Adsorption of some hazardous radionuclides on cerium (IV) antimonate

Cerium(IV) antimonate was prepared by dropwise addition of 0.6M antimony pentachloride and 0.6M cerium ammonium nitrate solutions by a molar ratio of Ce/Sb 0.75. Exchange isotherms for H⁺/Co²⁺, H⁺/Cs⁺, H⁺/Zn²⁺, H⁺/Sr²⁺ and H⁺/Eu³⁺ were determined at 25, 40 and 60°C. Besides, it was proved that europium is physically adsorped, while zinc, strontium, cobalt and cesium are chemically adsorbed. Moreover, the heat of adsorption of zinc, strontium, cobalt and cesium on cerium (IV) antimonate was calculated and indicated that cerium(IV) antimonate is of endothermic behavior towards these ions. Also the distribution coefficients of these ions were determined and it was found that the selectivity is in the order: Eu³⁺>Sr²⁺>Cs⁺>Na⁺.     

Chromatographic behaviour of metal ions on tin(IV) and titanium(IV) antimonate papers

Summary The chromatographic behaviour of 49 metal ions has been studied on papers impregnated with Sn(IV) and Ti(IV) antimonates in aqueous HNO₃ and mixed solvent systems containing dimethyl sulphoxide. Numerous separations have been achieved and the Alberti equation, for Sn(IV) and Ti(IV) antimonate papers, in the modified form: –nloga K⁺=R_M + constant (a K⁺=activity of K⁺), has been verified. The effect of the concentration of impregnating reagents on these papers has been determined and compared with other papers. The effect of pH on R_f, R_i, log R_f and R_M values of metal ions has also been examined in aqueous systems.     

Separation of trace elements,In(III), Sn(IV), Sb(V) and Te(IV) by adsorption on activated carbon and graphite

Adsorption behaviour of trace elements, In(III), Sn(IV), Sb(V) and Te(IV) on activated carbon and graphite powder was studied. Adsorption characteristics of the ions enabled the separation of In(III)–Sn(IV), Sn(IV)–Sb(V) and Sb(V)–Te(IV) pairs. Applications to practical separation, milking of^113mIn from¹¹³Sn, removal of tin impurity from¹¹⁹Sb, and milking of¹¹⁹Sb from^119mTe, are presented.     

Distribution studies of metal ions on arsenophosphates of Sn(IV) and Cr(III) and on amine Sn(II) hexacyanoferrates (II) using radio tracers: Separation of Sr2+−Cs+, Hg2+−Ag+ and Hg2+−Zn2+

Summary Distribution studies of some metal ions have been made on Sn(IV) and Cr(III) arsenophosphates and on some samples of Sn(II) amine hexacyanoferrates(II), using radiotracers. The K_d values of Cs⁺ and Rb⁺ have been followed at varying HNO₃ concentrations also. As a result 3 useful binary separations have been achieved on Sn(IV) and Cr(III) arsenophosphates, such as Sr²⁺–Cs⁺, Hg²⁺–Ag⁺ and Hg²⁺–Zn²⁺.     

Microcalorimetric Studies of Zn—Al Mixed Oxides Obtained From Hydrotalcite-type Precursors

A series of Zn–Al hydrotalcites with Zn/Al molar ratios of 1, 2, 3 and 6 were prepared by co-precipitation method. TG-DTG results showed that the hydrotalcites decompose in two stages, corresponding to the two endothermic peaks around 180 and 220°C. After calcination at 400°C, the samples were converted into Zn–Al mixed oxides with the only XRD pattern of ZnO, except for the sample with the ratio of 6. The Zn–Al mixed oxides possess similar surface acidity revealed by microcalorimetric adsorption of NH₃. The basicity of the samples increases with the order: ZnO>6Zn/Al>1Zn/Al>Al₂O₃.This revised version was published online in November 2005 with corrections to the Cover Date.     

Ion-exchange selectivity and chromatographic separation of trivalent metals on titanium antimonate

Summary The ion exchange selectivity of trivalent metal ions has been determined on titanium antimonate cation exchanger prepared by coprecipitation of antimony to titanium at different mole ratios. The selectivity sequence Al³⁺<Cr³⁺<Ga³⁺<In³⁺<Fe³⁺ was found for trivalent metal ions at an initial concentration of 10^–4 mol dm^–3 in nitric acid media. A high separation factor ^Ga/Al = Kd^Ga/Kd^Al, 4.8×10³, was observed for the Ga³⁺–Al³⁺ pair on titanium antimonate with an antimony to titanium ratio of 0.34. The effective separation of Ga³⁺ and In³⁺ from Al³⁺ was achieved using a 3 cm×0.5 cm i.d. column containing titanium antimonate with an antimony to titanium ratio of 0.34.     

UO<Subscript>2</Subscript>(VI), Sn(IV), Th(IV) and Li(I) complexes of 4-azomalononitrile antipyrine

UO₂(VI), Sn(IV), Th(IV) and Li(I) complexes of 4-azomalononitrile antipyrine (L) have been isolated and characterized based on IR spectra, ¹H NMR, elemental analyses, molar conductance and thermal analysis (DTA/TG). The study revealed that the ligand behaves as a neutral bidentate one and coordination takes place via the carbonyl atom of pyrazolone ring >C=O and the azomethine nitrogen >C=N. The thermal stability of the metal complexes were investigated by thermogravimetry (TG), differential thermal analysis (DTA) techniques and infrared spectra, and correlated to their structure. The thermal study revealed that Th(IV) complexes show lower thermal stability than both UO₂(VI) and Sn(IV) complexes.     

The ion exchange of strontium on sodium titanate Na4Ti9O20.xH2O

The ion exchange behaviour of the exchanger Na₄Ti₉O₂₀.xH₂O was studied with particular emphasis on Sr²⁺ exchange. Titration of H₄Ti₉O₂₀.xH₂O with 0.1M [Sr/OH/₂+SrCl₂] solution yielded a strontium ion exchange capacity of 5.30 meq g^–1 corresponding well with the theoretical value. When strontium was absorbed on Na₄Ti₉O₂₀.xH₂O from neutral solutions, Sr₂Ti₉O₂₀.xH₂O was formed. This compound decomposed to SrTiO₃ and TiO₂ when heated to 870 °C. From alkaline solutions strontium was absorbed both as Sr/OH/⁺ and Sr²⁺ with the proportion of the former species increasing with pH. At pH 12.8 only exchange of Sr/OH/⁺ was observed and the exchanged form was Na₂/SrOH/₂Ti₉O₂₀.xH₂O. This compound decomposed to Na₂Ti₆O₁₃ and an unidentified strontium titanate when heated to 870 °C. Distribution coefficients were determined for alkali and alkaline earth metal ions as a function of pH. The selectivity sequence for alkaline earth metal ions was Ba>SrCa>Mg, and that for alkali metal ions was Cs>K>Li /pH 2–6/ and Li>Cs>K /pH 7/.     

Polarization and ESR studies of thermally pretreated γ-irradiated TiO2

Pellets of TiO₂ thermally pretreated at 450 and 540°C and -irradiated were polarized by d. c. field. The depolarization curves were resolved into different first order components having two and three depolarization constants. By heating the polarized pellets the Current Glow Peak curves were recorded where there were only two peaks around 65 and 400°C in case of pellets heated at 450°C and heated at 540°C and irradiated; and one more additional peak around 20°C in case of pellets heated at 540°C and heated at 450°C and irradiated thereon. In addition to those signals of O ₂ ^– and Ti³⁺ reported earlier there were distinctly four more, signals at g 1.933 and g 2.03, 2.036 and 2.043 appeared in case of samples heated at 540°C and heated at 450°C and irradiated thereon. The signal at g1.933 is attributed to Ti³⁺ ions in new phase Ti₄O₇ developed in heating at 540°C or due to irradiation and the rest of the signals are due to O _2ad ^– or O _ad ^– over the new phase near anion vacancy created.     

Preparation and Characterization of SiO2-MxOy(M = V, Sn, Sb) Thin Films from Silicic Acid and Metal Chlorides

The preparation of SiO₂-M _x O _y (M = V, Sn, Sb) binary oxide thin films by sol-gel method was investigated. The reaction of silicic acid with metal chloride (M = Sn and Sb) or oxychloride (M = V) formed homogeneous solutions. The dip-coating of slide glass and silicon wafer followed by heat treatment gave oxide films having Si—O—M bond. The changes of FT-IR spectra as a function of heat treatment temperature and molar composition confirmed the Si—O—M bonds. The sheet resistance of films increased with an increase on heat treatment temperature and decrease in the content of metal oxide M _x O _y . X-ray diffraction peaks were observed for the SiO₂-V₂O₅ films with high V₂O₅ contents and heat-treated above 250°C, while the others were amorphous. Oxide films heat treated at 500°C had a thickness between 340–470 nm.     

Studies on the adsorption of plutonium (IV) on alumina from phosphoric acid-nitric acid solution

Results of experiments on the adsorption of plutonium (IV) on alumina and their application to the recovery of plutonium from analytical waste solutions containing phosphoric-nitric acid are reported. Distribution ratios of plutonium (IV) between alumina and solutions containing varying concentrations of phosphoric acid and nitric acid are determined. The influence of various ions like UO₂ ²⁺, Fe³⁺, MoO₄ ^2–, VO²⁺ and SO₄ ^2– on the distribution ratio is evaluated. Saturation values of adsorption of plutonium (IV) on alumina and optimum conditions for loading and elution of plutonium on a column packed with alumina are described.     

Adsorption of carbon dioxide and nitrogen on zeolite rho prepared by hydrothermal synthesis using 18-crown-6 ether

Zeolite rho was prepared by hydrothermal synthesis using an 18-crown-6 ether (18C6) as a structure-directing agent, and the effects of the calcination temperature for removal of 18C6 on the physicochemical properties and CO₂-adsorption properties were investigated. CO₂ adsorption on zeolite rho calcined at 150 °C was lower than that on samples calcined at temperatures above 300 °C. For samples calcined above 300 °C, CO₂ adsorption increased with increasing calcination temperature up to 400 °C. It is thought that the pore volume for adsorption of CO₂ increased as a result of 18C6 removal, resulting in increasing CO₂ adsorption. A decrease in CO₂ adsorption for calcination from 400 °C to 500 °C was observed. The particle size of zeolite rho increased with increasing 18C6 molar ratio. Particle sizes of 1.0-2.1 μm and 1.4-2.6 μm were found by field-emission scanning electron microscopy and dynamic light-scattering, respectively. The particle size is controlled in these regions by adjusting the 18C6 molar ratio. XRD showed that zeolite rho samples with 18C6 molar ratios of 0.25-1.5 had high crystallinity. The adsorbed amount of CO₂ is almost constant, at 3.4 mmol-CO₂ g⁻¹, regardless of the 18C6 molar ratio. However, CO₂ selectivity, which is the CO₂/N₂ adsorption ratio, decreased. The amount of CO₂ adsorbed on zeolite rho is lower than that on zeolite NaX, but higher than that on SAPO-34. The CO₂/N₂ adsorption ratio for zeolite rho was higher than those for SAPO-34 and zeolite NaX.     

Synthesis of Functional Resins Containing Heterocyclic Rings and Their Sorption Properties for Noble-Metal Ions

Five kinds of functional resins, 2-aminopyridine resin (2-APR), 3-APR, 4-APR, 2-hydroxypyridine resin (2-HPR), and 2-thiolbenzothiazole resin (2-TBTR), were synthesized. The functional group capacities of the resins were 3.0–4.2 mmol/g resin. The sorption capacities of 4-APR, 3-APR, and 2-APR for Au(III) and Pt(IV) were 3.12–3.22 mmol Au(III)/g APR and 1.27–1.60 mmol Pt(IV)/g APR. The molar complex ratios, Au(III)/NH-C₅H₄N and Pt(IV)/NH-Cs H₄N were 0.84–0.97 and 0.34–0.48, respectively. Selective sorption of 4-APR for various coexistent metal ions over a wide acidity range (1–5 N HCl) was in the following order: Pt(IV) > Au(III) > Cd²⁺ > Zn²⁺ > Pd(II) > Mn²⁺, Cu²⁺, Fe³⁺. The Au(III) adsorbed on APR can be quantitatively eluted with 2% aqueous thiourea. The regenerated APR can be reused without apparent decrease in the sorption capacity for Au(III). The separation of Au(III) and Cu²⁺ was studied preliminarily. The excellent properties show that APR may be used in the gold industry. The sorption capacities of 2-HPR for Au(III) is 0.99 mmol Au(III)/g 2-HPR. That of 2-TBTR for Au(III) is less than that of APR. 2-HPR is stable below 100°C, while 4-APR and 2-APR are stable below 80°C in air.     

Study on complexation adsorption behavior of dibenzo-18-crown-6 immobilized on CPVA microspheres for metal ions

Dibenzo-18-crown-6 (DBC) was immobilized on crosslinked polyvinyl alcohol (CPVA) microspheres, resulting in polymer-supported crown ether DBC–CPVA. The complexation adsorption behaviors of DBC–CPVA microspheres towards diverse metal ions were investigated. The experimental results show that among alkali metal ions, the complexation adsorption ability of DBC–CPVA for K⁺ ion is the strongest, and crown ether-metal complex in 1:1 ratio is formed, exhibiting a high adsorption capacity. The adsorption capacities of alkali metal ions on DBC–CPVA are in the order: K⁺ ? Na⁺ > LI⁺ > Rb⁺ > Cs⁺. Among several divalent metal ions, DBC–CPVA exhibits stronger adsorption ability towards Zn²⁺ and Co²⁺ ions, and a “sandwich”-type complex is formed probably in a molar ratio of 2:1 between the immobilized DBC and Zn²⁺ ion as well as between the immobilized DBC and Co²⁺ ion. The adsorption capacities of the several divalent metal ions on DBC–CPVA are in the order: Zn²⁺ > Co²⁺ ? Cd²⁺ > Cu²⁺ > Ni²⁺ > Pb²⁺. The complexation adsorption is exothermic physical physisorption process, and raising temperature leads to the decrease of the adsorption capacity. At the same time, the entropy during the complexation adsorption decreases, so the adsorption process is driven by the decrease of enthalpy.     

Cyclopropane Adsorption on Zeolites Studied by IR Spectroscopy: II. Adsorption and Conversion of Cyclopropane on Na- and Ca-Exchanged Zeolite Y

The adsorption and isomerization of cyclopropane on the calcium- and sodium-exchanged zeolite Y are studied by IR spectroscopy. Cyclopropane is adsorbed on CaY in two different forms. Weaker adsorption is related to residual sodium ions, which were not completely removed from the zeolite by ion exchange. This form can be removed from the surface after evacuation of the samples at room temperature. Stronger adsorption is attributed to the Ca ions. It is stable up to 100°C. The corresponding diffuse-reflectance spectrum indicates the C _2v symmetry of the cyclopropane complex with Ca ions. At 200°C cyclopropane adsorbed on the calcium-exchanged zeolite converts to propylene. On the sodium-exchanged zeolite, this reaction only occurs at 400°C. The reaction coordinate of cyclopropane isomerization on CaY is related to the simultaneous cleavage of the C–C bond in the cyclopropane ring and hydrogen atom transfer from one of the CH₂ fragments to another. The reaction coordinate corresponds to a combination of the stretching vibration of the C–C bond with the fan vibration of the CH₂ group and the stretching vibration of the CH bond. These composite vibrations result in the strong polarization of the C–C and C–H bonds and, hence, exhibit anomalously high molar absorption coefficients in the IR spectrum.     

Synthesis and applications of poly(acryl<Emphasis Type="Italic">p</Emphasis>-aminobenzenesulfonamideamidine-<Emphasis Type="Italic">p</Emphasis>-aminobenzenesulfonylamide) chelating fiber for pre-concentrating and separating trace Bi(III), Hg(III), Au(III) and Pd(IV) from solution samples

Poly(acrylp-aminobenzenesulfonamideamidine-p-aminobenzenesulfonylamide) chelating fiber containing "S", "N", and "O" elements was synthesized from polyacrylonitrile fiber and p-aminobenzene sulfonamide and used to enrich and separate trace Bi(III), Hg(III), Au(III), and Pd(IV) ions from wastewater and ore sample solution. The enrichment acidity, flow rate, elution conditions, reuse, interference ions, saturated adsorption capacity, constant of adsorption rate, analytical accuracy, and actual samples on chelating fiber were investigated by means of inductively coupled plasma optical emission spectrometry (ICP-OES) with satisfactory results. Solutions of 100 ng mL^–1 of Bi(III), Hg(III), Au(III), and Pd(IV) ions can be enriched quantitatively by this chelating fiber at a rate of 1.0 mL min^–1 at pH 4 and desorbed quantitatively with 20 mL of 0.25 M HCl and 2% CS(NH₂)₂ solution at 50 °C (with recovery 97%). When the chelating fiber was reused for 20 times, the recoveries of the analyzed ions enriched by the fiber were still over 95% (except for Hg(III)). One thousand-fold excesses of Mn²⁺, Ca²⁺, Zn²⁺, Mg²⁺, Fe³⁺, Cu²⁺, Ni²⁺, Al³⁺, and Ba²⁺ ions and thousands-fold excesses of Na⁺ and K⁺ cause little interference in the pre-concentration and determination of the analyzed ions. The saturated adsorption capacity of Bi(III), Hg(III), Au(III), and Pd(IV) was 4.850×10^–4, 3.235×10^–4, 2.807×10^–4, and 3.386×10^–4 mol g^–1, respectively. The constants of adsorption rate were 0.409 min^–1 for Bi, 0.122 min^–1 for Hg, 0.039 min^–1 for Au, and 0.080 min^–1 for Pd. The relative standard deviations (RSDs) for the enrichment and determination of 10 ng mL^–1 Bi(III), Hg(III), Au(III), and Pd(IV) were lower than 2.3%. The results obtained for these ions in actual samples by this method were basically in agreement with the given values with average errors of less than 1.0%. FT-IR spectra shows that the existence of –SO₂–Ar, –H₂N–Ar, O=C–NH–, HN=C–NH–, and –HN–SO₂ functional groups are verified in the chelating fiber. From the FT-IR spectroscopy, we can see that Hg(III), Au(III), and Pd(IV) are mainly combined with nitrogen and sulfur (or oxygen), and Bi(III) is mainly combined with nitrogen (or oxygen) of the groups to form a chelating complex.     

Competitive heavy metal removal by poly(2‐acrylamido‐2‐methyl‐1‐propane sulfonic acid‐co‐itaconic acid)

The competitive removal of Pb²⁺, Cu²⁺, and Cd²⁺ ions from aqueous solutions by the copolymer of 2‐acrylamido‐2‐methyl‐1‐propane sulfonic acid (AMPS) and itaconic acid (IA), P(AMPS‐co‐IA), was investigated. Homopolymer of AMPS (PAMPS) was also used to remove these ions from their aqueous solution. In the preparation of AMPS–IA copolymer, the molar percentages of AMPS and IA were 80 and 20, respectively. In order to observe the changes in the structures of polymers due to metal adsorption, FTIR spectra by attenuated total reflectancetechnique and scanning electron microscopy (SEM) pictures of the polymers were taken both before and after adsorption experiments. Total metal ion removal capacities of PAMPS and P(AMPS‐co‐IA) were 1.685 and 1.722 mmol Me²⁺/g_polymer, respectively. Experimental data were evaluated to determine the kinetic characteristics of the adsorption process. Competitive adsorption of Pb²⁺, Cu²⁺, and Cd²⁺ ions onto both PAMPS and P(AMPS‐co‐IA) was found to fit pseudo‐second‐order type kinetics. In addition, the removal orders in the competitive adsorption of these metal ions onto PAMPS and P(AMPS‐co‐IA) were found to be Cd²⁺ > Pb²⁺ > Cu²⁺ and Pb²⁺ > Cd²⁺ > Cu²⁺, respectively. Copyright © 2008 John Wiley & Sons, Ltd.     

Quantitative Separation of Pd(II) by TLC of Metal Ions on Cerium (IV) Antimonate

Abstract

A quantitative TLC separation of metal ions using cerium (IV) antimonate as the solid phase are described. Using an acetonitrile- HNO₃ solvent Pb²⁺ can be separated quantitatively (2–10 μg) from several other ions. A quantitative spectrophotometric assay using p-nitroso-dimethylaniline is proposed.     

Volumetric properties of dilute aqueous solutions of cobalt amine type salts. Part 2. Densities at 15 and 5°C

Apparent molar volumes have been determined by density measurements of aqueous solutions for a series of salts [Co(L)₃]X₃, where X=Cl^– and Br^– and L¹=1,2-diaminoethane (en), L²=1,2-diaminopropane (pn) and L³=1,3-diaminopropane (tn) at 15°C and 5°C. Apparent molar volumes at infinite dilution for the complex cations at 0°C are estimated. The resulting values are related to the structure of solvent water molecules around the ions.     

Preparation and structural studies of organotin(IV) complexes formed with organic carboxylic acids

The complexes of six organic carboxylic acids (containing {O,O} donor atoms) with Bu₂Sn(IV)²⁺ and Ph₃Sn(IV)⁺ with ligand to metal ratios of 1 : 1 and 1 : 2, were prepared by two different methods. The FtIR and Raman spectra clearly demonstrated that the organotin(IV) moieties react with the {O,O} atoms of the ligands. It was found that in most cases the -COO^-group was chelated to the central metal ions, but monodentate coordination was also sometimes observed. Complex formation was accompanied by a rearrangement of the hydrogen-bonding network existing in the ligands. The complexes probably have polymeric structures. Comparison of the experimental Mössbauer D values with those calculated on the basis of the point charge model formalism revealed that the organotin(IV) moiety has a trigonal-bipyramidal (tbp) geometry, and in certain cases a tetrahedral (tetr) geometry too. Finally, the local structure of the maleic acid complex formed with Bu₂Sn(IV)²⁺ was determined by an EXAFS method.