Thermal analysis of MgFe-Cl Layered doubled hydroxide (LDH) directly synthetized and produced “via memory effect”

Abstract

Layered doubled hydroxides (LDHs) are known to be an interesting class of 2D layered materials, with a wide range of possible composition and a flexible structure suitable for topochemical reactions. Thus, LDHs have been applying in different fields, such as catalysis, energy storage and all the applications in which a high exchange capability (of both cations and anions) is required. For remediation purpose, a MgFe-Cl LDH $${[({\mathrm{Mg}}_{0.66}^{2+}{\mathrm{Fe}}_{0.33}^{3+}{\left(\mathrm{OH}\right)}_{2}]}^{0.33+}{({\mathrm{Cl}}_{0.33}^{-})}^{0.33-}$$ [ ( Mg 0.66 2 + Fe 0.33 3 + OH 2 ] 0.33 + ( Cl 0.33 - ) 0.33 - (MFC in the following) could be a promising candidate to capture the toxic CrO 4 2− from water, in exchange with the Cl− in an efficient way. The synthesis of this compound might seem simple, consisting of a coprecipitation reaction, and actually, it is strongly affected by the environmental carbon dioxide able to replace the Cl− with the more stable CO 3 2− . To avoid this problem, LDHs could be also prepared with a rehydration of their calcinated oxide (memory effect). In this work were prepared two samples of MFC: one via coprecipitation (MFC-1 in the following) and one via “memory effect” (MFC-mem in the following). Both the compounds were characterized by means of X-ray powder diffraction (PXRD), Fourier transform infrared spectroscopy (FT-IR) and differential thermal analysis-thermogravimetry (DTA-TG) coupled with evolved gas analysis. The results demonstrated that the synthesis of pure MFC is very difficult, and only a minimum contamination of carbon dioxide led to the formation of the carbonate LDH in a massive way. It was also demonstrated that Mg-Fe LDHs in the presence of carbonate could catalyse the formation of the formic acid (HCOOH) at low temperature (< 300 °C).

High Efficient of Ca/Al-Graphite for Removal of Direct Orange

“…Ca/Al-graphite composite as functionalized material was characterized using XRD, FT-IR, BET, and TGA to observe the crystal structure changes, structure bonding that formed, surface area improvement, and structure transformation according to the different temperatures (Botan and de Bona Sartor, 2020;Cardinale et al, 2022;Shabanian et al, 2020;Walton and Snurr, 2007). Figure 1 shows the XRD pattern of the Ca/Al-graphite composite, which figures out the unique peak in every precursor of LDH and graphite.…”

Ultrasound-Assisted Adsorption of Perchlorate Using Calcined Hydrotalcites and the Thermal Stabilization Effect of Recycled Adsorbents on Poly(vinyl chloride)

“…Memory effect is the restoration of the original LDH structure by rehydration, applying decarbonation and subsequent reconstruction utilizing target anionic groups. − By this effect, both harmful organic and inorganic anions from wastewater can be intercalated into the interlayer and removed successfully. , Yang et al synthesized a novel material of calcined iron-based LDH for ClO 4 – adsorption from water using a co-precipitation method. In this study, ClO 4 – at 2000 μg/L concentration was almost all adsorbed within 720 min by 1.33 g/L MgFe-3CLDH (calcination temperature = 550 °C and [Mg]/[Fe] = 3) at 25 °C and initial solution pH of 4–10.…”

“…Memory effect is the restoration of the original LDH structure by rehydration, applying decarbonation and subsequent reconstruction utilizing target anionic groups. 32 − 34 By this effect, both harmful organic and inorganic anions from wastewater can be intercalated into the interlayer and removed successfully. 35 , 36 Yang et al 37 synthesized a novel material of calcined iron-based LDH for ClO 4 – adsorption from water using a co-precipitation method.…”