Sorption ability of chemically treated clinoptilolites with regard to cobalt and cesium

Clinoptilolites were treated by NaOH, NH₄NO₃, NaNO₃, KNO₃ and HCl solutions. The sorption ability has been measured by a radiochemical technique. The sorption coefficients were calculated for Co and Cs.     

Study of NaOH-treated clinoptilolites and their physical and ion-exchange characteristics with regard to Cs+ and Co2+

The ion-exchange ability of NaOH-treated clinoptilolites with regard to Cs⁺ and Co²⁺ have been studied by a radiochemical method, enabling to calculate the sorption coefficient. The surface characteristics, total cation exchange capacity and X-ray structural analysis were measured as well. The measurements were done on Slovak clinoptilolite. Comment are made on a possible explanation of increasing sorption coefficient.     

Sorption of cobalt on modified clinoptilolites

A method of radioactivation analysis has been developed for the substoichiometric determination of cobalt, copper and manganese in glass and glass-making materials. The substoichiometric extraction of cobalt with α-nitroso-β-naphthol was studied and simple procedures are suggested for the determination of the three elements. Cobalt is extracted substoichiometrically as α-nitroso-β-naphtholate into chloroform from solution of pH 6.2, copper as dithizonate in carbon tetrachloride from weak acidic solution, and manganese as tetraphenylarsonium permanganate into chloroform after oxidation to permanganate. Contents from 2 ppm to 3 ppb of cobalt, copper and managanese were analysed in glass-making materials, and it is shown that the method for their determination is reliable and superior in accuracy and reproducibility.     

Sorption properties of new nitrogen-containing wood-based ion exchangers with respect to gold(III) ions

Sorption properties of new nitrogen-containing wood-based ion exchangers with respect to gold(III) ions were examined in relation to the metal ion concentration in solution, pH of medium, and sorption temperature and time. The rate-limiting steps in the process were identified. The mechanism of sorption of aurate ions from solutions was considered in relation to their acidity.     

Sorption capacity of acetylacetonated humin-like compounds with respect to cations of heavy metals

A method of synthesis of acetylacetonated humin-like compounds was developed. The effect of modification on the sorption capacity of humin-like compounds with respect to heavy metals was studied.     

Sorption of mercury on chemically synthesized polyaniline

Summary Sorption of inorganic mercury (Hg²⁺) and methyl mercury, on chemically synthesized polyaniline, in 0.1-10N HCl solutions has been studied. Hg²⁺ is strongly sorbed at low acidities and the extent of sorption decreases with increase in acidity. The sorption of methyl mercury is very low in the HCl concentration range studied. Sorption of Hg²⁺ on polyaniline in 0.1-10N LiCl and H₂SO₄ solutions has also been studied. The analysis of the data indicates that the sorption of Hg²⁺ depends on the degree of protonation of polyaniline and the nature of mercury(II) chloride complexes in solution. X-ray photoelectron spectroscopy analysis (XPS) of polyaniline sorbed with mercury show that mercury is bound as Hg²⁺. Sorbed mercury is quantitatively eluted from polyaniline with 0.5N HNO₃. Polyaniline can be used for separation and pre-concentration of inorganic mercury from aqueous samples.     

Sorption of noble-metal ions on silica with chemically bonded nitrogen-containing ligands

A study has been made of the sorption of Ir(IV), Rh(III), Pt(IV), Ru(IV), Os(VIII), Pd(II) and Au(III) from aqueous solutions by silica chemically modified with nitrogen-containing organic ligands, as a function of hydrochloric acid concentration, time of contact, concentration of the element and the ionic strength. Sorption of noble-metal ions at pH > 1 on a sorbent containing monoamine groups seems to be due to a complexation mechanism, and to an anion-exchange mechanism at pH < 1. With aminopropyl-silica 1000-fold concentration of Ir(IV) and Rh(III) from their 10(-8)-10(-7)M solutions was achieved and these metals were subsequently determined on the sorbent surface by X-ray fluorescence. Detection limits were 10-20 ng/ml. There was no interference from 1000-fold quantities of non-ferrous metal ions and Fe(III). With the sorbent containing bonded diethylenetriamine groups, 1000-fold concentration of Au(III) was achieved, and it was then determined on the sorbent surface by an atomic-emission method. Conditions for desorption of Au(III) with pyridine and potassium thiocyanate were developed.     

Sorption and diffusion processes with134Cs and85Sr in natural sorbents

Sorption and diffusion processes with¹³⁴Cs and⁸⁵Sr in natural bentonites have been investigated. The distribution coefficients (K _d ) have been determined by a batch method. Various factors affecting theK _d value as water-to-bentonite ratio, concentration of the competitive cations in the aqueous phase or bentonite-to-sand ratio in the mixed sorbents have been evaluated. A comparison of the sorption and diffusion data has been made.     

Sorption of Cs,Pu and Am on clay minerals

Performance assessment of radioactive waste disposal requires modeling of long-term migration of radionuclides through the engineered barriers and the geological environment. The chemical complexity of sorption-desorption processes is usually reduced to integrated parameter distribution coefficients (K _d ). There are a great number of publications on K _d determination, however, the existing data on K _d of radionuclides on different geological materials are for general understanding only and are not very useful for performance assessment, since changes of the geological conditions result in variability of K _d values by two orders of magnitude. In order to obtain realistic sorption data sets for safety relevant radionuclides present in a cement/concrete based repository some preliminary studies were carried out. The development of sorption database for the near-surface repository was started with measurements of cesium, plutonium and americium K _d values. Several experiments were performed in order to determine the chemical composition of cement water which could originate from infiltration of precipitation and from contact of groundwater with concrete. More than 100 batch sorption experiments were conducted with two clay samples. Cs, Pu and Am K _d values were determined for rainwater, groundwater and cement-water of different chemical compositions. Cs, Pu, Am K _d values ranged from 450 to 9700, from 15000 to 21000 and 15000 to 80000 ml/g, respectively. Changes in the geochemical conditions resulted in the variability of Cs, Pu and Am K _d values.     

Porous structure of natural and modified clinoptilolites

The evaluation of the pore-size distribution (PSD) of natural and modified mesoporous zeolites, i.e., clinoptilolites is presented. We demonstrate the SEM results showing that the pores of fracture-type from 25-50 nm to 100 nm in size between clinoptilolite grains, as well as pores between crystal aggregates up to 500 nm in size are present in the studied material. The detailed distribution of pore sizes and tortuosity factor of the above-mentioned materials are determined from the adsorption-desorption isotherms of nitrogen measured volumetrically at 77 K. To obtain the reliable pore size distribution (PSD) of the above-mentioned materials both adsorption and desorption branches of the experimental hysteresis loop are described simultaneously by recently developed corrugated pore structure model (CPSM) of Androutsopoulos and Salmas. Evaluated pore size distributions are characterized by well-defined smooth peaks placed in the region of the mesoporosity. Moreover, the mean pore diameter calculated from the classical static measurement of nitrogen adsorption at 77 K correspond very well to the pore diameters from SEM, showing the applicability of the CPSM for characterization of the porosity of natural zeolites. We conclude that classical static adsorption measurements combined with the proper modeling of the capillary condensation/evaporation phenomena are a powerful method which can be applied for pore structure characterization of natural and modified clinoptilolites.     

Sorption of Co and Cd by zeolite Y

The sorption behavior of cobalt and cadmium by zeolite Y has been investigated. Cobalt and cadmium solutions were exchanged with the zeolite at different pH's. Cobalt, cadmium and sodium in the samples were determined by neutron activation analysis. The sorption of cadmium was higher than that of cobalt, however, the selectivity for both cations by the zeolite was low.     

Sorption of 134Cs radionuclide onto insoluble ferrocyanide loaded silica-gel

Journal of Radioanalytical and Nuclear Chemistry - Insoluble Ferrocyanide composites prepared for studying 134Cs sorption from aqueous solutions. Two different preparation techniques are used;...     

Determination of the surface properties of untreated and chemically treated kaolinites by inverse gas chromatography

Inverse gas chromatography is used to study the surface properties of the untreated and chemically treated kaolinite samples. Changes in the enthalpy of adsorption for a variety of probes and in the surface energy of clays are measured and the effect of modification of the natural clay after chemical treatment with Na₂CO₃ is determined. The surface energy of the natural clay increased by the modification due to an increase in the surface area. It can be concluded that the dispersive component of surface free energy, γ _s ^d , decreases with temperature in the 200–275°C temperature range for both samples. Temperature coefficients of γ _s ^d for untreated and modified kaolinites are −0.1185 and −0.3966 mJ/(m² °C) with the correlation coefficients (R ²) of 0.8479 and 0.965, respectively. From the retention data for polar probes at infinite dilution, information on the accessibility of surface sites to the probes and on the acid-base character of the surface is obtained. The specific free energy of adsorption, the specific enthalpy of adsorption (ΔH ^sp), and the specific entropy of adsorption of polar probes on initial and modified kaolinites are determined. The ΔH ^sp values correlated with the donor numbers and modified acceptor numbers of the probes to quantify the acidity (K _A) and basicity (K _D) parameters of clay surfaces. The values of K _A and K _D for initial and modified kaolinites are determined to be 0.1202 and 0.2803; 0.0130 and 0.0408 with the correlation coefficients of −0.9805 and −0.9782, respectively. The unmodified clay sample indicated a more acidic character, while the modified clay sample conferred a largely basic character. Consequently, the predominant surface basicity of the modified kaolinite agrees with expectation, bearing in mind the treatment with Na₂CO₃, taking into consideration that such a modification contributes to a decrease in the hydrophilicity of the surface and also results in the surface showing only weak Lewis acidity. The text was submitted by the authors in English.     

Sorption properties of polypropylene

The sorption properties of atactic polypropylene (APP) and isotactic polypropylene (IPP) were studied by equilibrium sorption of various organic solvents. The variation of the Flory-Huggins interaction parameter χ for the APP-CCl₄ system at 25°C was expressed as a function of the volume fraction v₂ of polymer by the relation: x = 0.113 exp {1.879 v₂}. The average molecular weight M _c of the polymer chains between successive crystallites for IPP subjected to different thermal treatments was calculated to be 250 to 350 by the equation of Flory and Rehner. From the variation of M _c with solvent concentration, we estimated the number fraction of polymer chains actually contributing to elastic deformation. The clustering function for solvent in the polymer calculated by the method of Zimm and Lundberg decreased linearly from a positive value to ?1 with increasing solvent concentration. Clustering of solvent molecules was found to occur more easily in APP than in IPP.     

Sorption properties of the complex-forming sorbent bis-1,3,5-dithiazinanee-5-yl-ethane with respect to palladium(II), silver(I), and mercury(II)

Sorption properties of the weakly basic complex-forming sorbent bis-1,3,5-dithiazinane-5-yl-ethane with respect to Pd(II), Ag(I), and Hg(II) were studied. The sorbent was prepared from ethylenediamine, formic aldehyde, and H₂S by a single-reactor procedure.     

Sorption properties of zirconogels

The effect of the pH of precipitation and the nature of the initial zirconium salt and the ionic medium on sorption properties (surface charge, kinetic parameters of sorption) of zirconogels formed due to alkaline hydrolysis of zirconium(iv) sulfate and zirconyl nitrate was studied. Zero point of charge methods, indicator reactions of heterogeneous hydrolysis, drop titration, and thermography were used in the study. The properties of the zirconogels are very close to those of Ferro- and titanogels obtained under similar conditions. The composition of zirconogels, the activation energies of the indicator reactions of heterogeneous hydrolysis, and the dependences of the rate constants of these reactions on the nature and concentration of the ionic medium were determined.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 2653–2657, November, 1996,     

Sorption of Co, Cs, Sr and I onto argillaceous rock as studied by radiotracers</p> </p>

Summary Sorption of⁶⁰Co,⁸⁵Sr, 137Cs and¹²⁵I have been studied on samples originated from Boda (siltstone-) claystone formation (BCF) (Hungary). The distribution of K_dvalues have been determined in static batch experiments using natural groundwater. The order of sorption of isotopes was Co>Cs>Sr>I, where iodine exhibits sorption properties in a modest extent. The sorption isotherm was determined for Cs from measurements carried out in 10^-5-10^-1M initial concentration range. The isotherm can be described with non-linear Freundlich approximation in the range of</o:p></p> 10^-7-10^-4M equilibrium concentration. At concentrations >10^-2M the isotherm achieves saturation. Hence, it is suggested that sorption of Cs on BCF is dominated by cation-exchange reactions on the illite mineral component. In the case of Co and Sr, precipitation reactions occurred during the experiments performed with carrier-containing solutions. This can be attributed to the low values of solubility product constants of SrCO₃, SrSO₄and Co(OH)₂, formed from anions present in the natural groundwater.</p> </p>     

Adsorption properties of modified multilayer carbon nanotubes with respect to benzoic acid

Multilayer carbon nanotubes were modified by ultrasonic treatment in nitric acid and subsequent calcination in an inert atmosphere of argon at temperatures of 500, 800, and 1200°C. The dependence of the adsorption of benzoic acid on carbon nanotubes on the temperature of their calcination was analyzed.