Search Results

You are looking at 41 - 50 of 183 items for

  • Author or Editor: X. Wang x
  • All content x
Clear All Modify Search

Summary  

The sorption and desorption of radionuclide 90Sr2+were investigated on untreated calcareous soil and two treated soils to remove organic matter and calcium carbonate using batch technique. The experiments were carried out at ambient condition, pH 7.8±0.1 and in the presence of 0.001M NaCl. Effects of fulvic acid and ionic strength on the sorption of 90Sr2+on calcareous soil were also studied. It was found that the sorption isotherms are linear in the strontium concentration range used herein, and the sorption of 90Sr2+on the calcareous soil can be described as a reversible sorption process and the sorption mechanism is mainly ion-exchange. The sorption is dependent on ionic strength, and fulvic acid enhances the sorption of 90Sr2+on calcareous soil. Organic matter present in the calcareous soil is a significant trap of 90Sr2+and is responsible for the sorption.

Restricted access

Abstract  

The thermal behaviors of four organic solvents with/without LiPF6 were measured by C80 microcalorimeter at a 0.2�C min−1 heating rate. With the addition of 1 M LiPF6, the ethylene carbonate (EC) and propylene carbonate (PC) show the exothermic peaks at elevated temperature, which lessen their stabilities. The exothermic peak temperatures of EC and PC based LiPF6 solutions are at 212 and 223�C, respectively, in argon filled vessel. However, two endothermic peak temperatures were detected in diethyl carbonate (DEC) based LiPF6 solution at 182 and 252.5�C, respectively, in argon filled vessel. Dimethyl carbonate (DMC) based LiPF6 solution shows two endothermic peak temperatures at 68.5 and 187�C in argon filled vessel at elevated temperature. Consequently, it is concluded that LiPF6 play a key role in the thermal behavior of its organic solution.

Restricted access

Abstract  

The effect of excipients on the secondary structure of lyophilized proteins was studied through second-derivative Fourier transform infrared (FTIR) spectroscopic analysis. The glass transition temperature (T g), denaturation temperature (T d) and moisture content were determined by differential scanning calorimetry (DSC) and thermogravimetry (TG). T g, T d and the preservation of protein secondary structure were found to be dependent upon the type and amount of the excipient included in the formulation. Meanwhile, the lyophilized proteins easily adsorbed amounts of moisture during storage to reduce their T gs and stability.

Restricted access

Abstract  

This article presents results of the experimental investigation on the adsorption of the water vapor on silica gel. Two independent experimental methods has been used, viz. the constant-volume-variable-pressure (CVVP) system and variable pressure thermogravimetry (TG). Results from these two methods are compared with each other. Also the isosteric heat of adsorption of this system has been determined from the equilibrium data. The silica gels investigated here are Fuji Davison type 'A' and type 'RD'. Adsorption isotherm of water vapor have been measured under a variety of conditions all referring to chiller operation cycles, i.e. temperatures from 303 to 358 K and pressures from 500 to 7000 Pa. The data collected from the two independent experiments compare very favorably with each other and their trends are consistent with those of the adsorption chiller manufacturer. This lends significant weight to our experimental data on silica gel+water systems as being valuable to the adsorption chiller manufacturers and the scientific community.

Restricted access

Abstract  

The decomposition kinetics of reference calcite and three ultra-fine samples with different morphologies are investigated. The kinetic parameters and rate equation are obtained according to the methods reported in our previous studies. Compared with the reference calcite, a considerable diminution of the activation energy E a up to 70–80 kJ mol−1 is observed in the case of three ultra-fine samples. There are also some distinct differences concerning the activation energy of each of the ultra-fine sample. This may have something to do with the particle morphology revealed by TEM and SEM measurements. XRD measurements of four calcite samples show that large strain exists in the crystal lattice in the case of ultra-fine calcite samples. This may give a reason to their abnormal decomposition behavior.

Restricted access

Abstract  

Effects of nano-metal powders (aluminum and nickel) addition on the thermooxidative degradation of binder PEG in air atmosphere from 20 to 350°C were studied by TG/DTA and in-situ FTIR. TG/DTA results showed that the addition of nano-Al slowed down the degradation process of PEG in the early period but accelerated the process in the late period; the addition of nano-Ni made the PEG degradation process begin as soon as melted. The in-situ FTIR results showed that nano-Ni promoted the thermooxidative degradation of PEG in air, and made the degradation process of PEG complete much earlier.

Restricted access

Abstract  

The method of high-temperature hydrolysis separating fluorine from UF4 is described. The determination of the content of fluorine by different methods is performed and compared.

Restricted access

Abstract  

An Al2(WO4)3 target bombarded with a proton beam (28.5 MeV, 20 A) for 1 hour was completely dissolved in about 5 ml of hot 2N NaOH and the clear solution was neutralized with 2N HCl. The resulted white precipitate of Al2(WO4)3 can be separated from the solution by centrifugation and decantation. The supematant containing radioactive Re as ReO 4 was loaded onto a column (1 cm×10 cm) of activated alumina (100–200 mesh). Eluted with 10 ml of saline, the carrier-free ReO 4 was collected, while the small amount of Al2(WO4)3 in the supematant was adsorbed on the column. The total yield of ReO 4 was 94.7% and the breakthrough of WO 4 2– , only 1.0·10–6 M. The whole separation process can be accomplished within 30 minutes. This rapid and efficient Re/W separation protocol is applicable to the preparation of carrier-free186Re, when an enrichel Al2(186WO4)3 target is used.

Restricted access

Abstract  

The residual fluorine in ammonium uranyl tricarbonate (AUC) cannot be removed, while a large part of residual fluorine in ammonium diuranate (ADU) can be removed, when AUC and ADU are decomposed and reduced under dry hydrogen atmosphere. UO2 was prepared by decomposing and reducing AUC and ADU in dry hydrogen atmosphere. The defluorination kinetics of UO2 at 500–700°C in atmosphere of 50% H2-50% H2O was investigated. The results show that the defluorination kinetics supports the Lindman's assertion that the residual fluorine forms a solid-solution in UO2.

Restricted access

Abstract  

Thermal and structural changes of lanthanum hexacyanocobaltate(III) pentahydrate, La[Co(CN)6]⋅5H2O were investigated by means of thermal analysis, visible electronic spectra, IR, powder X-ray diffraction, EXAFS and TG-MS. The dehydration of La[Co(CN)6]⋅5H2O proceeded reversibly through three steps and steps corresponded to the losses of H2O, 3H2O and H2O, and the enthalpy changes for these steps were 51.3, 211.0 and 38.7 kJ mol−1, respectively. After the dehydration, the colour of the anhydride changed from white to blue around 290C and an abrupt mass loss occurred at 350C. The colour change seems to be attributable to the change of coordination geometry around the Co ions from an octahedral structure to a tetrahedral one. LnCoO3 was obtained as a final product by heating the sample to 1000C.

Restricted access