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.     

Adsorption of N-tallow 1,3-propanediamine-dioleate collector on albite and quartz minerals, and selective flotation of albite from greek stefania feldspar ore

The adsorption behavior of tallow 1,3-propanediamine-dioleate (Duomeen TDO) collector on albite and quartz minerals is assessed through Hallimond flotation, zeta potential, and diffuse reflectance FTIR investigations, together with the species distribution of the collector. The collector performance on albite separation from a natural feldspar material is evaluated in bench scale flotation tests. The Hallimond flotation responses of the minerals as a function of pH and collector concentration indicate that albite can be selectively floated from quartz at pH 2 where the doubly positively charged collector species adsorb on albite but not on quartz. However, the zeta potential and infrared spectra reveal that the adsorption behavior of the collector is similar on both minerals. The discrepancy in the flotation and adsorption results is attributed to the coarse and fine particle size fractions, and the shorter and longer equilibration periods employed in these studies respectively. The comparable adsorption on fine particles of albite and quartz at pH 2 is explained by the interaction of ammonium ions on silanol groups by hydrogen bonding as well as electrostatic interactions. The changes in zeta potentials are in good agreement with the formation of ionic species and free molecular forms of the collector. The IR spectra show the coexistence of neutral oleic acid together with charged amine species at low pH values in accordance with the species distribution diagram. Selective flotation of albite is accomplished from a natural feldspar material with tallow diamine-dioleate collector at pH 2 using sulfuric acid, only when the feed is deslimed prior to the bench scale flotation tests. An albite recovery exceeding 85% is achieved from a feed material containing about 50% albite.     

Electrokinetic properties of wavellite and its floatability with cationic and anionic collectors

The reverse apatite flotation with fatty acids has been widely used for the reduction of phosphorus content of magmatic origin iron ores. However, the occurrence of phosphorus intensely disseminated as secondary minerals such as wavellite renders the anionic reverse flotation a challenge. Zeta potential measurements and microflotation tests of wavellite with the use of anionic and cationic collectors were carried out in this work. The wavellite's IEP value was achieved at pH 4.5. Below the IEP value, the surface positively charged sites are made up of aluminum ions. The species H(+), Al(OH)(2)(+), Al(OH)(2+), Al(3+), OH(-), H(2)PO(4)(-), HPO(4)(2-), and PO(4)(3-) play a role in the protonation and deprotonation reactions that will determine the wavellite-solution interface properties. The highest values of wavellite's floatability under basic pH conditions were achieved in the presence of cationic collectors (1 × 10(-4) mol L(-1)). The formation of surface complexes and the precipitation of insoluble salt of aluminum onto wavellite surface seems to be the most likely hypothesis for the chemical nature interactions between amines and wavellite. The surface formation of aluminum oleate on the wavellite's surface seems to be the most probable hypothesis for the adsorption mechanism and the resultant high floatability of wavellite between pH 7.5 and pH 10.0 in the presence of sodium oleate (1 × 10(-4) mol L(-1)). The results showed that the cationic reverse flotation of secondary phosphates is a promising route to reduce the phosphorus content of iron ores from deposits that underwent a supergene enrichment process, since wavellite floatability in the alkaline pH range, using amine as collector, was not significantly affected by the presence of corn starch.     

Negative adsorption due to electrostatic exclusion of micelles

Interactions of surfactants with solid substrates are important in the controlling of processes such as flotation, coating, flocculation and sedimentation. These interactions usually lead to adsorption on solids, but can also result in an exclusion of the reagents with dire consequences. In this work electrostatic exclusion of negatively charged dodecylbenzene sulfonate micelles from quartz/water, Bio-Sil/water and alumina/water interfaces has been investigated as a function of pH and ionic strength. Measurable negative adsorption of these surfactants from similarly charged solid/liquid interface was observed in the micellar region. In the case of porous samples with large surface area, comparison of pore size with the micelle size is necessary to avoid any erroneous conclusions regarding the role of electrostatic exclusion in a given system. A theoretical model for the electrostatic exclusion of micelles is developed and used to calculate the adsorption of negatively charged dodecylbenzene sulfonate on negatively charged quartz (pH 7), silica (Bio-Sil A, pH 3) and alumina (pH 11) in the micellar concentration region. The micellar exclusion values calculated using the model are in excellent agreement with the experimental results.     

The role of complex formation in the flocculation of negatively charged sols with anionic polyelectrolytes

Summary Flocculation of negatively charged colloids by anionic polyelectrolytes, resulting from the adsorption of polymers on the colloid surface and from bridging of polymer chains between solid particles, is only possible if an appropriate concentration of electrolyte is present in the solution. Complex formation in the immediate vicinity of the sol surface between the counter cation and the functional groups of the polyelectrolyte plays a major role in the attachment of anionic polyelectrolytes to negative hydrophobic sols.Stability constants for Cu(II) polyacrylate and for the Ca complexes of a polyacrylic acid, hydrolyzed polyacrylamide and polystyrene sulfonate have been determined, and the effect of solution variables upon flocculation of AgBr/Br^– sols by anionic polyelectrolytes have been investigated. Ca⁺² ions affect the adsorption of polystyrenesulfonate on a negatively polarized mercury surface, as reflected in measurements of the differential capacitance; the presence of complex bound functional groups apparently changes the structure and orientation ability of the adsorbed polymer.With 5 figures in 10 details and 2 tables     

Electrophoretic Mobility Study of the Adsorption of Alkyl Xanthate Ions on Galena and Sphalerite

The adsorption of ethyl and amyl xanthate ions on galena and sphalerite fines has been studied using electrophoretic light-scattering (ELS) measurements. It was performed on galena and sphalerite (<2&mgr;m) in aqueous solution at different potassium ethyl xanthate (PEX) and potassium amyl xanthate (PAX) concentrations. It has been observed that the presence of PEX or PAX caused the isoelectric points (IEP) of galena and sphalerite fines to shift and the electrophoretic mobility to reverse in sign, indicating that the xanthate ions chemisorbed on galena and sphalerite surfaces. This adsorption markedly broadened the electrophoretic mobility distribution of the mineral fines, suggesting that the populations of the particles have quite different adsorption densities of xanthate ions, and therefore the particle hydrophobicity was different. This phenomenon might be attributable to the effect of the hemimicelle adsorption of the xanthate ions on the minerals, the nonuniform distribution of active sites and their degree of activity, the effect of particle size and shape, etc. The nonuniform adsorption has been found to increase with increasing PEX or PAX concentration, reaching a maximum at a medium concentration followed by a decline. Also, experimental results have demonstrated that the nonuniform adsorption of the xanthate ions is much stronger on sphalerite than on galena, which may explain why sphalerite has a worse flotation response than galena when alkyl xanthates are used as collectors in flotation systems. Copyright 2001 Academic Press.     

Influence of Oleic Acid and Electrolyte on the Interfacial Dilational Properties of Surfactant/Polymer Systems at the Decane-Water Interface

The dilational properties of partly hydrolyzed polyacrylamide (HPAM) and 4,5-diheptyl-2-propylbenzene sulfonate (377) mixed systems in the absence or presence of electrolyte or oleic acid at the oil-water interface have been described by means of the oscillating barriers method and the interfacial tension relaxation method. The polymer plays different roles in influencing the nature of polymer-surfactant adsorbed layers at different surfactant concentrations. At low surfactant concentration, the addition of polymer perhaps weakens the “entanglement” of long alkyl chains, which decreases strikingly the dilational modulus of the adsorbed layer. At high surfactant concentration, the addition of the polymer increases the dilational modulus due to the hydrophobic interactions between polymer and surfactant molecules. On the case of adding electrolyte, the frequency dependence of dilational modulus increases due to the enhancement of exchange process of surfactant molecules and bivalent cation has more obvious effect than Na ion. Oleic acid plays dual roles in controlling interfacial dilational properties of mixed adsorption films: a small quantity of oleic acid increases the dilational modulus by forming densely packed mixed adsorption layer with surfactant molecules, while the superfluous addition of oleic acid could decrease the dilational modulus mainly due to the weakening of the “entanglement” among long alkyl chains in surfactant molecules.     

相对分子质量对烷基芳基磺酸盐复配体系固液吸附性能的影响

测定了5种平均相对分子质量和相对分子质量(以下简称分子量)分布不同的烷基芳基磺酸盐复配体系的吸附等温线,分别考察了分子量、分子量分布、温度和无机盐对复配体系在油砂/石英砂表面的吸附量的影响。 结果表明,对5种分子量分布复配体系吸附量依次降低的顺序为递增分布、正态分布、反正态分布、递减分布和均匀分布;复配体系在油砂表面的吸附量随着磺酸盐的平均分子量的增大而增大,随温度的升高而降低,随NaCl浓度的增加而增加。另外,在低浓度时,MgCl2、CaCl2和Na2SO4比NaCl对吸附的影响显著。 NaCl对复配体系在油砂表面的吸附影响比对石英砂表面吸附的影响略大。     

Tunable synergism/antagonism in a mixed nonionic/anionic surfactant layer at the solid/liquid interface

The use of mixed surfactants for modification of solid surfaces is important for many applications, since beneficial synergism often occurs depending on the surfactant type and mixing conditions. Systematical information on the properties of surfactant mixtures at the solid/liquid interface can be helpful for optimizing the interactions between the surfactants and then their corresponding performance. In this work, a nonionic/anionic surfactant combination, n-dodecyl beta-d-maltoside (DM) and sodium dodecyl sulfonate (SDS), was selected for the study of adsorption on an oxide solid, alumina. Interestingly, the mixture of the two surfactants with opposite pH-dependence of adsorption on alumina exhibits some unique synergistic or antagonistic features that were found to be tunable in the region of pH 4-10. In addition, the DM/SDS molar ratio in the adsorbed layer was found to decrease with concentration in the saturated region at all the pH and mixing ratios tested. The decrease is attributed to the monomer concentration changes in solution due to the difference in surface activities of the two surfactants. The tunable features of this mixture at the solid/liquid interface provide a way to optimize the properties by changing the mixing conditions. This can be valuable in many applications, such as enhanced oil recovery, flotation, and solubilization.     

Effect of anionic surfactant and short-chain alcohol mixtures on adsorption at quartz/water and water/air interfaces and the wettability of quartz

Measurements of the advancing contact angles for aqueous solutions of sodium dodecyl sulfate (SDDS) or sodium hexadecyl sulfonate (SHS) in mixtures with methanol, ethanol, or propanol on a quartz surface were carried out. On the basis of the obtained results and Young and Gibbs equations the critical surface tension of quartz wetting, the composition of the surface layer at the quartz-water interface, and the activity coefficients of the anionic surfactants and alcohols in this layer as well as the work of adhesion of aqueous solutions of anionic surfactant and alcohol mixtures to the quartz surface were determined. The analysis of the contact angle data showed that the wettability of quartz changed visibly only in the range of alcohol and anionic surfactant concentration at which these surface-active agents were present in the solution in the monomeric form. The analysis also showed that there was a linear dependence between the adhesion and the surface tension of aqueous solutions of anionic surfactant and alcohol mixtures. This dependence can be described by linear equations for which the constants depend on the anionic surfactant and alcohol concentrations. The slope of all linear dependence between adhesion and surface tension was positive. The critical surface tension of quartz wetting determined from this dependence by extrapolating the adhesion tension to the value equal to the surface tension (for contact angle equal zero) depends on the assumption whether the concentration of anionic surfactant or alcohol was constant. Its average value is equal to 29.95mN/m and it is considerably lower than the quartz surface tension. The positive slope of the adhesion-surface tension curves was explained by the possibility of the presence of liquid vapor film beyond the solution drop which settled on the quartz surface and the adsorption of surface-active agents at the quartz/monolayer water film-water interface. This conclusion was confirmed by the work of adhesion of aqueous solutions of anionic surfactants and short-chain alcohol mixtures to the quartz surface determined on the basis of the contact angle data and molar fraction of anionic surfactants and alcohols and their activity coefficient in the surface layer.     

Separation of Co(II) from dilute aqueous solutions by precipitate and adsorbing colloid flotation

Ion, precipitate and adsorbing colloid flotation of cobalt(II) have been investigated at different pH values, using N-dodecylpyridinium chloride (DPCl), A strong cationic surfactant, and sodium lauryl sulfate (NaLS), a strong anionic surfactant, as collectors. In case of adsorbing colloid flotation, hydrous manganese dioxide was used as an adsorbent. The precipitate flotation curves experimentally obtained with the two tested collectors were compared with the corresponding theoretical one calculated from the data published for Co(II) hydrolysis. The effects of the collector concentration, ageing of the water-MnO₂–Co(II) system, bubbling time period, cobalt(II) concentration and foreign salts on the percent removal of Co(II) by adsorbing colloid flotation using DPCl as collector were determined. Removals approaching 100% could be achieved under the optimum conditions.     

Smooth model surfaces from lignin derivatives. II. Adsorption of polyelectrolytes and PECs monitored by QCM-D

For the first time to the knowledge of the authors, well-defined and stable lignin model surfaces have been utilized as substrates in polyelectrolyte adsorption studies. The adsorption of polyallylamine (PAH), poly(acrylic acid) (PAA), and polyelectrolyte complexes (PECs) was monitored using quartz crystal microgravimetry with dissipation (QCM-D). The PECs were prepared by mixing PAH and PAA at different ratios and sequences, creating both cationic and anionic PECs with different charge levels. The adsorption experiments were performed in 1 and 10 mM sodium chloride solutions at pH 5 and 7.5. The highest adsorption of PAH and cationic PECs was found at pH 7.5, where the slightly negatively charged nature of the lignin substrate is more pronounced, governing electrostatic attraction of oppositely charged polymeric substances. An increase in the adsorption was further found when the electrolyte concentration was increased. In comparison, both PAA and the anionic PEC showed remarkably high adsorption to the lignin model film. The adsorption of PAA was further studied on silica and was found to be relatively low even at high electrolyte concentrations. This indicated that the high PAA adsorption on the lignin films was not induced by a decreased solubility of the anionic polyelectrolyte. The high levels of adsorption on lignin model surfaces found both for PAA and the anionic PAA-PAH polyelectrolyte complex points to the presence of strong nonionic interactions in these systems.     

An HPLC Method for the Determination of Amines in Flotation Pulp Based on Derivatization

Alkyl amines are surfactants used as quartz collectors in the reverse flotation of phosphate ores. It is important in both research and industrial practice to quantify amine concentration in the solution and/or wastewater. A simple and rapid method using high-performance liquid chromatography (HPLC) was developed to quantitatively determine the concentration of amine collectors (including dodecylamine, tetradecylamine, hexadecylamine, and octadecylamine) in a mineral flotation system. The method involved a sample derivatization procedure with 9-fluorenyl methoxycarbonyl chloride (FMOC-Cl) and separation/determination by HPLC coupled with a fluorescence detector. The calibration curves showed good linearity (R²?>?0.9956) in the range of 0.20–5.00 µg/mL, and the recoveries of dodecylamine, tetradecylamine, hexadecylamine, and octadecylamine were in the ranges of 84.93–97.64%, 89.93–101.92%, 85.29–98.37%, and 93.57–103.26%, respectively. The method was successfully used to quantify amines in wastewater from flotation experiments and artificial flotation wastewater (amine solution after activated carbon adsorption). The results from the analysis of four amines in the solution demonstrated that the proposed method is suitable for the simultaneous determination of amines in flotation pulp and wastewater.

     

Adsorption of <Emphasis Type="Italic">N</Emphasis>-hydrocinnamoyl-<Emphasis Type="Italic">N</Emphasis>-phenylhydroxylamine on pure minerals

Equilibrium adsorption studies of N-hydrocinnamoyl-N-phenylhydroxylamine (HCNPHA) on galena, sphalerite, pyrite, chalcopyrite and quartz at pH 9 and 10 are reported. All adsorption isotherms followed Langmuir model, however, Freundlich type was observed for quartz. As HCNPHA is a strong chelating agent, formation of monolayers by chemisorption appeared to be the most probable mechanism of adsorption on the base-metal sulphide minerals. Specific adsorption of HCNPHA on iron containing minerals, namely, chalcopyrite and pyrite, was about three times that on galena and sphalerite, and specific adsorption on quartz was the lowest amongst the minerals studied. Specific adsorptions (in μmol/g) of HCNPHA on the minerals at pH 9 are: sphalerite: 30.5; galena: 26.9; chalcopyrite: 112.3; pyrite: 145.4; quartz: 2.9. Compared to pH 9, specific adsorption of HCNPHA on the minerals decreased at pH 10, indicating hydroxylation of mineral sites due to higher hydroxide ion concentration at pH 10. A spectral-colorimetric procedure was developed for the quantitative estimation of HCNPHA. Due to deprotonation of hydroxamic acids direct estimation using UV absorption was not possible. Hence, complexation of HCNPHA with Fe³⁺ was used to develop a purple coloured complex that absorbs in the visible region with λ _max=500 nm. Change in concentration of HCNPHA was measured from absorbance of the HCNPHA- Fe³⁺ complex at 500 nm.     

1,2,3-苯三氧基三乙酸的浮选抑制性能

抑制剂;1;2;3-苯三氧基三乙酸的浮选抑制性能     

Interfacial Dilational Properties of Hydrophobically Modified Partly Hydrolyzed Polyacrylamide and Anionic Surfactants at the Water-Decane Interface

The dilational viscoelastic properties of hydrophobically modified partly hydrolyzed polyacrylamide and anionic surfactants (4,5-diheptyl-2-propylbenzene sulfonate and gemini surfactant C₁₂COONa-p-C₉SO₃Na) in the absence or presence of electrolyte have been investigated at the decane–water interface by means of longitudinal method and the interfacial tension relaxation method. Experimental results show that at low surfactant concentration, the increase of the dilational modulus by the addition of surfactant molecules at low frequency might be explained by the mix-adsorption of the polymer chains and surfactant molecules. At the same time, polymer chain could sharply decrease the dilational modulus of surfactant film mainly due to the weakening of the strong interactions among long alkyl chains in surfactant molecules. At high surfactant concentration, the addition of surfactant molecules can decrease the dilational modulus of polymer solution due to the fast process involving in the exchange of surfactant molecules between the interface and the mixed complex formed by surfactant molecules and hydrophobic micro-domains. The added electrolyte, which results in screening of electrostatic interactions between the ionized groups, generally increases the frequency dependence of the interfacial dilational modulus. The data obtained on the relaxation processes via interfacial tension relaxation measurements can explain the results from oscillating barriers measurements very well.     

Zinc Recovery from Wulagen Sulfide Flotation Plant Tail by Applying Ether Amine Organic Collectors

Separating oxidized zinc minerals from flotation tailings is always a challenge. In this study, a flotation tailing from Wulagen zinc mine in China (Zn grade < 1%) was processed using froth flotation with combinations of amines (OPA 10, OPA 1214, OPA 13, DDA) and Na₂S to study the effects of these amines on the zinc recovery as well as their interactions with other reagents, aiming to screen out a proper reagent scheme to improve zinc separation from extremely low-grade zinc flotation tailings. The results show that different amines led to different flotation performance, and the collectors were ranked as OPA 1214, OPA 13, OPA 10 and DDA in a decreasing order based on flotation collectivity and selectivity. An increase in the concentration of each collector increased the zinc recovery but reduced the concentrate zinc grade. Interactions were also observed between different amines and Na₂S and Na₂SiO₃, and OPA 1214 outdid the others in saving the usage of both the Na₂S and Na₂SiO₃. The measured adsorption of collector onto smithsonite was found to correlate well with flotation test results. It was concluded that hydrocarbon chains can be held accountable for the difference in the flotation performance with different amines. The longer the hydrocarbon chain, the stronger the hydrophobic association ability of amine, which is conducive to the selective amine adsorption onto sulfurized smithsonite particles and hence the smithsonite flotation.     

Removal of Zn(II) from dilute aqueous solutions and radioactive process wastewater by foam separation

Ion, precipitate and adsorbing colloid flotations of zinc(II) from dilute aqueous solutions have been investigated over a wide pH range using the anionic surfactant Aerosol OT or the cationic collector cetyl pyridinium chloride. In case of adsorbing colloid flotation (ACF) iron oxyhydroxide and aluminium hydroxide were used, either separately or together, as coprecipitants. The precipitate flotation curves were compared with the corresponding theoretical one calculated from the data published for Zn(II) hydrolysis. In addition to the effect of pH on the percent removal the effects of collector concentration, ionic strength, bubbling time and metal ion concentration were investigated and the optimum conditions were established. High removals could be achieved especially with ACF. The results obtained are discussed with respect to the chemical state of zinc, the ionization behaviour of the collectors and properties of the coprecipitants. The developed ACF process was applied to the removal of⁶⁵Zn from radioactive process wastewater.     

Kinetics of sodium dodecyl benzene sulfonate adsorption on hematite and its interaction with polyacrylamide

This article describes the adsorption of sodium dodecyl benzene sulfonate, an anionic surfactant, on a hematite surface and that when the surface is preadsorbed with polyacrylamide. The adsorption of surfactant on a hematite surface has been studied through equilibration and during kinetics measurements at three pH levels, viz. 4.0, 7.0, 8.9. The surfactant adsorbs strongly on the hematite surface. The adsorption density at equilibrium as well as the rate of adsorption are dependent on the suspension pH. The maximum adsorption density has been observed at pH 4, which reflects strong adsorption of negatively charged sulfonate ions on the oppositely charged Fe₂O₃ surface (point of zero charge, 6.4). The adsorption density reaches its equilibrium value sooner in the case of an alkaline suspension and later in the case of acidic pH. The polymer surfactant interaction has been noticed in the present study and is also a function of pH. The hematite mineral when preadsorbed with the polymer draws fewer of the surfactant molecules at lower surface coverage (during the initial period of the kinetics measurement) irrespective of the pH. When the adsorption of the surfactant reaches a value which is near the equilibrium one, the pH effect is evident. In the case of acidic pH, the surfactant adsorbs more on the hematite surface when preadsorbed with the polymer compared to the bare surface. In the case of neutral or alkaline pH, however, the density of surfactant adsorption remains lower throughout the kinetics measurement when the surface is preadsorbed with the flocculant compared to the bare surface. The particles also remain flocculated till the end of the experiment, whereas at pH 4 the particles are deflocculated. In addition to pH, the electrostatic nature of the adsorbent and the presence of anionic surfactant have an influence on the flocculation–deflocculation phenomena. The polymer–surfactant interaction has been schematically represented. The surfactant is bound with polymeric chains as a combination of its monomeric form as well as in the form of association in the case of acidic media and in competition with polymer in the case of alkaline media. Received: 18 April 2000/Accepted: 2 August 2000     

Effect of Alkyl Chain Length on the Interfacial Dilational Properties of Hydroxy-Substituted Alkyl Benzenesulfonates

Dilational rheological behaviors of adsorption layers of three surfactants, sodium 2-hydroxy-3,5-dioctyl benzene sulfonate (C₈C₈), sodium 2-hydroxy-3-octyl-5-decyl benzene sulfonate (C₈C₁₀), and sodium 2-hydroxy-3-octyl-5-dodecylbenzenesulfonate (C₈C₁₂) formed at air–water and decane–water interfaces, have been investigated as a function of concentration and frequency (0.002–0.1 Hz) by the oscillating bubble/drop method. The experimental results show that the dilational moduli of hydroxy-substituted alkyl benzenesulfonates are obviously higher than those of the common surfactants, because the interfacial interactions between alkyl chains are improved drastically by the unique arrangement of C₈C₈ molecules at the interface. However, the moduli at the decane–water interface are much lower than those at the surfaces because decane molecules will insert into the surfactant molecules adsorbed at the interface and destroy the interactions between alkyl chains. With an increase in the number of carbon atom of 5-alkyl, the surface dilational modulus decreases because the orientation of the surfactant molecules at the surface varies from parallel to tilt. On the other hand, the diffusion-exchange process dominates the interfacial behavior and the interfacial modulus improves with the increase in the length of the alkyl chain.