Dmitry Marinin

Polypropylene surface functionalization with chitosan

Chitosan coatings on oxygen-plasma pre-treated polypropylene (PP) surfaces were formed to improve their wettability, dyeing behavior and reactivity without altering material bulk properties. XPS, electrokinetic potential and contact angle measurements as well as dye uptake tests were carried out for surface characterization of modified PP, evaluation of chitosan coatings stability, and the effects of temperature and pH on coatings formation. About 20–30% of the total amount of chitosan immobilized on PP was found to be covalently bonded to the plasma pre-treated surface through the heat induced reactions with oxygen-containing functional groups at T > 80°C that corresponded to 47% of surface coverage. Subsequent cross-linking reaction with epichlorohydrin proved to be an efficient way to reduce the susceptibility of chitosan coatings to acidic hydrolysis.

pH-indicators doped polysaccharide LbL coatings for hazardous gases optical sensing.

Sensitive layer-by-layer (LbL) coatings for optical detection of gaseous NH(3) and HCl were prepared by self-assembly of oppositely charged polysaccharides (chitosan and λ-carrageenan) followed by doping LbLs with pH-sensitive dyes - bromothymol blue (BTB) and Congo red (CR). It has been shown that CR, being an amphoteric dye, diffuses into LbL films regardless of the charge of the outermost polyelectrolyte layer, and the dye loading increases linearly with the LbL film thickness, whereas BTB diffuses into LbL films only when the outermost layer is positively charged, and linearity between dye loading and film thickness holds only up to 8-12 double layers (DLs) deposited. Formation of dye-doped LbL coatings at the surface of K(+)/Na(+) ion-exchanged glass has allowed fabrication of composite optical waveguide (OWG) gas sensor for detection of ammonia and hydrochloric acid vapors. The response time of BTB-doped composite OWG for ammonia detection was below 1s, and the detection limit was below 1 ppm. CR-doped OWG sensors have shown high sensitivity to HCl vapor but slow relaxation time (up to several hours for 12 DL LbL films).

Decontamination of spent ion-exchangers contaminated with cesium radionuclides using resorcinol-formaldehyde resins

The origin of the emergence of radioactive contamination not removable in the process of acid-base regeneration of ion-exchange resins used in treatment of technological media and liquid radioactive waste streams has been determined. It has been shown that a majority of cesium radionuclides not removable by regeneration are bound to inorganic deposits on the surface and inside the ion-exchange resin beads. The nature of the above inorganic inclusions has been investigated by means of the methods of electron microscopy, IR spectrometry and X-ray diffraction. The method of decontamination of spent ion-exchange resins and zeolites contaminated with cesium radionuclides employing selective resorcinol-formaldehyde resins has been suggested. Good prospects of such an approach in deep decontamination of spent ion exchangers have been demonstrated.

Polymer-Inorganic Coatings Containing Nanosized Sorbents Selective to Radionuclides. 2. Latex/Tin Oxide Composites for Cobalt Fixation

Colloidal tin oxide with an average particle size of 3.5 nm, which was ex-situ synthesized by the sol-gel method, has been attached to the surface of amino-functionalized poly(acrylate-co-silane) latex particles with a diameter of 100 nm to yield a composite with selective sorption properties toward Co(2+) ions. Electrokinetic properties and the colloidal stability of the synthesized latex/SnO2 composites have been evaluated in dependence on SnO2 content and pH; the sorption capacity and distribution coefficients of composites for Co(2+) ions were in accordance with the SnO2 content and its sorption performance as an individual compound. Composite coatings obtained by casting latex/SnO2 dispersions on quartz sand spiked with (57)Co radionuclide have efficiently eliminated radionuclides migration from the surface when the SnO2 volume fraction in the film was 3.5-4.7%. Furthermore, at these SnO2 loadings, the composite coatings retained the coherent structure of the original latex coating with SnO2 particles homogeneously distributed over the film thickness. The presence of competing Ca(2+) ions in the leaching media at a concentration of above 0.01 mol/L results in a decrease of the distribution coefficients of the latex/SnO2 composite and significantly higher (57)Co leaching. The value of the distribution coefficient of the sorption material to be used in latex composite coatings to prevent migration of radionuclides shall be close to 10(6) mL/g.

Latex Particles Functionalized With Transition Metals Ferrocyanides for Cesium Uptake and Decontamination of Solid Bulk Materials

Decontamination of spent ion-exchange resins, corrosion-unstable metal structures, soil, ground, and construction materials contaminated by fission, corrosion and transuranic radionuclides remains one of the most urgent and complicated ecological problems. Among the existing methods having different efficiencies in regard to such materials decontamination, application of selective sorbents put into a humid medium to be decontaminated (ground, bulk materials) appears to be rather extensive. However, the efficiency of such an approach is significantly limited by difficulties concerned with uniform sorbent distribution in porous media and completeness of spent sorbents removal for final disposal. In this paper we suggest a principally new approach to preparation of colloid-stable selective sorbents for cesium uptake using immobilization of transition metals (cobalt, nickel, and copper) ferrocyanides in nanosized carboxylic latex emulsions. The effects of ferrocyanide composition, pH, and media salinity on the sorption properties of the colloid-stable sorbents toward cesium ions were studied in solutions containing up to 200 g/1 sodium nitrate or potassium chloride. The sorption capacities of the colloid sorbents based on mixed potassium/transition metals ferrocyanides were in the range 1.45–1.86 mol Cs/mol ferrocyanide with the highest value found for the copper ferrocyanide. It was shown that the obtained colloid-stable sorbents were capable to penetrate through bulk materials without filtration that makes them applicable for decontamination of solids, e.g. soils, zeolites, spent ion-exchange resins contaminated with cesium radionuclides. After decontamination of liquid or solid radioactive wastes the colloid-stable sorbents can be easily separated from solutions by precipitation with cationic flocculants providing localization of radionuclides in a small volume of the precipitates formed. Besides, functionalized latex particles can be used for preparation of carbon fiber/ferrocyanide composite materials for cesium uptake using electrodeposition method. Application of the carbon fibers as an inert support for ferrocyanides, in general, significantly improves the sorption kinetics, but washing out of ferrocyanide fines from the fiber surface limits the potential of such materials. When ferrocyanides are deposited in a form of nanocrystals stabilized by latexes which undergo electropolymerization on the fiber surface, the thin polymeric film formed substantially improves the stability of the composite and prevents loss of ferrocyanide during sorbent application. The effect of electrodeposition conditions on composite morphology, ferrocyanide loading and cesium distribution coefficient in media with different salinity has been discussed.Copyright

Novel Technology for Hydrothermal Treatment of NPP Evaporator Concentrates

A novel technology was developed for treatment of evaporator concentrates produced as a result of operation of evaporation devices comprising the main component of special water purification systems of nuclear power plants (NPP). The developed technology includes a hydrothermal (T = 250–300°C and P = 80–120 bar) processing of evaporator concentrates in oxidation medium in order to destruct stable organic complexes of cobalt radionuclides and remove these radionuclides by oxide materials formed during such a processing. The cesium radionuclides contained in evaporator concentrates are removed by a conventional method — through application of one of the developed composite sorbents with ferrocyanides of transition metals used as active agents. Extensive laboratory studies of the processes occurring in evaporator concentrates under hydrothermal conditions were performed. It was shown that hydrothermal oxidation of evaporator concentrates has a number of advantages as compared to traditional oxidation methods (ozonation, photocatalytic, electrochemical and plasma oxidation). A laboratory installation was built for the flow-type hydrothermal oxidation of NPP evaporator concentrates. The obtained experimental results showed good prospects for the developed method application. On the basis of the results obtained, a pilot installation of productivity up to 15 l/hour was developed and built in order to work out the technology of evaporator concentrates hydrothermal treatment. The pilot tests of the hydrothermal technology for evaporator concentrates hydrothermal treatment were performed for 6 months in 2006 at the 1st reactor unit of the Novovoronezhskaya NPP (Voronezh Region, Russia). Optimal technological regimes were determined, and estimations of the economic soundness of the technology were made. The advantages of the presented technology in terms of management of concentrated liquid radioactive wastes (LRW) at nuclear cycle facilities, as compared to other methods applicable for this type of LRW, were demonstrated. Application of the hydrothermal technology in the system of NPP LRW management enables one to reduce substantially the volume of solid radioactive waste sent for final disposal.Copyright

New sorbents and technologies for liquid radioactive waste management

The possibilities for using various technologies for liquid radioactive waste (LRW) management were considered. Technologies based on the application of sorbents highly selective to radionuclides were shown to have good prospects. Possible ways of increasing selective sorbent efficiency in cleaning radionuclide-polluted waters of various types were examined. The results of studying new high-selective sorbents produced in the Institute of Chemistry FEDRAS are given. The use of these sorbents enables one to treat LRW of various types in a single stage. The results of testing a sorption filter installation for management of LRW produced during operation, repair and disposal of nuclear reactors are presented. Use of this installation resolves a major portion of LRW disposal problems.

A new approach to determining the volume of the adsorbed phase depending on bulk concentration

Abstract A new thermodynamic approach has been devised to determine the volume of the adsorbed phase and its other parameters characterizing adsorption from binary solutions of nonelectrolytes on solids—composition, mole number, partial molar volumes, and activity coefficients of components. The thermodynamic treatment is based on experimentally measured values of excess adsorption and heterogeneous system excess volume. The ideal adsorption system, containing an ideal adsorbed phase and ideal bulk solution, has been considered. The adsorption volume is determined as a function of the bulk-phase equilibrium composition. This approach has been used to determine the thermodynamic parameters of several experimentally studied and simulated binary solution/solid systems.

Quantum chemistry and experimental studies of hydrothermal destruction of Co-EDTA complexes

Hydrothermal oxidation, a promising method for removal of cobalt radionuclides from EDTA-containing liquid radioactive waste streams, is in the focus of the present study. It has been demonstrated that Co(III)-EDTA complexes, which are very stable under normal conditions, undergo oxidation as a result of the electron transfer from the EDTA carboxyl group to Co(III) ions under elevated temperature. The electron transfer reaction follows the first-order rate law with an activation energy of 91.8 kJ/mol at рH 12 and time of Co(III) ions half-conversion of 0.2 s at 200 °C. The rate of EDTA oxidation is proportional to the concentration of Co(III) ions and solution pH. Based on quantum chemistry simulations, possible intermediate structures formed upon the electron transfer from EDTA to Co(III) ions have been suggested. It has been shown that the introduction of hydrogen peroxide provides a continuous generation of Co(III) ions and a sequential decarboxylation of the EDTA until complete degradation of the chelate structure. The pathways of cobalt immobilization have been clarified.

Concentrating cesium-137 from seawater using resorcinol-formaldehyde resin for radioecological monitoring

Abstract A method of preconcentrating cesium-137 from seawater using a resorcinol-formaldehyde resin, which enables one to optimize the ecological monitoring procedure, has been suggested. Studies of sorption of cesium-137 from seawater by resorcinol-formaldehyde resin have been performed, and it has been demonstrated that the cation exchanger is characterized by high selectivity with respect to cesium-137. It was found that the selectivity depended on the temperature of resin solidification and the seawater pH value. The maximal value of the cesium-137 distribution coefficient is equal to 4.1–4.5×103 cm3 g−1. Under dynamic conditions, the ion-exchange resin capacity is 310–910 bed volumes depending on the seawater pH, whereas the efficiency of cesium removal exceeds 95%. The removal of more than 95% of cesium-137 has been attained using 1–3 M solutions of nitric acid: here, the eluate volume was 8–8.4 bed volumes. Application of 3 M solution of nitric acid results in resin degradation with the release of gaseous products.