Flotation Of Hematite Research Articles

Adsorção de misturas de coletores em silicatos

Apesar de a prática industrial, na flotação, já considerar a mistura de óleos como "extensores" há mais de 70 anos, somente na década de 60 surgem estudos detalhados sobre interações entre reagentes na flotação. Os primeiros trabalhos dedicaram-se a misturas de reagentes aniônicos ou catiônicos com álcoois. Nos últimos 20 anos, foram publicados alguns trabalhos relacionados à adsorção de misturas de coletores na interface alumina-água, na flotação de feldspato e na flotação reversa de hematita. O presente trabalho revê os principais aspectos da mistura de coletores na flotação e mostra os resultados da microflotação de alguns silicatos com mistura de coletores aniônicos e catiônicos.

Flotation of hematite using C6–C18 saturated fatty acids

The homologous series of saturated fatty acids investigated in this study generally show a steady gradation of properties with chain length. The solution p K a values were assumed constant at 4.9, however reported p K a values could be lower or higher. Hematite flotation response and surface pressure for aqueous solutions of these fatty acids were measured as a function of pH. For the shorter chain fatty acids, the undissociated acid was shown to be the predominant surface active species with flotation, supplemented by the physical adsorption of acid anions as the chain length increased. The reduced solubility of the longer fatty acid carbon chains made these reagents ineffective as flotation agents. The maximum flotation response of hematite using tetradecanoic acid corresponded with the precipitation edge of the reagent. The results show that the values of surface pressure of the surfactants are not always a good indication of their effectiveness as flotation collectors.

Removal of hematite from Bitlis–Hürmüz kyanite for producing concentrates suitable for the refractory industry

The aim of this study is the removal of hematite from Bitlis–Hürmüz kyanite to produce kyanite concentrates of suitable specification for use in the refractory industry. For this purpose, two groups of flotation experiments were carried out. In the first group of experiments, flotation of hematite was performed at pH values between 2 and 9. The effect of the type and the amount of the collector was investigated during the flotation of hematite at pH values of 4 and 7. In the second group of experiments, kyanite flotation was performed in the presence of petroleum sulphonate + alkyl succinamate and oleic acid at a pH of 4. This resulted in a concentrate containing > 55% Al2O3 with a recovery of > 65%. The Fe2O3 content of the kyanite sample was reduced from an initial value of 2˙3% to a final value of 0˙9%.

Adsorption of starch, amylose, amylopectin and glucose monomer and their effect on the flotation of hematite and quartz

The depressant effect of corn starch, its polysaccharide components (amylose and amylopectin), the monomer glucose and the dimer maltose were studied on hematite and quartz, by means of infrared spectrometry, adsorption isotherms determination and microflotation tests. All the carbohydrates tested have been effective in maintaining hematite hydrophilic, including glucose and maltose; as for quartz, only a flocculation action (mainly by amylopectin) had a mild effect in decreasing its floatability by the amine collector. FTIR studies confirmed that the carbohydrates adsorbed intensively onto hematite and the spectra of the adsorbed polymers and monomer were very similar, even though the non-adsorbed monomer spectrum was markedly different. The common adsorption mechanism indicated is a surface reaction involving the iron ion.

A review of hematite flotation using 12-carbon chain collectors

A sample of naturally occurring, relatively pure hematite (98.5% Fe 2O 3) was used as a model for the study of the flotation of insoluble metal oxides. The isoelectric point of this sample was 2.7 and the point of zero charge was 6.7. A number of surfactants containing saturated 12-carbon chain groups were used as collectors over a wide range in pH. The flotation of this hematite with dodecanoic acid (lauric acid) showed a maximum recovery in the pH range 6–8.5, a sudden drop at pH 9, and a steady increase in recovery as the pH was raised from 9–12. The flotation of the hematite using potassium dodecyl hydroxamate showed a maximum recovery at pH 5.5, with little flotation at pH <3. At pH >10, the recovery fell except at high additions of collector. The flotation of hematite using sodium dodecyl sulphate showed a high recovery for pH <6, a trough in recovery between pH 7 and 9, and a secondary maximum in recovery at pH 10. Different flotation behaviour was observed when sodium dodecyl benzyl sulphonate was used. Using ARMAC C, (a commercially available dodecyl ammonium acetate), a flotation maximum was observed at pH 8, with steadily decreasing recovery as the pH was raised or lowered from this value. These results are discussed in terms of the surface chemistry of the hematite and the solution chemistry of the various collectors used.

Mycobacterium phlei as a flotation collector for hematite

Mycobacterium phlei has very good potential as a hematite flotation collector. The flotation recovery of hematite is dependent upon the solution pH and concentration of the microorganism. The critical pH for maximum recovery of hematite is around three, which corresponds to the point of zero charge of the microorganism. An excellent correlation between the flotation recovery and bacterial adhesion on hematite is observed. The adhesion of Mycobacterium phlei on hematite can be described by the potential energy of interaction calculations using an extended DLVO theory.

Mechanism of action of sodium silicate in the flotation of apatite from hematite

The mechanism of the action of sodium silicate in the flotation of phosphate was investigated by studying the nature of the silicate species both in solution and on the mineral surfaces and the influence of the silicate species on the flotation performances of the valuable mineral (apatite) and the gangue mineral (hematite). Two models of equilibria were used to calculate the distribution of silicate species in solution. The first was based on monomers and tetramers and the second, more sophisticated model, was based on 29Si NMR studies and potentiometric titrations (Sjoberg et al., 1985) which includes a variety of polymeric silicate species in solution. The latter is supported by our attenuated total reflection-Fourier transform infrared (ATR-FTIR) spectroscopic studies of the silicate solutions. X-ray photoelectron spectroscopic (XPS) analyses have also provided strong evidence for the adsorption of polymeric silicate species on hematite from silicate solutions with concentrations typical of those used in flotation, viz. 10 −3 to 10 −2 mol L −1. Polymeric silicate species have a stronger depressing effect than monomeric silicate species and colloidal amorphous silica particles. Selective depression of flotation of hematite from apatite can be achieved under conditions of moderate depression (Gong et al., 1992b) and this is shown to correspond to silicate solutions containing moderately polymerized silicates and/or very small colloidal silica particles. It is proposed that under such conditions of moderate polymerization the adsorbed silicate on hematite reduces oleate adsorption whereas on apatite, oleate can displace adsorbed silicate, and render the surface hydrophobic.

Effect of temperature on the emulsion flotation of hematite

Finely-ground hematitic ore, too high in silica (quartz) to be commercially viable, was treated by emulsion flotation. A three-component emulsion mixture was used at temperatures ranging from ambient (22° C) to 30° C, 40° C, 49° C, 59° C and 68° C. The optimal emulsion dosage and composition at ambient temperature were used to determine that dosage for higher-temperature flotation tests. The crushed ore (100%, −8 mesh) was repeatedly washed with tap water, and the filtrate’s ionic content was analyzed. The separation efficiency values (a measure of the selective separation and concentration of hematite from gangue minerals) demonstrated temperature dependence, with marked increases at temperatures above ambient. The optimal separation efficiency occurred within the range from 30° C to 60° C. The improved separation efficiencies at temperatures exceeding ambient are explained by quartz depression. This depression is attributed to:

ドデシルトリメチルアンモニウムブロマイド（ＤＴＡＢ）による微粒の石英とヘマタイトの浮選分離

Separation of fine quartz (-10μm) from a mixed suspension (1: 1 by weight) with fine hematite (-10μm) was investigated using a Denver-type laboratory flotation machine (250ml capacity). The collector used was dodecyltrimethylammonium bromide which is characterized by its complete dissociation at all tested pH conditions. The results are summarized as follows:1) At acidic condition pH=5, where quartz is negatively charged and hematite is positively charged, it was difficult to separate quartz because its floatability was significantly depressed in the presence of hematite fines. This was probably due to the heterocoagulation between the mineral particles.2) At alkaline condition pH=10, where both minerals are negatively charged, selective flotation of quartz was also difficult because of concurrent flotation of hematite, as in the case where dodecylamine acetate (DAA) was used as a collector.3) Fairly good results were obtained at pH 7-8, where quartz carries a relatively large number of negative charges and hematite carries a moderate number of negative charges. The case where both quartz and hematite carry negative charges provides the condition under which the heterocoagulation between the mineral particles is prevented. Where quartz carries more negative charges than hematite, the condition is set under which the adsorption of dodecylammonium cations in excess amounts onto hematite surfaces is avoided, thus preventing the concurrent flotation of hematite.4) The principle stated above is also applicable to the case where DDA was used. Better separation results were obtained at pH 7.2 than at pH 10.

Cationic flotation of quartz from an artificial mixture with hematite using hexylamine

The cationic flotation of quartz was carried out from an artificial mixture (1:1 by weight) of fine grained ( − 10 μm) quartz and hematite, using hexylamine acetate (HAA) and dodecylamine acetate (DAA) as collectors. Selective flotation of quartz was possible in the pH range 9–10 using HAA. The adsorption densities of DAA and HAA on quartz and hematite were measured at pH 9.8 and the relationship between the flotation behavior of both minerals and the surface coverage of collectors was established. Complete flotation of quartz and hematite required a surface coverage (θ) of DAA of about 100% at pH 9.8, while complete flotation of quartz took place at θ ⋍ 10% with HAA. The flotation behavior with DAA was explained by considering the adsorption of undissociated free amine. Zeta potential measurements were incorporated to interpret the difference in the adsorption behavior of both collectors on quartz and hematite.

Anionic depressant function in anionic flotation of hematite

The function of multivalent anionic depressants in sodium dodecylsulfate flotation of hematite was studied through Hallimond tube experimentation. Three inorganic and three organic modifiers were studied (sulfate, selenite, tellurate, L-ascorbate, succinate and citrate). It was found that a partial correlation exists between the pK a1 value of a modifier and the lowest pH value at which it functions as a depressant.

Flotation behavior of hematite fines flocculated with polyacrylic acid

The use of small quantities of polyacrylic acid (PAA) was found to significantly improve the flotation of fine-sized hematite particles at pH 4.1 and 0.001 M NaCl with sodium dodecylsulfonate (SDS). Low polymer dosages before collector addition aid flotation by forming flocs of primary particles, but excess polymer results in low flotation yields due to surface saturation by the hydrophilic polymer. Contact angles, measured on a hematite disk, substantiate the hydrophilic nature of an adsorbed polymer film. Pre-adsorbed PAA reduces the amount of SDS adsorbed on the hematite particles, but the flotation of hematite flocs occurs, even at reduced amounts of adsorbed SDS, and is not depressed until PAA dosages in excess of the saturation value are used. Separation of a hematite-quartz mixture can be achieved by SDS flotation of PAA-flocculated hematite. Maximum selectivity results with the addition of small quantities of PAA, while excess polymer is detrimental to the recovery of hematite. Consecutive flotation states on a single feed yield a higher grade hematite product at some expense to the overall recovery.

Interparticular phenomena in the flotation of hematite fines

The flotation of hematite from a sample of iron ore tailing material using fatty acid type collectors has been studied with a view to decreasing the consumption rate of collector. Significant interactions between coarse and fine hematite particles have been found to cause a major improvement in the selectivity between these latter particles and gangue mineralization. The roles of temperature, fuel oil addition, frother addition, pH and conditioning time are important in determining the degree of improvement observed. Several mechanisms are postulated to explain the observed phenomena.

ドデシルアミンを用いる逆浮選による石英とヘマタイトの分離 (第1報)

Cationic flotation of quartz and hematite was investigated by varying pH and collector (dodecyl ammonium acetate, DAA) concentration with the intention of elucidating the effect of particle size on the reverse flotation of quartz from hematite. Flotation tests were carried out on quartz and hematite, alone and in artificial mixtures (1: 1 by weight), of three different sizes, i. e. coarse particles (149 -210 μm), intermediate particles (44 -53 μm), and fine particles (-10 μm).Results obtained in acidic media (pH 5), where quartz aquires negative charge, while hematite does positive charge, are summarised as follows.1) In the case of coarse particles system complete reverse flotation of quartz was possible as expected from single flotation results.2) Fairly good separation was obtained in the case of intermediate particles system.3) Complete separation was also possible for the system consisting of fine quartz and coarse hematite.4) No reverse flotation of quartz was achieved for fine particles system (fine quartz -fine hematite) and for the system consisting of coarse quartz and fine hematite. One of the reasons of this difficulty is due to the heterocoagulation between quartz and hematite or slime coating of hematite fines onto quartz surfaces. Scanning electron micrographs taken at pH 5 indicated that a critical size below which hematite fines attach onto quartz surfaces was estimated to be about 0.3 μm.

The action of neutral oleic acid in the flotation of hematite

Acidification of solutions of oleate salts forms emulsions of oleic acid. It was found that these emulsions produce a different adsorption behaviour on different size fractions of the same mineral. At low oleate concentrations, for the finer fractions, adsorption at acid pH was higher than chemisorption at pH = 7.5; adsorption was lower for the coarser, flotation-size fractions. Therefore, the conclusions obtained in acid solutions for the adsorption of oleate on fine minerals cannot be applied to flotation-size minerals. At low oleate concentrations there is a good correlation between oleate adsorption and hematite flotation. This does not hold for oleate concentrations > 5· 10 −5 M, where there is poor flotability in the acid region, although the adsorption of oleic acid is very high. This is attributed to the disordered character of the layer of cooperatively adsorbed oleic acid.

The role of ionomolecular surfactant complexes in flotation

The formation of highly surface-active ionomolecular complexes has been suggested recently to be a phenomenon that governs the pH-dependence of hematite flotation using oleate. The differential thermogravimetric work reported in the literature on alkylamine-alkylamine hydrochloride mixtures shows complete complexing of them when present in equimolar amounts. The pH dependence of quartz flotation using amine, speculated in the past to be due to various mechanisms, is discussed in the light of these results. The additional correlation obtained for flotation with surfactant complex formation suggests the role of such complexes in froth flotation to be of wide application.

The effect of dissolved hydrocarbon gases in surfactant solutions on froth flotation of minerals

Hydrocarbon gases are known to dissolve in surfactant solutions and affect the solution/gas interfacial properties. In this study, their effect on the froth flotation of various minerals was investigated. Also, solubility of these gases in collector solutions and the resultant surface tension changes were simultaneously determined for elucidating the mechanisms responsible for the effects on flotation. Methane dissolved in sodium dodecylsulfonate collector solutions was found to increase the flotation of alumina by 10–30%. Corresponding increase obtained due to the dissolution of butane was 10–50%. Flotation of hematite or quartz was not affected by the presence of dissolved methane or butane. Dissolution studies using a new automated constant-pressure apparatus showed the solubility of gases to be lower in surfactant solutions than in water when the surfactant concentration was low and higher than in water when the concentration was high. This is explained on the basis of the predominance of the “salting-out” effect at lower surfactant concentrations and that of hydrophobic bond formation between the hydrocarbon molecule and the surfactant chains at higher concentrations. Measurements of surface tension properties of these hydrocarbon saturated solutions have indicated adsorption of the gas molecules at the solution/air interface. The selective effects of the dissolved hydrocarbons on froth flotation of minerals are discussed on the basis of possible changes in the properties of the solution surface and the mineral/solution interface.