic influence on the structural features and dynamics of the flotation froth. It is recognized that the structure and texture of a mineral froth is a good indicator of flotation separation performance. The surface froth feature and dynamics are presented by three features extracted from the digitized images of the froths, i.e. SNE, a rough indication of the average bubble size of the froth, froth stability and the average grey level of the froth, an indication of mineral loading. Particle size is an important parameter in flotation operation. Nowadays, particle size is often measured and controlled in flotation concentrators. In this study the dependence of the froth structures on the particle size variation was investigated on the batch flotation of a sulfide ore from the Merensky reef in South Africa, and the size by size recovery curves were studied as well. In general medium particles produced bubbles smaller than those observed in the presence of fine and coarse particles, and the recovery rates were larger. Entrainment was a contributory mechanism to the recovery of fine particles. The fluctuation of flotation indices on the particle size change can be diagnosed and predicted by the froth structures change with a high degree of accuracy.     

Effect of ultrasonic preconditioning of pulp on the flotation of sulphide ores

The variables affecting flotation during ultrasonic preconditioning, i.e. pulp concentration, particle size and density, temperature, pressure, as well as ultrasound frequency and amplitude, were studied. An ultrasonic process for the batch flotation of sulphide ores from the Merensky reef in South Africa was designed to improve flotation performance, by selectively altering the surface properties of the target mineral particles. After ultrasonic excitation, the floatability of the sulphides improved significantly, and the silicates were also depressed to some extent. Compared to mechanical conditioning, ultrasonic radiation can improve the flotation rate, value grades and recoveries and reduce the dosages of flotation reagents appreciably.     

磨矿介质对两种铜镍硫化矿石浮选行为的影响研究

磨矿作业对矿物浮游性及浮选分离有重要的影响。本研究以分别产自中国和南非的两种不同铜镍矿为研究对象,研究了磨矿介质种类对铜镍矿石浮选行为的影响。研究结果表明,磨矿介质种类对两种矿石中铜镍矿物浮选回收率、浮游速度和脉石矿物的浮选行为的影响规律并不相同,且与报道中纯矿物体系中磨矿介质的影响规律不完全一致。与铸铁介质磨矿相比,采用不锈钢球介质磨矿后,中国铜镍矿混合浮选硫化铜浮游速度更快,可以获得较高的铜、镍品位,混合精矿中脉石含量显著降低。南非铜镍矿经铁介质磨矿后的铜、镍回收率高于惰性介质磨矿。两种矿石的矿物组成差异可能是磨矿介质对其浮选行为影响规律存在差异的主要原因。     

会泽铅锌硫化矿浮游性评价新方法

采用分批刮泡浮选试验方法,根据模糊数学中的隶属度和隶属函数,提出从可浮性和浮游速度两个方面综合评价矿物浮游性的新方法,实现了矿物浮游性的量化。应用新方法分析了会泽方铅矿、闪锌矿和黄铁矿在矿浆pH值为7.5,乙基钾黄药浓度为2.0×10-4 mol/L,硫酸锌浓度为1.5×10-4 mol/L条件下的浮游性,结果表明3种矿物的浮游性依次是方铅矿>黄铁矿>>闪锌矿,这与浮选工业实践中的结果相符合。     

Influence of sodium thiosulphate on oxidation of sulphide minerals during selective flotation of copper-nickel ores

The studies of sulphur distribution in oxidation products of pyrrhotite and chalcopyrite being components of Cu-Ni ores showed that the elementary sulphur — sulphoxide ion ratio on the mineral surface and in the liquid phase of mineral suspensions changes in the presence of sodium thiosulphate. Sodium thiosulphate exhibits properties of a reducing agent and prevents formation of hydrophobic elementary sulphur on pyrrhotite surface due to oxygen absorption and oxidation of thiosulphate-ions to sulphates. The decrease in pyrrhotite floatability is observed, and more favorable conditions are provided for selective flotation of chalcopyrite on copper-nickel ore processing. __________ Translated from Fiziko-Tekhnicheskie Problemy Razrabotki Poleznykh Iskopaemykh, No. 4, pp. 89–94, July–August, 2006.     

The effect of breakage mechanism on the mineral liberation properties of sulphide ores

The effect of particle-bed breakage mechanisms on the liberation properties of ores remains unclear. Surprisingly few studies have been published in this area and limitations in liberation measurement techniques previously used have prevented definitive conclusions from being reached regarding whether particle-bed breakage enhances the liberation properties of mineral ores relative to conventional grinding mechanisms. In this study, two sulphide ores of differing textures were comminuted to various size distributions using impact and particle-bed breakage mechanisms in a hammer mill and a piston–die compression unit respectively. The liberation properties of the various discharge samples were then characterised using a mineral liberation analyser – a mineralogical characterisation system based on automated scanning electron microscopy. It was found that the size-by-size liberation properties of both valuable and gangue mineral phases were independent of both the method used to comminute the samples, as well as the particle size distribution of the final products. These effects are discussed in terms of how they may be exploited in liberation modelling and characterising comminution circuit performance.     

The critical importance of the grinding environment on fine particle recovery in flotation

This paper examines published and new experimental evidence on the effect of the grinding environment on fine (?10 μm) value mineral recovery in flotation. Reasons for increases in fine value mineral recovery from ores with fully electrochemically inert grinding media are discussed in relation to reduced surface contamination by iron hydroxide emanating from the grinding media. The application of stirred milling technology, which allows the use of fully inert grinding media, to primary grinding applications may lead to increased fine value mineral recovery in flotation rougher applications. It is suggested that the effect of the grinding media, which is important for fine particles and progressively becomes more important as the grind size becomes finer, is principally due to the abrasion mechanism of the minerals with the grinding media in the production of fine particles. Opportunities for research and industry application are discussed.     

Dispersion effect on a lead–zinc sulphide ore flotation

This investigation was performed with samples from a lead–zinc sulphide deposit aiming at studying the influence of the dispersion degree of the particles in the pulp on lead and zinc flotation. Samples of ore and also of the minerals sphalerite, galena, pyrite, and dolomite were selected for the experiments. Nine types of dispersing agents and six blends among them were employed.A set of three dispersing agents was selected for the lead flotation and another set of three was chosen for zinc flotation. The criteria for the reagents selection were: high dispersion degree for galena and low for the other species, high dispersion degree for sphalerite and low for the other species, low dispersion degree for pyrite and high for the other species, and high dispersion degree for all species.Lead flotation experiments were performed under three conditions aiming at verifying the influence of the dispersing agent, of the pH, and of sodium carbonate. The zinc flotation tests were carried out at pH 10.5, modulated with lime.The use of dispersing agents in lead flotation did not improve the overall efficiency of the circuit for, despite improving the lead metallurgical recovery, they increase significantly the zinc losses in the lead concentrate.Sodium carbonate presented a low dispersion degree and did not affect the lead flotation results when compared with those achieved at natural pH and at pH 9.8 modulated with lime.Two dispersing agents were particularly effective in zinc flotation: dispersant 3223, a sodium polyacrylate, and sodium hexametaphosphate. Both reagents significantly enhanced zinc recovery without impairing the concentrate quality.     

The effect of frother blends on the flotation performance of selected PGM bearing ores

Concentrators processing PGM bearing ores make use of polysaccharide depressants to reduce the recovery of the undesired naturally floatable gangue minerals, mainly silicates, present in the ore. Recent work has shown that high depressant dosages can completely depress naturally floatable gangue and thus prevent it from reporting to the concentrate. These high depressant dosages can, however, have a negative effect on the recovery of valuable minerals present in the ore by reducing the stability of the froth. In order to counterbalance the effects of depressant addition, frothers are added. It is, however, preferable to maintain independent control over bubble size and froth stability which is difficult to achieve with only one frother. An alternative strategy is to use a blend of frothers, e.g. a weaker frother in combination with a stronger frother. Such a system allows an additional degree of freedom: changing the ratio of the two frothers provides more independent control of bubble size and froth stability. This study demonstrates through the use of batch flotation tests how blending low molecular weight alcohols with commercially available frothers impacts the solids and water recovery, as well as the valuable mineral recovery and concentrate grade in different PGM ores. Higher water and solids recoveries together with higher valuable mineral recoveries (>90% copper and >70% nickel) were obtained from tests using frother blends.     

Selective flotation of carbon in the Pb–Zn carbonaceous sulphide ores of Century Mine,Zinifex

Century Mine, operated by Zinifex, is one of the largest zinc and lead deposits in Australia. The ore contains sphalerite and galena as valuable minerals, and carbonaceous material is present among the gangue minerals. The presence of carbonaceous matter is detrimental to the concentration of zinc and lead by flotation. Therefore, preflotation, which is flotation in the absence of collector and prior to galena flotation, is employed to remove some of the organic carbon, some of which is naturally hydrophobic, from the flotation feed. The main issues affecting the effectiveness of preflotation are: (i) low carbon recovery, (ii) low selectivity against zinc, and (iii) very high frother (methyl isobutyl carbinol, MIBC) consumption. The present study revealed that: (a) most of the MIBC added during flotation disappears from solution due to its high adsorption onto ore particles and especially on fine carbon enriched particles which have high surface area, (b) the addition of diesel oil can reduce MIBC consumption by 50% (in laboratory flotation tests) and (c) polypropylene glycol (PPG 192) showed lower affinity for carbon surfaces due to this reagent’s higher hydrophilic/lipophilic balance, producing stable froths at 50% of the current MIBC addition.     

铁介质磨矿对锂辉石和绿柱石浮选影响的分子模拟计算研究

利用分子模拟计算方法,研究了铁球作为磨矿介质,十二胺和油酸钠分别作为捕收剂,锂辉石和绿柱石与捕收剂在磨矿前后的相互作用能。结果表明,这两种典型硅酸盐矿物经过铁球磨矿后,矿物表面吸附的铁,使阳离子捕收剂十二胺与矿物的相互作用能增大,阴离子捕收剂油酸钠与矿物的相互作用能减小,进而影响捕收剂与矿物之间的相互作用。总体来讲,锂辉石和绿柱石经过铁球磨矿后,一般会阻止十二胺阳离子捕收剂在矿物表面的吸附,而对于油酸根阴离子捕收剂,则起到一定的活化作用,有利于油酸根离子在矿物表面的吸附。     

The effect of polysaccharides and polyacrylamides on the depression of talc and the flotation of sulphide minerals

Three polymers of varying chemistries and molecular weights have been used to depress talc in a model sulphide ore consisting of talc, pentlandite, and chalcopyrite. Flotation testing revealed a distinct hierarchy of effectiveness of the polymers in the depression of talc (HP Starch > Polymer-H > Dextrin-WY) but a different order of effectiveness for depression selectivity (Dextrin-WY > Polymer-H > HP Starch). Adsorption isotherm determinations for the gangue and valuable mineral phases indicate that the differences in selectivity are partially due to adsorbed amount variations, with Dextrin-WY adsorbing marginally less on the sulphides than Polymer-H. Contact angle measurements on packed particle beds have revealed that the polymers have differing abilities to reduce the contact angle of talc and the sulphide minerals. An explanation of the observed trends is given in terms of the binding mechanisms of the polymers on the talc and the sulphide mineral phases. Order of addition effects between collector and depressant were also investigated using adsorption isotherm determinations for the polymers (collector) in the presence of a pre-adsorbed layer of collector (polymer). Adsorption of the polymers was not affected by the presence of the collector and vice versa.     

Lower temperature flotation of carbonate-fluorite ores

The authors provide insight into the problem of selective flotation of fluorite from carbonate-fluorite ores. It is found that oxyhydrate collectors used in combination with sodium fluoride provide rather high level of selectivity in fluoride flotation from poor high-carbonate ores and make it possible to eliminate high-temperature pulp treatment with acceptable reduction in the flotation temperature to 15°C and below.     

Effects of grinding environment on the flotation of Rosh Pinah complex Pb/Zn ore

The Rosh Pinah orebody is a complex lead–zinc sulphide system with pyrite gangue and minor amounts of copper. Laboratory scale milling and flotation testing of ore samples taken from this operation was performed. Different grinding media and conditions were used, including ceramic, stainless steel and steel. Flotation tests used a sequential recovery protocol for selective flotation of first the lead and thereafter the zinc. The presence of species of oxidation products on the ore after milling was probed using ethylene diamine tetra-acetic acid (EDTA) leaching. The test data show that, for comparable grinds and reagent dosages, the choice of grinding media has a marked effect on the paymetals recoveries and the selectivity. The ceramic mill produced the highest recoveries but the poorest selectivity. The steel mill produced the converse result. It is proposed that this is because the ceramic mill produces an oxidizing environment, allowing sphalerite activation by copper ions, whilst the steel mill produces a reducing environment, preventing this activation.