Al-pillared acid-activated montmorillonite modified electrodes

The role of acid activation of the montmorillonite matrix before pillaring and the effect of calcination temperature on the efficiency of Al-pillared acid-activated clay modified electrodes have been investigated. The electro chemical behaviour of untreated and pillared montmorillonites was compared with that of two pillared acid-activated montmorillonites. The pillared aci d-activated montmorillonite modified electrodes present better electroactiv ity than the modified electrodes of the conventional pillared montmorilloni te towards cationic and anionic redox active species. Mild acid activation of the montmorillonite matrix and a calcination temperature up to 500 degre esC lead to modifying materials that efficiently concentrate the cationic s pecies. Lower calcination temperatures reverse the electrode activity. For anionic redox active species the best electroactivity was observed for pill ared acid-activated montmorillonite films corresponding to a medium acid ac tivation. In that case, a dependence of the electrochemical response on the pH was confirmed. The mechanism responsible for the observed cationic elec troactivity was investigated and the behaviour of the Al-pillared acid-acti vated montmorillonite modified electrodes was attributed to the particular structure as well as the enhanced meso-external surface area and acidity of the clay films. (C) 2000 Elsevier Science S.A. All rights reserved.