Yu. N. Pozhidaev

Adsorption of Copper(II) Ions by Calcium Heulandite

The sorption isotherms of copper(II) ions on natural calcium heulandite at a pH of 1.7 and temperature of 298–318 K have been obtained. The exchange sorption capacity with respect to Cu(II) ions at 298 K was 0.47 mg-eqv/g. The equilibrium constants of the ion exchange and thermodynamic functions including Gibbs energy and entropy and enthalpy of sorption have been calculated. The possibility of using calcium heulandite for purification of the wastewaters of the electroplating industry from ions of heavy metals has been assessed.

Adsorption of nickel(II) cations by natural zeolites

The composition of a natural specimen of zeolite-containing rock of a Transbaikal field including Ca[Al2Si7O18] · 6H2O calcium heulandite and KAlSi3O8 potash fieldspar impurity is confirmed with X-ray phase analysis and infrared spectroscopy. The time necessary for attaining adsorption equilibrium in a zeolite-aqueous nickel sulfate solution system is estimated. The limiting adsorption at different temperatures is found from the Langmuir equation. Thermodynamic and kinetic characteristics of the adsorption of nickel (II) cation on natural minerals are calculated.

Investigation of adsorption of heavy metal ions by natural aluminosilicate

The adsorption capacity of studied aluminosilicate samples was found to depend significantly on the sizes of grains of adsorbents. The equations for calculating the statistical exchange capacity of aluminosilicate of different fractions in relation to ions of heavy metals Ni(II), Cu(II), Zn(II), Fe(III), and Cr(III) were derived. The effective coefficients of diffusion in the adsorbent grain and in the film of solution were found. It was determined that external diffusion kinetics served as a limiting step of adsorption. The rate of the process was determined as varying from 0.16 × 10–6 to 2.8 × 10–6 mol/m2 s.

Copolymerization of vinyl chloride with 1-vinyl-4,5,6,7-tetrahydroindole and 2-methyl-5-vinylpyridine

The radical copolymerization of vinyl chloride with 2-methyl-5-vinylpyridine and 1-vinyl-4,5,6,7-tetrahydroindole is accompanied by dehydrochlorination. In the vinyl chloride-2-methyl-5-vinylpyridine system, the evolved hydrogen chloride interacts with a pyridine hydrogen atom to give charged units of a heterocycle. In the vinyl chloride-1-vinyl-4,5,6,7-tetrahydroindole system, the hydrogen chloride being formed initiates the cationic dimerization of a nitrogen-containing monomer. The synthesized copolymers based on vinyl chloride surpass the commercial poly(vinyl chloride) in terms of thermal stability and solubility in organic solvents.

Hybrid membranes based on silica and 2-hydroxyethylmethacrylate–4-vinylpyridine copolymers

Abstract4-Vinylpyridine–2-hydroxyethylmethacrylate copolymers have been synthesized by radical copolymerization. The composition and properties of the copolymers have been studied; the reactivity constants of the comonomers have been calculated. Sol–gel synthesis involving the resulting copolymers and tetraethoxysilane has yielded hybrid membranes comprising a polymer matrix with uniformly distributed hydrated silica particles and exhibiting a proton conductivity of up to 1.85 × 10−2 S/cm, an ion-exchange capacity of 2.1 meq/g, a heat resistance of 412°С, a tensile strength of 55.5 MPa, an elongation at break of 15%, and a proton-conductivity activation energy of 12 ± 2 kJ/mol.

Hybrid ion-exchange membranes based on heteroaromatic sulfonic acid derivatives

Membranes exhibiting proton conductivity have been prepared by sol-gel synthesis using tetraethoxysilane and heteroaromatic sulfonic acid derivatives (2-phenyl-5-benzimidazolesulfonic acid and 3-pyridinesulphonic acid) in the presence of phosphoric acid and polyvinyl butyral. The membranes are gels composed of a polyvinyl butyral polymer matrix with uniformly distributed particles of silica containing molecules of heteroaromatic sulfonic acid derivatives mechanically incorporated in its network structure. The membranes synthesized from 2-phenyl-5-benzimidazolesulfonic acid or 3-pyridinesulphonic acid exhibit a conductivity of 0.1 × 10−2 or 0.55 × 10−2 S/cm at 353 K, an ion-exchange capacity of 2.70 or 1.84 mequiv/g, and a proton-transfer activation energy of 24.93 or 21.73 kJ/mol, respectively; at a relative water content of 50%, the tensile strength is 4 or 6 MPa and the elastic modulus is 128 or 191 MPa, respectively.

Hybrid composites based on 3-aminopropyltriethoxysilane and nitrogen polybases

Process in which composites are formed in sol-gel systems based on 3-aminopropyltriethoxysilane and vinyl derivatives of nitrogen-containing heterocyclic compounds was studied. These products are highly dispersed and thermally stable interpenetrating polymers insoluble in water and organic solvents. Their composition and structure were examined.

Adsorption of Platinum (IV) by Sorbents Based on Hybrid Composites

We have investigated the adsorption of platinum(IV) ions by sorbents based on sol—gel synthesis products with the participation of vinylglycidyl ether ethyleneglycol copolymers with vinylchloride and organisilicon monomers: N,N′-bis(3-triethoxysilylpropyl)thiocarbamide and 2-([triethoxysilylpropyl] amino)pyridine. We have shown that the interaction of platinum(IV) with the composite surface is a result of both physical adsorption and chemical adsorption. We have used the Langmuir, Freundlich, and Dubinin—Radushkevitch models to describe the nature of adsorption. Boyd—Adams, pseudo-first and pseudo-second-degree, and Elovitch models were used to evaluate adsorption kinetics

N-vinylpyrazole copolymers

Copolymers of N-vinylpyrazole with N-vinyl-4,5,6,7-tetrahydroindole and vinyl acetate were prepared by radical copolymerization. The composition, structure, and properties of the copolymers were studied. The reactivity constants of the monomers were calculated. Copolymer films were prepared from solutions by casting, and the proton conductivity of the films was determined.

Adsorption of Nickel(II) and Copper(II) Ions by Modified Aluminosilicates

According to X-ray phase analysis, modification of natural aluminosilicates with hydrogen chloride is accompanied by the destruction of the main component—calcium heulandite—the content of which decreases from 64.3 to 42.9%. An increase in temperature during the modification process contributes to the packing of the cristobalite structure, which positively affects the adsorption properties of the materials. In the process of activation of aluminosilicates by hydrogen chloride, their texture characteristics change: the specific surface (from 33 to 75 m2/g) and the specific pore volume (from 0.015 to 0.036 cm3/g) increase more than double. The average pore size is reduced from 1.8 to 1.6 nm. The result of such changes is an increase in the adsorption capacity. Adsorption of nickel(II) and copper(II) ions on modified aluminosilicates is most adequately described by the Langmuir adsorption model.