High proton conductivity in pressed pellets of H-montmorillonite, HAl-montmorillonite and HAlFe-montmorillonite clays

High proton conductivities, of 0.01 to 0.04 ohm −1 m −1 at 290 K, have been found in pressed pellets of H +-exchanged montmorillonite clays which had been equilibrated in air to give mixtures of the mono- and bi-layer hydrates. The H + transport number was found to be 0.9 ± 0.1. Higher conductivities were found in the tri-layer hydrate. The nature of the conductivity is discussed in the light of pulse nmr and ir results.