Search

The rapid evolution of antimicrobial resistant genes (AMRs) in water resources is well correlated to the persistent occurrence of ciprofloxacin in water. For the first time, encapsulated nanoscale zerovalent iron (nZVI) with a shell of magnesium hydroxide (Mg/Fe0) was used to adsorb ciprofloxacin from water. Optimization of the removal conditions exhibited that 5% was the optimum mass ratio between magnesium hydroxide and nZVI [Mg(OH)2/nZVI)] as more than 96% of 100 mg L−1 of ciprofloxacin was removed. In addition, 0.5 g L−1 of Mg/Fe0 showed an extraordinary performance in removing ciprofloxacin over a wide range of pH (3–11) with removal efficiencies exceeded 90%. Kinetic analysis displayed that the kinetic data was well described by both Pseudo first-order and second-order models. Also, the equilibrium data was well fitted by Freundlich isotherm model. In addition, thermodynamic analysis evidenced that the removal of ciprofloxacin by Mg/Fe0 was exothermic, and spontaneous. The experiments also revealed that physisorption and chemisorption were the responsible mechanisms for ciprofloxacin removal. The proposed treatment system remediated 10 litters of 100 mg L−1 of ciprofloxacin solution with 100% overall removal efficiency. This treatment system could be a promising and practical solution to decrease ciprofloxacin concentration in different water bodies.

The development of antimicrobial resistance genes (AMRs) in water was globally accelerated due to the occurrence of ciprofloxacin (CIP) in water. This study aims to precipitate iron nanoparticles (Fe0) on the surface of titanium nanowires (TNWs) through a chemical process to overcome the limitations of Fe0 and efficiently remove CIP from water. TEM and XRD results confirmed the successful synthesis of Fe0 and TNWs. They also proved the successful deposition and dispersion of Fe0 on TNWs. Several (Fe0/TNW) nanocomposites were synthesised with different percentages of TNWs (5, 10, 20, 30, and 50%) to define the best TNWs ratio that will decrease the aggregation of Fe0 nanoparticles and achieve an outstanding removal efficiency of CIP. (Fe0/TNW) nanocomposite with 20% of TNW was nominated as the best nanocomposite because it demonstrated a promising performance, compared with other nanocomposites, by removing more than 67% of CIP with insignificant desorption behaviour during the treatment period (120 min). Dosage of (20%-Fe0/TNW), initial pH of CIP solution and reaction temperature were optimized through a group of batch experiments to efficiently remove CIP from water. The optimum removal of CIP was obtained by 1 g L−1 of (20%-Fe0/TNW) nanocomposite at initial pH of 7 under 35 °C.

The asymmetric Kharasch addition reaction was studied by using water as an environmentally friendly solvent. The reaction of styrene with BrCCl3 catalyzed by chiral rhodium species, “RhCl[(–)-DIOP]”, gave the corresponding adduct in moderate chemical and asymmetric yields “on water”, where all the reactants float on water. By reinvestigation of the literature procedure, the chemical and asymmetric yields “on water” were compared with those obtained in organic solvents. The reaction with FeCl2 / (–)-DIOP catalyst was examined to look at the metal effect. Possible reaction mechanisms were proposed based on these results. (93 words).

The selectivity of palladium catalysed hydrogenation can be improved by adding a homogeneous modifier (or poison) such as quinoline to the reaction mixture. Although such selectivity improvement by modifiers (selective catalyst poisoning) has been known for decades, we still know little about them. We, ultimately, cannot select a modifier to improve a particular process. In this study, 21 types of modifiers are screened for the semi-hydrogenation of alkynes with varying catalyst type, reaction time, and target substrate using an automated flow reactor system. All of the studied variables changed affected hydrogenation activity and selectivity confirming the effectiveness of a multi-parameter optimization. 1,10-phenanthroline marked the best selectivity beyond quinoline. The density functional theory (DFT) calculations suggest that 1,10-phenanthroline has a remarkable ability to adsorb on the irregular surface of the catalyst that effects undesirable reaction.\ud \ud

Herein, the influence of group 1 and 2 metal cations on base-catalyzed dehydrogenative coupling of formate to form oxalate is reported. Treatment of sodium formate with a various types of bases (group 1 and 2 metal carbonates or metal hydroxides) revealed that, compared with carbonate salts, group 1 metal hydroxides behaved as efficient bases for the formation of oxalate, in which cesium hydroxide (CsOH) showed the best catalytic activity. DFT calculation for the reaction mechanism suggested that its kinetic advantage was generated from not only an increase of basicity but also destabilization of the intermediate species due to Na/Cs mixed cation system. The effect of cations in formate salts were also discussed both experimentally and theoretically, in which the yield of oxalic acid depended on thermodynamic stability of both products (oxalate salts) and intermediates.

Removal of cesium from waters is an emerging issue after the accident at Fukushima Daiichi Nuclear Power Plant. In this work, new nanoscale zero valent iron–zeolite (nZVI–Z) and nano-Fe/Cu–zeolite (nFe/Cu–Z) composites for cesium removal were fabricated through ion exchange process followed by liquid-phase reduction. The characterization by XRD and SEM-EDS demonstrated that nZVI and nano-Fe/Cu particles were successfully loaded onto zeolite. The performance of the composites for the removal of cesium from aqueous solutions with the ability to separate the adsorbent magnetically was investigated. Batch sorption experiments were systematically carried out to assess the effect of different parameters such as pH, initial concentration, contact time, adsorbent dosage and temperature. The removal kinetics of cesium was adequately described by the pseudo-second-order kinetic model, which indicates that the uptake mechanism was chemisorption. The rate constant values for adsorption by nFe/Cu–Z were greater than the values obtained for nZVI–Z, meaning that nFe/Cu–Z had faster adsorption kinetics towards cesium solutions. The equilibrium adsorption data gave better mathematical fitting towards Langmuir and Freundlich isotherm models, where the maximum adsorption capacity of nFe/Cu–Z (77.51 mg/g) was found to be higher than that for nZVI–Z (71.12 mg/g). The observed thermodynamic parameters showed that the adsorption of cesium was endothermic process and spontaneous in nature. The composites were efficiently recovered from solution after the adsorption experiments by an easy, simple and rapid magnetic separation. The obtained results suggested that both composites could be used as a promising technique for the treatment of waters containing cesium.

Radioactive cesium was resealed to the environment as a result of many nuclear incidents. An effective treatment system is urgently needed to safely handle radioactive cesium-contaminated waters. Based on nanoscale zerovalent iron (nZVI) and zeolite, nine adsorbents were synthesized and applied to remove cesium from aqueous solutions. Magnetic zeolite composite (Ze/Fe0) was selected as the ideal adsorbent for treating cesium contaminated waters in a lab-scale continuous treatment system (LSCTS). The optimization process of the (Ze/Fe0) composite revealed that 1:1 is the optimum mass ratio between zeolite and nZVI. Furthermore, the optimization process proved that the initial pH and temperature have no significant effect on the adsorption of cesium by (Ze/Fe0) composite and the optimum dosage of (Ze/Fe0) composite is 5 g L−1. XRD and SEM results showed that the (Ze/Fe0) composite has an irregular shape with a poor crystalline structure. Kinetic and equilibrium data were best described by pseudo second order and Freundlich isotherm models. Seawater and groundwater experiments illustrated that the removal of cesium by (Ze/Fe0) composite was inhibited due to the existence of competing cations. Eight cycles of LSCTS were performed to examine the performance of (Ze/Fe0) composite in treating continuous streams of cesium contaminated waters. In all cycles except the cycle of treating contaminated seawater, LSCTS succeed to treat continuous flows of 1 mg L−1 cesium contaminated water with 100% overall removal efficiency. For treating contaminated seawater, pre-treatment unit is required to reduce the salinity of the contaminated seawater before staring the treatment process.

The hydrogenation of alkenes catalyzed by disilametallacyclic carbonyl complexes of iron, ruthenium or osmium was studied experimentally and theoretically. The disilaruthenacycle 2 with two CO ligands in the trans-configuration was prepared, characterized, and its ability to catalyze hydrogenation was studied. Similar to the corresponding iron analogue 1 in which the CO ligands are in the cis-configuration, 2 contains a H2MSi4 core with Si⋯H⋯Si SISHA (secondary interaction of silicon and hydrogen atoms) and catalyzed the hydrogenation of several alkenes under mild conditions. DFT calculations of 1 and 2 with cis- and trans-CO configurations (cis-1, trans-1, cis-2 and trans-2) revealed that the mechanism of ethylene hydrogenation comprises three catalytic cycles, and a key step involves the H-H bond of H2 being activated by an M-Si bond through oxidative hydrogen migration. These mechanisms are a variety of σ-CAM (σ-complex-assisted metathesis) mechanisms. Further calculations suggest that these catalytic ...

High functional group compatibility of iridium-catalyzed synthesis of enamines from amides and 1,1,3,3-tetramethyldisiloxane (TMDS) realized facile access of a series of donor (D)-π-acceptor (A)-conjugated enamines, in which enamine behaves as a donor functional group. The amide precursors containing reducible functional groups, such as halogen, carbonyl, and nitro groups, underwent reaction with TMDS to give the corresponding enamines in high yields. In most cases, chemoselective hydrosilane reduction of the amide group occurred while other reducible groups remained intact. Absorption and emission properties including solvatochromic behavior for the resulting D-π-A-conjugated enamines were determined using UV-visible and fluorescent spectra, which provided an understanding of the donor properties of the CH═CHNPh

Efficient separation of strontium ions (Sr2+) from waters has become a critical technological requirement after the nuclear accident at Fukushima Daiichi power station. In the present investigation, new nanocomposites of zero valent iron nanoparticles–zeolite (nZVI–Z) and nano-Fe/Cu–zeolite (nFe/Cu–Z) were synthesized via a simple liquid-phase reduction approach and tested to determine their effectiveness in the sorptive removal of Sr2+ from aqueous solutions. The sorption of Sr2+ on both nanocomposites was studied in a batch sorption mode as a function of various environmental conditions such as initial Sr2+ concentration, contact time, pH, temperature, dosage of sorbent and competing cations (Na+, K+, Mg2+ and Ca2+). The results indicated that initial pH and temperature were significant for Sr2+ sorption on both nanocomposites. The Sr2+ sorption efficiency increases with the increase in nanocomposite dosage and decreases with the Sr+2 concentration. It was also found that although the sorption of Sr2+ was decreased by the presence of coexisting cations, the nanocomposites still exhibited high uptake capacity of Sr2+ ions. The Sr2+ sorption kinetics can be satisfactorily fitted by a pseudo-second-order kinetic model. The sorption isotherm data were well predicted using the Langmuir model. The maximum sorption capacity for nFe/Cu–Z was found to be 88.74 mg/g, which was greater than that for nZVI–Z (84.12 mg/g). In addition to the high sorption capacity, the nanocomposites could be easily separated from aqueous media after Sr2+ sorption using an external magnetic field. The calculated thermodynamic parameters such as ∆H°, ∆S° and ∆G° revealed the endothermic and spontaneous nature of the sorption process. The nanocomposites were also applied in a real seawater medium. The present study confirmed that the prepared nZVI–Z and nFe/Cu–Z nanocomposites could be employed as promising methods for the removal of Sr2+ from wastewater streams.

The mechanisms associated with the hydrogenation of alkenes catalyzed by the iron complex Fe(cis-CO)2{o-(SiMe2)2C6H4}2(H)2 (1) were investigated by DFT calculations. The complex 1 has a structure in which the iron center is bonded to four silicon atoms and two hydrides. Secondary Si···H···Si interactions were also observed. The exchange of a 1,2-bis(dimethylsilyl)benzene ligand with ethylene and hydrogen gives a disilaferracycle bearing η2-(CH2═CH2) and η2-H2 ligands. The catalytic cycle initiated from the disilaferracycle involves cleavage of a H–H linkage assisted by an Fe–Si bond to form Fe–H and η1-(H–Si) moieties (step 1), hydrogen migration from the Fe–H group to the η2-(CH2═CH2) ligand which accomplishes the insertion of ethylene into the Fe–H bond (step 2), and reaction of the resulting β-agostic ethyl moiety with the η2-(H–Si) group to form ethane on the iron atom (step 3). The octahedral geometry of 1 as well as the presence of π-acidic CO ligands and Fe–Si σ-bonds contributes to all of the cata...

In this article we describe 5 rare cases of mumps-associated pharyngolaryngeal edema. To the best of our knowledge, this report includes the first case of mumps-associated pharyngolaryngeal edema in a patient who had previously received mumps vaccination, and these cases represent the sixth report of mumps-associated pharyngolaryngeal edema in the English literature. All 5 of our patients with mumps infection were adults and manifested airway stenosis due to pharyngolaryngeal edema. This edema responded favorably to steroid treatment without tracheotomy. We conclude that a pharyngolaryngeal examination is recommended for patients with mumps infection. Steroid treatment is usually effective against pharyngolaryngeal edema; however, in certain cases tracheotomy may be inevitable.

Effects of folic acid (FA) and folinic acid (FNA) on the embryotoxicity of pyrimethamine (PYR), an antifolate drug, were examined in mice. PYR and FA were administered orally, and FNA was injected intraperitonially for 7 days from day 9 to 15 of pregnancy. The incidence of embryotoxicity including intrauterine deaths and malformations, was 33.5 % in the PYR 50 mg/kg/day group. However, all the fetuses were resorbed in the PYR 50 + FA 50 mg/kg/day group, and FA potentiated the embryotoxicity of PYR. On the contrary, FNA reduced the embryotoxicity of PYR (PYR 50 + FNA 10mg/kg/day; 8.5%). Plasma concentrations of PYR and 5-methyltetrahydrofolic acid (5MF), a principal form of folate in plasma, were determined after single oral administration of PYR 50 mg/kg with or without FA 50 mg/kg to non-pregnant mice. Plasma 5MF concentration decreased drastically in the group receiving PYR with FA, compared with the PYR alone group. The pharmacokinetics of PYR were not affected by co-administration of FA. Therefore, we consider that the potentiated embryotoxicity of PYR by oral FA results from a decrease of plasma 5MF concentration in dams.