Preparation of natural zeolitic supports for potential biomedical applications

Considering the biological properties reported for the purified natural clinoptilolite, NZ, we prepared K- and Li-enriched forms aimed at release matrices for biomedical applications. The raw material and the obtained solid samples were characterized by means of atomic absorption spectroscopy, X-ray diffraction, ²⁷Al and ²⁹Si MAS nuclear magnetic resonance, and nitrogen adsorption. The results demonstrated the structural stability of the materials after the different transformations applied. The chemical behavior of the samples in bi-distilled water and hydrochloric acid was studied by pH and conductivity measurements. A preliminary study related with the liberation of K and Li in aqueous medium was carried out by atomic absorption spectroscopy. The studies showed that the release of both ions from the solid samples is favored in HCl solutions, and that lithium is released faster than potassium in both dissolution media.     

Influence of electrolytes on the heat-induced swelling of aqueous dispersions of native wheat starch granules

The gelatinization of native wheat starch granules in some monovalent salt solutions (i.e. sodium and potassium chlorides and nitrates) was studied as a function of type and concentration of electrolyte by different techniques. The granular swelling at different temperatures was derived on a macroscopic scale from the swelling volume, whereas particle size analysis yielded information on a microscopic scale. Crosscorrelation revealed a close relationship between both approaches. Differential scanning calori-metry (DSC) indicated that all studied monovalent salts had a similar (protective) effect at 0.1 M concentration. However, at higher concentrations, a markedly different effect was observed for chlorides as compared to nitrates. A highly similar tendency was also observed from the gelatinised starch viscosity: whereas the consistency coefficient gradually decreased with increasing chloride concentration, it displayed a minimum value at low nitrate concentrations followed by a steady increase at higher concentrations. The sensitivity of the swelling of native wheat starch granules to ions could be explained from a combination of a general electrolyte effect at low concentrations and specific ion effects (in line with the Hofmeister anion series) at higher concentrations.     

Tailoring the surface morphology of TiO2 nanotube arrays connected with nanowires by anodization

Different surface morphologies of TiO₂ nanotube arrays were formed by anodization of Ti foils in various water-containing electrolytes at various voltages. Field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM) were used to investigate the morphology of TiO₂ nanowires. The results show that the morphology of TiO₂ nanowires is apparently influenced by viscosity of electrolytes and voltage. In this case, we introduce a detailed formation mechanism of nanowires that shows a strong relationship between the formation of TiO₂ nanowires and TiF₆²⁻ concentration. It was also found that TiO₂ nanowires are polycrystalline with anatase phase after annealing at 450 °C for 3 h.     

Oxidation of Parachloronitrobenzene in Dilute Aqueous Solution by O3 + UV and H2O2 + UV : A Comparative Study

This laboratory study was designed to investigate the degradation of 4-chloronitrobenzene ([CNB] = 2.4 × 10^?6 mol L^?1; pH = 7.5) by H₂O₂/UV and by O₃/UV oxidation processes which involve the generation of very reactive and oxidizing hydroxyl free radicals. The effects of the oxidant doses (H₂O₂ or aqueous O₃), liquid flow rate (or the contact time), and bicarbonate ions acting as OH· radical scavengers on the CNB removal rates were studied. For a constant oxidant dose, the results show that the O₃/UV system appears to be more efficient than the H₂O₂/UV system to remove CNB because of the greatest rate of OH· generation by ozone photodecomposition compared to H₂O₂ photolysis. However, for a given amount of oxidant decomposed, the H₂O₂/UV oxidant system was found to be more efficient than O₃/UV. Moreover, high levels of bicarbonate ions in solution (4 × 10^?3 mol L^?1) significantly decrease the efficiency of CNB removal by H₂O₂/UV and by O₃/UV oxidation processes.     

Effect of top power on a low-k film during oxygen strip in a TCP etch chamber

The modification of a SiOCH based low-k by oxygen plasma in a transformer coupled plasma (TCP) is reported. Modification of the film is studied as function of TCP power and time. Spectroscopic ellipsometry (SE) and Fourier transformed infrared absorption spectroscopy (FTIR) measurements are used for characterization. Both techniques show that the modification (damage) depth increases with increasing TCP power. Optical emission spectroscopy (OES) indicates that adding TCP power increases the O/O₂⁺ ratio in the plasma. By means of FTIR and OES, evidence is found for the removal of hydrogen and carbon from the low-k during plasma exposure. Using a two-layer SE fitting model, and no TCP power a refractive index (RI) of 1.44 for the chemically altered top layer was found. This RI decreases with TCP power. Presumably, at increased TCP power, relatively more radicals are generated and they penetrate more easily because of a less dense top layer.     

Ion distribution and protein proteolysis affect water holding capacity of Longissimus thoracis et lumborum in meat of lamb subjected to antemortem exercise

Exercise has been shown previously to reduce the water holding capacity (WHC) of meat in lamb. The consequence of changes in the distribution of ions pre- and post-rigor and proteolysis on WHC is relatively unknown. Twelve crossbred lambs were used to investigate the effect of exercise on the meat quality traits of the Longissimus thoracis et lumborum (LTL) muscle. There were no treatment effects on Warner-Bratzler shear force (WBSF), myofibril and sarcoplasmic protein solubility, denaturation or sarcomere length. With exercise the initial pH of the muscle was lower and the rate of pH fall to rigor was faster compared to controls. Exercise caused increased purge and meat fluid had a lower osmolarity, magnesium, potassium and sodium concentration. Proteolysis of desmin occurred after day 3 and vinculin on day 7 of ageing with exercise. It was concluded that exercise caused changes in the distribution of ions and the proteolysis of muscle proteins that reduced the ability of the muscle to bind or hold water.     

Where is the Anion Extraction Going?

Reactive extraction processes represent efficient and smart technologies for separation and concentration of metal ions in solution, which are frequently used in industry. Despite the importance of anions in biology, medicine, environment and industry, practical examples of anion extraction are relatively limited compared to metal ion separation. Anion extraction processes are mainly based on the nonspecific ion pair formation with hydrophobic ammonium cations. In this case the phase transfer of anions is dominated by their lipophilicity. The reasons for this situation are closely connected with the specific features of anions in contrast to cations. Novel approaches for specific binding and selective transport of anionic components are based both on the better understanding of the biological role of anions and on the possibilities of supramolecular chemistry to create receptor architectures with complementary binding modes for anions. In the given review the authors discuss present research tendencies and application possibilities of new extractant types for separation and concentration of anionic species in solution.     

Catalytic Ozonation of Citric Acid by Metallic Ions in Aqueous Solution

Ozonation of citric acid in water catalyzed by different ions from the first row of transition metals (Mn²⁺, Co²⁺, Ti⁴⁺, Fe²⁺, Cu²⁺, Ni²⁺ and Zn²⁺) was investigated at room temperature. The results showed that at pH=2, where the decomposition of citric acid is negligible by only ozone, the following order of efficiency of metallic ions for the decomposition of citric acid by ozone, and also for the TOC removal, was obtained: Mn²⁺ > Co²⁺ > Ti⁴⁺ > Fe²⁺. Cu²⁺, Ni²⁺ and Zn²⁺ showed negligible efficiency under the same experimental conditions. At pH=5.5, Mn²⁺ and Co²⁺ showed slightly higher efficiency than at pH=2 while Ti⁴⁺ and Fe²⁺ showed insignificant effect at this pH value. On the other hand, at pH=7 the investigated catalysts showed no obvious catalytic efficiency for the decomposition of citric acid by ozone.     

Parametric studies on the performance of mixed-bed ion exchange at ultralow concentrations –1. Multicomponent system–

We experimentally evaluated the effects of multicomponent systems of divalent cations on the performance of mixed-bed ion exchange in the concentration range used for ultrapure water processing. Data were collected in the batch and continuous column systems with Dowex Monosphere resins used commercially for ultrapure water applications. The presence of divalent cations in the systems affects significantly the capacity of the units to remove a univalent cation. However, the anion exchange rate increases slightly in the multicomponent systems. The equilibrium and the breakthrough curves of ions, plotted as the ratio of the effluent to influent concentration versus run time or solution volume passed through the experimental column, give detailed results about the effects of the existence of other ionic species on the fate of each ion in MBIE units. The results of the present study are expected to be used to develop and simulate mathematical models and to understand the performance of mixed-bed ion exchange at ultralow concentrations.