Observation of characteristic IR band assignable to dimerized copper ions in montmorillonite

Copper ion-exchanged montmorillonite clays, which had been prepared by ion exchange in an aqueous solution of CuCl2 at a temperature above 323 K, exhibited the characteristic IR band in the region 3360–3310 cm−1. No such bands were observed for the samples prepared by using different ion-exchange solutions and at different temperatures. From the spectroscopic observations, it was revealed that the ion-exchanged copper ions (Cu2+) are in the form of dimerized species by bridging two hydroxyls, [Cu2+<(OH−)2>Cu2+Cu2+<(OH−)2>Cu2+], in montmorillonite.

Graphical abstractIt was revealed that the dimerized Cu2+ ions bridging two hydroxyls are formed in montmorillonite by ion exchange in an aqueous solution of CuCl2 at a temperature above 323 K.Figure optionsDownload full-size imageDownload as PowerPoint slide