Vermiculite was supplied by Aldrich. It is a naturally occurring
mineral which contains a small amount of crystalline silica in the
form of quartz.
The main properties of the clay are reported in a previous paper
(Malandrino et al., 2006). Altogether it has a good cation exchange
capacity (CEC = 40.08 meq/100 g) and a high pH at the point of zero
charge (pHzpc = 8.63). Potassium is the principal exchangeable ion
present in the interlayer of this clay