Impregnation-induced memory effect of thermally activated layered double hydroxides

1998 ◽  
Vol 13 (1) ◽  
pp. 35-48 ◽  
Author(s):  
A.J. Marchi ◽  
C.R. Apesteguı́a
Catalysts ◽  
2019 ◽  
Vol 9 (5) ◽  
pp. 454 ◽  
Author(s):  
Esthela Ramos-Ramírez ◽  
Francisco Tzompantzi-Morales ◽  
Norma Gutiérrez-Ortega ◽  
Héctor G. Mojica-Calvillo ◽  
Julio Castillo-Rodríguez

In recent years, the search for solutions for the treatment of water pollution by toxic compounds such as phenols and chlorophenols has been increasing. Phenols and their derivatives are widely used in the manufacture of pesticides, insecticides, paper, and wood preservers, among other things. Chlorophenols are partially biodegradable but not directly photodegradable by sunlight and are extremely toxic—especially 2,4,6-trichlorophenol, which is considered to be potentially carcinogenic. As a viable proposal to be applied in the treatment of water contaminated with 2,4,6-trichlorophenol, this paper presents an application study of the thermally activated Mg/Fe layered double hydroxides as photocatalysts for the mineralization of this contaminant. Activated Mg/Fe layered double hydroxides were characterized by X-ray diffraction, thermal analysis, N2 physisorption, and scanning electron microscopy with X-ray dispersive energy. The results of the photocatalytic degradation of 2,4,6-trichlorophenol in aqueous solution showed good photocatalytic activity, with an efficiency of degradation of up to 93% and mineralization of 82%; degradation values which are higher than that of TiO2-P25, which only reached 18% degradation. The degradation capacity is attributed to the structure of the MgO–MgFe2O4 oxides derived from double laminate hydroxide Mg/Fe. A path of degradation based on a mechanism of superoxide and hollow radicals is proposed.


Crystals ◽  
2019 ◽  
Vol 9 (3) ◽  
pp. 153 ◽  
Author(s):  
Alexandre Teixeira ◽  
Alysson Morais ◽  
Ivan Silva ◽  
Eric Breynaert ◽  
Danilo Mustafa

Layered double hydroxides (LDHs) containing Eu3+ activators were synthesized by coprecipitation of Zn2+, Al3+, and Eu3+ in alkaline NO3−-rich aqueous solution. Upon calcination, these materials transform into a crystalline ZnO solid solution containing Al and Eu. For suitably low calcination temperatures, this phase can be restored to LDH by rehydration in water, a feature known as the memory effect. During rehydration of an LDH, new anionic species can be intercalated and functionalized, obtaining desired physicochemical properties. This work explores the memory effect as a route to produce luminescent LDHs intercalated with 1,3,5-benzenetricarboxylic acid (BTC), a known anionic photosensitizer for Eu3+. Time-dependent hydration of calcined LDHs in a BTC-rich aqueous solution resulted in the recovery of the lamellar phase and in the intercalation with BTC. The interaction of this photosensitizer with Eu3+ in the recovered hydroxide layers gave rise to efficient energy transfer from the BTC antennae to the Eu3+ ions, providing a useful tool to monitor the rehydration process of the calcined LDHs.


2012 ◽  
Vol 207-208 ◽  
pp. 913-922 ◽  
Author(s):  
Tatjana J. Vulic ◽  
Andreas F.K. Reitzmann ◽  
Károly Lázár

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