Alkaline hydrolysis of nitrile groups in hydrazided nitron fibre

Conclusions The process of alkaline hydrolysis of nitrile groups in hydrazided Nitron fibre has been studied. It has been shown that introduction of hydrazidine groups into the polymer chain catalyzes the alkaline hydrolysis process because of a change in the basicity of the polymer chain.A cation-exchange VION KN-1 fibre has been prepared with higher physico-mechanical properties, which still retains satisfactory sorptive properties.Translated from Khimicheskie Volokna, No. 3, pp. 7–8, May–June, 1988.     

Preparation of amidoxime group-containing chelating fibers and their gold absorption properties. II. A preliminary investigation of the absorption behavior of Au3+ onto chelating fibers containing amidoxime groups

The absorption behavior of ionic gold onto chelating fibers containing amidoxime groups has been investigated. Chelating fibers not only present high absorption capacity, high absorption velocity and high selectivity to Au³⁺ ion, but also are able to reduce the absorbed Au³⁺ to metallic gold. When the fiber containing gold is burnt, spongy metallic gold is obtained. In the absorption process, the amidoxime group in the chelating fiber is gradually destroyed and a carboxyl group is formed.     

Properties of polyacrylonitrile yarns which have been modified with salts of alkali metals

Conclusions In modification of polyacrylonitrile fibres with alkali metal salts, a change in structure takes place, morphological nonuniformity in the transverse direction is increased, which aids in fibre crimpingAlkali metal salts interact with Nitron fibre both at the carboxyl groups of the polymer and also at its carbonyl groups.Translated from Khimicheskie Volokna, No. 3, pp. 34–35, May–June, 1988.     

Amidoxime-group-containg adsorbents for metal ions synthesized by radiation-induced grafting

Amidoxime-group-containing fibrous adsorbents for metal ions were synthesized by radiation-induced grafting of acrylonitrile followed by amidoximation of cyano groups with hydroxylamine. The degree of amidoximation and the distribution of amidoxime groups in the fiber were follwed by means of electron probe X-ray microanalysis. The efficiency of adsorbing metal ions was increased by alkaline treatment of the adsorbent at high temperature for a short period before use. The order of adsorption for various bivalent metal ions was Hg > Cu > Ni > Co > Cd. From the distribution pattern of metal ions in the fibrous adsorbent, the adsorption was found to be controlled by the diffusion of the solution containing metal ions inside the adsorbent. It was found that confining amidoxime groups superficially and making short chain length of grafts were effective to obtain a high degree of adsorption.     

Study of sorption of chromium(VI) ions by fibre anion-exchangers

Sorption of chromium(VI) ions by fibre anion-exchangers containing pyridine, imidazole, hydrazidine, and aliphatic amino groups was investigated. It was shown that the basicity of the sorbents has almost no effect on their selectivity in absorption of chromium ions from solutions. The fibres with pyridine and imidazole groups have higher distribution coefficients, and their capacity for chromium ions is 130 and 120 mg/g, respectively. Sorption of chromium(VI) ions by the fibre sorbent with pyridine groups also corresponds to a mixed diffusion mechanism in dynamic conditions and the internal diffusion coefficient is 3.10 ⁻¹⁰ cm²/sec. Fibres with low-basicity pyridine groups are resistant to the oxidizing effect of chromium(VI) ions and their exchange capacity is preserved in repeated sorption-desorption cycles. Conversion of pyridine groups to the form of a strong base decreases the chemical stability of the sorbent in absorption of chromium(VI) ions from solutions. Translated from Khimicheskie Volokna, No. 2, pp. 55–57, March–April, 1997.     

pH-sensitivity of swelling of polyurethane crosslinked polyacrylate network

Summary A pentacomponent acrylate copolymer containing hydroxyl and carboxyl groups was grafted with a semi-blocked polyurethane prepolymer and then deblocked to get polymer network with carboxyl groups. The network polymer can swell at pH range 6–13 and swell has reversible characteristic up to pH 11.Moreover, swelling kinetics is belong to a non-Fickian type.     

Synthesis of a new type of adsorbent containing carboxyl and amidoxime groups by preirradiation grafting and its absorption of metal ions

A new type of adsorbent containing amidoxime and carboxyl groups was synthesized by the preirradiation graft copolymerization of acrylonitrile (AN) and acrylic acid (AA) onto fibrous‐type poly(vinyl alcohol) followed by amidoximation with hydroxylamine. The radiation dose and ratio of AN and AA monomers influenced the degree of grafting, the content of the amidoxime group, and the adsorption capacity. The synthesis course, structure, and properties of the adsorbent were investigated with Fourier transform infrared, scanning electron microscopy, and thermogravimetry. The adsorption property of the adsorbent for palladium(II) ions was also studied systematically. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 1986–1992, 2002     

Application of a solid polymer electrolyte reactor to remove nitrate ions from wastewater

The application of a zero gap solid polymer electrolyte (ZGSPE) reactor to deminealise nitrate ions in aqueous wastewater is described. The following performance data for the reduction of a simulated alkaline solution with 16.1 mM nitrate ions under galvanostatic operation were achieved: percentage of nitrate removal up to 100%, rates of nitrate removal up to 0.057 mol cm^–2 h^–1, space–time yields up to 5.4 kg m^–3 h^–1, current efficiencies up to 24.5% and energy consumption between 40.1 and 63.3 kW h kg^–1. The beneficial effects of higher temperatures and nitrate ion concentrations and using a suitable electrolyte flow rate on the activity, selectivity and efficiency is reported. PdRh_1.5/Ti mini-mesh electrode used in the study was stable after a cumulative use of 1000 h.     

Evaluation of some new hyperbranched polyesters as binding agents for heavy metals

Different generations of hydroxyl and carboxyl terminated hyperbranched polyesters were synthesised and used as heavy metals chelating compounds. The adsorptive capacity of the 3rd generation of the polyesters (G3‐OH, G3‐COOH) as well as that of nanoclay (Nanofil 116) for cadmium removal was determined through adsorption isotherm studies. The highest metal ion removal capacity was observed for G3‐COOH sample. The extent of binding (EOB) values of various generations of hyperbranched polyesters having the same core structure, but different terminal groups, indicated that, irrespective of the type of terminal group, the higher generations are more effective than the lower ones. EOB data can be adequately described by a bidentate coordination model for carboxyl terminated polyesters [each Cd(II) ion coordinates with two carboxyl groups] and tetradentate coordination model for hydroxyl terminated polyesters [1Cd(II)/4OH]. The EOB and selectivity properties of all prepared polyesters towards the heavy metal ions Cd(II), Cu(II), and Pb(II), were investigated under competitive condition. The results showed that the carboxyl terminated polymers exhibit higher binding capacities than those of hydroxyl terminated ones and the selectivity follows the order: Cu(II) > Cd(II) > Pb(II) for all polymer samples, irrespective of the type of terminal group. © 2011 Canadian Society for Chemical Engineering     

Some special features in forming current-conducting structures in gel-fibres

Conclusions Structural-mechanical properties of metallized fibres have been studied. The correctness of hypotheses advanced about the mechanism of formation of current-conducting structures has been confirmed.The following mechanisms have been proposed for the interaction of the polymer with Ni²⁺, Ni, and NiS during the metallization process and for the formation of current-conducting structures in Nitron gel-fibre; formation of intra- and intermolecular salt bonds between carboxyl groups of the polymer and Ni²⁺; realization of donor—acceptor interaction of Ni²⁺ and NiS with functional groups of the polymer to form compounds of the chelate type.Translated from Khimicheskie Volokna, No. 1, pp. 20–22, January–February, 1990.     

The Nature of the Reaction of Chromium(III) Complexes with Poly(Ethylene Terephthalate) Fibres

The effect of the nature of the ligands in chromium(III) complexes on the affinity of chromium(III) complexes for poly(ethylene terephthalate) fibre materials is demonstrated. It was found that donor-acceptor bonds with terminal groups (hydroxyl and carboxyl) and oxygen heteroatoms in the macromolecule of the polymer are formed in the reaction of chromium cations with poly(ethylene terephthalate) macromolecules.__________Translated from Khimicheskie Volokna, No. 1, pp. 38–39, January–February, 2005.     

Thermal stability of montmorillonite polyacrylamide and polyacrylate nanocomposites and adsorption of Fe(III) ions

Poly(sodium acrylate), polyacrylamide and their copolymers were introduced into the interlayer spaces of raw montmorillonite (Mt) by in-situ polymerization. The obtained clay polymer nanocomposites (CPN) retained the layered structure. The polymers were intercalated at an intended polymer-to-clay mass ratio of 1:1. Differences in the mechanism of decomposition of samples depended on the type of polymer functional groups. The CPN were tested as adsorbents of Fe^3 + ions. The highest adsorption capacity was achieved for samples containing poly(sodium acrylate), which was due to their high swelling capacity and the attraction of iron ions by carboxyl groups.     

Surface modified Nylon 6,6 and application for adsorption and detection of uranium in potable water

Several types of novel, surface modified, Nylon 6,6 films were prepared. The polymer surfaces were first subjected to controlled oxidation with potassium peroxydisulfate at 80 °C. Subsequently, functionalization by covalent incorporation of specific reactive dyes, amidoxime, tetraisopropyl diphosphonate or acetamide functional groups was performed. The amidoxime functions were introduced using methods: grafting of polyacrylonitrile on oxidized Nylon 6,6 films and modification with acrylonitrile catalyzed by sodium methoxide. Then, the acrylonitrile groups were hydrolyzed to amidoxime. The modification with tetraisopropyl diphosphonate and acetamide groups was performed by reaction of oxidized films with tetraisopropyl vinylidene diphosphonate and respectively chloroacetamide. All the materials obtained showed a very good adsorption towards uranium (VI) ions in potable water. The adsorbed uranium was analyzed by alpha spectroscopy. The adsorption rate at different temperatures and the effect of pH were studied.     

Removal of heavy metal ions by dithiocarbamate-anchored polymer/organosmectite composites

In this study, the dithiocarbamate-anchored polymer/organosmectite composites were prepared for the removal of heavy metal ions (lead, cadmium and chromium) from aqueous media containing different amounts of these ions (50–750 ppm) and at different pH values (2.0–8.0). Initially, the modification of the natural smectite minerals was performed by treatment with quartamin styrene and chloromethylstyrene. Then, modified smectite nanocomposites were reacted with carbondisulfide, in order to incorporate dithiocarbamate functional groups into the nanolayer of organoclay. The dithiocarbamate-anchored nano-composites have been characterized by FTIR and used in the adsorption–desorption process. The maximum adsorptions of heavy metal ions onto the dithiocarbamate-anchored polymer/organosmectite composites from their solution was 170.7 mg g^− 1 for Pb(II); 82.2 mg g^− 1 for Cd(II) and 71.1 mg g^− 1 for Cr(III). Competition between heavy metal ions (in the case of adsorption from mixture) yielded adsorption capacities of 70.4 mg g^− 1 for Pb(II); 31.8 mg g^− 1 for Cd(II) and 20.3 mg g^− 1 for Cr(III). Desorption of the heavy metal ions from composite was studied in 0.5 M NaCl and very high desorption rates, greater than 93%, were achieved in all cases. Adsorption–desorption cycles showed the feasibility of repeated uses of this nanocomposite.     

Hydrolysis of aluminium on weakly acidic organic exchangers: Implications for phosphate adsorption

In contrast to its behaviour on soil clays and in aqueous solution, aluminium is more extensively hydrolysed between pH3 and 4.5 on organic exchangers because the weakly acidic carboxyl groups appear to act as sinks for the protons released by hydrolysis and polymerization of the Al(H₂O) ₆ ³⁺ ions. In consequence, the basicity (measured by the OH/Al mole ratio) of Al adsorbed on samples of acid peat, humic acid and Amberlite IRC-50 resin was closely correlated with the apparent pK_a of the acid groups. The amount of phosphate adsorbed depended not only on the amount of Al adsorbed but also on the basicity of the adsorbed Al. Phosphate and OH^– ions competed for Al on the exchange sites with the result that the P/Al mole ratio on the exchanger was inversely related to the basicity of the adsorbed Al. Once adsorbed, the Al was quite stable and P adsorption on the Al-exchanger was unaffected by a rise in pH from 4.5 to 6.4.     

Kinetics of Ion Formation in the Volumetric Reaction of Methane with Air

The formation of ions in the volumetric reaction of methane and hydrogen with air is analyzed. In methane–air mixtures, the highest concentrations are observed for NO⁺, NO₃ ^–, CO₃ ^–, CO₄ ^–, OH^–, and NO₂ ^– ions. In hydrogen–air mixtures, maximum concentrations are characteristic for NO⁺, OH^–, H₃O⁺, O^–, and O₂ ^– ions. In both rich and lean mixtures after ignition there is a long time interval during which the ion concentrations are far from equilibrium. The duration of this interval and the ion concentrations in it depend on the initial parameters of the mixture and the air–fuel ratio. Key words: volumetric reaction of methane with air, ion-molecular reactions, kinetics, ions.     

Development of novel adsorbent materials for recovery and enrichment of uranium from aqueous media

A new polymeric adsorbent bearing both hydrophilic groups providing swelling in water and amidoxime groups for chelating with uranyl ions (UO₂²⁺), has been developed and its adsorptive ability for recovering uranium from aqueous media has been investigated. The polymers obtained by irradiating the solution of polyethylene glycol (PEG) in acrylonitrile (AN) are defined as interpenetrating polymer networks (IPNs) and the adsorbent has been obtained by applying the amidoximation reaction to the IPNs with a conversion ratio of ∼ 60%. Kinetics of the conversion reaction of the cyano (CN) group to the amidoxime (HONCNH₂) group has been studied by reacting with hydroxylamine (NH₂OH) solution at a molar ratio of NH₂OH/CN = 1.25 in aqueous media at three different temperatures, 30, 40, and 50°C, for 3–4 days. The degree of amidoximation ratio was determined by UO₂²⁺ ion adsorption and FTIR spectrometry and the UO₂²⁺ ion adsorption values were found by both UV and gamma spectrometry and also by gravimetry. It was found that the polymeric adsorbent has a very high adsorption ability for uranium and quite a good stability in aqueous media. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 66: 2475–2480, 1997     

Investigation of the properties of a mixture based on the rigid-chain polyamidobenzimidazole and a flexible-chain thermoplastic polymer in dimethylacetamide by the sedimentation method

Conclusions -- The sedimentation character of PABI-S—thermoplastic polymer mixtures has been studied where these differ in molecular weight and in the thermodynamic stiffness of the chain; studies were in dimethylacetamide containing 3% by wt. lithium chloride.-- The character of the gradient curve shows that the stiff chain PABI-S fills the role of a matrix in change in polydispersity of the mixed system at PABI-S—thermoplastic ratios of 99:1, 95:5; 90:10; or 80:20%.-- The bimodality on the sedimentation curve for a PABI-S—thermoplastic mixture at a weight ratio of 50:50 indicates compositional nonuniformity.Translated from Khimicheskie Volokna, No. 4, pp. 16–17, July–August, 1991.     

Intensified Fischer–Tropsch synthesis process with microchannel catalytic reactors

A microchannel catalytic reactor with improved heat and mass transport has been used for Fischer–Tropsch synthesis. It was demonstrated that this microchannel reactor based process can be carried out at gas hourly space velocity (GHSV) as high as 60,000 h⁻¹ to achieve greater than 60% of single-pass CO conversion while maintaining relatively low methane selectivity (<10%) and high chain growth probability (>0.9). In this study, performance data were obtained over a wide range of pressure (10–35 atm) and hydrogen-to-carbon monoxide ratio (1–2.5). The catalytic materials were characterized using BET, scanning electron microcopy (SEM), transmission electron microcopy (TEM), and H₂ chemisorption. A three-dimensional pseudo-homogeneous model was used to simulate temperature profiles in the exothermic reaction system in order to optimize the reactor design. Intraparticle non-isothermal characteristics are also analyzed for the FT synthesis catalyst.     

Binding Properties of a Polymer Having Amidoxime Groups with Proton and Metal Ions

Abstract

The proton-binding behavior of a polymer having amidoxime groups was examined by the potentiometric titration method. Adsorptive properties of the polymer for UO₂(VI), Mg(II), Fe(II), Ni(III), Co(II), Ni(II), Cu(II), and Zn(II) were also examined at very low concentrations in the 1–9 pH range. The amidoxime polymer possesses adsorptive affinities of the following order: (Mg(II), Ca(II)) < Zn(II) < Co(II) < Ni(II) < Cu(II) < UO₂(VI). These adsorptive affinities are reasonably explained by the proton-binding and the metal ion-complexing abilities of the ligand, and are discussed from the standpoint of uranium recovery from seawater.