The structure and stability of CaFe layered double hydroxides with various Ca:Fe ratios studied by Mössbauer spectroscopy, X-ray diffractometry and microscopic analysis

Dehydration-rehydration induced structural changes in pristine and composite layered double hydroxides

“…In a parallel experimental study, it was revealed [109], in accordance with older [110] and very recent [111] studies, that phase-pure LDH could only be obtained when the molar ratio of the components was 2:1. However, we have found that the phase-pure LDH cannot be used in long-term applications, since it slowly but surely decomposes when exposed to air.…”

“…The 57 Fe Mössbauer spectrum of the pristine CaFe-LDH can be described with an asymmetric doublet as has been described in a previous study by our research group [109].…”

“…The observation that the Ca(OH)2 impurity does not alter the rehydration procedure dramatically, may mean that the Ca(OH)2 is not really a separate entity in the sample, but forms a Ca(OH)2/LDH solid protecting interface. This way, it protects the LDH from decomposition on ageing [109]. …”

Effect of formation pH, molar ratio and calcination temperature on the synthesis of an anionic clay based adsorbent targeting defluoridation

“…However, Chrysochoou and Dermatas (2006) suggested a higher pH of above 10.5 for calcium based HTlc. Generally, studies suggest a pH range of 11 to 13 for the preparation of calcium based LDH (Rousselot et al, 2002;Phillips and Vandeperre, 2011;Woo et al, 2011;Sipiczki et al, 2013;Rojas, 2014). As discussed in Section 1, the calcination should be conducted at an optimal range of temperature to enhance the adsorption capacity of LDH.…”

Removal behavior research of orthophosphate by CaFe-layered double hydroxides

“…Sipiczki et al [21] had formed CaFe-LDH in a co-precipitation method and studied the effect of Ca(II)/Fe(III) ratios on the stability of LDH. CaFe-LDH had been utilized to remove pyrophosphate with a maximum removal capacity of 4.54 mmol P/g LDH within 24 h [22].…”