Analysis of sedimentation behavior of flocculated Na-montmorillonite in a semi-dilute regime

— effects of the container height —

抄録

A systematic observation of the sedimentation behavior of montmorillonite suspension coagulated in 1.00 M NaCl solution was made using glass cylinders of different heights in the semi-dilute regime which starts from a very slow rate followed by gel collapse ending slow consolidation. Intensive analysis was done for the maximum interface settling rate (Q) as a function of the volume fraction of montmorillonite (φ ) using cylinders of different heights. The velocities were plotted against the reciprocal height of the cylinder to obtain the velocity of infinite height as a function of the volume fraction of montmorillonite. On the basis of Richardson-Zaki’s equation; Q=Q_f(1−αφ )^4.65, the swelling ratio of α, and the velocity of zero limit dilution (Q_f) were obtained from the slope of the plot and the intercept of the abscissa, respectively. Using the obtained values of αand Q_f, the representative diameter of the floc, d_f, is determined by the application of Stokes’ Law. The obtained values of Q_f and d_f were confirmed to be consistent with the result of the measurement of the settling velocity of a single floc against diameter independently determined by the method of Two-way camera.