Flocculating Activity Determination

The flocculation activity was evaluated according to the standard kaolin suspension method (Salehizadeh and Shojaosadati, 2001). In a 100-mL cylinder, one milliliter each of the sample and AlCl₃ solution were mixed with 48 mL of kaolin solution (4 g/L). After 5 min at room temperature, the upper phase of the mixture was measured at 550 nm. The control sample consisted of no flocculation agent in the cylinder. The flocculation activity was calculated according to the decrease in turbidity and the equation was as follow: Flocculation activity (%) = (A-B)/A × 100%, where A and B was the absorbance of the control and the sample at 550 nm, respectively. Each sample was tested independently in triplicate.