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[en] In this study, we examined the sorption and desorption behavior of U(VI) on/from a Chinese bentonite in the solid-liquid system using batch experiments, and the influence of pH, ionic strength and humic acid (HA) on the sorption-desorption hysteresis in the solid-liquid system were quantitatively calculated. It was revealed that the hysteresis was enhanced with increasing pH and increasing ionic strength. HA promoted the sorption, but lower the sorption-desorption hysteresis. Meanwhile, hysteresis in ternary bentonite-HA-U system was found to be higher than that in bentonite-U-HA system, indicating different sorption structures formed because of different addition sequence. (author)
[en] The sorption and desorption of uranium(VI) on GMZ bentonite was investigated as functions of contact time, pH, ionic strength, foreign ions, HSs and initial U(VI) using batch experiments. It is revealed that the sorption strongly depended on pH, cations (Li"+, Na"+ and K"+) and anions (CO_3"2"-, SO_4"2"- and PO_4"3"-). HA benefits the sorption at pH <7.0, while inhibited the sorption at higher pH. Moreover, the hysteresis occurred in the sorption-desorption process in the presence/absence of humic substances. The results could provide data base for the safety assessment of the deep geological disposal repository of high radioactive waste. (author)
[en] Selenium is both a nutrient and a toxin. Selenium—especially organic selenium—is a core component of human nutrition. Thus, it is very important to measure selenium in biological samples. The limited sensitivity of conventional XRF hampers its widespread use in biological samples. Here, we describe the use of high-energy (100 kV, 600 W) linearly polarized beam energy-dispersive X-Ray fluorescence spectroscopy (EDXRF) in tandem with a three-dimensional optics design to determine 0.1–5.1 μg g"−"1 levels of selenium in biological samples. The effects of various experimental parameters such as applied voltage, acquisition time, secondary target and various filters were thoroughly investigated. The detection limit of selenium in biological samples via high-energy (100 kV, 600 W) linearly polarized beam energy-dispersive X-ray fluorescence spectroscopy was decreased by one order of magnitude versus conventional XRF (Paltridge et al., 2012) and found to be 0.1 μg/g. To the best of our knowledge, this is the first report to describe EDXRF measurements of Se in biological samples with important implications for the nutrition and analytical chemistry communities. - Highlights: • The high-energy (100 kV, 600 W) linearly polarized beam energy-dispersive X-Ray fluorescence spectroscopy (EDXRF) was used to determine 0.1−5.1 μg g"−"1 levels of selenium in biological samples. • High-pressure pressed powder pellet technique (1500 kN) is used for sample preparation. • The detection limit of selenium in biological samples found to be 0.1 μg/g.
[en] A series of carbon nanotube (CNTs)-supported copper-cobalt catalysts were prepared and investigated in a slurry reactor for their ability to selectively convert syngas into higher carbon number alcohols. The 7.5Cu7.5Co/CNTs catalyst achieved superior selectivity towards the formation of ethanol (30.1%) and C2+ alcohols (57.7%), while the 10Co5Cu/CNTs catalyst exhibited the largest alcohol space-time yield (372.9 mg gcat-1 h-1). However, the pure Cu (15Cu/CNTs) catalyst displayed negligible activity. Cobalt reduction was enhanced in the presence of copper. In addition to the Cu0-Co0 center, Co0 -Co2+ also presented dual active sites for higher alcohols synthesis, the Co2+ site could terminate carbon chain growth to produce alcohols. The ratio of Cu/Co considerably influences the metal particle properties-synergistically effecting the active species. (author)
[en] (Ternary liquid + liquid) equilibria (tie-lines) of (water + acetone + α-pinene) at T = (288.15, 298.15, and 308.15) K and (water + acetone + β-pinene, or limonene) at T = 298.15 K have been measured. The experimental (ternary liquid + liquid) equilibrium data have been correlated successfully by the original UNIQUAC and modified UNIQUAC models. The modified UNIQUAC model reproduced accurately the experimental results for the (water + acetone + α-pinene) system at all the temperatures but fairly agreed with the experimental data for the (water + acetone + β-pinene, or limonene) systems.
[en] Mutual solubility data of imidazolium-based ionic liquid, 1-butyl-2,3-dimethylimidazolium tetrafluoroborate ([bmmim][BF4]) with the alcohols, 1-propanol, 2-propanol, 1-butanol, 1-pentanol, and 1-hexanol were obtained by a cloud point method. The upper critical solution temperatures of the ionic liquid and alcohol mixtures were determined from the mutual solubility data. The upper critical solution temperature of the binary mixtures gradually increased as the chain length of the alcohol increased. The mutual solubility data of binary systems ([bmmim][BF4] + alcohols) have been correlated by the original UNIQUAC model as well as the extended and modified form of the UNIQUAC model. The temperature dependence of the mutual solubility data could be represented in terms of the temperature dependence of the binary energy parameters obtained from the correlation. Additionally the influence of water contamination on the ionic liquid mixture was shown experimentally by adding pure water into the binary mixture ([bmmim][BF4] + 1-butanol).
[en] Mutual solubility data of the binary (methanol + limonene) mixture at the temperatures ranging from 288.15 K close to upper critical solution temperature, and ternary (liquid + liquid) equilibrium (tie-lines) of the (methanol + ethanol + limonene) mixture at the temperatures (288.15, 298.15, and 308.15) K have been obtained. The experimental results have been represented accurately in terms of the extended and modified UNIQUAC models with binary parameters, compared with the UNIQUAC model. The temperature dependence of binary and ternary (liquid + liquid) equilibrium for the binary (methanol + limonene) and ternary (methanol + ethanol + limonene) mixtures could be calculated successfully using the extended and modified UNIQUAC model
[en] Highlights: ► Mutual solubilities of imidazolium tetrafluoroborates with 1-alkanol were measured using light-scattering apparatus. ► UCSTs increased as increasing chain length of alcohol and decreasing alkyl chain length of cation ring. ► Experimental results were correlated accurately by extended UNIQUAC model. - Abstract: The mutual solubility of ionic liquids (ILs), 1-butyl-3-ethylimidazolium tetrafluoroborate, 1-butyl-3-propylimidazolium tetrafluoroborate, and 1,3-dibutylimidazolium tetrafluoroborate with alcohols, 1-propanol, 1-butanol, 1-pentanol, and 1-hexanol were measured at atmospheric pressure. Upper critical solution temperatures (UCSTs) were estimated from experimental results using a polynomial equation. The UCSTs increased as increasing the chain length of alcohol. On other hand, the decreasing UCSTs occurred when the alkyl chain length on the cation of ionic liquids increased. The (liquid + liquid) equilibrium data were correlated by the original UNIQUAC, extended UNIQUAC, and modified UNIQUAC models. The temperature dependence of the solubility of ILs in alcohols and alcohols in ILs is represented successfully using the UNIQUAC, extended UNIQUAC, and modified UNIQUAC models with a quadratic function of temperature for binary energy parameters.
[en] Zirconium phosphate (ZrP) was immobilized by microencapsulation process of polysulfone (PSF) to form the polysulfone capsules containing ZrP (PSF-ZrP capsules) successfully by using phase inversion precipitation technique, and the PSF-ZrP was employed as capsules adsorbents to remove Pb2+ presented in aqueous solution. The result shows that an encapsulation capacity of 50% (mass ratio, PSF: ZrP = 1:1) should be the optimal proportion of ZrP encapsulated with PSF. The characterization of the macroscopical and microcosmic physical properties of the resulting PSF-ZrP capsules was carried out by the DTA-TG, XRD, BET and SEM. Meanwhile, the adsorption properties of the PSF-ZrP capsules for Pb2+ were investigated by batch methods. It was found that the adsorption of the PSF-ZrP capsules for Pb2+ would be pH dependent due to the ion-exchange mechanism, and the uptake of Pb2+ was slightly influenced with the concentration of coexisting cations (Na+, K+) in a low range. Furthermore, the calculated thermodynamics parameters exhibit that the nature of the adsorption process is spontaneous and exothermic. After six times of adsorption-regeneration cycles, no significant loss of adsorption capacity was observed, indicating the good stability of the PSF-ZrP capsules. Consequently, the PSF-ZrP capsules in this work can provide a potential application for treatment process of Pb2+-containing wastewater.
[en] Batch sorption experiments were conducted using macroreticular poly(vinyl alcohol) (MR-PVA) beads as a adsorbent to adsorb Pb(II) from both single component system and multi-metal solution in which experimental parameters were studied including solution pH, contact time, adsorbent dose, initial concentration of metal ions and ionic strength. The equilibrium isotherms were determined at pH 6 under constant ionic strength and at different temperatures. The results showed that the maximum adsorption capacity of Pb(II) (213.98 mg g-1) with 1 g L-1 of adsorbent was observed at 300 mg L-1 at an initial pH value of 6.0 under temperature of 288 K. Removals of about 60% occurred in 30 min, and equilibrium was attained at around 150 min. The equilibrium data for the adsorption of Pb(II) on MR-PVA beads was tested with various adsorption isotherm models among which three models were found to be suitable for the Pb(II) adsorption. In addition, the kinetic adsorption fitted well to the pseudo-second-order model and the corresponding rate constants were obtained. Thermodynamic aspects of the adsorption process were also investigated.