Transparent thin films of Cu-TiO2 with visible light photocatalytic activity.

Thin films of Cu-TiO2 with a high level of transparency were prepared by a dip-coating procedure on the glass surface. CuCl2 was used as a copper precursor added during sol-gel synthesis of TiO2. The extension of optical absorption into the visible region of as-prepared thin films was indicated by UV/Vis spectroscopy. Only the anatase phase was detected by X-ray diffraction analysis (XRD). The presence of copper in the structure of thin films was confirmed by energy dispersive X-ray spectrometry (EDS). The significant rate of phenol and 4-chlorophenol mineralization was observed during visible light irradiation. The photocatalytic activity of the prepared thin films is correlated with the optimum copper content in the structure. Copper in metallic form and cupric oxides were not detected by XRD and scanning electron microscopy analysis. It is suggested that copper may exist as dispersed ions in the TiO2 lattice.

Solubilization of benzene, toluene, and xylene (BTX) in aqueous micellar solutions of amphiphilic imidazolium ionic liquids.

Water-soluble ionic liquids may be considered analogues to cationic surfactants with a corresponding surface activity and ability to create organized structures in aqueous solutions. For the first time, the enhanced solubility of the aromatic hydrocarbons, benzene, toluene, and xylene, in aqueous micellar systems of 1-alkyl-3-methylimidazolium chlorides was investigated. Above a critical micelle concentration, a gradual increase in the concentration of aromatic hydrocarbons in the miceller solution was observed. This phenomenon was followed by means of the molar solubilization ratio, the micellar/water partition coefficient, and the number of solubilizate molecules per IL micelle. The molar solubilization ratio for ionic liquid micelles was found to be significantly higher when compared to that of ionic surfactants of similar chain length. The incorporation of the hydrocarbon into the micelle affects also an increase of the aggregation number.

Changes in zeta potential of imidazolium ionic liquids modified minerals--Implications for determining mechanism of adsorption.

As the amount of industrial processes involving ionic liquids (ILs) increase the question of their environmental fate awaits an answer. Should ILs become a source of pollution they will primarily be found in soils and water. Interaction of imidazolium IL with soils is a complex interplay of many parameters making predicting their fate and mobility a challenging task. In order to shed more light on the mechanism of adsorption in soils we examined the interactions of imidazolium ILs with the major component of soils, namely mineral fraction. Within this work adsorption on kaolinite and quartz was investigated in terms of adsorption isotherms, partition coefficients and changes of zeta potentials of clays modified by ILs aggregates. The zeta potential was found to be dependent on the alkyl chain length of the imidazolium homologues. It can therefore be concluded that although adsorption seems to rely on electrostatic attraction, at least in the initial stage, the hydrophobicity of molecules is just as significant.

Influence of microbial adaption and supplementation of nutrients on the biodegradation of ionic liquids in sewage sludge treatment processes.

As ionic liquids are winning more attention from industry as a replacement of more hazardous chemicals, some of their structures have the potential to become persistent pollutants due to high stability towards abiotic and biotic degradation processes. Therefore it is important to determine the hazard associated with the presence of ILs in the environment, for example biodegradation under real conditions. Standard biodegradation testing procedures generally permit pre-conditioning of inoculum but do not allow for pre-exposition to the test substance. These are usually conducted in a mineral medium which does not provide additional organic nutrients. Though very valuable, as a point of reference, these tests do not fully represent real conditions. In in situ conditions, for example in wastewater treatment plants or natural soils and water bodies, the presence of readily available sources of energy and nutrients as well as the process of adaptation may often alter the fate and metabolic pathways of xenobiotics. Our results have shown that these are the opposing processes influencing the biodegradation rate of ILs in sewage sludge. The results have significant practical implications with respect to the assessment of biodegradability and environmental fate of ILs and other xenobiotics in environmental conditions and their potential remediation options.

Influence of the Hofmeister anions on self-organization of 1-decyl-3-methylimidazolium chloride in aqueous solutions.

Inorganic salts usually influence water structure affecting the hydration of the molecules which lead to a salting-in or a salting-out effect of hydrophobic compounds. Specific conductivity and isothermal titration calorimetry have been used to study the effect of inorganic salts on aggregation of the cationic surfactant 1-decyl-3-methylimidazolium chloride in aqueous solutions. The effect of the concentration, the nature of the anion and temperature on micelle formation were studied. A decreasing critical micelle concentration (CMC) due to the weakening electrostatic repulsion between the headgroups was observed. The salts used in this investigation decreased the CMC and degree of micelle ionization in the order of Cl(-)

1-methyl-3-octylimidazolium chloride--sorption and primary biodegradation analysis in activated sewage sludge.

Ionic liquids (ILs) are known to be non-volatile and thus to have low potential for atmospheric contamination or intoxication of humans by inhalation. However ILs have the potential to contaminate soil and water as they might be water soluble and can be sorbed onto solids. The investigation of possible natural ways of reducing the concentration of ILs in the environment is of high importance, especially because the requirement for biodegradable chemicals increases, together with pressure for reduction of incineration and landfill waste. It was found that the upper concentration threshold for primary biodegradation of 1-methyl-3-octylimidazolium chloride is 0.2 mM. At higher concentrations the dehydrogenase activity of the cells dropped markedly, indicating that the IL inhibits cell activity. This concentration is in good agreement with the minimal inhibitory concentration of the same compound found for a series of bacteria and fungi by this research group. The sorption of 1-methyl-3-octylimidazolium chloride was found to be significant, and the sorption coefficient was determined to be 98.2 L kg(-1).

Thermodynamics of micellization of imidazolium ionic liquids in aqueous solutions.

The structural similarity between some ionic liquids (ILs) and ionic surfactants, indicates that ILs are expected to exhibit surface adsorption and aggregation properties. The Krafft temperature and the temperature dependence of the critical micelle concentration (CMC) were determined for four imidazolium ionic liquids with varying chain length by measuring concentration dependence of electrical conductivity at different temperatures. The magnitude of the thermodynamic parameters of the micelle formation provide valuable information about the driving force of micellization of these compounds, therefore, the parameters of these chemicals were estimated from the degree of ionization, and the CMC. The thermodynamic parameters were correlated to directly measured values using isothermal titration calorimetry (ITC). It was found that the long-chained imidazolium ILs show similar thermodynamic characteristics as traditional cationic surfactants, whereas the Krafft temperature was shown to be lower than that of traditional cationic surfactants of similar chain length.

Flue gas treatment for SO2 removal with air-sparged hydrocyclone technology.

Laboratory results from an initial study on the removal of SO2 from gas mixtures are reported using air-sparged hydrocyclone (ASH) technology. Tap water and alkaline solutions were used for absorption, and the influence of gas flow rate, water flow rate, and length of the ASH unit were investigated. The research results indicate thatthe air-sparged hydrocyclone can be used as a highly efficient absorber for SO2 emissions. The ASH allows for 97% SO2 removal using water alone for sulfur dioxide content in the gas phase of 5 g/m3. All SO2 is removed in weakly alkaline solution (0.01 mol NaOH/dm3).