Research studying of ultrasonic effects on ion-exchange processes in uranium production by the in-situ leaching method

In the last few years, some advances have been made in the theoretical modelling of ion exchange processes in glass. On the one hand, the equations that describe the evolution of the cation concentration were rewritten in a more rigorous manner. This was made into two theoretical frameworks. In the first one, the self-diffusion coefficients were assumed to be constant, whereas, in the second one, a more realistic cation behaviour was considered by taking into account the so-called mixed ion effect. Along with these equations, the boundary conditions for the usual ion exchange processes from molten salts, silver and copper films and metallic cathodes were accordingly established. On the other hand, the modelling of some ion exchange processes that have attracted a great deal of attention in recent years, including glass poling, electro-diffusion of multivalent metals and the formation/dissolution of silver nanoparticles, has been addressed. In such processes, the usual approximations that are made in ion exchange modelling are not always valid. An overview of the progress made and the remaining challenges in the modelling of these unique processes is provided at the end of this review.

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Insight into the enhanced photocatalytic properties of AgBr/Ag4P2O7 composites synthesized via in situ ion exchange reaction

Journal of Environmental Chemical Engineering ◽

10.1016/j.jece.2020.104889 ◽

2021 ◽

Vol 9 (1) ◽

pp. 104889

Author(s):

Wyllamanney da S. Pereira ◽

Fabrício B. Destro ◽

Cipriano B. Gozzo ◽

Edson R. Leite ◽

Júlio C. Sczancoski

Keyword(s):

Ion Exchange ◽

Exchange Reaction ◽

Photocatalytic Properties ◽

Ion Exchange Reaction ◽

Insight Into

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Experimental and Theoretical Studies of Sonically Prepared Cu–Y, Cu–USY and Cu–ZSM-5 Catalysts for SCR deNOx

Catalysts ◽

10.3390/catal11070824 ◽

2021 ◽

Vol 11 (7) ◽

pp. 824

Author(s):

Przemysław J. Jodłowski ◽

Izabela Czekaj ◽

Patrycja Stachurska ◽

Łukasz Kuterasiński ◽

Lucjan Chmielarz ◽

...

Keyword(s):

Ion Exchange ◽

Ultrasonic Irradiation ◽

Active Phase ◽

Spectroscopic Studies ◽

In Situ Drifts ◽

Ft Ir ◽

Diffuse Reflectance Infrared ◽

Experimental And Theoretical Studies

The objective of our study was to prepare Y-, USY- and ZSM-5-based catalysts by hydrothermal synthesis, followed by copper active-phase deposition by either conventional ion-exchange or ultrasonic irradiation. The resulting materials were characterized by XRD, BET, SEM, TEM, Raman, UV-Vis, monitoring ammonia and nitrogen oxide sorption by FT-IR and Diffuse Reflectance Infrared Fourier Transform Spectroscopy (DRIFTS). XRD data confirmed the purity and structure of the Y/USY or ZSM-5 zeolites. The nitrogen and ammonia sorption results indicated that the materials were highly porous and acidic. The metallic active phase was found in the form of cations in ion-exchanged zeolites and in the form of nanoparticle metal oxides in sonochemically prepared catalysts. The latter showed full activity and high stability in the SCR deNOx reaction. The faujasite-based catalysts were fully active at 200–400 °C, whereas the ZSM-5-based catalysts reached 100% activity at 400–500 °C. Our in situ DRIFTS experiments revealed that Cu–O(NO) and Cu–NH3 were intermediates, also indicating the role of Brønsted sites in the formation of NH4NO3. Furthermore, the results from our experimental in situ spectroscopic studies were compared with DFT models. Overall, our findings suggest two possible mechanisms for the deNOx reaction, depending on the method of catalyst preparation (i.e., conventional ion-exchange vs. ultrasonic irradiation).

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