Volume 12, Issue 7 - 12(7) Special Issue: Chemistry and Chemical Engineering - Physical Chemistry

ZnO nanoparticles were synthesized in mixtures of ionic liquids based on imidazolium cation with organic solvents (dimethyl sulfoxide and ethylene glycol) by a simple, one-step solution route at low temperature. The effect of these mixtures on the morphology, size and properties of as obtained ZnO nanopowders was investigated. The obtained nanopowders have been characterized by X-ray powder diffraction (XRD), transmission electron microscopy (TEM), UV-Vis absorption spectroscopy (UV-Vis) and photoluminescence (PL). The effect of the ionic liquid mixture on the photocatalytic degradation of methylene blue has been analysed. The XRD studies confirmed the hexagonal wurtzite structure of the obtained ZnO powder. The UV-Vis absorption spectra present the typical shape for ZnO, with a broad band situated in the UV region, with the maximum around 360 nm. The calculated band-gap energy is in interval 3.25–3.28 eV. The synthesized ZnO nanopowders have high photocatalytic activity against methylene blue, the best results being obtained when 1-ethyl-3-methylimidazolium tetrafluoroborate was used as the solvent.

After oxidation of tannins (Tannins 1–3) extracted from grape seeds, Tanoxil compounds with increased solubility and enhanced antioxidant activities were synthesized. In this research, ABTS+· assay and a chemiluminescence method were used for antioxidant measurement of hydrophilic compounds (Tanoxils 1–3). It was observed that the antioxidant activity (AA, %) is very similar for the three samples, while at the same time AA is quite high (93.16%–96.48%). The percentage of inhibition by ABTS+· is higher for Tanoxil 2 (96.4%) as compared to Tannin 2 compound (14.34%). Moreover, the total content (TCF) of carboxyl and phenolic groups was investigated. TCF values, determined for Tanoxil products, revealed a double (Tanoxil 1) or triple (Tanoxil 2) increase as compared to the value of the TCF of Tannin 1. Tanoxil products represent an interest for future research as they have a high AA (96.4%) and the content of acidic groups is significant (TCF, 0.191 meq g−1).

Common waste glasses (window, bottle glass or tableware) with fly ash form a glass matrix for chromium waste immobilization. Soluble chromium from residual waters was adsorbed on fly ash; the resulting solid contained 23.7% Cr6+. The three glass wastes, chromium-containing fly ash, and borax were used to make glasses in weight ratios waste glass: borax: fly ash of 1: 1: 1 and 1.5: 0.5: 1. The hydrolytic stability ranged from 18.46 to 28.13 µg g−1 soluble Na2O, qualifying them in the HGB1 class. The chemical stability, characterized by the dissolution rate, was 0.011–0.077 µg cm−2 h−1, depending on the glass composition and the aggressive medium pH. The chromium leachability is influnced by the glass composition and the pH of the leaching solution, ranging between 0–0.015% of the total chromium. Chromium waste vitrification is a viabile solution with multiple economic advantages.

This paper characterizes uranium (VI) sorption from synthetic solutions using a fixed bed Purolite resin SGA 600 U/3472 system. The effect of the sulphate anion presence in the liquid phase on sorbtion dynamics and equilibrium is analysed. In the industrial processing of solutions obtained from leaching of uranium ore (alkaline/acid), in a continuous system, there are several compounds which strongly compete with uranium for ion exchange sites and consequently these substances depress the uranium adsorption. The influence of vanadate, molybdate, chloride, and nitrate is known, therefore, in this paper, the adsorption equilibrium isotherms for uranium (VI) are obtained for different sulphate ion concentrations in solution. The adsorption capacity variation of the Purolite resin SGA 600U/3472 with the number of adsorption/desorption cycles is also studied. The experimental results reveal the negative impact of high sulphate ion content in solution on the adsorption capacity of the resin Purolite SG 600 U / 3472 with uranium (VI) and therefore it is considered one of the compounds which strongly affect the uranium adsorption.

Electron beam (EB) irradiation is a useful method to generate stable silver nanoparticles without the interference of inherent impurities generated from chemical reactions. Our experiments were carried out using linear electron beam accelerators with two different EB absorbed dose rates: 2 kGy min−1 and 7–8 kGy s−1, and with different absorbed dose levels. The optimum conditions for silver nanoparticles (AgNPs) generation by radiolysis, or by radiolysis combined with chemical reduction, were established. In order to obtain a good yield for AgNPs synthesized by radiolysis, a high dose rate is required, resulting in a rapid production process. At low absorbed dose rates, the utilization of a stabilization agent is advisable. By modifying the experimental conditions, the ratio between the chemical and radiolytic reduction process can be adjusted, thus it is possible to obtain nanoparticles with tailored characteristics, depending on the desired application.

Magnetic fluid applications require stability under demanding conditions. Complete magnetic fluids and their component surfactants and dispersing oils were irradiated. Their subsequent thermal oxidation was characterized by chemiluminescence and DSC. Except for polyisobutylsuccinic anhydride, irradiation sensitized the components toward oxidation. The components were ranked by stability. Complete fluids were more stable than would be predicted from their components suggesting that they may be used for nuclear applications.

A light-responsive material, aminoazobenzene functionalized AlMCM-41, was synthesized and characterized in order to be used as carrier for drug delivery devices. The light-induced hydrophobic-hydrophilic switching effect of azobenzene functionalized aluminosilicate was exploited in the release of irinotecan, a cytostatic drug. To obtain the functionalized mesoporous support, an azobenzene-silane precursor was synthesized by coupling 4-(4′-aminophenylazo) benzoic acid with 3-aminopropyl triethoxysilane and further grafted on AlMCM-41. The azobenzene functionalized mesoporous aluminosilicate exhibited no significant toxicity towards murine fibroblast healthy cells and a reduced toxicity towards murine melanocyte cells. The hybrid materials obtained by loading irinotecan on AlMCM-41 (wt. 35.4%) and aminoazobenzene modified AlMCM-41 (wt. 22%), respectively were characterized by FTIR, small and wide angle XRD, N2 adsorption-desorption isotherms and DSC analyses. A two-fold increase in the drug release rate from azobenzene functionalized aluminosilicate in phosphate buffer solution under UV irradiation was noticed, as compared with dark conditions. Moreover, the azobenzene functionalization of AlMCM-41 significantly increased the irinotecan delivery rate and total cumulative release in comparison with the pristine AlMCM-41 in similar conditions.

The aim of this study is to evaluate the accuracy of three binary alloys’ composition, and their biocompatibility. Depending on the intended use of the medical devices made from these materials, dynamic or static tests should be performed. We have chosen static tests as we thought they may be used as knee or hip replacement, and not as cardiac valves. Three binary alloys ( Zr10Nb, Zr2.5Nb and Zr12Ta) were obtained from high purity powders (>99.9%), using an induction furnace first, and an electric arc furnace for a perfect homogenization. Their final composition was verified with a XRF analyzer-INNOV-X. Hemolysis tests can determine the degree of red blood cells lysis and the release of hemoglobin. The released hemoglobin quantity was extremely small, under 2%, in all cases, and the coagulation tests showed no risk for thrombosis. The electrochemical behavior was also studied in biological fluid, human female serum, and showed a low corrosion rate. The obtained alloys do not cause hemolysis, so they are hemocompatible with all blood types.

Glass foams are building materials that now compete with classic insulating polymeric and fiber materials for thermal enveloping. The low flammability, high chemical durability and thermal stability are distinct advantages over polymeric materials. The present paper proposes the possibility of producing glass foam using two types of recycled glass wastes (window panes and bottle glass) together with plaster wastes from used ceramic casting molds as foaming agent. Optical microscopy, measurements of apparent porosity and density, hydrolytic and chemical stability, as well as thermal conductivity were used in order to characterize the obtained glass foams as insulator materials for the building industry. The apparent porosity of glass foams ranges between 20.19–54.54% when using window glass wastes, and 18.77–51.75% with bottle glass wastes. Thermal conductivity was less than 0.25 W mK-1 for all the studied glasses. The obtained results confirm that there exists an alternative method for producing glass foams, for example, from glass wastes and used ceramic plaster molds, which are utilized as foaming agents with good chemical stability and insulating properties.