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1.
The effect of particle shape on the flotation process has been investigated in laboratory experiments with monosized spherical ballotini and ground ballotini. The particles were treated by partial methylation with trimethylchlorosilane to achieve varying degrees of hydrophobicity. In flotation, the process of film thinning and liquid drainage is critical in the formation of stable bubble–particle attachments and this is affected by the particle shape and surface hydrophobicity. Flotation tests with different particle sizes were conducted in a modified batch Denver cell. Predictions from a computational fluid dynamic model of the flotation cell that incorporates fundamental aspects of bubble–particle attachment were compared with data from flotation tests. Contact angles of the particles were measured using a capillary rise technique to indicate surface hydrophobicity. Ground ballotini generally has higher flotation rates than spherical ballotini; the results are consistent with effects from faster film thinning and rupture at rough surfaces and are well correlated by the sphericity index.  相似文献   

2.
In the UG2 ore (Bushveld Complex, South Africa) flotation, normally more than 3% of the gangue minerals, principally chromite with talc and pyroxene, report to the concentrate diluting the PGM recovery and contributing to subsequent processing costs. Previous studies have identified residual talc-like layers on orthopyroxene surfaces in Merensky ore flotation contributing to inadvertent flotation of relatively large particles (20–150 µm) of this mineral. Chromite (75–150 µm) from flotation of UG2 ore has been similarly examined. Statistical comparison of ToF-SIMS analysis of particles from concentrate and tails reveals no significant difference in Cu, Pb, Ni and collector (IBX and DTP) signals between these streams but surface exposure of Mg and Si is favoured in the concentrate. The flotation rate of coarse chromite correlates with the exposures of magnesium and silicon in patches on the chromite surface; higher exposures give earlier flotation. Conversely, there is a negative correlation with signals corresponding to the chromite surface, i.e. Cr, Fe, Al. Flotation of chromite without collector has confirmed this statistical discrimination. Hydrophobic talc-like residual layers, similar to those found on orthopyroxene surfaces, probably from partial alteration, explain this flotation mechanism.  相似文献   

3.
Bubble size distributions and flotation rates were determined as a function of air flow rate and frother concentration using a specially designed batch flotation cell. This cell permitted the unambiguous determination of the flotation rate from the slurry to the froth.Flotation rate constants were determined for different size classes of silica and galena. The flotation rate constants increased to a maximum and then decreased as air flow rate was increased. This maximum was predicted by a model which considered the effect of bubble size on both the total bubble surface area and the bubble-particle collision efficiency. This work shows that collision efficiency effects, shown to exist in single-bubble/single-particle systems, are also present in flotation systems where many bubbles and particles interact.A second model for hindered flotation is proposed which assumes that the particle-capturing bubble surface differs from the particle-retaining surface. This model predicts a sharp transition from hindered to free flotation. Experimental results are presented which agree well with those derived from the model.  相似文献   

4.
Electro-flotation tests were conducted on chalcopyrite particles with a modified Hallimond tube designed for electro-flotation, using platinum anode—copper cathode and graphite anode—copper cathode systems. Flotation tests were carried out for fines of chalcopyrite of size below 20 microns with potassium ethylxanthate as collector. Studies were done on flotation with hydrogen and oxygen separately with the usual variables. Dissolution of chalcopyrite at various current densities, with reagent at optimum conditions and without reagent was also studied. It is observed that electro-flotation particularly with oxygen, is effective in the flotation of fine particles of chalcopyrite.  相似文献   

5.
The detailed flotation behaviour observed in industrial zinc cleaning circuits at Broken Hill differs markedly from that commonly reported for rougher and scavenger flotation. Flotation is strongly influenced by solids to liquid ratio (pulp density) and the behaviour can be described by an exponential relationship between the flotation rate coefficient and the pulp density in each cell. The dependence on pulp density is largely independent of mineral type but does depend upon particle size. The largest variation is observed for coarse particles.The observations are of considerable significance to control of circuit performance. The results of simulations incorporating the dependence of rate coefficient upon pulp density differ substantially from those obtained from conventional models which assume constant rate coefficients.  相似文献   

6.
Flotation experiments have been carried out in a cell in which bubbles of known size could be generated independently of the turbulence levels, which could be controlled by varying the impeller speed. The mean bubble size ranged from 75 μm to 655 μm.Results are reported for the flotation rates of fine particles, less than 50 μm diameter. The materials floated were polystyrene latex particles, quartz and zircon. These were chosen to give a wide range of specific gravity.It was found that the flotation rate was very strongly affected by the bubble size, there being an increase of up to one hundred-fold when the bubble size was reduced from 655 μm to 75 μm. Effects of particle density and impeller speed are also reported.  相似文献   

7.
The adsorption and action of various polymers on talc has been investigated. Two families of polymers (starch-based polysaccharides and synthetic polyacrylamides) with specific molecular weights and functional group chemistry were studied. Adsorption isotherms, acoustophoresis, and contact angle studies enabled polymer adsorption behaviour, adsorbed layer thickness, and the hydrophilicity of the polymer-treated talc surface to be determined. Flotation testing on the treated talc revealed a hierarchy of effectiveness within the group of polymers studied. The observed trends in flotation performance are discussed with reference to the measured polymer layer properties. A 3D correlation plot of adsorbed layer thickness and contact angle against flotation recovery indicates that it may be feasible to predict an order of effectiveness for polymeric depressants based solely on measurements of the adsorbed layer properties, without recourse to flotation testing. This approach would be desirable when screening large numbers of potential depressants.  相似文献   

8.
The modification of a Hallimond tube enabling flotation of very fine particles at low recovery by mechanical entrainment is described. Flotation yields of closely sized fractions of quartz and chalcocite are presented.  相似文献   

9.
A series of flotation experiments was carried out in three Rushton turbine cells of volumes 2.25, 10 and 50 dm3 using hydrophobic quartz particles to determine a set of scale-up criteria that would produce the same size-by-size flotation rate constants. Flotation was performed at a constant Sauter mean bubble diameter over a range of superficial gas velocities and impeller rotational speeds.  相似文献   

10.
The ability of O-isopropyl-N-ethyl thionocarbamate (IPETC), O-isobutyl-N-ethoxycarbonyl thionocarbamate (IBECTC) and butyl ethoxycarbonyl thiourea (BECTU) collectors to increase the flotation of the sulphide minerals, chalcopyrite, galena and pyrite, has been studied. For each collector, the flotation characteristics of these minerals, flotation rate constant and flotation recovery maximum, have been calculated from the flotation data and compared as a function of pH and collector concentration. Overall, the flotation performance of these collectors is stronger for chalcopyrite than for galena and pyrite. Flotation increases with collector concentration and decreasing pH values. For chalcopyrite, the collector performances of BECTU are slightly better than those of IPETC but far superior to those of IBECTC, especially at high pH values or at low collector concentrations. The flotation performance of these collectors has been shown to be in good agreement with the amount of collector adsorbed at the mineral surface. The affinity of BECTU for the various minerals has been calculated using a multilayer adsorption model.  相似文献   

11.
The surface analytical techniques of X-ray Photoelectron Spectroscopy (XPS) and Time of Flight Secondary Ion Mass Spectroscopy (ToF-SIMS) have provided information on the type and concentration of species on the surface of sphalerite and pyrite particles in flotation concentrate and tail samples, but also on their distribution on each particle and across particles of different sizes. From this surface analytical study, a more accurate interpretation of the flotation results of sphalerite and pyrite minerals in a mixed mineral system could be made as a function of the concentrations of copper sulphate activator and xanthate collector, and particle size. In particular, it was found that sphalerite particles reporting to the concentrate are larger in size and contain less iron hydroxide on their surface than particles reporting to the tail. As for the pyrite particles, their lower recovery than the sphalerite particles is the result of a larger proportion of iron hydroxide on their surface inhibiting copper and collector adsorption.  相似文献   

12.
Effects of particle size and chain length on flotation of quaternary ammonium salts (QAS) onto kaolinite have been investigated by mico-flotation tests. The two kinds of quaternary ammonium salts [RN(CH3)3] with different chain lengths, dodecyltrimethylammonium chloride (DTAC) and cetyltrimethylammonium chloride (CTAC) were used as collectors for kaolinite in different particle size fractions (0.075–0.01 mm, 0.045–0.075 mm, 0–0.045 mm). The anomalous flotation behavior of kaolinite have been further explained based on crystal structure considerations by adsorption tests and molecular dynamics (MD) simulation. The results show that the flotation recovery of kaolinite in all different particle size fractions decreases with an increase in pH when DTAC and CTAC are used as collectors. As the concentration of collectors increases, the flotation recovery increases. The longer the carbon chain of QAS is, the higher the recoveries of coarse kaolinite (0.075–0.01 mm and 0.045–0.075 mm) are. But the flotation recovery of the finest kaolinite (0–0.045 mm) decreases with chain lengths of QAS collectors increasing, which is consistent with the flotation results of unsifted kaolinite (0–0.075 mm). It is explained by the froth stability related to the residual concentration of QAS collector. In lower residual concentration, the froth stability becomes worse. Within the range of flotation collector concentration, it's easy of CTAC to be completely adsorbed by kaolinite in the particle size fraction (0–0.045 mm), which led to lower flotation recovery. Moreover, it is interesting that the particle size of kaolinite is coarser, the flotation recovery is higher. The anomalous flotation behavior of kaolinite is rationalized based on crystal structure considerations. The results of MD simulations show that the (001) kaolinite surface has the strongest interaction with DTAC, compared with the (001), (010) and (110) surfaces. On the other hand, when particle size of kaolinite is altered, the number of basal planes and edge planes is changed. It is observed that the finer kaolinite particles size become, the greater relative surface area of edges is, and the more the number of edges is. It means that fine kaolinite particles have more edges to adsorb less cationic colletors than that of coarse kaolinite particles, which is responsible for the poorer floatability of fine kaolinite.  相似文献   

13.
Coal flotation studies were carried out in ultrasonically assisted flotation cells. Representative hard coal slime samples from Prosper-Haniel Coal Preparation Plant located in Bottrop, Ruhr Region of Germany were used for this purpose. A Wemco type flotation cell was fitted with transducers and tests were carried out at variable frequency and power. The reagent for coal flotation was Ekofol-440 with variable dosages during conventional and ultrasonic flotation experiments. The results showed that ultrasonic coal flotation yields more combustible recovery and lower ash values in concentrates than conventional flotation by using similar reagent dosages. These results are explained on the basis of efficient surface cleaning of the coal particles.  相似文献   

14.
The flotation cell is quantified as a mixing device for one, two, and three phase systems using combinations of water, air, and solids. To do this, power consumption was measured as a function of impeller speed, rate of aeration, and solids concentration. Initial suspension of solids and dispersion of suspended solids throughout the water or water/air system were also studied as influenced by impeller speed, particle size and solids concentration. The power number and air flow number were used to correlate the data.Flotation studies with a zinc ore using three sizes of cells of the same design, showed that aeration had to be controlled in the smaller cells to duplicate the results in the cell of commercial size. For optimum results the flow number range in the smallest cell was less than the critical value for suspension of coarse particles. Operating flow numbers for the three cell sizes under optimum conditions were close; commercial cells of the same size operating elsewhere appear to have two to three times higher flow numbers.The general relationships among air flow, impeller speed, particle suspension and flotation are discussed with particular reference to scale-up problems and coarse particle flotation. Both impeller speed and aeration should be considered as variables requiring systematic study and independent adjustment.  相似文献   

15.
The effect of humic material on the flotation response of coal has been examined. The results show that while hydrogen ions do not adversely affect the flotation of coal particles, they interact with humic material adsorbed on the surface of the clay particles and render their surfaces oleophilic. This behaviour enables the clay particles to adsorb collector in preference to the coal particles and thus inhibit coal flotation.  相似文献   

16.
Flotation of sphalerite with ethyl, propyl, butyl, amyl, and hexyl xanthate is presented as a function of pH and concentration. Surface species have been identified with infrared spectroscopy and correlated with flotation and electrophoretic results. Flotation is postulated to be controlled by the formation and adsorption of bulk precipitated zinc xanthate on the alkyl chains of chemisorbed collector species.  相似文献   

17.
Flotation tests were conducted in a Hallimond tube on chalcopyrite, with a collector system of cupferron and fuel oil. The reagent concentration, pH and conditioning time were studied as variables. The necessity of the fuel oil was verified by conducting experiments without it. Contact-angle measurements have been conducted by the captivebubble technique. From the results it was found that fuel oil is necessary to promote adhesion of the conditioned mineral particles to the air bubbles. Adsorption experiments were carried out in a column apparatus under similar conditions as in flotation, except for the addition of fuel oil. The adsorption density and flotability were high at weakly acidic range where the reagent complexes the metal ions effectively in an aqueous medium.  相似文献   

18.
Column flotation, which is a very effective process in mineral processing especially for easily floatable minerals, is one of the most important new developments to emerge in mineral processing technology in the last years. In this study, the flotation behavior of talc products having different particle shapes produced by different grinding mills (ball and rod mill) was determined by using column flotation process. Shape characteristics of the particles were investigated by the two dimensional measuring technique based on the particle projections obtained from the SEM microphotographs using a COREL Draw 10.0 program. The results showed that particles possessing higher elongation and flatness properties were recovered better during column flotation, whilst roundness and relative width had a negative effect on the flotation behavior of the talc mineral studied. Consequently, as the shape of the particles produced by the mill deviated from the ideal sphere, their floatability was increased.  相似文献   

19.
Flotation tests for sphalerite, smithsonite and dolomite were carried out in a Hallimond tube at various pH values and two concentrations of collector.Adsorption of 5-alkylsalicylaldoximes on the surface of minerals was examined and isotherms for 5-butylsalicylaldoxime plotted.It was shown that sorption intensity of 5-alkylsalicylaldoximes on the surface of minerals decreased in the order: smithsonite, sphalerite and dolomite.Relationship between length of aliphatic chain and collecting activity of 5-alkylsalicylaldoximes was investigated in microflotation tests in a Hallimond tube.5-Propylsalicylaldoxime proved to have the best selectivity in flotation for the range of parameters studied, taking the difference in flotation rates of smithsonite and dolomite as a criterion.It was found that modifications of pH value resulted in changes in both adsorption and flotation.  相似文献   

20.
Conventional and non-conventional flotation for mineral processing and for water (and wastewaters) treatment and reuse (or recycling) is rapidly broadening their applications in the mining field. Conventional flotation assisted with microbubbles (30–100 μm) finds application in the recovery of fine mineral particles (< 13 μm) and flotation with these fine bubbles is being used as a solid/liquid separation to remove pollutants. The injection of small bubbles to conventional coarse bubbles flotation cells usually leads to general improvements of the separation parameters, especially for the ultrafines (< 5 μm) ore particles. Results obtained are believed to occur by enhancing the capture of particles by bubbles, one of the main drawbacks in fine ore flotation. It is believed that by decreasing the bubble size distribution (through the injection of small bubbles), increases the bubble surface flux and the fines capture. DAF or dissolved air flotation with microbubbles, treating water, wastewater and domestic sewage is known for a number of years and is now gradually entering in the mining environmental area. This technology offers, in most cases, advantages over settling, filtration, precipitation, or adsorption onto natural and synthetic adsorbents. The targets are the removal of oils (emulsified or not), ions (heavy metals and anions) and the reuse or recirculation of the process waters. Advantages include better treated water quality, rapid start up, high rate operation, and a thicker sludge. New applications are found in the mining vehicles washing water treatment and reuse, AMD (acid mining drainage) neutralization and high rate solids/water separation by flotation with microbubbles. This work reviews some recent applications of the use of microbubbles to assist the recovery of very small mineral particles and for the removal of pollutants from mining wastewaters. Emphasis is given to the design features of innovative devices showing the potential of conventional and unconventional DAF flotation.  相似文献   

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