Purification of waste waters containing 60Co2+, 115mCd2+ and 203Hg2+ radioactive ions by ETS-4 titanosilicate

Summary The sorption of ⁶⁰Co²⁺, ^115mCd²⁺ and ²⁰³Hg²⁺ from diluted solutions (as analogues for radioactive waste waters) on ETS-4 microporous titanosilicate was studied at 277, 293, 313 and 333 K by measuring the sorption kinetics using a batch-method. The sorption of these radiocations was compared by means of the distribution coefficient and of the sorption capacity. The maximum sorption capacities follow the order: ²⁰³Hg²⁺>^115mCd²⁺3⁶⁰Co²⁺. The thermodynamic functions of the sorption processes have been estimated. The increase of the absolute value of DG° with increasing temperatures shows that higher temperatures favor ionic exchange.     

Infrared matrix isolation and quantum chemical studies of the nitrous acid complexes with water

The 1:1 and 2:1 complexes between water and trans- and cis-isomers of nitrous acid have been isolated in argon matrices and studied using FTIR spectroscopy and DFT(B3LYP) calculations with a 6-311++G(2d,2p) basis set. The analysis of the experimental spectra indicate that 1:1 complexes trapped in solid argon involve very strong hydrogen bond in which acid acts as the proton donor and water as the proton acceptor. The perturbed OH stretches are −248, −228 cm⁻¹ red shifted from their free-molecules values in complexes formed by trans- and cis-HONO isomers, respectively. The calculated spectral parameters for the two complexes are in good agreement with experimental data. The calculations also predict stability of two more 1:1 weakly bound complexes formed by each isomer. In these the water acts as the proton donor and one of the two oxygen atoms of the acid as the acceptor. The experimental spectra demonstrate also formation of 2:1 complex between water and trans-HONO isomer in an argon matrix. The performed calculations indicate that the complex involves a seven-membered ring in which OH group of HONO forms very strong hydrogen bond with the oxygen atom of one water molecule and nitrogen atom acts as a weak proton acceptor for the hydrogen atom of the second water molecule of the water dimer. The observed perturbations of the OH stretch of trans-HONO (750 cm⁻¹ red shift) is much larger than that predicted by calculations (556 cm⁻¹ red shift); this difference is attributed to strong solvation effect of argon matrix on very strong hydrogen bond.     

Capillary zone electrophoresis of alpha-helical diastereomeric peptide pairs with anionic ion-pairing reagents

The present study uses an unique capillary electrophoresis (CE) approach, that we have termed ion-interaction capillary zone electrophoresis (II-CZE), for the separation of diastereomeric peptide pairs where a single site in the centre of the non-polar face of an 18-residue amphipathic alpha-helical peptide is substituted by the 19 L- or D-amino acids. Through the addition of perfluorinated acids at very high concentrations (up to 400 mM), such concentration levels not having been used previously in chromatography or CE, to the background electrolyte (pH 2.0), we have been able to achieve baseline resolution of all 19 diastereomeric peptide pairs with an uncoated capillary. Since each diastereomeric peptide pair has the same sequence, identical mass-to-charge ratio and identical intrinsic hydrophobicity, such a separation by CZE has previously been considered theoretically impossible. Excellent resolution was achieved due to maximum advantage being taken of even subtle disruption of peptide structure/conformation (due to the presence of D-amino acids) of the non-polar face of the amphipathic alpha-helix and its interaction with the hydrophobic anionic ion-pairing reagents. In addition, due to the excellent resolution of diastereomeric peptide pairs by this novel CZE approach, we have also been able to separate a mixture of these closely-related alpha-helical peptides.     

Capillary electrophoresis of cationic random coil peptide standards: effect of anionic ion-pairing reagents and comparison with reversed-phase chromatography

The present study compares a charge/hydrophobicity capillary electrophoresis (CE) approach to reversed-phase high-performance liquid chromatography (RP-HPLC) for the separation of three series of four synthetic, random coil peptide standards. Each series has peptides of the same positive charge (+1, +2 and +3 series) and length but differing in hydrophobicity. Complete resolution of the 12 peptides was achieved via a novel CE approach: a capillary zone electrophoresis (CZE) mode effected a separation of identically charged peptides; within each charged group of peptides, the addition of perfluorinated acid anionic ion-pairing reagents allowed resolution of the peptides through a mechanism based on peptide hydrophobicity which we have termed ioninteraction (II)-CZE. The peak capacity and peptide resolution of this CE approach was superior to that of RP-HPLC and stresses an important role for CE for peptide/proteomic applications.     

The sorption of some radiocations on microporous titanosilicate ETS-10

The microporous titanosilicate ETS-10 synthesized from gel with following molar composition: 1.0 Na₂O: 1.49 SiO₂ : 0.2 TiO₂ : 0.6 KF : 1.28 HCl : 39.5 H₂O was subjected to sorption of radioactive cations ¹¹⁵Cd²⁺, ²⁰⁴Hg²⁺, ⁶⁰Co²⁺ and ¹³⁷Cs⁺ (M) from aqueous solution, in the absence of ionic competition. The uptake of these cations on the ETS-10 was compared by means of the distribution coefficient (K_d) versus contact time and sorption capacity (R) at equilibrium. The FT-IR spectra of M-ETS-10 sorption products exhibit a modification of the absorption band, principally at 381 cm^-1.     

Preliminary evaluation of the cadmium concentration in seawater of the Salvador City, Brazil

A method for preconcentration and determination of trace amounts of cadmium in high saline samples is described. It is based on the adsorption of the metal in the activated carbon as complex cadmium(II)-4-(2-pyridylazo-resorcinol) (PAR). The final determination was carried by flame atomic absorption spectrometry (FAAS). The optimization of extraction parameters such as the pH effect, PAR mass, activated carbon mass and shaking time was carried out using a two-level full factorial design (2⁴) and two Doehlert matrix designs. The results of the factorial design, considering the analysis of variance (ANOVA), demonstrate that all these factors are statistically significant, as well as the interactions (pH×PAR mass), (pH×activated carbon mass) and (activated carbon mass×shaking time). The final optimization was carried out using Doehlert matrix designs considering the results of the factorial design. The recoveries were quantitative (96.0-106.7%) for seawater samples spiked with Cd at concentrations of 0.125 and 0.625 μg l⁻¹. A preconcentration factor of 149 was obtained. The effect of diverse metallic ions on the proposed procedure was investigated too. The procedure was used for cadmium determination in surface seawater samples collected in Salvador City, Brazil. The cadmium content in the analysed samples varies from 0.035 to 0.17 μg l⁻¹. These results are agreement with other data reported in the literature.     

Infinite divisibility and a non-commutative Boolean-to-free Bercovici–Pata bijection

We use the theory of fully matricial, or non-commutative, functions to investigate infinite divisibility and limit theorems in operator-valued non-commutative probability. Our main result is an operator-valued analogue for the Bercovici–Pata bijection. An important tool is Voiculescu?s subordination property for operator-valued free convolution.     

Micro- and nano-mechanical characterization of polyamide 11 and its composites containing cellulose nanofibers

Nanocomposites from polyamide 11 and dried cellulose nanofibers (CNs), 16–30 nm in thickness and 50–400 nm in length, were prepared via direct melt mixing and their micro- and nano-mechanical properties were studied. (PF) QNM (Quantitative Nanomechanical Mapping) method was used to map nanomechanical properties at the surface of polyamide 11 and nanocomposites. This new AFM method emphasized both the increased modulus in nanocomposites as compared to the matrix and the microstructure on different levels in polyamide 11 and its nanocomposites. PF QNM showed that their crystalline structure consists of bundles of lamellar stacks, 200–350 nm in width and 20–40 nm wide lamellar stacks. Moreover, PF QNM study emphasized higher structural order in nanocomposites with 3 and 5 wt.% CNs and lower in the nanocomposite with 8 wt.% CNs as compared to the reference. These observations were verified and are consistent with both crystallinity values determined by DSC and micro-mechanical test results. The oriented bundles of lamellar stacks, observed by PF QNM, could be considered as the main blocks determining high mechanical properties for the studied nanomaterials.     

The Vapor-Liquid Polycondensation of Cyclohexylphosphoric Dichloride with Hydroquinone

The vapor-liquid polycondensation of cyclohexylphosphoric dichloride with hydroquinone was investigated. The influence of the temperature, reaction time, base concentration, and molar ratio of reagents on the yield, inherent viscosity, and molecular weight of the obtained polymer was studied. Second order, central, composite, rotatable experimental design was used in order to carry out this work and to mark limits of the experimental field for optimal yields and high inherent viscosities.