Talc Surface Research Articles

Insights into the adsorption performance and mechanism of hydrated Ca ion on talc (0 0 1) basal surface from DFT calculation

The utilization of Ca ion as assistant depressant of CMC on talc has been widely reported. Thus, the study on the adsorption mechanism of Ca ion on talc surface is very crucial for understanding the performance of CMC on talc depression. In this paper, mechanism insights into hydrated Ca ion adsorption on talc (0 0 1) basal surface were creatively provided using DFT calculation. [Ca(H 2 O) 6 ] 2+ and [Ca(OH)(H 2 O) 3 ] + were determined as the effective hydrate components for Ca ion adsorption, and the top O site was the most favorable position for their adsorptions on talc surface. Furthermore, the adsorption mechanisms of [Ca(H 2 O) 6 ] 2+ and [Ca(OH)(H 2 O) 3 ] + on talc surface were found to be not the Ca—O chemical bond, but the hydrogen bonding formed by the H atom of the H 2 O ligand and the surface O atom. H 2 O acted like a bridge to connect them to the talc surface. Moreover, the hydrogen bonding was formed due to the hybridization of H 1s orbital with the O 2s, O 2p orbitals. Simultaneously, electrons transferred between the H atom and the surface O atom. This work provides theoretical insights into the Ca ion adsorption on talc surface, which can help deeply understand the talc flotation using CMC as depression.

Using Green, Economical, Efficient Two-Dimensional (2D) Talc Nanosheets as Lubricant Additives under Harsh Conditions

Two-dimensional (2D) nanomaterials have attracted much attention for lubrication enhancement of grease. It is difficult to disperse nanosheets in viscous grease and the lubrication performances of grease under harsh conditions urgently need to be improved. In this study, the 2D talc nanosheets are modified by a silane coupling agent with the assistance of high-energy ball milling, which can stably disperse in grease. The thickness and size of the talc nanosheet are about 20 nm and 2 µm. The silane coupling agent is successfully grafted on the surface of talc. Using the modified-talc nanosheet, the coefficient of friction and wear depth can be reduced by 40% and 66% under high temperature (150 °C) and high load (3.5 GPa), respectively. The enhancement of the lubrication and anti-wear performance is attributed to the boundary adsorbed tribofilm of talc achieving a repairing effect of the friction interfaces, the repairing effect of talc on the friction interfaces. This work provides green, economical guidance for developing natural lubricant additives and has great potential in sustainable lubrication.

Synergistic mechanism of acidified water glass and carboxymethyl cellulose in flotation of nickel sulfide ore

• The effect mechanisms of serpentine and talc on sulfide flotation are different. • Acidified water glass can eliminate heterocoagulation between serpentine and talc. • Carboxymethyl cellulose can inhibit talc flotation . • When serpentine and talc coexist, dispersants and inhibitors need to be used together. Efficiently utilizing nickel sulfide ores containing multiple magnesium silicate gangue minerals through flotation is difficult. Therefore, in this study, we investigated the flotation behavior and discussed the mechanism of a refractory nickel sulfide ore with multiple MgO gangue minerals. The synergistic mechanism of acidified water glass (AWG) and carboxymethyl cellulose (CMC) in the flotation of the nickel sulfide ore was studied through flotation tests, zeta potential measurements, adsorption capacity tests, Fourier transform infrared ray (FTIR) spectroscopy, and observation under a microscope. The results showed that the addition of AWG could change the electrical properties on the surface of serpentine, weaken the heterogeneous aggregation of serpentine and talc, and increase the selective adsorption of CMC on the talc surface. The actual ore flotation test was conducted with the synergistic effect of AWG and CMC. In the practical flotation test of the ore, the concentration of MgO in the concentrate, compared with the original process with CMC alone, was reduced from 9.62% to lesser than 5.92%, with the combined synergistic action of acidified sodium silicate and CMC acting as the depressant. Simultaneously, the grade and recovery of Ni from the Ni-mixed concentrate remained unchanged, and the inhibiting effect of the magnesium-bearing gangue minerals improved.

Mechanism insights into the hydrated Al ion adsorption on talc (001) basal surface: A DFT study

Al ion was reported to have an enhanced depression of Carboxymethyl cellulose (CMC) on talc flotation. However, how Al ion is adsorbed on talc surface remains unclear. Herein, the hydrated Al ion adsorption on talc (001) basal surface was creatively studied by DFT calculations. The effective number of H2O ligands in hydrated Al ion was probed and the optimal adsorption structure was investigated. We found that Al(OH)3(H2O) was the preferred hydrate structure, and the top O site was its optimal adsorption position on talc surface. Furthermore, Al-O chemical bond was not formed, and H2O was found to act as a bridge to connect the Al(OH)3(H2O) to talc surface by H-bond between H of H2O ligand and surface O instead of H-bond between H of Al(OH)3 in Al(OH)3(H2O) and surface O. However, [Al(OH)4]− cannot form the H2O bridge due to the electrostatic repulsion, and its adsorption on talc surface was energetically unsupportive. Moreover, we found that the formation of H-bond was due to the hybridization reaction between O 2p and H 1s orbitals, and slight electron transfers between O and H atoms were also observed. Finally, the Al(OH)3(H2O) was adsorbed on talc surface, which is consistent with the performed experimental result.

Selective depression of talc in azurite sulfidization flotation by tamarind polysaccharide gum: Flotation response and adsorption mechanism

In this study, tamarind polysaccharide gum was first used in the sulfidization flotation of azurite to improve the Cu grade of the concentrate via the depression of talc. The flotation and contact angle test results indicated that the hydrophobicity and floatability of talc were weakened, and the recovery decreased with the addition of tamarind polysaccharide gum, but the flotation behavior of azurite was barely influenced. At pH 8.0, using 30 mg/L tamarind polysaccharide gum with 200 mg/L Na2S and 400 mg/L NaBX to separate azurite and talc, the recoveries of which were 80.42% and 18.07%, respectively. To explore the adsorption mechanism of tamarind polysaccharide gum, zeta potential measurements, X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy analyses were conducted. The results indicated that tamarind polysaccharide gum selectively adsorbed on the talc surface, thus the flotation separation of azurite and talc was achieved, and the concentrate grade in the sulfidization flotation of azurite was increased.

Comparison and Mechanism Analysis of Three-Phase Contact Formation onto Hydrophilic/Hydrophobic Mineral Surfaces in the Presence of Cationic/Anionic Surfactants during Flotation Process

This article presents the dynamic process of the three-phase contact (TPC) formation by colliding bubbles onto muscovite and talc surfaces in water and two types of solutions including cationic CTAC surfactant (cetyltrimethyl ammoniumchloride) and anionic NaOL surfactant (sodium oleate). The TPC formation process was observed through the high-speed camera between bubbles and layered silicate minerals (hydrophilic muscovite and hydrophobic talc). It was found that the rupture of the liquid film between the bubbles and the mineral surface is a prerequisite for TPC formation. In the case of muscovite, TPC was formed only with cationic CTAC, and as the surfactant concentration increased, the time needed for TPC formation was shortened. Due to electrostatic repulsion, TPC did not occur in water and NaOL. However, for talc, TPC occurred both in water and in surfactant solutions. In contrast to muscovite, the time of TPC formation on the talc surface was prolonged with the increase in the surfactant concentration. It was concluded that hydrophobic attraction and electrostatic attraction between mineral surfaces and bubbles can significantly promote the localized foam film rupture, which was the main reason for the TPC appearance in water and surfactants. For the hydrophilic muscovite, CTAC adsorption improved the surface hydrophobicity; I3/I1 in fluorescence spectroscopy increased, and the micro-polarity faded, making TPC formation need more time. However, for the natural hydrophobic talc, the increasing surfactant adsorption decreased I3/I1 values and enhanced the local micro-polarity, causing the extension of time for TPC. Therefore, TPC formation for different minerals resulted from different reasons.

Selective flotation separation of chalcopyrite from talc by a novel depressant: N-methylene phosphonic chitosan

• NMPC can conduct effectively flotation separation of chalcopyrite from talc. • NMPC can selectively adsorb on the surface of talc. • The flocculation effect of NMPC can accelerate the precipitation of talc. • A physisorption process for NMPC– talc interaction is revealed by surface analysis. In this work, we investigated the flotation performance and selective adsorption mechanism of a chitosan derivative NMPC (N-methylene phosphonic chitosan) as an novel talc depressant in the flotation separation of chalcopyrite from talc. The single mineral flotation experiments demonstrated that without the talc depressant, both chalcopyrite and talc showed excellent floatability, thus the separation was difficult in the pH range of 3–11. When NMPC was added, the recovery of talc was reduced drastically but the recovery of chalcopyrite decreased slightly in the pH range of 3–9 at a concentration of 10 mg/L in pulp. Artificial mixed mineral flotation experiments also demonstrated that the effective separation of talc and chalcopyrite could be achieved when NMPC was employed as the depressant. The results showed that better grade and recovery were obtained in different proportions of chalcopyrite and talc, which meant the NMPC is better than CMC, Arabic gum in flotation separation of talc and chalcopyrite. Analysis of adsorption tests, FT-IR measurements, and XPS measurements suggested that NMPC was selectively adsorbed on the talc surface by physical adsorption which might result from the hydrogen bonding and hydrophobic interaction between NMPC and talc. Moreover, the sedimentation experiments disclosed that NMPC plays an important role in the flocculation and settling of fine talc.

The flotation separation of molybdenite from talc using zinc sulfate in sodium silicate system and related mechanism

The function of sodium silicate is similar to that of sodium carbonate in flotation processes. In particular, in the presence of many different kinds of silicate gangue in minerals, sodium silicate performs better than sodium carbonate in inhibiting gangue formation by flotation. The results of this study showed that sodium silicate can replace sodium carbonate and inhibit talc flotation in combination with zinc sulfate; the associated depression mechanism was also investigated. The flotation results demonstrated that sodium silicate had a certain depressing effect on talc flotation compared with molybdenite, and that zinc sulfate could selectively inhibit talc flotation at pH ~10 in the sodium silicate system. Contact angle measurements further confirmed that the hydrophobicity of talc decreases upon the addition of zinc sulfate to the sodium silicate system. Fourier-transform infrared spectroscopy and zeta potential analysis provided strong evidence that zinc sulfate and sodium silicate underwent physical adsorption on talc surfaces. Additionally, zeta potential analysis, solution chemical analysis, and time-of-flight secondary ion mass spectrometry showed that sodium silicate may be hydrolyzed to form silicic acid micelles, which formed metal cation complexes with zinc sulfate and were intertwined and physically adsorbed on the talc surface.

Evolution of Black Talc upon Thermal Treatment

Black talc is a natural silicate clay mineral with a typical 2:1 layered structure, low electrical conductivity, large specific surface area, and high thermal stability. The world’s largest black talc mine, with known reserves of one billion tons, is located in China’s Jiangxi province. Due to the restriction of its color, the application of black talc is only limited to ceramic raw materials, coating filler, waterproof materials, and other low-end application industries. Thermal treatment is a common method of clay mineral modification. It is vital to examine the structural and physical changes of black talc during calcination in order to prepare black-talc-based composites and to broaden their applications. This work discusses the evolution of black talc upon thermal treatment (30–1000 °C) and the corresponding structural changes. The thermal stability of minerals was analyzed via thermogravimetric (TG) analysis and thermogravimetry–mass spectrometry (TG-MS). The decomposition of minerals during calcination consists of four processes: dehydration, organic carbon decomposition, dihydroxylation, and phase transformation. In situ FTIR and in situ XRD were employed to track changes in black talc in real time during thermal treatment. At 800 °C, black talc was found to begin to go through dihydroxylation, and the crystallinity index decreased significantly. The XRD pattern of samples at 950 °C (T950) showed the reflection of the enstatite structure, and the relative crystallinity index was 27.3%, indicating that the mineral had undergone phase transformation. In addition, the Brunauer–Emmet–Teller (BET), laser particle size analyzer, Zeta potential, scanning electron microscopy (SEM), and transmission electron microscopy (TEM) techniques were used to systematically characterize the physicochemical properties of minerals at different temperatures. The results show that black talc’s particle size and specific surface area increase with the calcination temperature. The surface charge changes, and more amorphous SiO2 and MgO appear, indicating that thermal treatment could induce structural changes and activate the surface of black talc.

Effect of Point Defects on Electronic Properties and Structure of Talc (001) Surface by First Principles

The surface structure and electronic properties of Mg vacancy defects on talc (001) and impurity defects with Fe, Mn, Ni, Al, and Ca replacing Mg atoms were calculated by using density functional theory. The calculation results show that the order of impurity substitution energy is Mn < Ni < Al < Ca < Fe. This indicates that Fe impurity defects are most easily formed in talc crystals. The covalent bonding between Si atoms and reactive oxygen atoms adjacent to impurity atoms is weakened and the ionic property is enhanced. The addition of Fe, Mn, and Ni atoms makes the surface of talc change from an insulator to a semiconductor and enhances its electrical conductivity. The analysis of electron state density shows that surface states composed of impurity atoms 4S orbital appear near the Fermi level.

Improved flotation of molybdenite from talc using a selective reagent scheme

Talc is one of the most problematic gangue minerals for molybdenite flotation owing to its strong natural hydrophobicity. In this work, pullulan polysaccharide (PU) was evaluated as a potential depressant in the flotation separation of molybdenite from talc. Bench flotation tests of single mineral samples and multi-mineral samples were carried out to evaluate the performance of PU in flotation. And the results show that under the preferable reagent scheme of 40 mg/L PU, 160 mg/L butyl xanthate (BX) and 25 μL/L MIBC, molybdenite can be effectively separated from talc over a wide pH range (from 2.0 to 8.0). Furthermore, FTIR and XPS analyses demonstrate that BX can desorb the pre-adsorbed PU on the surface of the molybdenite by competitive adsorption, but has only a slight effect on the PU adsorbed on surface of the talc. The results also confirm that PU has a strong and stable adsorption on the surfaces of talc and molybdenite, whereas BX adsorbs more strongly on the surface of molybdenite. Hence, the reagent scheme of PU + BX, with biodegradability, low toxicity, low cost and synergistic selectivity, has great potential for industrial application in the flotation separation of molybdenite from talc.

Efficiently separating malachite from talc using new collector famciclovir via reverse flotation

In this study, famciclovir was used as a new collector in the flotation separation of malachite from talc. The results of flotation tests demonstrated that famciclovir had higher selective collection ability to talc than malachite. Famciclovir could remove talc from malachite-talc mixture, including −10 μm talc. The adsorption behaviors of famciclovir onto the surfaces of malachite and talc were researched by contact angle measurement, X-ray photoelectron spectroscopy (XPS) analysis and FTIR spectrum measurements, which indicated that famciclovir can selectively adsorbed onto talc surface. Thus, famciclovir could be used as a high-selectivity collector to efficiently separate malachite from talc and reduce the covering of talc slime on malachite surface. Therefore, famciclovir is expected to have great potential for pre-desliming in the flotation of copper oxide minerals.

Flotation separation of molybdenite from talc using a new inhibitor Artemisia sphaerocephala Krasch gum

In the flotation of sulfide minerals, the separation of molybdenite and talc is a difficult problem. Talc is the main gangue mineral of molybdenite, it has good natural hydrophobicity and a similar layered structure as molybdenite, so inhibitors are often used to separate them. But the reverse flotation method is often used to inhibit molybdenite, and the separation effect is not satisfactory. Therefore, an effective inhibitor is greatly needed. Here we showed a new inhibitor ASKG to separate molybdenite from talc. In microflotation tests, it was found that ASKG has a good depression effect on both molybdenite and talc. By adding collector SBX, the floatability of molybdenite can be enhanced without affecting the depression of ASKG on talc, and the effective separation of the two can be realized. The FTIR analyses and adsorption measurements revealed that the adsorption of ASKG on the talc surface occurred through hydrogen bond and hydrophobic interaction in physical adsorption. In addition, the competitive adsorption of ASKG and SBX on the surface of molybdenite was explored, and it was found that the first reagent reacted with molybdenite will hinder the adsorption of the later reagent on molybdenite and affect the floatability of molybdenite. The results showed that ASKG plays an excellent role in the separation of molybdenite and talc by positive flotation, which is of great significance for the separation of other minerals in mineral processing.

AFM Slip Length Measurements for Water at Selected Phyllosilicate Surfaces

Most reported slip length measurements have been made at the surfaces of synthetic materials and modified synthetic materials. In contrast, few slip length measurements at the surface of unmodified natural mineral surfaces have been reported. In this regard, flow at the silica face surfaces of the phyllosilicate minerals, talc and mica, was considered. A slip boundary condition was expected at the nonpolar hydrophobic silica surface of talc leading to enhanced flow, and a no-slip boundary condition was expected at the hydrophilic silica surface of mica. Atomic force microscopy (AFM) slip length measurements were made at the talc and mica surfaces. The slip length results for the hydrophobic silica surface of talc were contrasted to the results for the hydrophilic silica surface of mica (no-slip flow). The results are discussed based on molecular dynamics simulations (MDS), as reported in the literature, and AFM images of surface nanobubbles. For nonpolar hydrophobic surfaces (such as talc), it is doubtful that the MDS interfacial water structure and the water exclusion zone (3.2 Å) account for the AFM slip flow with slip lengths as great as 95 nm. Rather, a better explanation for the AFM slip flow condition is based on reduced interfacial viscosity due to the presence of dissolved gas and the accommodation of pancake nanobubbles at the talc surface having a height dimension of magnitude similar to the slip length.

How polar hydroxyl groups affect surface hydrophobicity on model talc surfaces

Based on molecular dynamics simulations, we have studied the wetting behaviors of water on the talc-like surface with different surface polarity by modifying the charge distribution of surface hydroxyl (–OH) groups. With the change of the charge of the hydrogen atom (denoted as δ q ) in –OH group, the contact angle decreases from 91° to 50° and then remains constant. On the surfaces with the larger charge of hydrogen atoms (δ q ≥ 0.2 e), a water droplet is formed above a water monolayer, which is exactly contacted on the surface. Each water molecule in the monolayer forms one hydrogen bond (H bond) with surface –OH groups, without participating in any H bond with the water molecules within the monolayer or with the water molecules above the monolayer. The polarity of the –OH group also has a great influence on the dynamic behaviors of the interface water, such as residence time, hydrogen bond lifetime and self-diffusion coefficient. The diffusion of water molecules in the water monolayer near the highly polar surface is greatly suppressed, and the residence time of water molecules in the water monolayer even exceeds 12 ns.

Biological fabrication and electrostatic attractions of new layered silver/talc nanocomposite using Lawsonia inermis L. and its chitosan-capped inorganic/organic hybrid: Investigation on acceleration of Staphylococcus aureus and Pseudomonas aeruginosa infected wound healing

In the present study, new-layered inorganic/organic hybrid of silver/talc nanocomposites (Ag/Tlc-NPs) and its chitosan-capped derivative (Ag/Tlc/Csn NCs) were biochemically synthesized utilizing Lawsonia inermis L. extract. The silver nanoparticles (Ag NPs) were synthesized employing green method on the exterior surface layer of talc mineral as a solid substrate. The negatively charged surface layer of talc might function as templates and can attract the chitosan cations from a solution to yield a layered hybrid structure, whose inorganic phase is formed by Si-O-Ag bonds. Our results revealed that Ag NPs were formed on the exterior surface of talc with a diameter with size of 124–215 nm. In addition, cytotoxicity, in vitro antibacterial activity, and clinical effects of wound-healing ointments containing talc were investigated. The results implied the successful synthesis of Ag/Tlc/Csn NCs using the extract. The structures were safe up to 0.50 mg/mL. In vitro studies confirmed antioxidant and antibacterial properties of Ag/Tlc/Csn NCs. In sum, our findings showed that the ointments improve wound healing process by inducing an anti-inflammatory M2 phenotype and bFGF, CD206, collagen1A, and IL-10 production that causes fibroblast migration and wound closure through influencing M2 macrophage. Ag/Tlc/Csn is suggested to be taken into consideration as a medical combination for improving infected wound healing and as a promising agent for clinical administration.

Talc Flotation—An Overview

Talc is a naturally hydrophobic gangue mineral in most sulfide ores. However, talc has vast applications in the cosmetics, paper, and paint industries due to its high chemical stability, and its demand continues to grow. Since flotation is the most effective beneficiation technique for upgrading sulfides, the high hydrophobicity of talc has made its selective separation challenging. This paper explored the different properties of talc and the different factors that affect its flotation separation performance as a proven versatile beneficiation technique. Surface properties, zeta potential measurements, contact angles, and other factors affecting the talc flotation efficiency were discussed in detail. It was observed that the surface face/edge ratio (particle size) has a direct relationship with the level of talc hydrophobicity. Talc surfaces are negatively charged in a wide pH range (pH 2–12). Different depressants have already been studied; however, most of them showed low selectivity. The addition of ions such as Ca2+ could enhance talc depression. Pretreatment methods such as ultrasonic and thermal treatments were reported to decrease the talc floatability. It was demonstrated that the development of new selective depressants or pretreatment options for talc flotation requires attention in future investigations to improve its selective separation.

Effect of aluminum ions on the adsorption of carboxymethyl cellulose onto talc

Talc is a gangue mineral of many sulfide minerals, which is naturally hydrophobic. The depression of talc is very important and challenging in sulfide ore flotation. This research introduced aluminum ions into the process of using carboxymethyl cellulose (CMC) to depress talc. Flotation experiment results showed that aluminum ions used alone exerted a weak depression effect on talc, and that aluminum ions used in conjunction with CMC effectively depressed the flotation of talc at pH 8.5. Results of X-ray photoelectron spectroscopy and adsorption tests showed that the interaction of aluminum ions with talc changed the surface of talc, and Al(OH)3 formed on the talc surfaces, thereby promoting the adsorption of CMC onto talc and depressing the flotation of talc. On this basis, the morphology of CMC on the talc surface was observed by atomic force microscopy imaging. With the addition of aluminum ions, CMC aggregated to a greater extent, multiple layers adsorbed onto the surface of talc, and the coverage of CMC substantially increased. Based on all tests and analysis, the mechanism of the synergistic effect of CMC and aluminum ions on talc flotation was also proposed.

Selective separation of chalcopyrite and talc using pullulan as a new depressant

As a gangue mineral, talc is usually associated with chalcopyrite. Therefore, the depression of talc is required in the field of sulphide mineral flotation. Herein, the depression mechanism of pullulan in the flotation separation of chalcopyrite from talc was investigated via flotation tests and characterisation techniques, such as Fourier transform infrared analysis (FTIR), X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM). The flotation test results showed that chalcopyrite can be selectively separated from talc with 20 mg/L pullulan as a depressant, and that the separation effect remains unaffected when the depressant dosage is increased to 80 mg/L. Additionally, the zeta potential, FTIR and adsorption measurements indicated that pullulan is selectively adsorbed on talc surfaces, and that talc surfaces adsorb more depressants than chalcopyrite. The XPS results indicated that the pullulan adsorption on talc surfaces is physical. The AFM results indicated that pullulan adsorption on talc surfaces forms polymer layers. Therefore, pullulan is considered a potential depressant of talc in the flotation industry.

Anisotropic robustness of talc particles after surface modifications probed by atomic force microscopy force spectroscopy

As a versatile mineral, the crystalline hydrated magnesium silicate talcum, or talc, has been widely used in numerous industries from pharmaceutical formulations to composite material designs. Its efficient application as filler/additives incorporates the improvement in concomitant properties within materials, e.g., strength, which involves interactions between talc particles and aqueous/nonaqueous matrices. Successful property enhancement imposes ideal mixing and homogenous adhesion within a talc particle, but they are limited by the coexistence of face and edge surfaces of talc, which exhibit different level of hydrophobicity. Here, using atomic force microscopy force spectroscopy, we showed that although hydrophilic talc particles obtained from acid treatment or aminosilanization better adhered with materials representing a matrix, the anisotropic characters of the two surface types persisted. Conversely, the degree of talc’s surface anisotropy reduced with the surface hydrophobization by aliphatic methylsilanization, but followed by the decrease in adhesion. With ten-fold difference in Hamaker constants of the probe/talc surface interacting pairs, we showed that the adhesions resulted from van der Waals interactions that suggested the influence of surface polarity. The insight from this work would provide grounds for strategies to modulate talc’s adhesion, hydrophobicity and surface uniformity.