VAPOR-PHASE SORPTION OF P-XYLENE ON CO-EXCHANGED AND CU-EXCHANGED SAZ-1 MONTMORILLONITE

Sorption of p-xylene and water on homoionic Cu- and Co-exchanged montmorillonite clay films has been investigated using a gravimetric/Fourier transform infrared (FT-IR) cell along with a tandem UV-visible/FT-IR cell. The gravimetric/FT-IR cell provided an unambiguous method to determine the relative contributions of water and p-xylene to the total mass of solute sorbed by the clay. The spectroscopic data indicated that p-xylene was chemisorbed on the surface of Cu-montmorillonite under dry conditions. An intense band developed at 455 nm in the UV-visible spectrum and new bands appeared in the FT-IR spectrum which could not be assigned to p-xylene or to the clay matrix. These new bands are assigned to the formation of a radical organic cation of p-xylene resulting from a single-electron-transfer reaction on the surface of the clay. No spectroscopic evidence for chemisorption of p-xylene on Co-montmorillonite was found.