Adsorption of poly (4‐sodium styrene sulfonate) on kaolinite clays

The adsorption of polymer on clay particles has great importance in many industrial applications. This work aimed to study the adsorption of anionic polymer, poly (4‐sodium styrene sulfonate), on kaolinite clay surfaces. Three different Egyptian kaolinite clay samples were used. The kaolinite clays were saturated with sodium or calcium cation. It was found that the Freundlich isotherm is applicable for this polymer adsorption on kaolinite. The parameters of the Freundlich equation are very close, indicating a comparable nature for the binding behavior between the different samples of kaolinite and the adsorbed polymer. The adsorption process was examined at different pH values (3, 6, and 9 ± 0.1) to cover the range below and above the point of zero charge of kaolinite surfaces. It was found that, below this point, the polymer adsorption increased, while above it the polymer adsorption decreased. The polymer adsorption on calcium kaolinite was higher than that of sodium kaolinite at the same pH value. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 1712–1719, 2006     

Rheological,electrokinetic, and morphological characterization of alginate–bentonite biocomposites

We prepared biocomposite gel dispersions involving sodium alginate (Na‐Alg) and calcium bentonite (Ca‐B) with various solid concentrations and characterized their rheological, electrokinetic, and morphological properties. The flow properties, such as the apparent and plastic viscosities, shear stress, and yield value point, changed with increasing clay dosage. The viscosities of the homogeneous dispersions were represented by the Herschel–Bulkley model. The ζ‐potential results were examined in the light of different characterization methods (X‐ray diffraction, Fourier transform infrared spectroscopy, and atomic force microscopy) to understand the interactions between the Na and Ca ions of the alginate biopolymer and bentonite clay. A plausible structural model for the alginate–bentonite composite gel, known as the egg‐box model, is proposed. The presence of Ca ions in the Ca‐B partially crosslinked Na‐Alg may be regarded as an excellent example of a self‐assembling process. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011.     

Preparation of organoclay by a precipitation–adsorption method

Organoclay was prepared by a precipitation–adsorption process in which sodium‐montmorillonite (Na‐MMT) suspension was fully mixed with an anionic surfactant, sodium dodecylbenzene sulfonate, and then precipitation agent CaCl₂ was added to produce a precipitate of organophilic montmorillonite (OMMT). The Na‐MMT suspension was obtained by ion‐exchange reaction of bentonite with sodium cation resin. Fourier transform infrared spectroscopy spectral analysis confirmed the adsorption of organic groups on the MMT, and the organic groups content was calculated from the results of thermal gravimetric analysis. X‐ray diffraction results indicated that the OMMT prepared was exfoliated. In this article, the mechanism of the precipitation–adsorption process was discussed. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Poly(sodium 4‐styrene sulfonate) and poly(2‐acrylamido glycolic acid) polymer–clay ion exchange resins with enhanced mechanical properties and metal ion retention

This research presents the synthesis of novel nanocomposite ion exchange resins based on poly(sodium 4‐styrene sulfonate) and poly(2‐acrylamido glycolic acid). Nanocomposites were synthesized by in situ radical polymerization using organic modified montmorillonite as filler and different clay contents. Loaded resins showed improvements in mechanical properties compared with unloaded resins: specifically, when the nominal montmorillonite content was 2.5 wt%, poly(sodium 4‐styrene sulfonate) nanocomposite increased its shear modulus from 323 to 910 Pa and doubled its elastic recovery ratio, and the yield point was almost 20 times higher than for unloaded resins. In the case of metal ion retention, the effect of pH and clay content were studied for Cd(II), Pb(II), Cu(II), Cr(III) and Al(III) by a batch procedure. Results showed high efficiency, reaching over 80% after only 1 h of contact. Poly(2‐acrylamido glycolic acid) presented a higher pH dependence than poly(sodium 4‐styrene sulfonate). In addition, it was observed that montmorillonite contributes to retention capacity from the increase in distribution coefficients for loaded resins compared with unloaded resins. Copyright © 2011 Society of Chemical Industry     

Radiation‐induced grafting of acrylic acid and sodium styrene sulfonate onto high‐density polyethylene membranes. II. Thermal and chemical properties

Strong acid cation‐exchange membranes were obtained by radiation‐induced grafting of acrylic acid and sodium styrene sulfonate onto high‐density polyethylene (HDPE). Thermal and chemical properties of the cation‐exchange membranes were investigated. The effectiveness of ? SO₃Na containing membranes was conformed in inducing high resistance to oxidative degradation. The char residue of the grafted HDPE is greater than that of ungrafted HDPE. It shows that the branch chains, including ? SO₃Na and ? COOH groups, give catalytic impetus to the charring. The crystallinity of the grafted membranes was decreased when increasing the grafting yield. It was assumed that the decreased crystallinity was due to collective effects of the inherent crystallinity dilution by the amorphous grafted chains and the crystal distortion of the HDPE component. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 99:3396–3400, 2006     

Injection of saline solutions to improve the electro-osmotic pressure and consolidation of foundation soil

Injection of saline solutions can enhance the effect of electro-osmotic pressure. This study considers the consolidation and stability of foundation soil for building construction. Kaolinite (KGa-1) and Taipei silty clay were subjected to zeta potential (ZP), electro-osmosis and laboratory vane shear tests with injection of saline solutions. The ZP values decrease (i.e., less negative potential) with increased cationic valences and concentrations. The increased electro-osmotic permeability from injecting CaCl₂ (1 N, EOC5) solution is about 172% higher than that without injection due to an increase of drained water from the cathode and the resulting increase of undrained shear strength. Average undrained shear strength for injecting CaCl₂ solution over a period of 7 days is about 4 to 5 times greater than that without injection during electro-osmosis tests. Electro-osmosis tests with injection of saline solutions reveal that the increase of undrained soil shear strength (ΔS_u) is proportional to the ZP tests.     

Electrokinetic Properties of Acid-Activated Montmorillonite Dispersions

In this study, the influence of pH, electrolyte concentration, and type of ionic species on the electrokinetic properties (zeta potential and electrokinetic charge density) of the acid-activated montmorillonite mineral have been investigated using the microelectrophoresis method. The electrokinetic properties of acid-activated montmorillonite dispersions have been determined in aqueous solutions of mono-, di-, and trivalent salts and divalent heavy metal salts. Zeta potential experiments have been performed to determine the point of zero charge (pzc) and potential determining ions (pdi). The zeta potential values of the acid-activated montmorillonite particles were negative and did not vary significantly within the pH range studied. Acid-activated montmorillonite dispersions do not have point of zero charge (pzc). The valence of the electrolytes has a great influence on the electrokinetic behavior of the suspension. A gradual decrease in the zeta potential (from ?25 mV to ?5 mV) occurs with the monovalent electrolytes when concentration increased. Divalent and heavy metal electrolytes have less negative z-potentials due to the higher valence of ions. A sign reversal of z-potential has been observed at AlCl₃, FeCl₃, and CrCl₃ electrolytes (potential determining ions) and zeta potential values have had a positive sign at high electrolyte concentrations.

The electrokinetic charge density of acid-activated montmorillonite has shown similar trends for variation in mono- and divalent electrolyte solutions. Up to concentrations of ca. 10^?3 M, it has remained practically constant at approximately 0.5 × 10^?3 C m^?2 For higher concentrations of monovalent electrolytes more negative values (?16 × 10^?3 C m^?2) were observed. It has less negative values in divalent electrolyte concentrations according to monovalent electrolytes (?5 × 10^?3 C m^?2). For low concentrations of trivalent electrolytes, the electrokinetic charge density of montmorillonite particles is constant, but at certain concentrations it rapidly increased and changed its sign to positive.     

Flocculation and coagulation of Ca- and K-saturated montmorillonite in the presence of polyethylene oxide

The objective of this work is to study the flocculation of Ca- and K-montmorillonite in the presence of some coagulant (CaCl₂ and KCl) and mixtures of coagulants and polyethylene oxide (600,000 mol wt) through measuring the zeta potential. The action of Ca²⁺ was more effective than K⁺ in decreasing the zeta potential of Ca-montmorillonite; consequently, the electrical double layer of the clay particles has been reduced. On the other hand, the action of K⁺ was more pronounced than Ca²⁺ in decreasing the zeta potential of K-montmorillonite. This contradicting result was attributed to the change of the partial molal volume of Ca- and K-montmorillonite. The flocculation of Ca- and K-montmorillonite by polyethylene oxide was enhanced when the clay was initially treated with electrolyte. This electrolyte reduces the thickness of the electrical double layer. Under this condition, the polymer segments collapse on the clay surfaces, leaving polymer loops and tails available for contacting adjacent clay particles. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 659–662, 1999     

Spontaneous Vesicle Formation in Mixtures of Quaternary Ammonium Compounds with Carbamate and Sodium Dodecylbenzene Sulfonate

Spontaneous vesicles formation in the aqueous mixtures of 2,3‐bis (dodecylcarbamoyloxy)‐N, N‐dimethyl‐N‐(2‐hydroxyalkyl) propyl ammonium chloride (C₁₂PAC) and sodium dodecylbenzene sulfonate at different mixing molar ratios have been investigated. The characterizations are demonstrated by electrical conductivity measurements, dynamic light scattering and zeta (ζ) potential measurements. The ζ‐potential results indicate the C₁₂PAC/SDBS systems are stable. The shapes of the catanionic vesicles are observed by negative‐staining transmission electronic microscopy. Meanwhile, from the viewpoint of molecular geometry structure, the electrostatic interaction between anionic and cationic molecules is regarded as the main driving force for spontaneous formation of vesicles.     

Synthesis of microphase‐separated poly(styrene‐co‐sodium styrene sulfonate) membranes using amphiphilic urethane acrylate nonionomers as an reactive compatibilizer

Microphase‐separated poly(styrene‐co‐sodium styrene sulfonate) random copolymer (PSSU) membranes were fabricated through a new copolymerization process. Two immiscible monomers, styrene and sodium styrene sulfonate were dissolved in a single solvent and formed homogeneous solutions, which were directly converted to wall‐to‐wall membranes via radical copolymerization process with microphase separation. Since urethane acrylate nonionomer (UAN) chain has amphiphilicity as well as reactivity with vinyl monomers, UAN chain could act not only as compatibilizer for polystyrene and poly(sodium styrene sulfonate), but also as macrocrosslinker, which makes it possible for the formation of crosslinked copolymer of two immiscible polymers without macrophase separation. TEM image of the PSSU membranes showed that nanosized hydrophilic domains formed by hydrophilic/hydrophobic microphase separation were dispersed at hydrophobic matrix phase. PSSU membranes fabricated using UAN chain having longer chain length of polyethylene oxide showed bigger size of hydrophilic domains, which was also confirmed by TEM images. Fabricated PSSU membranes showed proton conductivity higher than 10^?2 S/cm and methanol permeability lower than 10^?7 cm²/s of Nafion® 117 membranes. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2008     

Mechanisms and Models Describing Sodium and Lead Scavenging by a Kaolinite Aerosol at High Temperatures

High temperature mechanisms of interaction between a dispersed kaolinite aerosol and vaporized sodium and lead were investigated using experimental data obtained from an 18 kW downflow furnace. The validity of using aerosol size fractionation to determine the extent of reaction between metal and substrate was confirmed through a series of specialized tests. The reaction stoichiometries for the Na/kaolinite and Pb/kaolinite systems were found to differ from literature values but were similar to each other. New light was shed on the nature of the reaction products for the Na/kaolinite and Pb/kaolinite systems, and for semivolatile metal/kaolinite sorbent systems in general. Modified reaction mechanisms were developed that accommodate key-observed processes (i.e., both enhancing and inhibitory substrate-melting processes). Rate coefficients for each system were quantitatively determined. Mechanisms are interpreted in the light of known information on the structure and nature of kaolin clay and based on observed phase transformations of the Na/kaolinite and Pb/kaolinite systems. The new models for high temperature Na/kaolinite and Pb/kaolinite interactions compared well to both new and literature data. These models can be used to predict and optimize the scavenging of vaporized sodium and lead by kaolinite mineral particles in fossil fuel-fired systems and waste incinerators.     

Electrokinetic Properties of Vermiculite and Expanded Vermiculite: Effects of pH,Clay Concentration and Mono- and Multivalent Electrolytes

Abstract

In this study, the zeta potential values of vermiculite and expanded vermiculite were measured to determine the effect of pH, clay concentration, and various mono- and multivalent electrolytes including NaCl, KCl, NH₄Cl, NaNO₃, NaClO₄, Na₂SO₄, Na₂CO₃, Na₃PO₄·12H₂O, MgCl₂·6H₂O, CaCl₂·2H₂O, BaCl₂, SrCl₂·6H₂O, CuCl₂·2H₂O, CoCl₂·6H₂O, NiCl₂, AlCl₃, and CrCl₃·6H₂O on the electrokinetic properties of vermiculite samples. It was found that generally the measured zeta potential values of expanded vermiculite for the studied systems were slightly more negative than that of vermiculite. The pH profiles of vermiculite and expanded vermiculite at acidic, natural, and basic pH values were obtained to determine the effect of time on the pH values of clay suspensions. The zeta potential measurements showed that the surface charge of clay particles was negative in water. The isoelectric point of vermiculite and expanded vermiculite were determined as pH 2.30 and 2.57, respectively. Divalent cations (Mg²⁺, Ca²⁺, Sr²⁺, and Ba²⁺), heavy metal ions (Cu²⁺, Ni²⁺, and Co²⁺) and trivalent cations (Al³⁺ and Cr³⁺) were potential determining ions for vermiculite and expanded vermiculite particles. Moreover, divalent and trivalent cations caused the change of surface charge from negative to positive. On the other hand, monovalent cations (Na⁺, K⁺ and NH₄ ⁺), monovalent anions (Cl^?, NO₃ ^?, and ClO₄ ^?) and multivalent anions (SO₄ ^2?, CO₃ ^2?, and PO₄ ^3?) acted as indifferent ions for these clay particles.     

Effect of montmorillonite on properties of styrene–butadiene–styrene copolymer modified bitumen

Clay/styrene–butadiene–styrene (SBS) modified bitumen composites were prepared by melt blending with different contents of sodium montmorillonite (Na‐MMT) and organophilic montmorillonite (OMMT). The structures of clay/SBS modified bitumen composites were characterized by XRD. The XRD results showed that Na‐MMT/SBS modified bitumen composites may form an intercalated structure, whereas the OMMT/SBS modified bitumen composites may form an exfoliated structure. Effects of MMT on physical properties, dynamic rheological behaviors, and aging properties of SBS modified bitumen were investigated. The addition of Na‐MMT and OMMT increases both the softening point and viscosity of SBS modified bitumens and the clay/SBS modified bitumens exhibited higher complex modulus, lower phase angle. The high‐temperature storage stability can also be improved by clay with a proper amount added. Furthermore, clay/SBS modified bitumen composites showed better resistance to aging than SBS modified bitumen, which was ascribed to barrier of the intercalated or exfoliated structure to oxygen, reducing efficiently the oxidation of bitumen, and the degradation of SBS. POLYM. ENG. SCI., 47:1289–1295, 2007. © 2007 Society of Plastics Engineers     

“Click” Polymer‐Supported Palladium Nanoparticles as Highly Efficient Catalysts for Olefin Hydrogenation and Suzuki Coupling Reactions under Ambient Conditions

Complexation of palladium(II) acetate [Pd(OAc)₂] or dipotassium tetrachloropalladate [K₂PdCl₄] to “click” polymers functionalized with phenyl, ferrocenyl and sodium sulfonate groups gave polymeric palladium(II)‐triazolyl complexes that were reduced to “click” polymer‐stabilized palladium nanoparticles (PdNPs). Transmission electron microscopy (TEM) showed that reduction using sodium borohydride (NaBH₄) produced PdNPs in the 1–3 nm range of diameters depending on the nature of the functional group, whereas slow reduction using methanol yielded PdNPs in the 22–25 nm range. The most active of these PdNPs (0.01% mol Pd), stabilized by poly(ferrocenyltriazolylmethyl)styrene, catalyzed the hydrogenation of styrene at 25 °C and 1 atm hydrogen, with turnover numbers (TONs) of 200,000. When stabilized by the water‐soluble poly(sodium sulfonate‐triazolylmethyl)styrene, the PdNPs (0.01% mol Pd) catalyze the Suzuki–Miyaura coupling between iodobenzene (PhI) and phenylboronic acid [PhB(OH)₂] in water/ethanol (H₂O/EtOH) at 25 °C with TONs of 8,200. This high catalytic activity is comparable to that obtained with “click” dendrimer‐stabilized PdNPs under ambient conditions.     

Method for the characterization of electrophoretic properties of clay slips

The present study presents experiments performed in an aqueous dispersion of clays and clay minerals using three different instruments, which were prepared to measure electric conductance, relative viscosity, and electrophoretic mobility of slip in flow. Smectite–kaolinite and Cloisite Na⁺ were used, in addition to an aqueous solution of sodium silicate in deionized water. Laboratory tests of zeta potential and viscosity were also carried out. The starting point was the natural behavior of the electric current when sodium silicate was added to the aqueous dispersion of clay or clay minerals. The results were analyzed and correlated considering the electrophoretic phenomenon. The method proved to be effective for understanding electrophoretic properties acting on the dispersion slips.     

Influence of granulometry and organic treatment of a Brazilian montmorillonite on the properties of poly(styrene‐co‐n‐butyl acrylate)/layered silicate nanocomposites prepared by miniemulsion polymerization

The influence of granulometry and organic treatment of a Brazilian montmorillonite (MMT) clay on the synthesis and properties of poly(styrene‐co‐n‐butyl acrylate)/layered silicate nanocomposites was studied. Hybrid latexes of poly(styrene‐co‐butyl acrylate)/MMT were synthesized via miniemulsion polymerization using either sodium or organically modified MMT. Five clay granulometries ranging from clay particles smaller than 75 μm to colloidal size were selected. The size of the clay particles was evaluated by specific surface area measurements (BET). Cetyl trimethyl ammonium chloride was used as an organic modifier to enhance the clay compatibility with the monomer phase before polymerization and to improve the clay distribution and dispersion within the polymeric matrix after polymerization. The sodium and organically modified natural clays as well as the composites were characterized by X‐ray diffraction analysis. The latexes were characterized by dynamic light scattering. The mechanical, thermal, and rheological properties of the composites obtained were characterized by dynamical‐mechanical analysis, thermogravimetry, and small amplitude oscillatory shear tests, respectively. The results showed that smaller the size of the organically modified MMT, the higher the degree of exfoliation of nanoplatelets. Hybrid latexes in presence of Na‐MMT resulted in materials with intercalated structures. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Physico-chemical effects on clay due to electromigration using stainless steel electrodes

The physico-chemical changes in clay soils due to the application of electrokinetics are difficult to predict with accuracy because of the very wide range of parameters interacting. The effects of the application of an electrical gradient across controlled specimens of a pure form of kaolinite using stainless steel electrodes and a deionised water feed to the electrodes, to mimic electrokinetic stabilisation without the stabiliser added, are reported. The specimens in which electrical and chemical changes were induced over different time periods (3, 7, 14 and 28 days) were subsequently tested for Atterberg limits, undrained shear strength, water content, pH, conductivity, Fe concentration and zeta potential. Changes in strength and plasticity indices were attributed to electrolysis, electro-osmosis, electrode degradation, clay mineral dissolution, ion movement due to electromigration, cation exchange reactions and precipitation of reaction products.     

Differences in the rheology and surface chemistry of kaolin clay slurries: The source of the variations

Kaolinite clays from two sources were found to display different rheological and electrokinetic behaviour despite having similar mineral composition. This difference is mainly due to the surface chemistry at the edges of the clay particles. Making the edge surface chemistry similar with an adsorbed small anionic additive such as citrate, produced a similar yield stress-pH behaviour for the different kaolin clay slurries. Heterogeneous attraction between positively charged edges and negatively charged faces of the clay particles is responsible for the yield stress behaviour of the clay slurry. However, the different points of zero charge of the edge caused the clay slurries to display different yield stress-pH behaviour. Adsorption of anionic citrate on negatively charged kaolin clay particles is reflected in a significant increase in the magnitude of the negative zeta potential. The adsorption is likely to be on the edge of the clay particles. Adsorbed citrate generally reduces or eliminates heterogeneous charge attraction leading to a much denser sediment being formed in the kaolin slurries with a coarser particle size distribution.     

Oxidation of cod phospholipids in liposomes: Effects of salts,pH and zeta potential

This work examines how different salts and pH influence both the zeta potential and the lipid oxidation rate of liposomes made from cod phospholipids. The rate of Fe²⁺‐induced lipid oxidation was measured by consumption of dissolved oxygen by liposomes in a closed vessel. Cations (Na⁺, K⁺, Ca⁺, Mg⁺) did not influence the rate of oxidation in the tested range [ionic strength (I) 0–0.14 M). Among the tested anions, sulphates and nitrates did not significantly change the oxygen uptake rate, but chlorides (KCl, NaCl, CaCl₂) reduced the oxidation rate down to approximately 45%, and dihydrogen phosphate down to 14%, when I = 0.14 M. The effect of Cl^? and H₂PO4₄^? was additive. Addition of salts increased the zeta potential of the liposomes, divalent cation salts even resulted in a positive zeta potential. When the liposomes contained different concentrations of chlorides, a linear relationship between oxygen uptake rate and zeta potential was observed. When phosphate was added, the oxygen uptake rate was not related to the changes in zeta potential. The decrease in pH was followed by an increase in zeta potential. The oxygen uptake rate did not change significantly at different positive zeta potentials (pH <3). When the zeta potential was negative, the oxygen uptake rate was influenced by the zeta potential and may also be influenced by iron solubility. Absolute values of the zeta potential alone cannot be used to predict oxidation rates.     

The effect of mercerisation on the electrokinetic potential of cotton

Mercerisation changes the fine structure, morphology and conformation of cotton cellulose chains (cellulose I to cellulose II), resulting in a variation in fibre strength and lustre as well as adsorption properties. Recently it has been shown that mercerisation also changes the electrokinetic behaviour of cotton. The aim of the work presented here is to study the behaviour in unmercerised and mercerised cotton. The zeta potential of cotton fibres was measured by the streaming current method, using an EKA electrokinetic analyser. The relationships between zeta potential and the pH of a potassium chloride solution on the one hand and the point of zero charge (PZC) on the other, determined by titration with a cationic surfactant (cetylpyridinium chloride), were investigated.