Use of inorganic catalysts in production of carbon fibres. Properties of the sorbents obtained

The efficiengy of using diffeent inorganic catalytic additives in fabrication of carbon fibre mateials was evaluated by TGA. The important possibility of obtaining CFM with a high yield on the existing equipment at the Svetlogorsk Khimvolokno Industrial Association was demonstrated. The structure and properties of TS and NS carbon materials fabricated with the technology developed were investigated by methods of mercury porosimetry, electron microscopy, cryosorption of nitrogen, sorption of benzene vapors, and sorption of large organic ions. The possibility of using the developed carbon sorbents in purification of virus-containing solutions and for removal of organic contaminants from aqueous solutions was investigated.St. Petersburg State University of Technology and Design. Translated from Khimicheskie Volokna, No. 6, pp. 27–31, November–December, 1996.     

Thermooxidative stability of carbon fibres and methods of increasing it

It is necessary to introduce an additional stage of elimination of sodium ions to obtain carbon fibre with elevated thermooxidative stability based on PAN fibre by the water—thiocyanate spinning method. This can be done in different stages of the technological process of fabrication of CF. CF fabricated from PAN with sodium impurities washed off by the water—thiocyanate spinning method has thermooxidative stability close to CF fabricated from PAN by the dimethylformamide method. Several ways of eliminating sodium ions are reported, but their actual implementation will probably be a function of the economy and technical expediency of each one.All-Russian Scientific-Research Institute of Polymer Fibres, Mytishchi. Translated from Khimicheskie Volokna, No. 2, pp. 27–28, March–April, 1995.     

Continuous treatment of filament with a dosed amount of reagent

The characteristics of treatment of filaments with a dosed amount of reagent were examined on the example of elimination of sodium ions from PAN twist. It was shown that a 2 g/liter concentration of H₂SO₄, required for elimination of sodium ions from 0.026–0.35 to 0.01–0.03%, is attained over the entire section of the twist on contact of PAN twist with a solution of H₂SO₄ of high concentration, 20–30 g/liter, for 0.2–0.8 sec. The diffusion coefficients of H₂SO₄ and the thermal conductivity of the twist were determined. It was shown that heating of the twist takes place two orders of magnitude more rapidly than diffusion of sulfuric acid.All-Russian Scientific — Research Institute of Polymer Fibres, Mytishchi. Translated from Khimicheskie Volokna, No. 3, pp. 20–23, May–June, 1994.     

Sorption of transition metals by polyfunctional vion fibre sorbents

The selectivity and sorption capacity of polyfunctional fibre sorbents containing carboxyl, hydrazidine, and amidoxime groups are a function of the ratio of these groups in the polymer chain in absorption of transition metal ions from low-concentration solutions. The selectivity for nickel ions is determined by the ratio of carboxyl and hydrazidine groups, while the selectivity for copper ions increases significantly when 3–5 wt. % amidoxime groups are incorporated in the polymer chain in addition to the indicated units.All-Russian Scientific-Research Institute of Polymer Fibres, Mytishchi. Translated from Khimicheskie Volokna, No. 3, pp. 24–26, May–June, 1995.     

Copper Sorption from Aqueous Solutions by Plasma Modified Polyacrylonitrile Beads

Summary The adsorption of Cu(II) ions from aqueous solutions on acrylonitrile(AN) copolymer sorbents has been studied. Porous sorbents from acrylonitrile copolymer-90.6% acrylonitrile (AN), 8.1% methylmethacrylate (MMA) and 1.4% 2-acrylamido-methylpropensylfonic acid (AMPSA) have been prepared and modified by ammonia, air and ethylenediamine plasma. Fourteen types of sorbents have been obtained changing plasma agent and plasma vacuum. The Cu(II) ions uptake has been studied and the sorbent with best sorption characteristics determined. The best sorption uptake has been achieved for the modified sorbent obtained at ethylenediamine plasma modification under 5 Pa plasma vacuum (PAN1-1.20 mgeq/g). Effect of sorbents regeneration after different elution cycles has also been investigated . The sorbents showed high effectiveness of regeneration towards Cu(II) ions, which was above 50% after the IV cycle of elution.     

Recovery of purified radiocesium from acidic solution using ammonium molybdophosphate and resorcinol formaldehyde polycondensate resin

Separation of Cs⁺ from acidic solution was investigated using ammonium molybdo- phosphate (AMP) based sorbents. Four sorbents including two AMP powders and two composites prepared by coating of AMP powder on polymethylmethacrylate (PMMA) beads were used in this study. Equilibrium sorption isotherms for Cs⁺ on AMP sorbents were determined. The effect of H⁺ concentration on Cs⁺ uptake by AMP–PMMA beads was examined. Two column runs were carried out to establish the Cs⁺ separation performance of AMP–PMMA beads from 1.0 M nitric acid having Cs⁺ concentration equivalent to 10 Ci of ¹³⁷Cs per litre. Recovery of Cs⁺ from loaded AMP–PMMA column was carried out by dissolution of AMP using NaOH solution. The feasibility of ion exchange purification of the recovered Cs⁺ solution was examined using resorcinol formaldehyde polycondensate resin (RFPR). The Cs⁺ sorption isotherm on RFPR from Cs-bearing dissolved AMP solution was determined. Purification of Cs⁺ from dissolved AMP solution was studied in two column runs using RFPR in loading-elution cycles. The results of these studies are useful in formulating a scheme for the recovery of purified ¹³⁷Cs product from high level waste for large-scale utilization as a radiation source in industrial irradiators.     

Ferrite process of electroplating sludge and enrichment of copper by hydrothermal reaction

In this paper, ferrite process of electroplating sludge and enrichment of copper by hydrothermal reaction was investigated. By the hydrothermal treatment, Zn, Ni, Cu, Cr-bearing electroplating sludge can be transformed into high value-added Ni–Zn–Cr ferrite by adding iron source (FeCl₃·6H₂O) and precipitator. The most optimum reaction conditions were explored: 1.57 g/g dry sludge as the dosage of FeCl₃·6H₂O, pH 8.5 of the slurry adjusted by ammonia, 4 h as the reaction time, and 200 °C as the reaction temperature. Under these conditions, the purer Ni–Zn–Cr ferrite could be prepared, and Cu was extracted to the range from 76 wt% to nearly 84 wt%, when ammonia was selected as the precipitator. Leaching toxicity of heavy metals from Ni–Zn–Cr ferrite prepared with additional iron source and precipitator, was much lower than the regulated limit of Toxicity Characteristic Leaching Procedure (TCLP), indicating that Ni–Zn–Cr ferrite synthesized hydrothermally from electroplating sludge had a better chemical stability. Therefore, the ferrite process by hydrothermal reaction is a feasible method with respect to the reuse and self-purification of electroplating sludge.     

The problem of refining cellulose triacetate solutions with fibrous ion-exchange resins

Conclusions The process of cleaning up cellulose acetate spinning solutions and model solutions from traces of acid dyes with polyacrylonitrile fibre anion-exchangers has been investigated. Optimum conditions for carrying out the clean-up have been determined.It is recommended to use ion-exchange resin type PAN(2)cp-PEA, prepared using a polyamine preparation, to clean up the spinning solution.Translated from Khimicheskie Volokna, No. 5, pp. 16–17, September–October, 1985.     

Adsorption of heavy metal ions from aqueous solutions by porous polyacrylonitrile beads

The adsorption of Cu(II), Ni(II), Zn(II), and Pb(II) from aqueous solutions on acrylonitrile copolymer sorbents was studied. We prepared five types of sorbents from polyacrylonitrile by varying its concentration in the initial polymer solution and the composition of the coagulation bath, aiming to achieve a different porous structure. The specific area, pore volume, and pore radius of the sorbents were determined on a porosimeter. The porous structure was studied by scanning electron microscopy. Modification of sorbents with sodium hydroxide and hydroxylamine was carried out to form amidooxyme and carboxylic groups with proven complex‐forming properties toward heavy metal ions. The optimal pH of the sorption of metal ions was found. The adsorption kinetics were investigated. The order of polymer sorbents toward the sorption of Pb(II), Cu(II), Ni(II), and Zn(II) ions, and the order of heavy metal uptake were determined for all types of sorbents. The effectiveness of heavy metal desorption and the coefficient of recovery of sorption ability were determined. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 3036–3044, 2002; DOI 10.1002/app.2334     

Mine water purification with the use of humic preparations

Six carbon-containing sorbents prepared from brown coals were used to purify mine water from the Kizelovskii basin. The main physicochemical characteristics and process regimes of the purification of acidic mine water were determined under laboratory conditions. The initial coals and spent carbon-containing sorbents were characterized. It was found that this purification process resulted in a decrease in the total hardness and sulfate content by 15–27% and to the almost complete removal of harmful metal cations from mine water. The results of the analysis of spent carbon-containing sorbents demonstrate that they can be utilized by thermal oxidation.     

Investigating the process of washing out sodium thiocyanate from polyacrylonitrile tows

Conclusions -- A procedure has been developed for determining the diffusion coefficient of sodium thiocyanate in freshly formed PAN tow during wash-out which is based on refractometry.-- The temperature dependence of the diffusion coefficient of NaSCN has been investigated using a thermostattable cuvette.-- The distribution of NaSCN concentrations in PAN tow during the process of wash-out has been given.Translated from Khimicheskie Volokna, No. 6, pp. 25–26, November–December, 1990.     

Electrochemistry of the SUCOPLATE® Electroplating Bath for the Deposition of a Cu–Zn–Sn Alloy; Part I: Commercial bath

The deposition of a Cu–Zn–Sn alloy from a commercial alkaline cyanide electroplating bath operated at 333 K has been investigated using voltammetric techniques and electron microscopy. It is shown that a highly reflecting alloy deposit with a composition in the range 47–51% copper, 8–12% zinc and 38–43% tin can be produced under a range of conditions. In addition, it is concluded that the rate of alloy deposition is partially limited by mass transport and partially by the kinetics of reactions in homogeneous solution.     

Thermal transformations in fibre blends

The reciprocal effect of polycaproamide and polyacrylonitrile in the presence of phosphorus-containing compounds on thermooxidation and carbonization was determined. It was found that in blends of PCA and PAN fibres previously undergoing thermal oxidation, the thermoplasticity of the polycaproamide decreases and they decompose with a lower rate, retaining approximately 50% of their mass at 600°C.Translated from Khimicheskie Volokna, No. 5, pp. 48–51, September–October, 1995.     

Fibre Chemisorbents for Treatment of Industrial Sewage

An industrial method was developed for treatment of electroplating plant sewage to remove heavy metal ions [zinc, chromium (VI)] with chemisorption materials. The high efficiency of removal of toxic contaminants from aqueous medium with fibre sorbents is demonstrated.     

Preparation of polyacrylonitrile fibre by spinning into organic baths

Conclusions -- The spinning of polyacrylonitrile copolymers into organic baths containing dimethyl sulfoxide and isopropyl alcohol has been investigated. It has been found that the optimum DMSO:IPA ratio in the precipitation bath is 60:40% by wt..-- It has been discovered that the strength of the spun yarn is higher the lower the jet stretch.-- The effect of temperature on orientation stretch ratio has been studied. It has been shown that the optimum temperature for heat stretching of PAN yarn lies in the range 155–160°C.-- The dimethyl sulfoxide content of yarn has been determined by technological transitions. In the final yarn it does not exceed 0.3–1.2% by wt.VNIIPV. Translated from Khimicheskie Volokna, No. 3, pp. 15–16, May–June, 1991.     

Experimental study of the structure of polyacrylonitrile gel fibres

The structure of PAN gel fibres spun by the water-thiocyanate method is investigated. It is shown that in identical spinning conditions, the packing density of the structural elements in gel fibres based on poly(AN-co-MA-co-ItA)terpolymer is lower than in gel fibres based on poly(AN-co-MA-co-AMPS). A structural model of PAN gel fibre is composed and substantiated. It is shown that the lower packaging density of the structural elements in PAN gel fibres is responsible for the higher sorption power with respect to different inorganic and organic compounds and higher rate polymer-analog transformations.Translated from Khimicheskie Volokna, No. 5, pp. 40–45, September–October, 2004.     

Chemical transformations in high-temperature treatment of polyacrylonitrile fibre (review)

Possible compounds separated from the heteroaromatic structure of oxidized PAN fibre during its high-temperature treatment were analyzed with the data on the change in the chemical composition. It was shown that a reaction involving hydroxyl and carbonyl groups in neighboring chains is the most probable reaction in the initial stage of intermolecular polycondensation. The proportions of structures with different degrees of condensation and the change in them with an increase in the treatment temperature in a wide range of heating rates were investigated. The nonsimultaneous character of the chemical transformations in the entire PAN fibre related to the different mobility of segments of the polymer chain in heat treatment of the fibre in air was demonstrated.Avtor Scientific-Production Association, Mytishchi. Translated from Khimicheskie Volokna, No. 1, pp. 18–24, January–February, 1994.     

Use of high-efficiency liquid-chromatography in determining the metal content of waste-water

Conclusions -- New sorbents have been synthesized for the separation of transition heavy-metal ions by the high-performance liquid-chromatography method.-- The possibility has been demonstrated for a rapid and selective chromatographic separation of six metal ions.Klinskii Khimvolokno PO. Translated from Khimicheskie Volokna, No. 5, pp. 56–57, September–October, 1992.     

Sorption of hydrogen fluoride by the chemisorptive fibres VION AN-1 and VION AN-3

Conclusions -- It has been found that to remove hydrogen fluoride from a gas-air mixture at a concentration down to 15 mg/m³, one should use the chemisorptive fibrous sorbents VION AN-1 or VION AN-3; this ensures a high degree of clean-up down to a concentration considerably lower than the limiting allowable one in the workplace.-- In the sorption of hydrogen fluoride from a gas-air mixture, it is recommended to use the KHVF filter instead of scrubber purification; this ensures high technical-economic indices for the process.Translated from Khimicheskie Volokna, No. 5, pp. 22–24, September–October, 1990.     

Removal of toxic metal Cr(VI) from aqueous solutions using sawdust as adsorbent: Equilibrium, kinetics and regeneration studies

In the present study, a low-cost adsorbent is developed from the naturally and abundantly available sawdust which is biodegradable. The removal capacity of Cr(VI) from aqueous solutions and from the synthetically prepared industrial effluent of electroplating and tannery industries is obtained. The batch experiments are carried out to investigate the effect of the significant process parameters such as initial pH, change in pH during adsorption, contact time, adsorbent amount, and the initial Cr(VI) concentration. The maximum adsorption of Cr(VI) on sawdust is obtained at an initial pH value of 1. The value of pH increases with increase in contact time and initial Cr(VI) concentration. The equilibrium data for the adsorption of Cr(VI) on sawdust is tested with various adsorption isotherm models such as Langmuir, Freundlich, Redlich–Peterson, Koble–Corrigan, Tempkin, Dubinin–Radushkevich and Generalized equation. The Langmuir isotherm model is found to be the most suitable one for the Cr(VI) adsorption using sawdust and the maximum adsorption capacity obtained is 41.5 mg g⁻¹ at a pH value of 1. The adsorption process follows the second-order kinetics and the corresponding rate constants are obtained. Desorption of Cr(VI) from sawdust using acid and base treatment exhibited a higher desorption efficiency by more than 95%. A feasible solution is proposed, for the disposal of the contaminant (acid and base solutions) containing high concentration of Cr(VI) obtained during the desorption process. The interference of other ions which are generally present in the electroplating and tannery industrial effluent streams on the Cr(VI) removal is investigated.