Influence of pH on Flocs Formation, Breakage and Fractal Properties-The Role of Al13 Polymer

Weiying Xu, Baoyu Gao, Qinyan Yue, Xiaowen Bo



The Al13 ([Al13O4(OH)24(H2O)12]7+) polymer and polyaluminum chloride (PACl) were comparatively investigated for the coagulation of humic acid (HA). The growth, breakage, and fractal nature of flocs under different pH conditions were investigated using a laser diffraction particle-sizing device. The results showed that the floc properties were essentially dependent on pH. The flocs were small but compact under acidic conditions; as the pH increased, large flocs were produced with loose structures. Compared to PACl, Al13 polymer displayed better stability and functioned more rapidly after addition; and the flocs formed by Al13 were denser across the pH values investigated. It was also found that flocs formed at pH 5.50 were the strongest for both coagulants in the pH range investigated. Additionally, the increased shear rate could improve the flocs structures by conducing higher fractal dimension flocs.


Keywords: Al13 polymer, Floc growth, Floc breakage, Fractal dimension