Observation on reversibility of flocculation in fine quartz suspensions

Abstract

ABSTRACT A series of flocculation and ultrasonication tests were performed on dilute fine quartz suspensions flocculated with the use of three polyacrylamide-based flocculants of similar molecular weights but of different degrees on anionicity to investigate the reversibility of floc destruction and formation. The tests were performed as a function of ultrasonication duration and flocculant dosage. It was demonstrated that breakage of flocs did not occur down to the primary particles over the studied range of experimental conditions. Measurement of settling rate and image analysis indicated that depending on the dosage and degree of anionicity of the flocculant, broken flocs reach a steady state size following continuous breakage. In contrast to the anionic flocculants, a higher dosage of the non-ionic flocculant did not result in regrowth of larger flocs following breakage. Adsorption studies indicated that adsorption density of the polymers on mineral surface did not change as a result of breakage of flocs. A gradual increase in the size of the broken flocs was observed following ultrasonication. The results suggest that flocculation using higher than optimum dosage of anionic flocculants could facilitate regrowth of flocs following breakage.