Search Results

You are looking at 11 - 20 of 58 items for

  • Author or Editor: Wei Zhang x
  • All content x
Clear All Modify Search

Summary  

The Minor Actinides Recovery from HLW by Extraction Chromatography (MAREC) process was used mainly for the separation of minor actinides (MAs) and some specific fission products (FPs) from highly active liquid waste (HLW) by the composite CMPO/SiO2-P of the macroporous silica based polymeric octyl(phenyl)-N,N-diisobutylcarbamoylmethylphoshine oxide (CMPO) and others. In this study a cascade of chromatographic separation was performed on a 3.0M HNO3 solution containing 5.0 . 10-3M of 13 elements, at 323 K. The cascade consisted of three columns the first and second ones were packed with CMPO/SiO2-P and the third with SiO2-P particles. The first column was employed to prepare various eluents containing saturated CMPO. The second column was used for separation into groups. The CMPO of CMPO/SiO2-P was recovered from the effluent by the third column and a CMPO-free effluent containing minor actinides was obtained. The elements contained in the simulated HLW of 3.0M HNO3 were separated into (1) a non-adsorption group (Sr, Cs, and Ru etc.), (2) a MA-hRE (heavy rare earth)-Mo-Zr group, and (3) a lRE (light rare earth) group by eluting with 3.0M HNO3, 0.05M DTPA (diethylenetriaminepentaacetic acid) (pH 2.0) and HNO3 (pH 3.5), respectively. The resultant MA-hRE-Mo-Zr mixture containing minor actinides was then separated into the groups (1) Pd-Ru, (2) MA-hRE, and (3) Mo-Zr by utilizing 3.0M HNO3, distilled water, and 0.05M DTPA (pH 2.0) as eluents. More than 92% of CMPO in the MA-hRE containing effluent was adsorbed by SiO2-P particles. The effectivity and technical feasibility of MAREC process were demonstrated.

Restricted access

Abstract  

Peroxynitrite is a potent oxidant in vivo which can result in serious diseases such as cardiopathy, acute inflammation and even cancer. Iron porphyrins have been shown to catalyze the efficient decomposition of peroxynitrite and are therefore important to detoxify the cytotoxic oxidant as therapeutic agents. A kinetic and theoretical study on peroxynitrite decomposition catalyzed by iron porphyrins is carried on in order to search and synthesize more effective scavengers of peroxynitrite. Kinetic experiments and quantum chemistry calculations were applied to iron porphyrins with different substituents for catalyzing peroxynitrite decay. Kinetic experiments suggested that the catalytic ability of iron porphyrins for peroxynitrite decomposition were dependent on the type and location of substituents on the porphyrin rings. Density functional calculations further reveal that the variation of substituent leads to a difference in structure-related quantum chemical descriptors including charges of central metal ion, energy of the highest occupied molecular orbital and energy of the lowest unoccupied molecular orbital.

Restricted access

Abstract

A series of CuO–V2O5/Al2O3 catalysts were prepared and characterized by various techniques such as XRF, BET, XPS and XRD. These catalysts were used for liquid-phase amination of toluene to toluidines. It was found that adding copper species to V2O5/Al2O3 catalyst showed a peculiar behavior, maintaining a high activity toward toluene amination. An optimum CuO content appeared at 1.6 wt% with a CuO/V2O5 molar ratio of 0.25. More than 60% total yield of toluidines was obtained over 1.6%CuO–15%V2O5/Al2O3 catalyst under optimized conditions. Catalyst characterizations revealed that the addition of copper improved the formation of V5+ species, thus enhancing the activity of the catalyst.

Restricted access

Abstract

To improve the properties of steel slag blended cements, a chemical activator was added into blended cements, the mechanical properties and durability of steel slag blended cements were investigated. The results show that steel slag in blended cement pastes presents low hydraulic activity and makes practically no contribution to strength development. After the addition of chemical activator, the mechanical properties and durability of ternary blended cements are increased significantly. The hydration process and micro-structural development of blended cement was investigated by isothermal calorimeter and scanning electric microscope, respectively. Steel slag started hydration in the first 3 days in the presence of chemical activator, steel slag and granulate blast furnace slag reacted with Ca(OH)2 to form a dense microstructure as curing proceeded. Therefore, both early and late compressive strengths of steel slag blended cement with 35% cement clinker and 30% steel slag can be comparable with those of Portland cement.

Restricted access

Abstract

Titanium dioxide (TiO2), polythiophene and polythiophene/TiO2 were prepared by sol–gel and solid-state reaction methods. Water-free iron(III) chloride (FeCl3) was used as an oxidant. The phase composition, morphology and the spectral properties of the products were characterized by XRD, TEM, UV–Vis and FT-IR techniques. The photocatalytic activity of the products was evaluated by the degradation of methyl orange under sunlight irradiation. TEM results showed that the polythiophene/TiO2 composite particles were well dispersed, rod-like shaped with 20 × 80 nm dimensions. UV–Vis analysis indicated that the absorption edge of polythiophene/TiO2 was 605 nm. Compared with the unmodified TiO2 and bare polythiophene, polythiophene/TiO2 exhibited largely enhanced activity for the photocatalytic degradation of methyl orange under sunlight irradiation. A degradation efficiency of methyl orange of 85.6% could be obtained within 120 min. The sensitization mechanism of polythiophene for the TiO2 photocatalyst is discussed briefly.

Restricted access

Abstract

A novel temperature-controlled phase transfer catalytic system based on [(C18H37)2(CH3)2N]7[PW11O39] for olefin epoxidation was demonstrated. The reaction was conducted in a non-chlorinated solvent of ethyl acetate with hydrogen peroxide. The catalyst was easily recovered and reused even ten cycles without loss in activity and selectivity.

Restricted access

Abstract

A facile and reusable catalytic system for alcohol oxidation with hydrogen peroxide was designed based on a temperature-responsive catalyst. Several kinds of alcohols were efficiently oxidized in high yields under relatively mild conditions. The catalyst could be easily recovered and reused.

Restricted access

Abstract

Cationic polymerization of α-pinene with silicotungstic acid (SiW12) as a catalyst was investigated. The structure of polymers and the catalysts were characterized by FT-IR, 1H-NMR and GPC. The experiments show that SiW12 is more active than both phosphotungstic acid and phosphomolybdic acid. The protons dissociating from the catalysts are the reactive species. SiW12 is found to be both the polymerization initiator and the counter-anion of the growing cationic center. The polymerization conditions are optimized by the single factor method as follows: monomer concentration is 50% (v/v), the dosage of catalysts is 7 wt% referred to α-pinene, reaction temperature is 50 °C, reaction time is 1 h. Under these conditions, the overall conversion of α-pinene is up to 90.87%, the polymer yield is 62.46% and its average number molecular weight is about 600. GC–MS analysis shows that there are six isomers of α-pinene after the reaction, but their content is very low. Most of α-pinene are changed to poly(α-pinene).

Restricted access

Abstract  

A conjugate of 6-hydrazinopyridine-3-carboxylic acid (HYNIC) with aminomethylenediphosphonic acid (AMDP) was synthesized through a multiple-step reaction. HYNIC–AMDP could be labeled easily and efficiently with 99mTc using N-(2-hydroxy-1,1-bis(hydroxymethyl)ethyl)glycine (tricine) as coligand to form the 99mTc–HYNIC–AMDP complex in high yield (> 95%). Its partition coefficient indicated that it was a good hydrophilic complex. The biodistribution studies of 99mTc–HYNIC–AMDP in normal ICR mice showed that this complex had high bone uptake and low or negligible accumulation in non-target organs. As compared with 99mTc–MDP, 99mTc–HYNIC–AMDP had a higher bone uptake and the ratios of bone/blood and bone/muscle at early time after injection, suggesting that it could be potentially useful for bone imaging at an earlier time after injection according to further investigations of the biological behavior of this complex.

Restricted access

Abstract  

Neuroscience is one of the most active research fields in many countries including China, an economically and scientifically emerging country, where a rapid development has been occurred since the 1970s. In this study, a MEDLINE-based bibliometric analysis of Chinese international output in neuroscience was conducted for the period from 1984 through 2001. An attempt was made to identify the pattern of the growth and to obtain some quantitative indicators over the literature studied in order to review at the developing steps of neuroscience in China during the period.

Restricted access