Search Results
Abstract
A fine-crystalline stannous ferrocyanide (SCF) has been prepared by adding tin(II) chloride to potassium hexacyanoferrate(II) solution. The material was characterized by chemical analysis, thermogravimetry, X-ray diffraction and infrared spectra. The solubility of SCF, kinetics and sorption mechanism of palladium in hydrochloric acid solutions were investigated. The palladium exchange capacity of 2.20 mM/g dry weight have been found.
Abstract
The bentonite/iron oxide magnetic composites were prepared by co-precipitation method, and characterized by Fourier transform infrared spectroscopy, X-ray powder diffraction and scanning electron microscope. The prepared bentonite/iron oxide magnetic composites were used as a sorbent for the removal of Co(II) ions from radioactive wastewater. The results demonstrated that the sorption of Co(II) was strongly dependent on pH and ionic strength at low pH values. The sorption of Co(II) was dominated by outer-sphere surface complexation or ion exchange at low pH whereas inner-sphere surface complexation was the main sorption mechanism at high pH. The presence of iron oxide in the composites also contributes to the sorption of Co(II) ions on the magnetic composites. The experimental data were well described by Langmuir model. The thermodynamic parameters (∆G °, ∆S °, ∆H °) calculated from the temperature-dependent sorption isotherms indicated that the sorption of Co(II) on bentonite/iron oxide magnetic composites was an endothermic and spontaneous processes.
Summary
The sorption of uranium-Arsenazo III complex was studied using Dowex-1x8 and carbonized apricot stone. The results show a similarity between the two sorbents since the percentage uptake of a uranium complex in the ratio 1 : 1 reaches 100% and 92% on the Dowex-1x8 and the carbonized apricot stone, respectively. Also the uptake of the complex on either sorbents increases with increasing the hydrogen ion concentration to reach a maximum value at pH 2.5. The two sorbents are used to study the sorption of uranium(VI) from seawater in the presence of 0.002% of Arsenazo III and 10-3M EDTA, where it is found that uranium is completely sorbed by the two sorbents.
Abstract
The chelating resins Dowex A1 and its purified form, Chelex 100, contain the iminodiacetate functional group. The resins can exchange cations from solutions of high pH and anions from low pH solutions. Further, the iminodiacetate functional group provides chelating capability leading to special selectivity for multivalent ions such as Sb(V) and Hg(II). A systematic study of the sorption characteristics of Chelex 100 was initiated in our laboratory. Distribution coefficient values (Kd) were measured for Zn(II), Cd(II), Sn(IV), Sb(V) and Hg(II) as a function of HCl concentration and for Cu(II) and Pb(II) as a function of pH. The results obtained thus far indicate that Sb(V) and Hg(II) have high Kd values in acid chloride solutions. A radiochemical separation procedure was developed for the determination of Hg by neutron activation analysis using sorption onto Chelex 100.
Abstract
Selective sorption characteristics of electrolytic manganese dioxide (EMD) were investigated by dynamic tests using different types of water under varying conditions of235U activity, chemical species and flow rate in the presence of226Ra. EMD showed selectivity for ions having an effective ionic radius of about 1.4 Å indicating a selective sieve mechanism supporting a tunnel type structure. Sorption of235U under all experimental conditions is small (<1%) due to the larger sizes of urano-complexes (>3.54 Å). The Ra2+ ion (size 
2.86 Å) was selectively extracted by EMD so that226Ra can be measured directly by gamma spectrometry using the 186 keV gamma line.
Abstract
The ability of some antural Mexican clays to sorb radioactive Co from aqueous solution and then desorb it has been measured. The clay cations seem to be exchanged with cations present in the solution. It was observed that the amount of sorbed Co2+ depends nearly linearly on the Na++K+ content in the montmorillonites. It was found that the crystallinity was not altered after Co2+ sorption. Crystallinity of clays, before and after cobalt exchange, was determined by X-ray diffraction.
Abstract
The kinetics of radiocesium sorption and desorption by cation solutions and the corresponding radiocesium distribution profiles in sediment cores were investigated. The results have shown that a significant percentage of radiocesium is adsorbed in the sediments during the first 3 d. Radiocesium reaches rapidly (< than 5 d) at a depth which does not exceed 3.5 cm. The desorption of radiocesium was found to depend on cation concentrations. Empirical laws are derived both for cesium adsorption and desorption.
Abstract
Mesoporous materials MCM-41 with the hexagonal arrangement of pores were obtained using dodecyltrimethylammonium bromide and octadecyltrimethylammonium bromide as templating surfactants. Adsorption of toluene and propan-1-ol on the as-synthesized MCM-41 silica samples was investigated using the TG-DTG, DTA and DSC techniques. The sorption mechanism of used adsorptives is discussed in terms of hydrophobicity of pore interior filled with template as well as pore dimensions.
Abstract
In this paper, the special sorption properties of mercury(II) on calcium-montmorillonite is shown. Mercuric hydroxide (Hg(OH)2) produced by the hydrolysis of mercuric ions is fairly soluble, solubility is 3.2 × 10−4 mol/dm3. As a result, indifferently of the usual behavior of other hydroxides, it remains in the aqueous solution. The sorption properties are determined by the fact: there is no precipitation at higher pH values. Montmorillonite contains permanent as well as pH-dependent charges, so the cation exchange on the permanent changes, in the interlayer space of montmorillonite and the sorption of neutral mercuric hydroxide molecules can be studied simultaneously. So, two interfacial processes of the same substance, namely the ion exchange of hexahydrate mercuric(II) ions and the sorption of neutral mercuric hydroxide molecules, can be studied in the same system.
Abstract
Information about the sorption of radionuclides on natural materials used for cementation of liquid radioactive wastes (RAW) is important for predictions of migration rates of radionuclides in the products of fixation. Cementation process for conditioning liquid RAW uses, besides cement, materials which improve quality of products. In Czechoslovakia technology among these materials are clinoptilolite tuffit, mordenite tuff, tobermorite and fly ash. Liquid RAW issued from nuclear power plants contains the principal radionuclides60Co,134Cs and137Cs, therefore, a sorption study of these radionuclides was carried out. pH of liquid RAW was 12.5–13.7 and salt content ca. 200 g·dm–3. Results of sorption are given by distribution coefficients. The best results for cesium in those pH region and salt content had mordenite tuff DCs=100 dm3·kg–1 and the worst results had fly ash DCs=4.1 dm3·kg–1. The best results for cobalt in those solutions had tobermorite DCo=38 dm3·kg–1 and the worst results had fly ash DCo=6.9 dm3·kg–1.
