Talc Surface Research Articles

Hydrophobicity of talc basal surface

The hydrophobicity of the talc basal surface is considered in the framework of the concept which relates the properties of layered silicates and their dispersions to the differences between the characteristics of the basal and side surfaces of their particles. The ab initio calculations of the energetics and geometry of the microclusters formed by water molecules adsorbed on the active sites (oxygen ions) located at the perfect basal surface of talc are performed. It is shown that the typical property of the hydrophobic surface is the adsorption of single molecules of water on extremely scarce or weak active sites of the surface, which act as secondary adsorption sites, and subsequent adsorption of water molecules on these secondary sites which results in the formation of ring-like structures. The heat of adsorption on this surface is shown to be essentially lower than the water condensation heat, which is also indicative of the hydrophobicity of the basal surface of talc.

Interactions between sulfa drug sulfadiazine and hydrophobic talc surfaces

Interactions between sulfadiazine (SDZ), a sulfa drug antibiotic, and talc, a low charge 2:1 phyllosilicate, were investigated under batch experimental conditions. The SDZ adsorption on talc was instantaneous, with a very large rate constant and a fast rate, although with a low amount. SDZ adsorption followed a linear sorption isotherm, suggesting that the hydrophobic interact instead of cation exchange was more like responsible for the uptake of SDZ. Solution pH had a unique influence on SDZ adsorption. The solute distribution coefficient was low in pH 3–7 range and increase at even lower and higher pH conditions. Molecular simulation suggested that the interactions between the benzene ring as well as the O of SDZ and the Mg in the octahedral site of talc was partially responsible for SDZ uptake. In addition, the hydrogen bonding between the N in the amine as well as in the hetero ring and the broken bond of O on the 010 plane of talc also contributed to SDZ uptake by talc.

Kinetic features of the adsorption of sodium oleate on talc

Kinetic features of the adsorption of sodium oleate on dispersed talc samples of Onotskoe deposit are studied. It is shown that adsorption proceeds in two steps with different rate constants of adsorption ka and desorption kd. It is found that at the first step, lasting for nearly one hour under experimental conditions, the process is characterized by high ka and kd values (1.23 × 10−2 m2/(mol min) and 1.06 × 10−5 m2/(L min), respectively). It is concluded that the final stage associated with the rearrangement of molecules on a talc surface lasts for a long time with ka = 2.12 × 10−3 m2/(mol min) and kd = 1.82 × 10−6 m2/(L min).

Size-controlled synthesis of Fe3O4 magnetite nanoparticles on the exterior of talc layers

The purpose of this study was to investigate the effect of OH concen- tration on the size of Fe3O4 nanoparticles (Fe3O4-NPs). Fe3O4-NPs with different cubic nanocrystal structure and percentage Fe3O4 content were successfully pre- pared, by use of the chemical co-precipitation method, on the exterior surface of talc, as solid substrate, by an environmentally friendly process. Ferric chloride, ferrous chloride, and sodium hydroxide were used as iron oxide precursors and reducing agent. The results showed that the morphology of the Fe3O4-NPs can be adjusted by changing the reaction conditions, for example volume of reducing agent and concentration of iron salts. Different size, dispersal, and the magnetic properties were obtained by changing the concentration of iron salts and NaOH. The products were characterized by powder X-ray diffraction, scanning electron microscopy, transmission electron microscopy, energy-dispersive X-ray spectroscopy, and Fourier-transform infrared spectroscopy. The reaction was conducted in a non- oxidizing, oxygen-free environment. Because the interlamellar spacing of the talc was almost unchanged (ds = 0.94-0.87 nm), the Fe3O4-NPs were formed on the exterior surface of the talc. The average diameter of the Fe3O4-NCs could be varied from 6.62-8.13 nm in adjusting the concentration of NaOH. The size of the nanoparticles decreased as the amount of reducing agent was increased. These talc- Fe3O4 nanocomposites (talc-Fe3O4-NCs) may have potential applications in the chemical and biological industries.

Anisotropic Surface Charging of Chlorite Surfaces

AbstractChlorite is a layered silicate mineral group of importance in geology, agriculture, and in the processing of mineral resources. A more detailed analysis of the surface charge of chlorite minerals is important in order to improve our fundamental understanding of such particle structures and their behavior in suspension. In this study, the anisotropic surface charging of chlorite has been established using Atomic Force Microscopy surface-force measurements with a silicon nitride tip. The surface-charge densities and surface potentials at the chlorite basal-plane surfaces and edge surface were obtained by fitting force curves with the Derjaguin-Landau-Verwey-Overbeek theoretical model. The results show that at pH 5.6, 8.0, and 9.0 the chlorite mica-like face is negatively charged with the isoelectric point (IEP) less than pH 5.6. In contrast, the chlorite brucite-like face is positively charged in this pH range and the IEP is greater than pH 9.0. The surface charging of the chlorite edge surface was found to be pH-dependent with the IEP occurring at pH 8.5, which is slightly greater than the edge surfaces of talc and muscovite due to the larger content of magnesium hydroxide at the chlorite edge surface. Findings from the present research are expected to provide a fundamental foundation for the analysis of industrial requirements, e.g. collector adsorption, slime coating, and particle interactions in the area of mineral-processing technology.

Synthesis of talc/Fe3O4 magnetic nanocomposites using chemical co-precipitation method

The aim of this research was to synthesize and develop a new method for the preparation of iron oxide (Fe3O4) nanoparticles on talc layers using an environmentally friendly process. The Fe3O4 magnetic nanoparticles were synthesized using the chemical co-precipitation method on the exterior surface layer of talc mineral as a solid substrate. Ferric chloride, ferrous chloride, and sodium hydroxide were used as the Fe3O4 precursor and reducing agent in talc. The talc was suspended in deionized water, and then ferrous and ferric ions were added to this solution and stirred. After the absorption of ions on the exterior surface of talc layers, the ions were reduced with sodium hydroxide. The reaction was carried out under a nonoxidizing oxygen-free environment. There were not many changes in the interlamellar space limits (d-spacing = 0.94−0.93 nm); therefore, Fe3O4 nanoparticles formed on the exterior surface of talc, with an average size of 1.95–2.59 nm in diameter. Nanoparticles were characterized using different methods, including powder X-ray diffraction, transmission electron microscopy, emission scanning electron microscopy, energy dispersive X-ray spectroscopy, and Fourier transform infrared spectroscopy. These talc/Fe3O4 nanocomposites may have potential applications in the chemical and biological industries.

The effect of impurities and cleavage characteristics on talc hydrophobicity and polymer adsorption

We have investigated three natural talc samples from different geographical locations (Rhode Island (USA), Delaware (USA), and Flinders Range (Australia)) to determine the effect of impurities and cleavage characteristics on hydrophobicity and polymer adsorption. Bulk (electron microprobe) and surface (X-ray photoelectron spectroscopy) composition measurements have indicated that the Rhode Island and Delaware talcs have the lowest level of Al atoms substituted within the talc structure (0.008%), and detectable at the cleaved basal plane surface (1.5 and 1.7%), and that the Flinders Range talc has the highest level of Al atoms (8.5% bulk; 8.2% surface). Contact angle measurements have highlighted the role of Al atom substitution and step-edge density (as revealed by AFM imaging) on the measured hydrophobicity of the cleaved surfaces, with the Flinders Range talc and the Rhode Island talc having significantly lower contact angles than the Delaware talc (65° and 83°, respectively, versus 90° for the Delaware). In addition, we have characterised the adsorption of two polysaccharide polymers on the three talc samples (CMC and Dextrin TY) using in situ tapping mode AFM. CMC adsorbs with the same morphology on all three talc samples, whereas Dextrin TY presents three different morphologies on the talc surfaces. The potential implications of the observed variation in adsorption behaviour on mineral flotation are discussed.

Preparation and Property Characterization of Talc/Phthalocyanine Blue Composite Powder

To improve the dispersion of phthalocyanine blue powder, decrease its consumption and increase the use value of talc, TPBCP (Talc / Phthalocyanine Blue Composite Powder) was prepared by liquid phase mechanochemical method. By means of paint performance test, scanning electron microscopy (SEM) and fourier transform infrared spectroscopy (FT-IR), the properties and microstructure of composite powder were characterized. The hiding power and oil absorption value of talc/phthalocyanine blue composite powder were 12.88 g/m2 and 32.50 g/100g respectively, and the International Commission on Illumination (CIE) colorimetric data L, a, and b were 44.95, 1.65 and -17.18 respectively. It was equivalent for the hiding power of composite powder to 77.6% of that of pure phthalocyanine blue with a equivalent CIE. The formation of TPBCP was marked by phthalocyanine blue particles uniformly coated on talc surface. The results showed that TPBCP had similar performances with phthalocyanine blue and could instead of phthalocyanine blue to be applied in several fields.

Influence of talc genesis and particle surface on the crystallization kinetics of polypropylene/talc composites

AbstractTalc is a laminar silicate, considered as an excellent nucleating agent for polypropylene (PP) crystallization. However, properties of PP/talc composites depend on the morphology, size, and surface of mineral particles. In this sense, talc from several ores, having different morphology, imparts specific characteristics on these materials. Also, taking into account that PP‐talc adhesion is not necessarily good due to the apolar character of PP, talc surface has been modified in order to increase this parameter. In this work, the effects of talc genesis, geomorphologic aspects, and particle surface characteristics on crystallization of PP/talc composites are analyzed. Isothermal crystallization of PP/talc composites was studied by using differential scanning calorimetry, based on Avrami model. The final crystalline morphology of talc‐filled PP was analyzed by means optical microscopy. The results show that the blocky talc morphology favors even more the crystallization compared to the platy one, at the same particle size. Taking into account the surface treatment studied in this work, the talc surface is made hydrophobic and the particle delamination is favored. As a consequence, so‐modified talc is very effective in increasing the crystallization temperature of PP and the nuclei number that grow during the crystallization with respect to the untreated talc. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012

Talc–serpentine interactions and implications for talc depression

The interactions of serpentine with talc and implications for talc depression by carboxymethyl cellulose (CMC) have been investigated through flotation tests, sedimentation tests and zeta potential measurements. Talc is a hydrophobic mineral and CMC is effective for talc depression. At pH value 9, where flotation of nickel sulfide ores is routinely performed, the two magnesium silicate bearing (MgO) gangue minerals are oppositely charged and therefore attract through an electrostatic mechanism. Slime coatings of serpentine adhere to the surface of talc, reducing talc flotation recovery to some extent, but also causing problem to its depression by CMC as serpentine is a hydrophylic gangue mineral which cannot be depressed by CMC depressant. Pretreatment of serpentine with acid leaching results in a shift of the zero charge points, from pH value 10.2 to 6.8 and the leached serpentine is negatively charged at pH 9. The negatively charged serpentine does not interfere with the talc depression by CMC. Adsorption of sodium hexametaphosphate (SHMP) at the serpentine/solution interface also compensates the positive charge on the serpentine particle and its zeta potential is rendered negative. When the serpentine surface is negatively charged, a repulsive interaction energy generates and serpentine slimes drop off from the surface of talc, allowing talc to once again be depressed by CMC.

Probing the interactions between chlorpheniramine and 2:1 phyllosilicates

Interactions between chlorpheniramine (CP), an antihistamine drug used to treat allergy, and 2:1 phyllosilicates were studied under batch kinetic and different solution conditions to investigate the effect of charge density of the substrates on CP removal from solution. The CP removal by Na-montmorillonite was instantaneous, with a very large rate constant and a fast rate, reaching a capacity of 0.64mmol/g, compared to its cation exchange capacity of 0.85mmolc/g. In contrast, CP removal by talc was 10 times lower at 0.06mmol/g. Stoichiometric desorption of exchangeable cations accompanying CP removal by Na-montmorillonite confirmed cation exchange as the dominant interaction mechanism. Solution pH had a minimal effect on CP removal by Na-montmorillonite until pH 11. On the contrary, a slight increase in CP removal by talc was observed as the solution pH increased, due to increased negative charges on the pH-dependent surfaces of talc. Interactions between CP and Na-montmorillonite occurred on both external and interlayer sites, resulting in a d-spacing expansion from 12.5Å to 15.2Å. In contrast, interactions between CP and talc were only limited to the external surfaces. It was the charge density that ultimately controlled the amount of CP removal by 2:1 phyllosilicates. Thus, montmorillonite offers a superior option for the removal of cationic drugs from aqueous solution.

Molecular explanation for why talc surfaces can be both hydrophilic and hydrophobic.

While individual water molecules adsorb strongly on a talc surface (hydrophilic behavior), a droplet of water beads up on the same surface (hydrophobic behavior). To rationalize this dichotomy, we investigated the influence of the microscopic structure of the surface and the strength of adhesive (surface-water) interactions on surface hydrophobicity. We have shown that at low relative humidity, the competition between adhesion and the favorable entropy of being in the vapor phase determines the surface coverage. However, at saturation, it is the competition between adhesion and cohesion (water-water interactions) that determines the surface hydrophobicity. The adhesive interactions in talc are strong enough to overcome the unfavorable entropy, and water adsorbs strongly on talc surfaces. However, they are too weak to overcome the cohesive interactions, and water thus beads up on talc surfaces. Surprisingly, even talc-like surfaces that are highly adhesive do not fully wet at saturation. Instead, a water droplet forms on top of a strongly adsorbed monolayer of water. Our results imply that the interior of hydrophobic zeolites suspended in water may contain adsorbed water molecules at pressures much lower than the intrusion pressure.

Adsorption performance of talc for uranium removal from aqueous solution

Adsorption of uranyl ions onto talc from aqueous solutions was investigated in batch adsorption experiments. The study has been conducted to investigate the effects of the pH of solution, contact time, initial concentration and presence of other metals that could compete with uranium for adsorption sites. The kinetic sorption data were found to fit the first-order kinetic model. The experimental isotherm data of uranium sorption were examined using the Freundlich, the Langmuir and the BET models. The results obtained showed three segments separated by characteristic steep slopes in the respective experimental isotherms. This could be indicative of uranium adsorption in multimolecular or cluster states onto talc. Moreover, the detected talc surface area of 3.5 m 2/g was too small for adsorption of uranium as a monolayer. The surface area occupied by the maximum amount of uranium adsorbed (41.6 mg/g) as a monolayer was 58.3 m 2/g.

The effect of acrylamide-co-vinylpyrrolidinone copolymer on the depression of talc in mixed nickel mineral flotation

Copolymers of acrylamide and vinylpyrrolidinone with varying compositions have been synthesised and employed to depress talc in a model flotation system with process plant operation conditions. Adsorption isotherms indicated that the hydrophilic acrylamide homopolymer has a very low affinity for the hydrophobic talc surface, whereas vinylpyrrolidinone homopolymer strongly adsorbs onto the talc surface. Micro-flotation experiments revealed that the copolymer system can induce stronger talc depression than the homopolymer variants, with the most effective copolymer depressant having 25–30% vinylpyrrolidinone incorporation. The copolymer system is observed to have inherited the strong talc affinity of vinylpyrrolidinone polymer and the strong hydrophilic property from polyacrylamide. This combined effect facilitates the desired strong talc depression in single mineral flotation. However, this copolymer system has similar adsorption affinity on both the talc and pentlandite, hence depressing both talc and pentlandite in the mixed mineral flotation system. This research shows that a sufficient hydrophobic balance on the polymer is necessary for the adsorption and subsequent depression for talc. However, polymer with high adsorption selectivity is required to be a successful synthetic talc depressant for mixed mineral system.

Surface modifications of talcs. Effects of inorganic and organic acid treatments

A multipurpose acid treatment, which comprises purification, delamination, particle size reduction, and surface modification on milled talc samples, is proposed. Talcs of different origins and composition were studied in order to assess and compare the effects of different acid treatments. Associated minerals were dissolved away by both inorganic and monocarboxylic organic acids, rendering more pure and lower particle size talcs. The main results obtained from hydrochloric acid treatment were purified talcs, having silanol groups onto their surfaces. This treatment allowed the complete removal of carbonates and chlorite from initial talcs, allowing for a length and thickness reduction of talc particles and the change to hydrophilic character by breakage of siloxane bonds. The so-treated talc achieved a purity level enough to be used in plastic and paper industry, paints among other upgraded talc applications. On the other hand, organic acid attacks were able to graft carboxylic groups onto the talc surface. The occurrence of this reaction was verified by independent characterization techniques both direct (Fourier Transform Infrared Spectroscopy, Energy Dispersive X-ray) and indirect (X-ray Diffraction, Scanning Electronic Microscopy, hydrophobicity/hydrophilicity test).

Ultrastructural Characteristics of Talcs Including General Cosmetics

In this study, we analyzed the components and microstructure characteristics of four kinds of talc produced within and out of the country using energy-dispersive X-ray spectroscope and scanning electron microscope. By dividing four kinds of talc into domestic and foreign one, we could observe the differences in the particle size as well as in the components of them. For domestic talc, it was observed that the particles were 3 to 90 μm in diameter, which indicated that they were in an irregular form with a big difference in size. Under low-resolution scanning electron microscope, the surface of talc was observed as very rough. On the contrary, the particles of foreign talc were 6 to 18 μm in diameter, indicating that they were in a regular form and quite even in size. Especially, it was observed that the particles of foreign talc made by maker D were 6 to 7.5 μm in diameter, indicating that they were in a very regular form with little differences in size. It was found that under low-resolution examination, the surface of the particle of foreign talc was very smooth and even. When observing the particles of foreign talc under scanning electron microscope, we found that the particle of talc was in a tabular structure and 0.2 to 0.4 μm in thickness. It was also found that foreign talc was layered in a certain thickness of 600 to 700 nm. For the components of talc, as it is known, oxygen (O), magnesium (Mg) and silicon (Si) were found for both domestic and foreign talc and calcium (Ca) was additionally found from domestic talc only.

Adsorption of surfactant-rich stickies onto mineral surfaces

"Stickies" are tacky species, present in recycled paper and coated broke, derived from coating formulations, adhesives etc. They impact negatively on paper quality and cause web runnability problems by deposit build-up. To sustain recycling, stickies are controlled by adsorbing them onto minerals added to the recycled stock. We report isotherms for a fatty acid ester defoamer and an acrylic acid ester copolymer adsorbing from colloidal suspension onto various talcs and modified calcium carbonates. We used commercial preparations of the fatty acid ester defoamer and acrylic acid ester copolymer to provide a simple analogue to the industrial process. The modified calcium carbonates are hydrophilic with anionic and cationic sites present. Adsorption isotherms for low surface area modified calcium carbonate conform to the Langmuir model, while those for high surface area modified calcium carbonate reflect a two stage process involving the formation of a monolayer over the mineral surface and subsequent partial aggregation. Talc platelets display hydrophilic edges and hydrophobic surfaces. Adsorption onto them appears to involve three stages; specifically, a hydrophilic interaction between hydrophilic groups on the molecules and the talc edges, followed by hydrophobic interactions between the molecules and the talc surfaces, and finally by formation of multilayers.

Anticorrosive performance of titanium dioxide‐talc hybrid pigments in alkyd paint formulations for protection of steel structures

PurposeThe purpose of this paper is to investigate the anticorrosive effects of a new pigment based on bulk of talc covered with a surface layer of titanium dioxide.Design/methodology/approachThe new pigments were characterized using different analytical and spectro‐photometric techniques. Characterization of these pigments using X‐ray diffraction, scanning electron microscopy and transmission electron microscopy. The energy‐dispersive X‐ray analysis technique was used to assure the presence of titanium dioxide on talc surface, then X‐ray fluorescence (XRF) was employed to elucidate the concentration of different elements in the prepared pigments. Evaluation of these pigments was undertaken using international standard testing methods. The pigments were then incorporated in solvent‐based paint formulations based on medium oil alkyd resin. The physico‐mechanical properties of dry films and their corrosion properties were tested using accelerated laboratory tests in 3.5 percent NaCl for 28 days.FindingsThe results of this work reveal that as the layer of titanium dioxide is increased in thickness, enhanced anticorrosive properties of the new pigments are obtained.Practical implicationsThese pigments can be applied in other polymer composites, e.g. rubber and plastics, as a reinforcing agent.Originality/valueThese prepared pigments are environmentally friendly and impart high anticorrosive behavior to paint films, a unique homogenous texture, and deliver concomitant cost savings.

Adsorption of tailored carboxymethyl cellulose polymers on talc and chalcopyrite: Correlation between coverage, wettability, and flotation

A carefully chosen selection of CMC polymers was used to probe the depression of talc and chalcopyrite and to highlight the effect of specific alterations of the bulk polymer chemistry on the power and selectivity of the depressants. In situ tapping mode atomic force microscopy (AFM), captive bubble contact angle measurements, and flotation tests were used to study the adsorption of the CMC polymers on chalcopyrite and talc. The degree of substitution and distribution of substitution of carboxymethyl groups on CMC was seen to have a strong influence on the ability of the polymers to adsorb onto the surface of talc and chalcopyrite. High substitution results in low coverage on both minerals whereas low substitution results in higher coverage. The influence of distribution of substitution (random or clustered) was also seen to affect the adsorption, with more random/even substitution giving rise to greater adsorption on talc and chalcopyrite. The contact angle of talc and chalcopyrite is significantly altered in the presence of the three polymers, with increased surface coverage (determined by AFM) correlating with the ability of the polymers to decrease the wettability of talc and chalcopyrite. This trend was also followed in single and mixed mineral talc and chalcopyrite flotation.

In situ atomic force microscopy of modified dextrin adsorption on hydrophobic and hydrophilic layered silicate minerals

We have used in situ atomic force microscopy (AFM), captive bubble contact angle measurements, and colloid-probe AFM to investigate the adsorption of two modified dextrins (a phenyl succinate substituted dextrin, PS Dextrin, and a styrene oxide substituted dextrin, SO Dextrin) on the basal plane surfaces of talc and clinochlore. The experiments have probed the effect that the polymers have on the mineral hydrophobicity and on the expected particle–particle interactions in single mineral aggregation. Distinct correlations were seen between the adsorbed polymer layer morphology (coverage, thickness) and the ability of the polymers to reduce the contact angle of the talc basal plane surfaces (SO Dextrin > PS Dextrin). Both polymers were seen to lower the contact angle of clinochlore to an apparent limiting value of approximately 25°. The effect of the polymers on the forces between hydrophobic surfaces (talc basal plane and a hydrophobised titania sphere) and between hydrophilic surfaces (clinochlore cleaved surface and a silica sphere) was seen to be a complicated relationship between the adsorbed layer morphology and bulk polymer properties, with polymers exhibiting a clear tendency to bridge between hydrophobic surfaces. Neither of the dextrins was found to encourage attraction between hydrophilic surfaces, in spite of adsorbing to a significant extent on the clinochlore cleaved surface.