DETACHMENT OF COLLOIDS FROM SEDIMENTS AND SAND GRAINS

The mechanisms of colloid transport and attachment have been studied i n several fields and a reasonable understanding of the overall process has been developed over the past several decades. However, there is l ittle fundamental understanding of the mechanisms of colloidal particl e detachment from larger grains. The ongoing research explores particl e detachment from both theoretical and experimental viewpoints. The th eoretical studies have developed expressions that may be used to deter mine the magnitude of forces that would control particle detachment, i ncluding electrostatic and van der Waals forces. The results indicate differences when the computations are based on energies of interaction compared with forces of interaction. The initial experimental studies were performed on laboratory scale model systems with well-defined sp herical particle suspensions. Latex particles (2 and 5 mum) were attac hed to a packed column containing glass beads as collector grains. Par ticle number concentrations were monitored using a laser, time of tran sition type, particle size analyzer (Brinkmann, Particle Size Analyzer ). The detachment of particles during fluidized bed operations was stu died in relation to the chemical characteristics of the water. Prelimi nary experimental results indicated that the detachment of latex parti cles was (a) independent of ionic strength of solution phase during at tachment, but (b) was dependent on the ionic strength during detachmen t. Detachment efficiency was higher with lower ionic strength waters.