Improving copper flotation recovery from a refractory copper porphyry ore by using ethoxycarbonyl thiourea as a collector

In this paper, N-propyl-N-ethoxycarbonyl thiourea (PECTU) collector was investigated to concentrate copper minerals from a refractory copper porphyry ore through bench-scale and industrial flotation tests. The flotation results indicated that PECTU had strongly collecting power for copper sulfide minerals and excellent selectivity against iron sulfide minerals under moderately alkaline conditions. Compared with sodium butyl xanthate (SBX), PECTU increased the grades and recoveries of Cu, Au and Mo in the copper concentrates, and performed the flotation separation of Cu/Fe sulfide minerals at cleaner pH ∼10.5 as well as decreased 2/3 lime consumption. The results of UV-visible measurements further demonstrated that PECTU could be used as a high selective collector for copper minerals. The experimentally obtained results have been explained from the structure-reactivity relationship of collector by density functional calculation.     

The flotation separation of scheelite from calcite using a quaternary ammonium salt as collector

The flotability of scheelite and calcite was studied with Dioctyl dimethyl ammonium bromide (BDDA). The experiments were conducted on individual and mixed minerals as a function of pH with a micro-flotation cell. And oleic acid was tested for comparison. The flotation results revealed that the performance of BDDA is better than that of oleic acid and the best separation could be achieved with BDDA over the pH range 8-10. Through preliminary analysis, it is concluded that BDDA reacts with scheelite through electrostatic interaction.     

The effect of acrylamide-co-vinylpyrrolidinone copolymer on the depression of talc in mixed nickel mineral flotation

Copolymers of acrylamide and vinylpyrrolidinone with varying compositions have been synthesised and employed to depress talc in a model flotation system with process plant operation conditions. Adsorption isotherms indicated that the hydrophilic acrylamide homopolymer has a very low affinity for the hydrophobic talc surface, whereas vinylpyrrolidinone homopolymer strongly adsorbs onto the talc surface. Micro-flotation experiments revealed that the copolymer system can induce stronger talc depression than the homopolymer variants, with the most effective copolymer depressant having 25-30% vinylpyrrolidinone incorporation. The copolymer system is observed to have inherited the strong talc affinity of vinylpyrrolidinone polymer and the strong hydrophilic property from polyacrylamide. This combined effect facilitates the desired strong talc depression in single mineral flotation. However, this copolymer system has similar adsorption affinity on both the talc and pentlandite, hence depressing both talc and pentlandite in the mixed mineral flotation system. This research shows that a sufficient hydrophobic balance on the polymer is necessary for the adsorption and subsequent depression for talc. However, polymer with high adsorption selectivity is required to be a successful synthetic talc depressant for mixed mineral system.     

The behavior of N,N-dipropyl dodecyl amine as a collector in the flotation of kaolinite and diaspore

The flotation behaviors of kaolinite and diaspore were investigated using N,N-dipropyl dodecyl amine (PN). Maximum recoveries of kaolinite and diaspore were about 90% and 50%, respectively. Both recoveries of kaolinite and diaspore increased with the increasing dosage of PN. On the basis of the zeta potential and FT-IR spectra, the ionization of surface hydroxyl and the isomorphic exchange of surface ions account for the charging mechanisms of surfaces of kaolinite and diaspore. The adsorption mechanism of PN on the surface of two minerals was mainly electrostatic. After reacting with PN, the zeta potential of kaolinite and diaspore both increased, and comparing with the original zeta potentials, potential of kaolinite increased much more than that of diaspore, this can explain why recovery of kaolinite is higher than that of diaspore.     

The effect of the reagent suite on froth stability in laboratory scale batch flotation tests

In batch flotation tests conducted on ores from the Merensky reef, changes in froth stability invariably occur with variations in the reagent suite. The main reagents are collectors (primary and secondary), activators, depressants and frothers. Since the particles entering and leaving the froth in a batch flotation system are continuously changing, the stability of the froth can vary. Under these conditions the simplest measure of froth stability is the measure of water recovery at a fixed froth height. The batch flotation system developed at UCT allows for the separation of gangue which is entrained relative to gangue which is floated. It has been found that the presence of naturally floatable gangue (NFG) leads to froth stabilisation, whereas the presence of hydrophobic sulfide minerals may lead to destabilisation of the froth depending on the hydrophobicity (contact angle) of the sulfide minerals. This can vary with ore type since particle shape and amount of particles present can influence the extent of destabilisation. At low depressant dosages sodium isobutyl xanthate (SIBX) always results in lower froth stability than sodium ethyl xanthate (SEX). The frothing nature of dithiophosphate leads to increased froth stability and the addition of copper sulfate results in destabilised froths. Increasing depressant dosage reduces the stabilising influence of NFG and the depressant type (guar gum or CMC) also affects froth stability. Frother can be used in an attempt to overcome the destabilising effects of high depressant dosage. This work examines the effect of variations in the reagent suite and uses water recovered at a fixed froth height as an indication of froth stability in order to analyse these effects on the recovery of sulfide minerals, floatable gangue and entrained gangue.     

The influence of the oxidation state of pyrite and arsenopyrite on the flotation of an auriferous sulphide ore

In this paper, the influence of the oxidation state of pyrite and arsenopyrite on the flotation of an auriferous sulphide ore was investigated by different techniques, including electrode, pulp potentials, DRIFT spectroscopy and microflotation tests. In addition, the gold and sulphide recoveries were also investigate, in a laboratory-scale cell, as a function of pulp potential and reagent concentration. It was verified that the presence of oxidation products on the sulphide mineral surface demands a higher collector concentration in order to achieve a satisfactory sulphide recovery. The electrochemical behaviour of pyrite and arsenopyrite indicated that a nitrogen atmosphere can lead to a low pulp potential, which inhibits the formation of oxidation products, enhancing both the free gold and sulphide recoveries. Although copper sulphate activates even oxidised sulphide surfaces, it does not improve free gold recovery.     

The role of a flash flotation circuit in an industrial refractory gold concentrator

In order to determine the contribution of the flash flotation circuit to the overall plant performance of the Kanowna Belle concentrator, two survey campaigns both with and without the flash circuit in operation have been conducted on two distinctly different ore types: a very high grade ore, and a very low grade ore of higher hardness. Using two different ores with the same target valuable mineral species (gold and pyrite) through the same treatment route allows any trends in performance to be more easily identified. As both survey campaigns involved running the plant with and without the flash flotation circuit in operation, the significant contribution of the flash flotation cell to overall plant recovery and final concentrate grade is highlighted. The flash circuit on this plant may be considered as the primary rougher, contributing in excess of 42% of the valuable material that is recovered to the final concentrate stream, at a grade of approximately 35% sulphur; and in-so-doing reducing the overall plant footprint that would otherwise be required to achieve the same recoveries at the target concentrate grade.Mineralogical analysis of survey samples shows that the feed to the flash flotation cell (cyclone underflow) is of a much higher grade and contains a higher proportion of well liberated valuable material as compared to the conventional flotation circuit feed (cyclone overflow). Maximising the recovery of this material before it re-enters the milling circuit should be of paramount importance to optimising overall plant performance.When the flash flotation circuit is taken off-line the recovery of sulphur (and hence pyrite) is observed to decrease dramatically, and whilst the recovery of gold also decreases, it is to a much lesser extent. The difference in the recoveries of gold and pyrite that is observed without the flash flotation circuit in operation is most likely attributable to a change in the way the gold is being liberated as a function of the change in grinding circuit operation that is required when the flash circuit is taken off-line. The distribution of valuable material in the cyclone overflow stream (conventional flotation feed) undergoes a step change when the flash circuit is taken off-line with an increase in the amount of valuable fines being generated, which is further reflected in the flotation tails with a higher proportion of both pyrite and gold being present in the intermediate and fine size classes. This increase in the amount of pyrite fines in particular may have contributed to the loss in recovery that was observed when the flash flotation circuit was taken off-line.Pulp chemistry data from various points around the flotation circuit highlight the different processing conditions in the flash cell, compared to the conventional circuit, which will impact on the type of minerals able to be recovered by flotation, as well as reagent selection for this type of processing application.     

The effect of a new polysaccharide on the depression of talc and the flotation of a nickel–copper sulfide ore

The effect of the depressant galactomannan (KGM) on the depression of talc and the flotation of a nickel–copper sulfide ore have been investigated through microflotation, batch flotation and industrial flotation tests, zeta potential and infrared spectrum measurements. The flotation results indicated that KGM had a straining influence on the depression of talc while had little effect on nickel minerals flotation. Compared with the depressant carboxymethyl cellulose (CMC) and guar gum, the KGM increased the nickel recovery dramatically, it not only negated the need for a talc removal process, but also achieved a significant decrease in the depressant consumption by half. Zeta-potential and infrared spectrum measurements illustrated that chemical adsorption was seen between KGM and talc, and a possible weak physical adsorption was seen between KGM and pentlandite. This was the reason why KGM had high depression selectivity for talc and little depression effect on nickel minerals.     

Effect of slurry rheology on gas dispersion in a pilot-scale mechanical flotation cell

This paper investigates the effect of slurry rheology on gas dispersion in a 100 l pilot-scale Batequip mechanical flotation cell. The study is conducted using Kaolin, Bindura nickel and Platreef slurries. All three ores display typical non-Newtonian rheological behaviour. The slurry yield stress and viscosity increase exponentially with solids concentration. Bubble size and gas hold-up vary from 0.60 to 1.10 mm and 2% to 15%, respectively. At low/moderate solids concentrations, bubble size and gas holdup display characteristic trends, as noted in numerous literature studies. At high solids concentrations, both bubble size and gas holdup decrease significantly, which is an unexpected finding. This is attributed to the formation of a ‘cavern’ of slurry around the impeller, due to the very high slurry yield stresses. This ‘cavern’ results in the generation of small bubbles in the impeller zone, but poor dispersion of these bubbles throughout the cell, resulting in low gas hold-ups.     

Bank profiling and separation efficiency

Various authors have discussed methods of optimising a bank of flotation cells. In this paper, JKSimFloat is used to investigate the effect of recovery profiling and mass pull profiling (i.e., mass distribution to cells in a bank) on the separation efficiency between floatable minerals and against entrained gangue.In the case of two floatable minerals, a balanced recovery profile was found to be optimal: supporting and extending previous analysis. In the case of separation of a floatable mineral from entrained gangue, the entrainment model that links water overflow rate to solids overflow rate was employed. When the value of b in the entrainment model is greater than one, a balanced mass pull profile was found to be optimum. The evidence for b > 1 is briefly reviewed; no example has been found where b < 1. Most of the profiles were controlled in the software by altering the bubble surface area flux distribution; a sensitivity analysis was performed using other variables.Recovery profiling was tested as part of a bank optimisation campaign at a talc operation in Timmins, Canada. Using air and frother as manipulated variables, it was found that as the rougher bank was moved toward a balanced profile the final plant product showed improvement in grade and yield.     

Examination of NaCl and MIBC as bubble coalescence inhibitor in relation to froth flotation

With scarcity of fresh water resources, flotation plants are increasingly under pressure to supply their water needs from other sources such as bore water, seawater or recycled plant water. This water generally contains a high concentration of inorganic electrolytes which may have a substantial influence on the performance of the flotation operation. In this study, the stabilisation mechanism of bubbles by salt was investigated using a specifically designed experimental set-up. Two bubbles of approximately the same size were produced at the tip of two adjacent capillaries in concentrated solutions of an inorganic electrolyte (NaCl). Their coalescence behaviour was recorded using high speed video imaging in which information such as coalescence time and deformation of the resultant bubble upon coalescence could be extracted. The results were then compared against a similar system using MIBC. It was found that delayed coalescence in NaCl required a relatively concentrated solution in the order of 0.1-0.5 M to achieve coalescence times comparable to MIBC. Unlike NaCl, it appears that a small amount of MIBC, in the order of 10⁻⁵ M, is sufficient to delay the coalescence of bubbles, which reach a maximum at a concentration of 3 × 10⁻³ M. The analysis of oscillation patterns during the coalescence process revealed that the oscillation is noticeably damped in the presence of MIBC at high concentrations, although this is not the case in NaCl solutions. Results are discussed in terms of bubble stability, froth stability and their possible implications on particle recovery.     

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.     

Flotation frother mixtures: Decoupling the sub-processes of froth stability,froth recovery and entrainment

The flotation process consists of two distinct phases: the pulp and froth phase. One of the main roles of the froth phase is to create a suitable environment for the separation of floatable, valuable minerals from non-selectively recovered, entrained gangue minerals. As a result the froth phase plays a significant role in the metallurgical performance of industrial flotation cells. Froth stability is important for the recovery of valuable minerals. However, a stable froth may contribute to increased entrainment and, consequently, a lower grade.This study compares the effect of frother mixtures with that of their single component frothers on the froth stability, froth recovery and entrainment of a platinum-bearing UG2 ore using polyglycol and alcohol frothers. The study showed that frother mixtures resulted in a greater froth stability than either of their component frothers. The increased froth stability was reflected in increased froth recoveries and greater overall recoveries. However, the important aspect in the use of frother blends was that they altered the froth structure and resulted in a lower degree of entrainment. This, together with the increased recovery, resulted in higher grades of valuable mineral recovered to the concentrate when using the frother mixtures.     

The dependency of the critical contact angle for flotation on particle size - Modelling the limits of fine particle flotation

The flotation behaviour of fine particles is studied in this work. Fine methylated quartz particles within the size range from 0.2 to 50 μm, and with varying contact angles, were floated in a mechanical flotation cell. Results indicate that particles of a given size need to possess a minimum critical contact angle, which increases in value as particle size decreases, for flotation to be initiated. As a consequence, a non-floating component exists within a given size fraction. This is interpreted as a fraction consisting of particles below the critical contact angle for flotation for that size. The critical contact angle for flotation is explained in terms of the existence of an energy barrier for bubble-particle attachment. The flotation results are interpreted by means of [Scheludko et al., 1976] and [Drelich and Miller, 1992] models for the floatability of fine particles. The experimental data compared very well with calculations using the Drelich and Miller equation, allowing extension to the prediction of the critical contact angle for flotation down to particle sizes well below the previous limits investigated, bridging the gap existing in the literature.     

The development of a composite collector for the flotation of rutile

A study was carried out to find a replacement for benzyl arsenic acid (BAA) that was used in the rutile flotation circuit of a hard rock rutile mine in China. Several types of oxide collectors were tested, including sodium oleate, sodium laurate, sodium dodecyl sulphate, amino acids, diphosphonic acid and styryl phosphonic acid. It was found that styryl phosphonic acid (SPA) was the most effective, and that an aliphatic alcohol (e.g., octanol) was required to maintain the effectiveness of SPA.However, octanol was insoluble in water. The composite collector that was mixed with SPA and octanol had to be well emulsified before addition to flotation pulp. Poorly emulsified composite collectors destroyed flotation froths. Several surfactants were tested as emulsifiers and one was found to have the least adverse effects on the selectivity of the composite collector. By using the composite collector that contained SPA, octanol and the emulsifier, a rutile rougher concentrate assaying 71.3% TiO₂ was floated at 81.6% recovery from a feed containing 8.78% Ti0₂ in a single stage rougher flotation.     

铜硫浮选分离药剂的研究现状

重点叙述了近些年来铜硫分离的捕收剂和抑制剂的研究成果.指出高效的硫化铜矿捕收剂以及有效的黄铁矿抑制剂是铜硫分离成功的关键,同时对它们的作用机理进行了简要的阐述.     

Study on Cu2S mineral surface modification by low temperature Ar/O2 plasmas

The oxidation of mineral and synthetic chalcocite (Cu₂S), using low temperature plasmas, has been investigated and compared to thermodynamic calculations. The main aim of this work is to understand the fundamental interaction between mineral surfaces and low temperature plasmas, with a view to improving froth flotation by mineral pretreatments. Capacitive radio frequency (RF) discharge Ar/O₂ plasmas, operating at different external parameters, have been used to treat powder samples, which resulted in surface modifications. These were analyzed by X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD). In situ mass spectrometry (MS) was used to determine oxidation reaction rates. The energy flux density from the plasma on the sample surface was determined by active thermal probe measurements, and the density of atomic oxygen produced within the plasma zone was obtained by optical emission spectroscopy (OES). Sulfur dioxide (SO₂), one reaction product of mineral Cu₂S plasma oxidation, was emitted with a certain delay, which depends on energy flux density and atomic oxygen density. In contrast, no delay was found as synthetic Cu₂S was treated. This indicates that the contamination by pyrite (FeS₂), found in mineral samples, plays an important role, significantly influencing the mechanisms of plasma surface interaction. Comparisons of mass spectrometry (MS)-, XPS- and XRD-measurement results with thermodynamic calculations give evidence for a stepwise plasma processing, whereas the transition of sulfur atoms from FeS₂ to Cu₂S could be identified as a first step in forming cupric sulfate ( CuSO₄). This effect might be used to develop selective plasma surface pretreatments for mineral mixtures in order to improve their separation efficiency of froth flotation.     

Geometrical optimization of xanthate collectors with copper ions and their response to flotation

Quantum chemical calculations have been employed to understand the nature of interaction between xanthate and Cu—as part of an ore and Cu—as part of a slag. A semi-empirical parameterized model, (PM3) is used to study ethyl xanthate, propyl xanthate, iso-propyl xanthate, iso-butyl xanthate and amyl xanthate. The total interaction energy, E, is interpreted in terms of the highest occupied molecular orbital (HOMO) energy of the individual collectors with copper ions. The electron density map along with the change in heat of formation, binding energy and dipole-moment, indicate that amyl-xanthate binds to surface of copper ions strongly in comparison to other xanthates. The numerical results obtained with potassium amyl xanthate also support the experimental data on recovery of copper values from a copper ore by flotation.