Gas dispersion properties of collector/frother blends

The addition of frothers in the flotation process has a significant effect on the hydrodynamic properties of the pulp phase as well as the stability of the froth phase. Some flotation collectors have been reported to have similar hydrodynamic effects, but there are few published quantitative studies. In this paper, the pure forms of the main families of sulfhydryl collectors from thiophosphates, xanthates and xanthate derivatives are tested. The aim was to determine the hydrodynamic properties of each reagent and to examine frother-collector interactions in terms of hydrodynamics. Experiments were carried out in a two phase air-water system using a 3 in. diameter column. Gas holdup (ε_g) and foam height (Hf) were measured to construct hydrodynamic characterization curves. The collectors tested have varied hydrodynamic activity with the xanthogen subgroup of collectors showing different degrees of hydrodynamic activity depending on their structure. In general, sulfhydryl collectors used in salt formulations showed very little hydrodynamic activity, while the oily collectors showed varied hydrodynamic effects from frother-type behavior to defoaming. In all frother-collector blends tested, a variable degree of foam stability loss was observed with this effect more pronounced in blends of weak frother and collector. A slight increase in ε_g was measured for almost all of the collector-frother blends.     

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 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.     

Cu-S flotation separation via the combination of sodium humate and lime in a low pH medium

The flotation separation of chalcopyrite and pyrite was studied in the presence of sodium humate. The results of flotation tests indicated that pyrite can be selectively depressed by sodium humate, and the activity of sodium humate was strongly affected by the pH of the pulp. At high pH values, pyrite was strongly depressed by sodium humate; however, the content of chalcopyrite was not affected. Ore flotation tests were successfully conducted in the laboratory and at the Dexing Copper Mine by applying sodium humate as a pyrite depressant. By adding 40-60 g/t of sodium humate to the pulp and adjusting the pH to 10-10.5 with CaO, a concentrate with a Cu content of 24% was obtained without reducing the Cu recovery rate. In addition, the dosage of CaO was reduced, and the recovery of Au, Ag and Mo in the copper concentrate was enhanced due to the reduced pH of the pulp. The zeta potential, adsorption of xanthate and contact angle of the mineral surface were measured, and the results from surface measurements indicated that there was a strong hydrophilic interaction between sodium humate and the surface of pyrite. Moreover, the results revealed that the interaction between sodium humate and chalcopyrite was weak. Infrared (IR) spectra of pyrite and sodium humate were obtained, and the results indicated that sodium humate was chemically adsorbed on the surface of pyrite.     

Adsorption of copper sulphate on PGM-bearing ores and its influence on froth stability and flotation kinetics

Copper sulphate is used as an activator in the flotation of base metal sulphides as it promotes the interaction of collector molecules with mineral surfaces. It has been used as an activator in certain platinum group mineral (PGM) flotation operations in South Africa although the mechanisms by which improvements in flotation performance are achieved are not well understood. Some investigations have suggested these changes in flotation performance are due to changes in the froth phase rather than activation of minerals by true flotation in the pulp zone. In the present study, the effect of copper sulphate on froth stability was investigated on two PGM containing ores, namely Merensky and UG2 (Upper Group 2) ores from the Bushveld Complex of South Africa. Froth stability tests were conducted using a non-overflowing froth stability column. Zeta potential tests and ethylenediaminetetraacetic acid (EDTA) tests were used to confirm the adsorption of reagents onto pure minerals commonly found in the two ores. The results of full-scale UG2 concentrator on/off copper sulphate tests are also presented. The UG2 ore showed a substantial decrease in froth stability in the order of reagent addition: no reagents > copper > xanthate > copper + xanthate, while Merensky ore showed a slight decrease. It was shown through zeta potential measurements that copper species were to be found on plagioclase, chromite, talc and pyrrhotite surfaces and through EDTA extraction that this copper was in the form of almost equal amounts of Cu(OH)₂ and chemically reacted copper ions on the Merensky and UG2 ore surfaces. In certain cases, the presence of copper sulphate and xanthate substantially increased the recovery, and therefore the implied hydrophobicity, of pure minerals in a frothless microflotation device. It was, therefore, proposed that increases in hydrophobicity beyond an optimum contact angle for froth stability, were the cause of instabilities in the froth phase and these were found to impact grade and recovery in a full-scale concentrator. Differences in the extent of froth phase effects between the different ores can be attributed to differences in mineralogy.     

The effect of flotation and parameters for bioleaching of printed circuit boards

Waste electrical and electronic equipment (WEEE) is currently one of the fastest growing waste streams in the world. Typical for WEEE is the high content of valuable and precious metals, as well as harmful contaminants like halogens, flame retardant chemicals and plastics. Currently, WEEE treatment and metal recovery methods are imperfect, polluting and energy intensive. In this paper, novel treatment possibilities are outlined for printed circuit boards (PCB) utilizing both the flotation separation technique and acid bioleaching. Flotation, conducted after crushing and sieving of PCB, produced two fractions: metal-rich concentrate, which is more suitable for pyrometallurgical treatment than untreated PCB, and metal-poor froth suitable for acid bioleaching. It was seen that especially low pH (1.6), high initial Fe²⁺ concentration (7.8 g/l) and low PCB froth concentration in the bioleaching solution (50 g/l) were beneficial for the rapid and selective dissolution of copper. With these parameters, 99% of copper was solubilized from PCB froth in bioreactor treatment, with Cu (6.8 g/l) and Fe (7.0 g/l) being the only major metallic elements in bioleaching solution.     

The effect of using different comminution procedures on the flotation of Platinum-Group Minerals

The use of High Pressure Grinding Rollers (HPGR) has been widely reported to have major benefits in the treatment of minerals such as iron ore and diamonds. To date there have been few investigations into its use in the treatment of ores containing Platinum-Group Minerals (PGMs). HPGRs are known to reduce energy consumption and wear costs and improve the throughput in the circuit. In the present investigation the effect of the comparative use of HPGR and conventional crushing in combination with either dry or wet rod milling on the flotation of PGMs was studied using batch flotation. Previous studies of a base metal sulphide had shown that either HPGR or conventional crushing followed by dry milling produced the highest grades and recoveries (Palm et al., 2010). However in the present study it was observed that a similar treatment of Platinum-Group Minerals produced the poorest results and the highest grades and recoveries were obtained for the case of conventional crushing in combination with wet milling. The HPGR showed no advantages in terms of flotation performance and dry milling produced particularly poor flotation results.The results were investigated further using various surface characterization techniques in order to determine the reason for the decrease in grades and recoveries of platinum when using dry milling and HPGR as opposed to the case for base metal sulphides. The feed and product samples were analysed using ToF-SIMS, XPS and MLA. The paper will propose reasons to explain the different flotation behaviour of the two ore types following the various comminution processes focusing on the surface characteristics of the ores, the particle size distribution and the pulp chemistry.     

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 role of frother on the detachment of particles from bubbles

The influence of frother on the coalescence dynamic of bubbles coated with particles was investigated. Two bubbles grown at the tips of adjacent capillaries were loaded with methylated glass particles and pushed against each other to provoke coalescence. The event was recorded by a high speed camera and the change in the bubble shape at the moment of coalescence was analysed using an image analyser. Trends in oscillation behaviour and particle detachment in the absence and presence of frother were presented.     

Numerical and experimental study of the effect of a froth baffle on flotation cell performance

In this work, the effect of a froth baffle on flotation performance is investigated both experimentally and numerically. Flotation experiments with an artificial ore comprised of 80% silica as gangue and 20% limestone as floatable component were carried out to compare the flotation performance of a baffled froth system against an un-baffled froth system. The effect of the baffle’s inclination angle to the horizontal was also studied. Results indicated that a froth baffle has a profound effect on both recovery and grade. The presence of a froth baffle resulted in an increase in grade at the expense of recovery. The decrease in limestone recovery with the introduction of a froth baffle was found to be a function of the baffle’s inclination angle i.e. recovery decreased as the inclination angle becomes more acute. Water recovery as well as entrainment recovery herein represented by silica recovery decreased with decrease in baffle’s inclination angle. Numerical techniques were employed to model the experimental results. The 2D stream function equation/Laplace equation which is known to be adequate in describing froth transport was solved subject to boundary conditions that represent the presence of baffles. A solution was developed using finite difference methods on a rectangular map obtained using Schwarz–Christoffel (SC) mapping. Results from the simulations indicated a change in particle residence time distribution in a manner that reduces spread. The changes in residence time distribution helped in developing an explanation of the experimental data.     

The effect of ionic strength of plant water on valuable mineral and gangue recovery in a platinum bearing ore from the Merensky reef

As the restrictions on water usage become more prevalent throughout the world, mining operations are required to understand the impact that water recycling will have on them. Not only owing to operational needs, but also from an environmental stand point. As would be expected recycling is likely to lead to increased dissolved ions, increasing the ionic strength, which may impact plant performance. By conducting flotation tests under varying degrees of ionic strength of synthetic plant water it is possible to better understand the effect that water recycling could have on the recovery of a mining operation. The effect of such an increase in ionic strength is discussed.     

Assessment of the floatability of chalcopyrite,molybdenite and pyrite using biosolids and their main components as collectors for greening the froth flotation of copper sulphide ores

Biosolids and representative compounds of their main components – humic acids, sugars, and proteins – have been tested as possible environment-friendly collectors and frothers for the flotation of copper sulphide ores. The floatability of chalcopyrite and molybdenite – both valuable sulphide minerals present in these ores – as well as non-valuable pyrite was assessed through Hallimond tube flotation tests. Humic acids exhibit similar collector ability for chalcopyrite and molybdenite as that of a commercial collector (Aero 6697 promoter). Biosolids show more affinity for pyrite. The copper recovery (85.9%) and copper grade (6.7%) of a rougher concentrate obtained using humic acids as main collector for the flotation of a copper sulphide ore from Chile, were very similar to those of a copper concentrate produced by froth flotation under the same conditions with a xanthate type commercial collector. This new and feasible end-use of biosolids and humic acids should be new environment-friendly organic froth flotation agents for greening the concentration of copper sulphide ore. Now, further research is needed in order to scale current laboratory assays to operational mining scales to determine efficiencies to industrial scale.     

The entrainment effect on the performance of iron ore reverse flotation

An iron ore mineral processing plant in Brazil treating Itabirite ore was assessed by sampling a circuit consisting of Wemco 144 mechanical cells, as part of the AMIRA P9P collaborative research project. This paper presents and discusses the results of entrainability, water recovery and quartz and hematite grades associated to hydrodynamic parameters. The results indicated strong correlation between water recovery and hematite losses which was intensified by the operating conditions of the circuit.A potential alternative to reduce the hematite losses through entrainment and to increase quartz removal was to modify the traditional circuit design to treat rougher and cleaner/recleaner tails in different stages. In addition, the scavenger residence time must be matched to the quartz floatability. Changes to design and operation of these circuits are needed to sustain concentrate recovery and grade as iron ores become finer.     

复配起泡剂强化低阶煤浮选的试验研究

为了探究复配起泡剂对低阶煤浮选的强化效果,选取正戊醇、MIBC、仲辛醇和聚乙二醇(PEG)进行浮选动力学试验,通过表面张力和泡沫稳定性试验,揭示了复配起泡剂强化低阶煤浮选的作用机理.浮选结果表明:起泡剂单独使用时,PEG浮选精煤产率最高,浮选速率最快,正戊醇浮选效果最差;三种短链醇和PEG复配后,浮选精煤产率随着复配药...     

The role of citric acid in the flotation separation of rare earth from the silicates

The Nechalacho project is the most advanced large heavy rare earth elements (HREE) project outside of China. Open circuit and locked cycle flotation tests along with pilot plant testing of rare earth elements (REE) concentration from the host rocks are accomplished with collectors of alkyl phosphates and the modifier of citric acid. In this study, the function of citric acid in the separation of rare metals against silicates is investigated by a combination of micro-flotation tests and time of flight secondary ion mass spectrometry (ToF-SIMS) surface chemical analysis. It was observed that there was little effect of citric acid on the REE recovery in the micro-flotation tests conditioned with de-ionized water (DIW). To evaluate the flotation response with excess secondary ions in the pulp, micro-flotation tests were performed to look at changes in recovery as a result of adding Al ions and the subsequent presence of citric acid. The results from three micro-flotation tests (DIW, DIW with the addition of 100 mg/L Al and DIW + 100 mg/L Al and 500 g/t citric acid) revealed that the addition of Al ions led to a decrease of REE grade, a lower REE minerals recovery and/or an unexpected promotion of silicates to the concentrate. Citric acid reduced the negative effect generated by the Al ions in the flotation, which was shown by an improvement in REE grade. ToF-SIMS surface analysis of undifferentiated grains from the tests with and without citric acid revealed that grains reporting to the concentrate are doing so in response to collector attachment in combination with having more secondary Al on their surface. Citric acid may partially form aqueous soluble metal–ligand complexes resulting in less Al ions on the grains surface, which were rejected to the tailings. Citric acid also may form chelation competing for adsorption on gangue minerals, resulting in a diminished effectiveness of the activation site.     

浮选柱选用适宜起泡剂的试验研究

气含率在旋流-静态微泡浮选柱分选过程中起到很重要的作用,而起泡剂是影响气含率的关键因素。通过对730系列起泡剂在浮选柱应用中的气含率研究以及结合云南大红山铜矿的选矿实践,比较5种起泡剂的性能指标,综合精矿品位和回收率得出730C更适配于旋流-静态微泡浮选柱。     

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 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.     

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 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.