Investigation of the leaching behavior of Na and Si in simulated HLW borosilicate glass obtained from the waste of a 1000 MWe class PWR reactor: using the response surface method.

The immobilization of high-level nuclear waste (HLW) in glass waste matrices provides the key safety function of slowing down radionuclide emissions from an underground disposal site. This study examines the leaching behavior of two major elements, Na and Si, in HLW borosilicate glass simulated from waste of a 1000 MWe class pressurized water reactor (PWR) using response surface methodology and Box-Behnken Design. The design of the experiment was carried out considering three independent variables: the pH of the solution, the contact time, and the leaching temperature, leading to 17 leaching runs performed using the static product consistency test (PCT). The results of statistical analysis (ANOVA: analysis of variance) indicated that the effects of the individual variables and the interactions between them were statistically significant, and the relative consistency of the data further confirmed the model's applicability. Data obtained from the PCT experiments revealed that the leaching behavior of Na and Si in the evaluated waste glass exhibited similar behavior to previously researched glasses for each condition tested.

Adsorption and safe immobilization of Sr ions in modified zeolite matrices.

In the present study, an Iranian natural zeolite (Sabzevar region) was evaluated as a natural adsorbent for the elimination and immobilization of strontium ions from an aqueous solution. For improving the adsorption efficiency of strontium ion, the zeolite surface was modified by the Schiff base ligand of bis (2-hydroxybenzaldehyde)1,2-diaminoethane (H2L). The natural zeolite and zeolite/H2L were characterized using Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), X-ray fluorescence (XRF), BET and scanning electron microscope (SEM). Analysis of the natural zeolite showed that the zeolite is from the type of clinoptilolite and has a crystalline structure with the specific surface area 29.74 m2/g. The results showed that strontium adsorption onto modified zeolite increases compared to unmodified zeolite from 64.5% to 97.2% (at pH = 6). The effective parameters pH, adsorbent dosage, initial concentration of strontium ions, contact time, temperature, and interfering ions, were studied and optimized. The maximum adsorption efficiency was confirmed by modified zeolite and found to be 97.5% after 60 min of equilibrium time at pH 6, 0.05g as adsorbent dosage, and at 25 °C. Adsorption of strontium was confirmed by Langmuir model with maximum adsorption capacity of 10.31 mg/g. Kinetic studies showed that the adsorption of strontium ions on the adsorbent follows pseudo-second-order (PSO) model. Also, the thermodynamics of the adsorption process indicated that the adsorption of strontium on zeolite/H2L is an endothermic and spontaneous process, and the adsorption mechanism is a combination of physical and chemical adsorption. Finally, to manage the secondary waste generated from the adsorption process, strontium ions were immobilized in a zeolite structure. The results showed that the stabilization is well done with the thermal preparation process. After thermal treatment at 25-900 °C, modified zeolite satisfactorily retains strontium during back-exchange tests with NaCl solution. According to the results, the amount of strontium released from the adsorbent phase decreases from 52.6 to 1.6% with increasing heat treatment temperature.

DFT exploration of adsorptive performances of borophene to small sulfur-containing gases.

Density functional theory (DFT) calculations were applied to study the ability of B36 to adsorb H2S, SO2, SO3, CH3SH, (CH3)2S, and C4H4S gases. Several exchange-correlation including B97D, PBE, B3LYP, M062X, and WB97XD were utilized to evaluate adsorption energies. The initial results showed that boundary boron atoms are the most appropriate interaction sites. The adsorption energies, electron density, electron localized function, and differential charge density plots confirmed the formation of chemical covalent bonds only between SOx and B36. The results of thermochemistry analysis revealed the exothermic nature of the adsorption of sulfur-containing gases on B36; the highest values of ∆H298 were found for SO3/B36 and SO2/B36 systems. The electronic absorption spectra and DOS of B36 did not exhibit significant variations after gases adsorption, while the modeled CD spectra showed a remarkable change in the case of the SOx/B36 system. Accordingly, B36 is not suggested for detecting the studied gases. The effect of imposing mono vacancy defect and external electric field to the adsorption of titled gases on the sorbent showed, while the former did not affect the adsorption energies significantly the later improved the adsorption of gas molecules on the B36 system. The results of the current study could provide deeper molecular insight on the removal of SOx gases by B36 system.

Cu(OAc)2/MCM-41: an efficient and solid acid catalyst for synthesis of 2-arylbenzothiazoles under ultrasound irradiation.

A new, convenient method for the syntheses of 2-arylbenzothiazoles is described in the presence of catalytic amounts of Cu(OAc)(2)/MCM-41 under ultrasonic irradiation. Short reaction times, easy and quick isolation of the products, reusability of the catalyst and excellent yields are the main advantages of this procedure.

Ultrasound promoted rapid and green synthesis of 1,8-dioxo-octahydroxanthenes derivatives using nanosized MCM-41-SO(3)H as a nanoreactor, nanocatalyst in aqueous media.

An efficient and green procedure has been developed for the synthesis of 1,8-dioxo-octahydroxanthenes derivatives. The reaction was carried out in water under ultrasound irradiation, using nanosized MCM-41-SO(3)H. In this method, several types of aromatic aldehyde, containing electron-withdrawing groups as well as electron-donating groups, were rapidly converted to the corresponding 1,8-dioxo-octahydroxanthenes in good to excellent yields. This novel synthetic method is especially favored because it provides a synergy of the nanosized MCM-41-SO(3)H and ultrasound irradiation which offers the advantages of high yields, short reaction times, simplicity and easy workup compared to the conventional methods reported in the literature.