Effects of low temperature on coagulation kinetics and floc surface morphology using alum

The effects of low temperature on coagulation kinetics and floc surface morphology were examined in this study. The results show that low temperature slowed down the coagulation process as reflected in the decrease in aggregation rate and rate constants. The aggregation constant in the coagulation process was found to follow the Arrhenius law. The activation energy of the aggregation of kaolinite particles in water was 18.7 kJ/mol. Furthermore, the study on the surface morphology of the flocs indicates that those flocs formed at low temperatures had a more irregular structure in terms of perimeter-based fractal dimension, Dpf. Dpf increased from 1.19 to 1.33 as the temperature was downshifted from 22°C to 2°C. The examined shape factor of the flocs, elongation E, was found to follow the probability rule of statistics. Out of two thousand flocs, around 75% of them have an E value ranging from 1.2 to 2.0.