Abstract
Electrophoretic mobilities of allophane and imogolite were determined by microelectrophoresis. The influence of pre-treatments, viz., air-drying and pre-acidification, on the isoelectric point (i.e.p.) of allophane was investigated. The i.e.p.(pH ca. 5.8) of Na-saturated allophane was shifted to higher pH (7.3) by pre-acidification, while the effect of airdrying on the i, e.p, was not so significant. Imogolite particles began to flocculate as pH increased beyond 7 to 7.5. The pH at which imogolite had no charge (zero electrophoretic mobility) was shown to be 9 to 10. The floccule of imogolite dissolved in part as time passed at pH 12. The different electrokinetic behavior between allophane and imogolite at higher pH was discussed in relation to the structural differences between the two.
