Effect of Coagulation and Applied Breakage Shear on the Regrowth of Kaolin Flocs

Abstract

Abstract A computer-controlled digital camera was used to examine the formation, breakage, and regrowth of flocs formed by kaolin or the mixture of kaolin and humic acid with aluminum sulfate (alum) at different intensities of applied shear, as well as for continuous optical monitoring (Photometric Dispersion Analyzer). The computer-controlled digital camera could record the flocs size and morphology. There was full regrowth of flocs in kaolin suspension when their zeta potential was close to zero, regardless of intensity of the applied shear, which indicated a significant reversibility of the floc break-up process. However, such a process displayed a distinct irreversibility at higher alum dosage when the flocs were positively charged as the intensity of applied shear increased, though there was full reversibility of floc breakage at low applied breakage shear. Addition of humic acid weakened the reversibility of broken flocs in all cases, especially at high breakage shear. Two-dimensional fractal dimens...