Collector Ions Research Articles

Evolution of sulfur species on malachite surfaces in the presence of calcium and magnesium ions and implications for xanthate flotation

The depletion of mining resources has led to a sharp increase in gangue minerals. The use of flotation technology with seawater, which is rich in Ca2+ and Mg2+, has gradually increased. However, these ions may affect the flotation process. Herein, we study the effects of the addition of Ca2+ and Mg2+ on the process and products of malachite sulfidization. Analysis of the S layer on the mineral surface indicates that the quantities of S components generated on the malachite surface decrease in the presence of Ca2+ and Mg2+. Additionally, Ca2+ and Mg2+ induce the excessive generation of oxidized S species (SOn2−) during sulfidization, which inhibits the formation of Cu2S. Furthermore, both the solubility of malachite and the consumption of collector ions in the solution increase in the presence of Ca2+ and Mg2+. Microflotation experiments confirm that Ca2+ and Mg2+ result in insufficient sulfidization properties on the malachite surface and reductions in the activity of the sulfidization products, leading to a decrease in sample floatability.

Understanding the role of water quality in separation of rare earth minerals from iron oxide minerals in a flotation circuit

In many mineral processing plants, using saline water has become necessary to improve water efficiency. However, the dissolved ions in the water such as Ca2+ and Mg2+ may have a significant negative impact on the flotation of RE (rare earth) minerals due to the chemical reaction with flotation reagents used in RE flotation. Although some researchers investigated flotation performance of pure rare earth minerals, there is no study investigating the role of water quality in the separation of rare earth minerals from iron oxide minerals in a flotation circuit. This study focused on investigating the effect of divalent cations like Ca2+ and Mg2+ on the flotation of RE minerals using a fatty acid collector and Na2SiO3 depressant. The results showed that the presence of Ca2+ and Mg2+ decreased the selectivity and recovery of RE minerals due to the formation of insoluble calcium and magnesium carboxylate, leading to the reduced residual collector concentration. Furthermore, the divalent cations acted as a bridge between the oxygen atoms of the adsorbed SiO32− and carboxylate ions, resulting in increased adsorption of fatty acid collector ions and higher recovery of FeO. Rheological measurements also revealed that the presence of Ca2+ and Mg2+ significantly increased the flotation pulp viscosity, which could be attributed to the reduced repulsive forces between particles due to the compression of electrical double layer. This study provides valuable insights into the mechanisms underlying the effects of Ca2+ and Mg2+ on RE mineral flotation.

Binder-free fabricated transparent Nb4+ implanted Nb2O5-x ultra-thin negatrode with enhanced areal capacitance and exceptional cyclic stability in aqueous electrolyte

Direct coating and surface engineering of Nb2O5-based active storage materials are important techniques for improving their interfacial interactions with the current collector and electrolyte ions, which have been difficult to achieve in a facile and energy-efficient way. Herein, we report the binder-free coating of shear-structured Nb4+ implanted Nb2O5 (Nb2O5-x) sub-micron thin pseudocapacitive negatrode with wide negative operating voltage (−1.20 V vs Ag/AgCl), improved electronic and ionic conductivity, reduced charge transfer resistance and enhanced energy storage capacity. The Nb4+ implanted electrode exhibits 3.5 mF/cm2 c. a. At 5 mV/s and 100% capacity retention after 3000 constant charge-discharge cycles. The unique electrode was realized via mild de-oxidation of electrodeposited Nb2O5 in a vacuum-less, low-temperature surface engineering process. This simple strategy is suitable for improving current collector-Nb2O5-x-electrolyte interfacial interactions and for industrial-scale production of improved pseudocapacitive negatrodes.

Flotation assessment and adsorption mechanism of wulfenite with three anionic collectors

ABSTRACT Wulfenite is a useful mineral containing both lead and molybdenum. Although the Mo theoretical content of wulfenite is too low to meet the sales requirement, how to pre-concentrate the wulfenite more efficiently and economically becomes increasingly important for subsequent leaching process. Using sodium oleate (NaOL), benzohydroxamic acid (BHA) and sodium dodecyl sulfonate (SDS) as collector, the flotation behavior of wulfenite has been investigated by micro-flotation tests, and the adsorption capacity of the three collectors on wulfenite has been measured and listed as below: NaOL (pH = 9.5) > SDS (pH = 6.5) > BHA (pH = 7.5). According to the frontier orbital theory analysis, when the collector ions act on the {112} surface of wulfenite, the effective mass of NaOL is the lowest, followed by SDS and BHA. Moreover, the molecular dynamics simulation of the three collector ions on wulfenite {112} surface reveals that the two adjacent outermost molybdenum atoms of wulfenite have strong adsorption due to the fracture of the original Mo-O bonds and could easily react with the single-bond oxygen atom outside the polar groups of the three collectors. Comparing the adsorption energy, NaOL has the best adsorption performance to wulfenite {112} surface, during which the O-Mo1 distance and O-Mo2 distance are both below 2.5 Å. By associations of the simulation results with flotation tests, when the feed contains 0.14% Mo, using NaOL as collector, a rough molybdenum concentrate with molybdenum grade of 17.25% and molybdenum recovery of 86.32% has been obtained by conventional flotation tests, which provide theoretical guidance and practical evidence to promote the wulfenite flotation performance.

Effects of Al(III) Ions at Magnetite Flotation from Quartz by Dodecylamine Al(III)

The flotation separation of magnetite and quartz is a long-term challenge for the beneficiation industry. For high-quartz magnetite, conventional flotation shows poor separation effect, resulting in the waste of resources and low flotation efficiency. In this paper, dodecylamine acts as a collector and Al(III) ions in water act as a depressant to selectively separate magnetite and quartz at high alkalinity. The experimental results are analyzed by a micro-flotation experiment, solution chemical calculation, zeta potential, contact angle measurement, and Fourier transform infrared spectroscopy (FTIR). The results of micro-flotation experiments showed that Al(III) ions in water inhibited magnetite more strongly than quartz. The calculation results of solution stoichiometry and zeta potential showed that the phase formed by Al(III) ions on the surface of magnetite and quartz are mainly Al(OH)3(s), which covers the surface of magnetite and quartz, The contact angle measurement results showed that with the addition of Al(III) ions, the contact angle of magnetite varies significantly than that of quartz, and the floatability of magnetite is lower than that of quartz. The FT-IR results further indicated that the addition of Al(III) ions could hinder the adsorption of dodecylamine on the magnetite surface. Meanwhile, the addition of Al(III) ions has no obvious effect on the adsorption of dodecylamine on the quartz surface.

Electronic structure and flotation behavior of Ag-bearing galena

The Ag-bearing galena is a typical resource of base metal sulfide accompanied by noble metal, and has always been the world's major mineral resource for silver output. In this paper, the flotation behavior of Ag-bearing galena has been investigated by using ammonium dibutyl dithiophosphate (ADD), ethyl xanthate (EX) and diethyldithiocarbamate (DDC) as collector, respectively, and unlike that galena could still remain its floatability in high alkaline pulp by DDC, the Ag-bearing galena is much favorable of flotation in low alkaline pulp at pH value of 9.5 by ADD. The electronic structures study indicates that the Ag atom in galena crystal has not changed the type of semi-conductivity, but narrows the band gap to benefit the transfer of electrons, which could enhance the electrochemical reaction activity of Ag-bearing galena. Analysis of frontier orbital also illustrates that the existence of silver could reduce the occupied molecular orbital of Ag-bearing galena, which is advantageous to the collector ion adsorption, and the interaction strength of the three collector ions suggests that ADD shows better selectivity to Ag-bearing galena. Moreover, the molecular dynamics models of the three collectors ions interacting with Ag-bearing galena {100} surface are constructed and simulated, and the results proved that ADD has the best adsorption performance to Ag-bearing galena of the three collectors, during which the S1-Pb distance and the S2-Ag distance are both below 3 Å, indicating that S1 and S2 both have strong bonding with Ag and Pb on the Ag-bearing galena surface. Thus, ADD is suggested to be an excellent collector to recover the Ag-bearing galena, especially in the low alkaline pulp at pH value of 9.5, which provide theoretical guidance and practical evidence to promote the Ag-bearing galena flotation performance in Ag-bearing lead-zinc deposits.

Structures of Pb-BHA Complexes Adsorbed on Scheelite Surface.

Previous studies have shown that Pb-BHA complexes (lead complexes of benzohydroxamic acid) have better collecting ability and can be used in flotation experiments with BHA acting as a collector and lead ions acting as activators. However, the structures of Pb-BHA complexes adsorbed on a mineral surface remain unclear. In this work, the adsorption behavior of Pb-BHA complexes on the scheelite surface was studied by flotation experiments and adsorption capacity measurements, and the structures of the adsorbed Pb-BHA complexes were determined using X-ray photoelectron spectroscopy (XPS) and time-of-flight secondary ion mass spectrometry (TOF-SIMS). The adsorption capacity results showed that more BHA was adsorbed on the scheelite surface in Pb-BHA flotation, and the XPS and TOF-SIMS analysis showed that the species of Pb-BHA complexes adsorbed on the scheelite surface were similar in activation flotation and Pb-BHA flotation. Therefore, the different contents of the complexes on the scheelite surface were responsible for the flotation behavior. XPS and TOF-SIMS showed that BHA combined with lead ions to form complexes with different structures, such as five- and four-membered ring structures. Structure fragment inference based on the measurements indicated that lead ions formed monomer complexes with two BHAs, and that lead hydroxide polymers with a certain degree of polymerization bonded with oxygen atoms in the complexes. The Pb-BHA complexes combine with oxygen atoms on the scheelite surface to form an adsorbate, rendering the surface hydrophobic.

Effect of Al (III) Ions on the Separation of Cassiterite and Clinochlore Through Reverse Flotation

Most hydrophobic clay minerals, such as clinochlore, are known to cause problems in the recovery of cassiterite. In this study, a new reagent scheme, i.e., sodium oleate (NaOL) as a collector and Al (III) ions as a depressant, for reverse flotation separation of cassiterite and clinochlore was investigated. The flotation performance and interaction mechanism were studied by microflotation tests, adsorption tests, contact angle measurements, and X-ray photoelectron spectroscopy (XPS) analysis. Results of single mineral flotation experiments showed that NaOL had a different flotation performance on cassiterite and clinochlore, and the addition of Al (III) ions could selectively inhibit the floatability of cassiterite. Reverse flotation tests performed on mixed minerals indicated that the separation of cassiterite and clinochlore could be achieved in the presence of NaOL and Al (III) ions. Adsorption experiments demonstrated that Al (III) ions hindered the adsorption of NaOL on cassiterite surfaces but exerted little influence on the adsorption of NaOL on clinochlore surfaces. Results of contact angle measurements indicated that Al (III) ions could impede the hydrophobization process of cassiterite in NaOL solution. XPS results showed that aluminum species were adsorbed onto the cassiterite surfaces through the interaction with O sites.

Prediction of Hydrophobic Reagent for Flotation Process Using Molecular Modeling.

The interaction or nonbonded energies of base organic ions and water molecules during the flotation process of minerals have important meanings for organizing hydrophobic and stable collectors. Furthermore, the interaction, cross-term, and valence energies of optimized structures are important for understanding the properties and structures of selective collectors. The simulation of pure scheelite mineral (PSM) surfaces with four different negative ions, using an adsorption locator module is demonstrated. The interaction energies for base organic ions and water molecules were resolved and detected by shaping the best hydrophobic interaction and the most stable suspension over the PSM surface (112) and (101). The adsorption locator results for base organic ions and water molecules on PSM surfaces (112) and (101) using buffer width 0.5 Å and temperature range from 318.15 to 283.15 K confirmed the results obtain from Forcite calculations. The results have demonstrated that the possibilities of using consistent valence force field implemented by Forcite and adsorption locator modules in the selection of flotation reagents are cost saving. Furthermore, hydrophobicity of the main negative ions in soaps were solved by the simulation methods and results are in a good agreement with the experimental methods that proved that mustard soap is more selective on the mineral surfaces than sunflower soap when used as a collector. Increasing the molecular weight of negative ions increases the interaction energy between base collector ions and PSM surfaces (112) and (101) significantly.

Effects of surface properties of (010), (001) and (100) of MnWO4 and FeWO4 on absorption of collector

The atom distribution and electronic properties of (010), (001) and (100) planes of MnWO4 and FeWO4 were studied based on a DFT calculation. The surface stabilities of the three planes were compared according to their surface energies. The most stable one is (010) plane, followed by (001) and (100). (010) and (001) are the main planes for absorption of anion collector ions, which is supported by their bonding relationship and charge density distribution of surface atoms and finally proved by the results of flotation test and stereomicroscope analysis. In addition, the tungsten atoms can be viewed as the absorption site for collectors in (001) plane but not in (010) plane, which can explain the phenomenon in flotation test that the recovery of wolframite can hardly be further boosted even with a high dosage of BHA.

The joint action of saline water and flotation reagents in stabilizing froth in coal flotation

The previous study indicates that both reagent usage and the variation of water conductivity affect froth stability and therefore coal flotation behavior. In this study, Central Composite Rotatable Design (CCRD) was conducted to investigate the interaction11A term in statistics meaning that the effect of two or more variables is not simply additive. of saline water with collector (diesel) and frother (MIBC) in controlling froth stability which was indicated by air recovery. The results show that a significant interaction (see footnote 1) existed between flotation reagents and water conductivity, which affected froth stability, combustible matter recovery and the mineral matter content of flotation concentrate. Frother and salt ions had a joint action in producing a more stable froth. On the other hand, collector and salt ions had a joint action in reducing the combustible matter content of flotation concentrate and the combustible matter recovery. A methodology was developed to avoid overly stable froth and maximize coal flotation performance by adjusting reagent additions based on water conductivity.

Interaction thermodynamics of sulfides of heavy nonferrous metals with sulfhydril collectors for incomplete information on the standard formation energies of starting substances and reaction products (by the example of galenite)

A procedure of calculating the Gibbs free energy of the half-reaction in the absence on values of free standard formation energies of their starting substances and reaction products is investigated. It is shown by the example of galenite that the use of the proposed procedure made it possible to solve the problem of the thermodynamic calculation of the PbS-H2O-CO2-(C4H9O)2PSS− system and construct the corresponding thermodynamic stability diagram. The possible composition of the sorption layer on the galenite surface in the presence of dibutyl phosphate ions is determined by our data and its relation with the concentration of collector ions and the redox potential at the specified pH is revealed. The constructed diagram is compared with the similar one for the PbS-H2O-CO2-C4H9OCSS− system.

Improved statistical methods applied to surface chemistry in minerals flotation

Diagnosis of the surface chemical factors playing a part in flotation separation of a value sulfide phase requires measurement of the hydrophobic and hydrophilic species that are statistically different between the concentrate and tail streams. Statistical methods, based on the monolayer-sensitive time of flight secondary ion mass spectrometry (ToF-SIMS) technique, have been developed towards this ultimate aim by measuring hydrophobic species (collector ions, dimers and metal complexes, polysulfides) as well as hydrophobic metal ions, precipitates and added depressant species. Reliable identification of specific mineral particles is central to this statistical analysis. A chalcopyrite/pyrite/sphalerite mineral mixture conditioned at pH9 for 20 min to study transfer of Cu from chalcopyrite via solution to the other two mineral surfaces, since this mechanism can be responsible for their inadvertent flotation in copper recovery, showed no statistical difference in the copper intensities on pyrite and sphalerite (selected from Fe and Zn images) after this conditioning. Principal component analysis (PCA) identifies combinations of factors strongly correlated (positively or negatively) in images or spectra from sets of data. In images, PCA selects these correlations from the mass spectra recorded at each of 256 × 256 pixels in a selected area of particles. In the image mode, PCA has proved to be a much better method of selecting particles by mineral phase with clearer definition of particle boundaries due to multi-variable recognition. It has clearly separated a statistical difference in copper intensities between the sphalerite and pyrite phases. The PCA method has been applied to concentrate and tails samples collected from the Inco Matte Concentrator demonstrating extensive CuOH and NiOH transfer between the chalcocite (Cc) and heazlewoodite (Hz) minerals. Statistical differences illustrate the important discriminating depressant action of NiOH in flotation despite the activation of Hz by Cu transfer. The adsorption of the collector at specifically-identified Cu sites has been elucidated by the study. Importantly, the statistical analysis has been able to confirm some mechanisms and deny others proposed to control recovery and selectivity giving more focus on the control factors.

Nanobubbles, hydrophobic effect, heterocoagulation and hydrodynamics in flotation

It has been shown in recent years that the long-range attractive interaction forces between hydrophobic surfaces in aqueous systems are caused by the capillary forces of gas bridges which form at the coalescence of nanobubbles adhering on the surfaces. The coalescence of nanobubbles on selectively hydrophobized particles with coarser bubbles initiates the jump into the three-phase contact at the attachment events in flotation. Therefore, one should no longer speak of hydrophobic forces in these events but of hydrophobic effects because they are caused by capillary forces. However, in the selective hydrophobization of particles by long-chain collectors (surfactants), there is another situation. Here, the association of nonpolar groups in the adsorption layers plays an important role in the energy balance of adsorption. This association is caused by “truly” hydrophobic interactions, which support the spotty distribution of the adsorbed collector ions on the particle surfaces and promote the formation of nanobubbles. This paper is intended to show to what extent the results obtained by basic research on the nanobubble formation as well as the force–distance dependence of collision events can be applied to flotation processes. This particularly requires the consideration of the highly turbulent flow conditions in the impeller stream of the flotation machines, in which the attachments almost exclusively occur. Various phenomena which occur in these machines and affect the reagent regime and the hydrodynamics point to the fact that nanobubbles can form, exist and even grow into microbubbles in that region. Therefore, so-called combined attachment events should predominate as already imagined several decades ago. The highly turbulent pressure fluctuations in the impeller stream in addition to the dispersion of the bubbles effect also their oscillations in size and shape, so that adsorption equilibria in the interfaces liquid/gas cannot be supposed. However, the pressure fluctuations present the possibility to overcome potential barriers in the wetting films at attachment events.

Molecular modeling study on the relative stabilities of the flotation products for arsenic-containing minerals: dixanthogens and arsenic(III) xanthates

The interactions of As(III) ion with C 2H 5OCS − 2 and C 2H 5SCS − 2, known as the most popular collector ions, were studied by density functional theory (DFT) at the B3LYP/6-31G** level in connection with the arsenic-containing minerals realgar, orpiment, and arsenopyrite. The dixanthogen formations of these ions were also investigated at the same level of theory. The central purpose of this paper is to compare the stabilities of the major flotation products, namely As(III) xanthates and dixanthogens. The results show that the magnitudes of the interaction energies for the formations of As(III) xanthates and dixanthogens increase when the oxygen atom is replaced by the sulfur atom in C 2H 5OCS − 2. Therefore, the C 2H 5OCS − 2 ion is preferred in these formations. The results obtained are in agreement with the experimental data reported.

Reactivities of some thiol collectors and their interactions with Ag (+1) ion by molecular modeling

The most commonly used collectors for sulfide minerals in the mining industry are the thiol collectors for the recovery of these minerals from their associated gangues by froth flotation. For this reason, a great deal of attention has been paid to understand the attachment mechanism of thiol collectors to metal sulfide surfaces. The density functional theory (DFT) calculations at the B3LYP/3-21G* and B3LYP/6-31++G** levels were employed to propose the flotation responses of these thiol collectors, namely, diethyl dithiocarbamate, ethyl dithiocarbamate, ethyl dithiocarbonate, ethyl trithiocarbonate and ethyl dithiophosphate ions, and to study the interaction energies of these collectors with Ag (+1) ion in connection to acanthite (Ag2S) mineral. The calculated interaction energies, ΔE, were interpreted in terms of the highest occupied molecular orbital (HOMO) energies of the isolated collector ions. The results show that the HOMOs are strongly localized to the sulfur atoms and the HOMO energies can be used as a reactivity descriptor for the flotation ability of the thiol collectors. Using the HOMO and ΔE energies, the reactivity order of the collectors is found to be (C2H5)2NCS2− > C2H5NHCS2− > C2H5OCS2− > C2H5SCS2− > (C2H5O)(OH)PS2−. The theoretically obtained results are in good agreement with the experimental data reported.

The effect of organic solvents on the recovery of fine mineral particles by liquid-liquid extraction

This paper deals with a study of the cooperative effect of organic solvents in recovering fine mineral particles by liquid-liquid extraction. With dodecylamine acetate as a collector, iso-octane as the main oil phase and n-butanol and methyl isobutyl ketone (MIBK) as sub-oil phases, the cooperative effect between polar neutral organic molecules and non-polar hydrocarbon oil droplets on the extraction of fine quartz from the aqueous phase into the oil phase was estimated by measuring the oil/water interfacial tensions and contact angles of oil droplets on a quartz surface in water. From the results obtained, it was found that the neutral organic molecules made the extraction of fine quartz particles more efficient, i.e., increasing the recovery of quartz in the oil phase and reducing the collector addition. It is surmised that coadsorption of the neutral organic molecules with collector ions plays the most important role.

浮選捕収剤の白金上への吸着に対する電気化学的研究

The adsorption of flotation collectors such as 2-mercapto-benzothiazole (MBT) or potassium ethyl xanthate (EX), on platinum was electrochemically studied by the cyclicvoltammetry technique. The current-potential curve presents a definite peak of the oxidation of MBT ion or EX ion due to one electron release. The charge transfer step is more slowly in the adsorption of MBT ion than EX ion on platinum. The anodic oxidation of MBT ion com-mences at potentials greater than by the oxidation of EX ion on platinum. A hydrophobic layer of adsorbate was formed on the platinum electrode surface by the electrochemical processes, an anodic oxidation of the collectors, and that of absorbate was hardly reduced back to collector ions, not giving rise to the cathodic current peak.

Influence of collector ions on operation of magnetically insulated diode

We studied the formation of the collector ion flow in magnetically insulated diodes (MID) with plate-, sphere-, and cone-shaped cathodes. The ions are formed as a result of the ionization of residual gas by electron bombardment and are focused into the cathode plasma region. This effect can negatively influence diode operation in the microsecond range of pulse duration.

New reagent systems for the flotation of kaolinite

The selective flotation of kaolinite for the separation from feldspar is difficult because the two minerals have very similar surface properties and the flotation feed contains a high proportion of extremely fine particles (< 5 μm); nevertheless, this process is of great practical importance. The alkyl amines usually used as collectors in kaolinite flotation processes only give satisfactory results in strongly acidic pulps. Reagent systems based on cationic surfactants were developed to enable kaolinite to be separated from feldspar by flotation in weakly acidic to neutral pulps. Special importance is attached to the addition of suitable multivalent cations in this context. Furthermore, in the presence of these multivalent cations flotation can be carried out with suitable anionic surfactants that previously could not be used because of their low effectiveness. With the help of basic studies of the charge on the minerals and the adsorption of the surfactants and the multivalent cations on the mineral surfaces, a good understanding of the action mechanism of the developed reagents was obtained. During flotation with cationic surfactants the recovery of feldspar is reduced, and the selectivity of the flotation is thus improved, as a result of aluminium ions being competitively adsorbed rather than collector ions. By contrast, in the case of flotation with anionic surfactants the activation of the kaolinite surface by the multivalent cations is the crucial precondition for selective flotation. The effectiveness of the new reagent systems was demonstrated in laboratory scale flotation tests on natural kaolinite ores.