Galena Particles Research Articles

Statistical comparison of hydrophobic and hydrophilic species on galena and pyrite particles in flotation concentrates and tails from TOF-SIMS evidence

A comparison of the amount of collector sodium diisobutyl dithiophosphinate (DBPhos) adsorbed on the surface of galena and pyrite has been investigated by time of flight secondary ion mass spectrometry (TOF-SIMS). Statistical comparison of spectra from both galena and pyrite particles showed that there was approximately 12 times more collector on galena compared to pyrite. Galena particles that reported to the concentrate showed statistically less calcium, lead hydroxide and oxy-sulphur species on their surfaces compared to tail particles. The major contributions that assisted the flotation of galena were the presence of hydrophobic DBPhos and PbDBPhos. Reduced collector adsorption and increased hydrophilic species concentrations inhibited the flotation of pyrite.

Colloidal iron oxide slime coatings and galena particle flotation

Microflotation was used to investigate the influence of colloidal iron oxide “slimes” on galena (PbS) particle flotation. Complementary particle adsorption (heteroaggregation) studies were undertaken to investigate the formation of iron oxide slime coatings and to develop methods for their removal. Trace quantities of hematite (Fe 2O 3) colloids have a significant depressant action on both the collector-induced and collectorless flotation of galena particles. For example, slime particle surface coverage as low as 10% of an equivalent close-packed particle monolayer decreased the flotation rate constant of galena by an order of magnitude. In the pH range 4 to 7, high affinity Fe 2O 3 particle adsorption was observed on PbS and the surface coverage approached that of an equivalent particle monolayer. In contrast, in mildly alkaline solutions, particle adsorption isotherms were of low affinity, with plateau surface coverages significantly less than an equivalent particle monolayer. These observations are discussed in terms of the surface chemistry of galena and slime coating mechanisms. The use of shear, sonication, pH control and chemical reagent addition to quantitatively remove iron oxide slime coatings is also reported. A combination of physical and chemical methods is most effective at iron oxide particle removal and synergistic effects have been observed.

Prediction of the settling velocity of irregularly shaped particles

This work presents a new empirical relationship between Reynolds number Re t and Archimedes number Ar. From this relationship it is possible to calculate the free settling (terminal) velocity of irregularly shaped (e.g. crushed) solids in water. Experimental terminal velocities for various size fractions from earlier works were correlated with the new equation. The data refer to crushed quartz and galena particles. The new relationship gives for a very wide range of Archimedes numbers (flow regimes) a good correlation between experimental and calculated terminal velocities. Comparisons with the Ganguly relationship also showed a good agreement for the prediction of the terminal velocities. The current work shows that the terminal velocities in water can be calculated with a single equation for various irregularly shaped solids and for various size fractions.

Statistical comparison of surface species in flotation concentrates and tails from TOF-SIMS evidence

The coverage of potassium isobutyl xanthate (IBX) and sodium diisobutyl dithiophosphinate (DBPhos) adsorbed on the surface of galena has been investigated by Time of Flight Secondary Ion Mass Spectrometry (TOF-SIMS). Differences in surface concentrations and distributions between particles and across individual particle surfaces were sought comparing flotation concentrate and tail samples. This study has shown that a large difference is found in collector adsorption for both IBX and DBPhos between different faces of galena particles. The amount of collector adsorbed on galena particles of different sizes was statistically inseparable. However, a large variation in collector concentration on particles of the same size was observed. Statistical analysis of DBPhos on galena particles in the first concentrate and tail indicated that TOF-SIMS can be used to quantitatively investigate the flotation response of galena based on hydrophobic/hydrophilic ratios for each particle. Differences between collector distributions on concentrate and tail samples can be statistically separated. TOF-SIMS data also produced various hydrophilic and hydrophobic indices derived from the selected pairs of related spectral measures: Ca +/Pb +, Al +/Pb +, PbOH +/Pb +, SO 3 −/S 2 −, DBPhos −/SO 3 −. Linear regression and mean analyses were used to estimate these indices; the results correlated closely with the flotation response. Hydrophilic species concentrations such as calcium, aluminium and metal hydroxides were found to be statistically greater on tailings than on the concentrate particle surfaces. The method suggests that it will be possible to assess conditioning of sulphide surfaces for optimum selectivity.

Selectivity in the polymer assisted separation of galena from quartz by flotation

The flotation of ultrafine (< 5 μm) sulphide minerals is notoriously poor. A method of selectively aggregating ultrafine galena particles with coarse galena particles has been developed. Key features of this method include: minimising entrapment of non-values into the aggregate structure and; provision of adequate free surface to allow collector adsorption after aggregation so that separation can be achieved using conventional flotation methods. Results from particle interaction and polymer adsorption experiments are presented. Flotation experiments on mixed mineral, galena-quartz, slurries using both traditional and the newly proposed aggregation method, over a range of polymer concentrations, are reported.

An electrochemical study of galena concentrate in perchlorate medium at pH 2.0: the influence of chloride ions

An electrochemical study of galena flotation concentrates in solutions of perchlorate and chloride ions at pH 2 has been carried out, through the use of carbon paste electrodes and cyclic voltammetry. The analysis of the voltammetric results indicates that in perchlorate solutions the galena is oxidized forming several products dependent on the applied potential. When the potential is below to 0.54 V/saturated calomel electrode (SCE), Pb(II) and elementary sulfur are formed. Galena oxidation to higher oxidation state of sulfur (e.g. thiosulfate and sulfate) requires a higher overpotential ( E>0.8 V vs. SCE), in the presence of perchloric acid, while in chloride medium a considerable lower overpotential is needed. From this reaction, the Pb(II) reacts with the chloride ions in order to form a lead–chloride complex that could precipitate depending on the concentration of chloride in solution and also could remain adsorbed on the galena particle surface. In the chloride media, the galena is reduced into metallic lead and hydrogen sulfide.

Rheological Investigations of DLVO and Non-DLVO Particle Interactions in Concentrated Mineral Suspensions

The rheological behaviour of galena, sphalerite and gibbsite mineral particle suspensions has been studied using a concentric cylinder rheometer. The influence of pulp density, pH, salt concentration and processing reagents on the rheology and particle interaction behaviour is reported. The Bingham or extrapolated yield value is used to characterise particle interactions in both a qualitative and quantitative manner. For many mineral suspensions, over a wide range of conditions, the rheological behaviour can be described in terms of electrostatic and dispersive interactions, i.e., DLVO behaviour. In some circumstances however, non-DLVO interactions are observed, the sign and magnitude of these depend primarily on the mineral particle surface chemistry. For ultrafine galena (PbS) particle suspensions an attractive, non-DLVO interaction is observed which increases with decreasing pH. This finding correlated with flotation behaviour and a hydrophobic interaction was confirmed. For colloidal gibbsite (Al(OH)3) suspensions a repulsive non-DLVO interaction becomes apparent at pH values greater than 10. Hydration or steric interactions are thought to be responsible for this behaviour.

Rheological investigations of ultrafine galena particle slurries under flotation-related conditions

Abstract The theological behaviour (viscosities and extrapolated yield values) of ultrafine galena particle slurries under flotation-related conditions has been studied using a concentric cylinder rheometer. The influence of pulp density, pH and ethyl xanthate concentration is reported. The observed aggregation phenomena are discussed with respect to galena surface chemistry as probed by electrokinetic studies, microflotation and X-ray photoelectron spectroscopy. At greater than 50% solid contents non-Newtonian theological behaviour is evident, with high yield values and shear thinning properties indicative of pulp aggregation. Under mildly alkaline conditions, galena slurry theology is controlled by repulsive electrostatic forces, with a high level of galena particle dispersion, whereas under mildly acidic conditions the rheology is significantly influenced by hydrophobic interactions. The introduction of galena particle hydrophobicity through ethyl xanthate addition results in enhanced galena particle attraction and increased floatabilities; these have been correlated. The magnitude of the hydrophobic attraction between ethyl xanthate treated galena particles, as determined from extrapolated yield data, has been shown to be greater at pH 5.5 than pH 10 and strongly concentration dependent. Rheological measurements of galena particle interactions are shown to enhance our understanding of fine particle flotation and may be utilised to optimised flotation performance.

Electroacoustic measurements of sulfide mineral particles

Electroacoustic measurements (AcoustoSizer, Matec Applied Sciences) of zeta potential and particle size distribution are reported on well characterised ultrafine (−5 μm) sphalerite and galena particles. For both sulfide minerals the zeta potentials determined electroacoustically are in good agreement with those determined using the more conventional microelectrophoresis. The applicability of the electroacoustic technique to sulfide mineral particles is discussed, in particular the influence of interparticle interactions, surface oxidation, pH and particle solids concentration.

Rheological investigations of galena particle interactions

The rheological behaviour of ultrafine (<5 μm) galena particle slurries has been studied using a concentric cylinder rheometer. The influence of solids content and pH on viscosities and extrapolated yield values are reported and discussed in the context of the level of particle interaction. These studies, coupled with microflotation, microelectrophoresis and X-ray photoelectron spectroscopy (XPS) surface chemical analysis, have furthered our understanding of the role of interparticle forces in controlling the collectorless floatability of galena. In the pH range 6–10, the rheological behaviour of oxidized and effectively hydrophilic galena particles is controlled by electrostatic repulsive forces and the yield values scale with the zeta potentials squared. At pH values less than 6 this relationship breaks down and yield values cannot be predicted by electrostatic and van der Waals considerations alone. A non-DLVO contribution to the extrapolated yield value τ′ B is required to describe the observed rheological behaviour. The magnitude of τ′ B is influenced by pH, hydrodynamic conditions, the particle volume fraction and time scale of any conditioning periods. τ′ B is controlled to a minor degree by hydrodynamic, gravitational and inertial forces, but is mainly due to an attractive hydrophobic force between galena particle surfaces. This attractive hydrophobic particle interaction has been probed by microflotation. XPS has confirmed a pH-controlled surface cleaning mechanism which is responsible for the formation of hydrophobic galena surfaces.

Contact Angle Studies of Ethyl Xanthate Coated Galena Particles

The wettability of ethyl xanthate coated galena particles has been determined from measurements of the equilibrium capillary pressure across a packed bed. Both the advancing liquid powder contact angle, θp, and the specific wettable surface area,Awet, of galena particles have been obtained. The influence of particle size and ethyl xanthate surface coverage on the powder contact angle have been investigated and compared with floatability. Ethyl xanthate at a surface coverage of less than ten percent of an equivalent monolayer significantly increases both θpand particle floatability.

Contact angle studies of particulate sulphide minerals

The flotation separation of sulphide minerals is achieved by controlling particle hydrophobicity, which is often described in terms of the liquid-vapour contact angle determined from wettability studies on single surfaces. These may not be representative of the true hydrophobicity of mineral particles in a pulp and there is a requirement to determine “particle contact angles”. We report an experimental approach, based on equilibrium capillary pressure measurements across a packed bed of particles, which reliably and routinely determines the powder contact angle of mineral particles in the size range 10 to 200 pm. The influence of particle size and surface treatment on the powder contact angle and flotation response of galena particles are reported. The natural hydrophobic nature of galena was shown to depend on the hydrodynamic conditions during particle conditioning. The high shear environment experienced during cyclosizing resulted in galena particles of greater hydrophobicity than those prepared by sieving. A mechanism is proposed to explain the relationship between hydrodynamic conditions, surface chemistry and hydrophobicity; this may give insight into the role of high intensity conditioning and sonication in sulphide mineral flotation. The correlation between collector coverage, particle wettability and flotation recovery was also investigated. Ethyl xanthate at surface coverages in excess of 0.1 equivalent monolayers significantly increased the particle contact angle and particle floatability. The influence of other reagents on galena particle contact angles is discussed.

Two-wavelength pyrometry study of the combustion of sulfide minerals: Part I. Apparatus and general observations

The temperatures of individual sulfide particles combusting in air have been measured with a two-wavelength radiation pyrometer. The pyrometer design allowed the temperature of the combusting particles to be measured for 15 to 30 ms; and the response of the system was sufficient to determine the heating rates of particles during reaction. The combustion of galena, pyrite, and pyrrhotite, in air, at 1130 K was investigated. The different minerals produced distinct combustion pulses which were recorded repeatedly. Galena particles reacted in air at a relatively constant apparent temperature of between 1400 and 1700 K. Reaction product fume was observed trailing behind the combusting particles. The pyrometer pulses recorded during the combustion of pyrite and pyrrhotite particles were similar; however, pyrite tended to ignite more rapidly than pyrrhotite. During combustion in air, the temperature of the iron sulfide particles increased at a constant rate up to a maximum of 2200 to 2600 K after which rapid cooling occurred; a sudden rise in combustion energy at peak temperature was likely due to an merease in the particle size resulting from the formation of cenospheres.

Contact Angle Studies of Galena Particles

The wettability of galena particles has been determined from measurements of the equilibrium capillary pressure across a packed bed. Both the macroscopic advancing liquid contact angle, θp, and the specific wettable surface area, Awet, of the galena particles have been obtained. The influence of particle size and surface preparation method on θp has been investigated. The hydrophobic nature of galena is at least partly controlled by hydrodynamics during particle conditioning. The high shear environment experienced during cyclosizing results in galena particles of greater hydrophobicity compared with those prepared by sieving; these findings are in agreement with the measured flotation recoveries. A mechanism has been proposed to explain the relationship between hydrodynamic conditions, surface chemistry, and surface hydrophobicity. X-ray photoelectron spectroscopy studies support this mechanism.

Collectorless liquid-liquid extraction of fine mineral particles using various organic liquids as the oil phase

As part of the fundamental studies on the recovery of fine mineral particles by liquid-liquid extraction, the transfer of fine quartz and galena particles from a water phase to an oil phase or to the oil-water interface was investigated in the absence of a surfactant collector. Various organic liquids of paraffin, aromatic hydrocarbous, ether, ketone, and higher alcohols were test oils. High recoveries of the galena particles were obtained using comparatively low polar liquids, while the recovery of quartz was impossible using any organic liquids. Calculations of the wetting property, the work of adhersion, of these solid surfaces with the liquids, based upon contact-angle measurements and the liquid surface free energy, indicated that the wetting on the quartz surface with water was most likely to occur, while the wettabilities of the two solids with the organic liquids were comparable. In addition, a thermodynamic criterion of collectorless liquid-liquid extraction were discussed in terms of the surface free energy change in the oil-water-solid, three-phase system during the oil-to-solid adhesion in water.

Interactions between sulfide minerals and alkylxanthate ions 3. A vibration spectroscopic, calorimetric and atomic absorption spectrophotometric study of the interaction between galena and ethylxanthate ions in aqueous solution

The reaction between galena powder and ethylxanthate ions has been studied in aqueous solution. Qualitative analysis of the compounds present on the galena surfaces before and after treatment with potassium ethylxanthate has been performed by means of diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy. Atomic absorption spectrophotometry has been used to determine the total lead concentration in the aqueous phase of galena slurries. Calorimetric techniques have been used to study the heats of reaction. Galena surfaces are easily oxidized to lead(II) sulfate and thiosulfate, and lead(II) carbonate is found on the galena surfaces as well. DRIFT measurements have shown that solid lead(II) ethylxanthate is formed on the surfaces of oxidized galena after treatment with a dilute, 0.2 m M, aqueous solution of potassium ethylxanthate. The amount of lead(II) ethylxanthate on the surfaces increases with increasing concentration of potassium ethylxanthate solution. A previously proposed monolayer complex has been questioned. The mechanism for the hydrophobation of oxidized galena surfaces involves: (1) fairly soluble lead(II) salts, present or formed on the galena surface, which are dissolved from the surface during slurrying in water, and a concentration gradient of lead(II) species formed around the galena particles; (2) small islands of solid lead(II) ethylxanthate which are formed on the galena surface in the presence of alkylxanthate ions in the aqueous phase during slurrying. The degree of hydrophobicity of a galena particle depends on the amount and the degree of coverage of hydrophobic compounds on its surface. The degree of coverage of hydrophobic compounds on the galena surface necessary for a successful flotation increases with increasing particle size and weight. A redesigned titration calorimeter is described in this paper.

Grain size effect on the polarity of seebeck coefficient of natural galena

Thermoelectricity studies on semiconductors in the 1980s have established that pellets made by cold pressing from natural galena particles, followed by sintering, show polarity changes with grain size. At grain sizes < 61 μm, galena shows p-type conduction, while in the 104–124 μm rangem, and n-type conduction is observed at different temperatures up to 570 K. A peculiar behaviour is observed in pellets made from 76–104 μm galena particles, which show n-type conduction at room temperature and become p-type on increasing the temperature. The change of polarity is suspected to be due to surface oxidation effects.

The relationship between flotation and adhesion of galena particles to the air-solution interface

The adhesion of aggregates of galena particles to an air-solution interface was investigated experimentally by measuring the critical centrifugal force necessary to detach and sink the aggregates. Theoretical detachment-force calculations based on the Nutt (1960) and Scheludko (1968/69) theory for a single spherical particle could be correlated with the experiment results but the quantitative theoretical predictions appeared to give values one order of magnitude less than the experimental data. In addition, a series of flotation experiments were carried out with the same particle-size fractions using a small-scale flotation cell. It was found that the flotation efficiency could be directly related to the experimentally determined detachment forces for a series of particle-size fractions in the absence and presence of xanthate collector. It is suggested that the adhesion forces may play a more important role than the capture forces in determining the flotation performance of rough and angular particles. Finally the centrifuge technique could prove to be a useful method for characterizing the floatability of minerals.

The kinetics of leaching galena with ferric nitrate

The kinetics of leaching galena with ferric nitrate as oxidant has been studied. Experimental results indicate that the rate of galena dissolution is controlled by surface chemical reaction. Rate is proportional to the square root of the concentration of ferric ion. The addition of more than one mole/liter sodium nitrate decreases reaction rate. With nitrate additions below this concentration, rate either remains constant or is slightly enhanced. An activation energy of 47 kJ/mol was measured, and rate is proportional to the inverse of the initial size of galena particles. These results are explained in terms of mixed electrochemical control. The anodic reaction involves the oxidation of galena to lead ion and elemental sulfur, and the cathodic reaction involves the reduction of ferric ion to ferrous ion.

Pulmonary alveolar lipoproteinosis in rats following intratracheal injection of pyrite particles.

Wistar rats were injected intratracheally with pyrite particles and after 6 and 12 mo, lungs were evaluated for histological changes. Results were compared with rats that were given particles of galena, lead silicate, travertine, and quartz. Under the light microscope no significant changes were observed in the lungs from animals treated with galena, lead silicate, and travertine. In the lungs from animals that received quartz, a typical nodular fibrosis was observed. Moreover, both pyrite-treated rats and quartz-treated rats developed pulmonary alveolar lipoproteinosis; the lesions were much less prominent and severe in animals injected with pyrite than with quartz. These results indicate that pyrite, like only a few other types of dust that are different from quartz, can evoke the development of pulmonary alveolar lipoproteinosis in rats.