[Show abstract][Hide abstract] ABSTRACT: The ion equilibrium at the interface of solution within compacted bentonite, and the external solution is an important factor influencing the diffusion of ionic species in the compacted bentonite. The ion equilibrium can be calculated by the Donnan model using macroscopic compacted bentonite parameters. By constructing a single pore type structure model for compacted bentonite, where the montmorillonite TOT-layers are depicted as a parallel array of rectangles, the ion equilibrium can also be calculated by the Poisson-Boltzmann (PB) model with a scale-defining variable H. We demonstrated that the ion equilibrium coefficients calculated by the PB model are always larger than those calculated by the Donnan model, and the models are linked by the factor H. The mathematical transition from the PB model to the Donnan model occurs in the limiting case H→0. The application of the two models to diffusion problem is also discussed, and the PB model is shown to be more realistic and suitable for solving actual diffusion problems.
[Show abstract][Hide abstract] ABSTRACT: We performed a molecular dynamics simulation to investigate the adsorption of uranyl ions onto the basal surfaces of kaolinite using a simulation cell containing 0.01 mol?L-1 uranyl carbonate and 9× 9×3 kaolinite unit cells. The adsorption sites of the uranyl ions on kaolinite were clearly shown by serial snapshots and the coordination of uranyl ions to oxygen were determined using a radial distribution function. The adsorption trends of uranyl ions on two distinct basal surfaces were discussed using an atomic density profile. Outer-sphere complexation of uranyl on kaolinite was confirmed using the atomic density profile and the mean squared displacement. Confirmation of the outer-sphere complexation supports the theoretical simplification of the adsoption sites in the surface complexation model.
[Show abstract][Hide abstract] ABSTRACT: The adsorption of Se(IV) onto crushed Beishan granite (BS03, 600 m) was studied by a batch experimental method. The results showed that the distribution coefficient (Kd) remained almost constant in the pH range of 3-7 and decreased at pH>7. The adsorption of Se(IV) did not vary with ionic strength. The presence of Ca2+ (4.10×10-3 mol·L-1) and SO42- (3.17×10-3 mol·L-1) had no effect on Se(IV) adsorption. Moreover, we found that the adsorption of Se(IV) (1.46×10-5 mol·L-1) and Eu(III) (3.33×10-6 mol·L-1) on Beishan granite had no effect on each other in the ternary adsorption system consisting of Se(IV)/Eu(III)/ granite. The adsorption of Se(IV) onto Beishan granite was quantitatively interpreted by considering the two surface complexation reactions of HseO3- to form ≡SHSeO3 and ≡SSeO3- on the ≡SOH general adsorption sites.
[Show abstract][Hide abstract] ABSTRACT: Anatase-type TiO2 fine powders were synthesized under hydrothermal condition. The precursor was obtained via precipitation route using Ti(SO4)2. The characterization of the as-prepared sample was confirmed by TEM, XRD, UV-Vis and low temperature N2 adsorption measurements (BET). The photocatalytic activity was also investigated by the degradation of methyl orange solutions. The particles of the as-synthesized sample with narrow size distribution had an average diameter of about 24 nm. The specific BET surface area of the as-synthesized sample was about 56 m2 x g(-1), which is similar to the commercial TiO2 (P25). The prepared materials showed the similar photocatalytic activity when compared with the performance of commercial TiO2 (P25).
Guang pu xue yu guang pu fen xi = Guang pu 03/2010; 30(3):767-9. · 0.29 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The influence of pyrite irradiated by γradiation from 60Co on the reductive environment of groundwater was investigated. The dose rate was 200 Gy·min-1 and the total absorbed dose was 5×106 Gy. Our results indicate that the radiolysis reactions of the γradiation of 60Co in groundwater can help to oxidize pyrite, while the structure of pyrite is not changed. The oxidizing of pyrite consumes the radiolysis product in groundwater, which helps to maintain a reductive environment and increase the safety of the repository.
[Show abstract][Hide abstract] ABSTRACT: The solubility of americiumin Yuci groundwater was analyzed using a newly developed geochemical code CHEMSPEC and the influence of pH, groundwater composition, and temperature on its solubility was also investigated. The results indicate that the pH, the total carbonate concentration, and the temperature have obvious influences on solubility while the sulfate and chloride concentrations do not. The solubility of americiumin Yuci groundwater is 1.4×10-10-6.3×10 -3 mol·L-1. The maximum solubility was obtained at 25 , pH=6.0, and a total carbonate concentration of 1×10-5 mol·L-1. These data can be used to predict the diffusion and migration behavior of americiumin the aquifer.
[Show abstract][Hide abstract] ABSTRACT: Titania nanotubes (TNTs) were synthesized by hydrothermal treatment of rutile-phase TiO2 nanoparticals in NaOH solution at 110 degrees C for 24 hours. After drying in aceton for 36 h, the TNTs were under vacuum drying for 24 h at room temperature. The Pt-inserted titania nanotubes (Pt/TNTs) were obtained by filling H2 PtCl6 ethanol solution into the TNTs after vacuum drying. The characterizations of the as-synthesized samples were confirmed by TEM, XRD, and UV-Vis. The photocatalytic activity of the Pt/TNTs was investigated by photo-induced decomposition of methyl orange(MO)under the main 365 nm UV-light. In order to comparison, the photocatalytic activity of both the rutile-phase TiO2 nanoparticles and pure TNTs were also investigated at the same time under the same experimental conditions. The TEM images show that the TNTs are hollow, a few hundred nanometers long, and the inner/outer diameter is about 6/10 nm. The crystal structure of TNTs is H2Ti2O5 x H2O with a little Na. Both the shape and the crystalline of the TNTs are not changed after the modification. The oval or round Pt0 nanoparticals, about 3 nm in diameter, are found only in the nanotubes. Pt/TNTs exhibit enhanced absorption at the visible range in the UV-Vis spectra and its start absorption band edge(lambda0 approximately 457 nm)is obviously redshifted compared to the rutile-phase TiO2 nanoparticals and pure TNTs. The Pt nanoparticles are found to significantly enhance the photocatalytic activity of TNTs. Pt/TNTs are demonstrated to be highly efficient for the UV-light induced photocatalytic decomposition of MO compared to both the rutile-phase TiO2 nanoparticals and pure TNTs. After irradiation for 60 min, the photocatalysis decomposition rate of MO in rutile-phase TiO2 nanoparticals, TNTs and Pt/TNTs are 46.8%, 57.2% and 84.6% respectively.
Guang pu xue yu guang pu fen xi = Guang pu 06/2009; 29(6):1623-6. · 0.29 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Titania nanotubes (TNTs) were synthesized by hydrothermal treatment of rutile-phase TiO2 nanoparticles in 10 mol·L-1NaOHsolution at 110 for 24 h. The Ag loaded titania nanotubes (Ag/TNTs) were obtained by chemical deposition method with the TNTs suspending in the AgNO3 solution (pH=8) at 50 . The characterizations of the as-synthesized samples were performed by TEM, EDS, XRD, XPS, and UV-Vis spectra. The photocatalytic performance of the Ag/TNTs was investigated by UV-light induced photocatalytic decomposition of methyl orange(MO). The results showed that the inner/outer diameters of TNTs were about 6/10 nm and the length was several hundred nanometers. Both the shape and the crystalline of the nanotubes were not changed after the modification. The zero oxidation state Ag quantumdots, about 4 nmin diameter, were well dispersed on the external surface of the nanotubes. Ag/TNTs exhibited enhanced absorption at the visible range in the UV-Vis spectra. The Ag nanoparticles were found to significantly enhance the photocatalytic activity of TiO2 nanotubes, and the catalyst system was demonstrated to be highly efficient for the UV-light induced photocatalytic decomposition of MO compared to both rutile-phase TiO2 nanoparticles and pure TNTs. After irradiation for 60 min, the decomposition rates of MO solution in rutile-phase TiO2 nanoparticles, TNTs, and Ag/TNTs systemwere 46.8%, 57.2%, and 92.2%, respectively.