Some effects of trivalent chromium exchange of thermo-exfoliated commercial vermiculite

This manuscript presents the investigation on some effects of the CrIII adsorption from aqueous solution by thermally expanded commercial vermiculite. Three effects were studied: 1) contact time between the adsorbent and chromium dissolved in the retention process; 2) adsorbent mass; and 3) concentration of chromium in adsorption. The original and treated vermiculite samples were characterized by X-ray diffraction and infrared spectroscopy. The findings of this study showed, on the one hand, that vermiculite with high mica-like content, after abrupt heating to high temperatures, is very suitable for the recovery of traces of CrIII in waters of relatively high salt content due to its high degree of exfoliation and adsorption coefficient (Kd = 0.74 × 105 μg kg− 1). On the other hand, that the mica-type structure originated by the sudden heating of vermiculite would have shifted again to that of the vermiculite, due to adsorption of CrIII (probably by ion exchange) and probably its binding with the water trapped in the structure.