Memory Effect on a LDH/zeolite A Composite: An XRD In Situ Study

Abstract

In this memory effect study, hydrotalcite-type compounds in the lamellar double hydroxide-like (LDH)/zeolite A composite material were analyzed using X-Ray Diffration XRD) in situ experiments. Three samples were analyzed: Al,Mg-LDH, Al,Mg-LDH/ZA composite, and a physical mixture (50/50 wt%) of zeolite A and Al,Mg-LDH. The Al,Mg-LDH sample was treated at 500 °C in an O2 atmosphere and subsequently rehydrated. The Al,Mg-LDH/ZA composites had three treatments: one was performed at 300 °C in a He atmosphere, and two treatments were performed with an O2 atmosphere at 300 and 500 °C. In the physical mixture, two treatments were carried out under O2 flow at 500 °C and under He flow at 300 °C. Both went through the rehydration process. All samples were also analyzed by energy dispersive spectroscopy (EDS) and scanning electron microscopy (SEM). The results show that the LDH phase in the Al,Mg-LDH/ZA compounds has memory effects, and thus, the compound can be calcined and rehydrated. For the LDH in the composite, the best heat treatment system is a temperature of 300 °C in an inert atmosphere.

Structured LDH/Bentonite Composites for Chromium Removal and Recovery from Aqueous Solutions

“…The XRD patterns of the as-synthesized adsorbents are represented in Figure 2 and for clarity reasons, the signals that also correspond to quartz (i.e., an additional component of bentonite) are not indicated. All non-calcined adsorbents display signals characteristic of both LDH and bentonite phases [ 46 , 47 , 48 ]. Both clay types exhibit XRD basal at low 2 theta angle and non-basal planes at higher 2 theta angles, respectively.…”

Special Issue: Layered Double Hydroxides (LDH) and LDH-Based Hybrid Composites

“…It leads to the reconstruction of layered structures after its calcination under appropriate conditions. Bezerra et al [ 10 ] investigated the memory effect phenomena by in situ XRD for Mg/Al-LDH, as well as for its composite with zeolite.…”