The difference in adsorption capacity between Fe-PILCs and modified Fe-BuA- and Fe-Zr-PILCs

Iron(III) oxide pillared clays have low micropore volumes (0.04 cm³ g⁻¹) and surface areas (95 m² g⁻¹). In order to increase the porosity and thereby the adsorption capacity, two different modification procedures were carried out. The first modification is based on the preadsorption of butylammonium ions between the clay sheets prior to the pillaring procedure with the iron precursors. This gives rise to a decrease of the Fe pillar density which results in an increased porosity (Fe-BuA-PILC). Preadsorption of butylammonium ions doubles the adsorption capacity of an Fe-PILC. A second modification is the incorporation of Zr into the Fe precursors to create mixed Fe-Zr pillars with entirely new properties (pillar charge, pillar symmetry, etc.) creating a pillared clay with a different enhanced porosity. These pillared clays were tested with respect to their adsorption and desorption capacities towards CCl₄, CHCl₃, CH₂Cl₂ and CH₄ at 0 °C. These experiments indicate that the adsorption capacity of the mixed Fe-Zr-PILC is four times higher than pure Fe-PILC. Not only does the capacity differ, but the isotherm type also changes, indicating that adsorbents with different properties can be created by means of simple modification techniques.