Pillared clays (PILCs) with magnetic properties have significant potential for application in industry and the environment, but relatively few studies of these types of materials have been carried out. The aim of the present work was to gain insight into the magnetic and structural properties of pillared clays by examining in detail the influence of the calcination temperature and the nature of different pillared clays on these properties.
Magnetic layered systems from different pillared clays were prepared and characterized. Firstly, Ti-, Al-, and Zr-pillared clays (Ti-PILCs, Al-PILCs, and Zr-PILCs, respectively) were produced at different calcination temperatures and then magnetic pillared clays (Ti-M-PILCs, Al-M-PILCs, and Zr-M-PILCs) were prepared at ambient temperature. The synthesis involves a reduction in aqueous solution of the original Fe-exchanged pillared clay using NaBH4. The structural properties of pillared clays and their magnetic forms were investigated using X-ray diffraction, N2 adsorption, cation exchange capacity determination, and X-ray fluorescence (XRF) measurements. The properties of the magnetic pillared clays were investigated by superconducting quantum interference devices and Mössbauer spectroscopy. An evaluation of the data obtained allowed an estimation of the pillared structure in one PILC-model before and after magnetization. The model was determined on the basis of a simple geometric model and experimental data leading to the calculation of a filling factor (FF) which contained information about the number of intercalated pillared layers and the unaffected layers. In the case of Ti precursors, the best calcination temperature was 400ºC, which maintained the highest specific surface area and pore volume with magnetic parameters suitable for magnetic application. Similar experiments with Al- and Zr-pillars have been discussed. A correlation between the XRF data, porosity, FF calculation, and magnetic properties led to the conclusion that the sample Al-M-PILC previously calcined at 500ºC was the most stable material after the magnetization process. The same examination in the case of Zr materials suggested that the most stable sample had been calcined at 300ºC (sample Zr-M-PILC-300).
