Abstract
We examined the effect of clay mineralogy and interfacial chemistry of clay suspensions on the performance of a flocculant prepared from weathered volcanic ash rich in allophane and imogolite. Upon addition of the flocculant into the clay suspension and stirring, fluffy flocs formed and settled after a standing time. The absorbance of the supernatant gradually decreased to near zero at an optimum addition and then increased again when more flocculant was added. The optimum flocculant addition differed significantly among the clay suspensions. Inspection of the results of the flocculation tests and characterization of the sample clays, particularly stepwise multiple regression analyses, suggested that the major factors affecting the performance were the effective cation exchange capacity (ECEC), content of micaceous minerals and average particle size, of which the contribution of the former two factors seemed weightier. This was interpreted as indicating the importance of the amount of negative charge on the external surfaces of particles in the clay suspensions.
