Materials
Protamine sulfate from salmon, Sodium alginate, Quartz sand and kaolin were purchased from Wako Pure Chemical Industry (Japan). was purchased from Kanto Chemical (Japan). Hydrochloric acid and sodium hydroxide were used analytical grade reagents. These reagents were used without further purification.
Preparation of suspensions
The quartz sand was washed with distilled water and was dried at 60℃. Then, it was pulverized for 48 h using ceramic ball mill. The quartz powder was washed with distilled water repeatedly and was dried at 60℃ for 48 hr. The size distributions were measured with a laser-scattering size distribution analyzer (LA-300 HORIBA, Ltd., Japan). The mean particle diameters for kaolin and quartz were 6.5 and 47.3 μm, respectively. In most experiments, concentrations of both powder suspensions were 3 g/L.
Clarification experiments
Quartz or kaolin (3 g/L, 100 mL) suspension was poured into a 100 mL glass graduated cylinder. The protamine and alginate solutions prepared at desired concentrations were mixed each 2 mL, respectively. Then, the mixture solution (4 mL) was stirred hardly and 2 mL of the mixture was immediately added to the 100 mL of suspension with a macro pipette. The suspension added flocculant was agitated with a magnetic stirrer at 500 rpm for 5 minutes. After this, the suspension was left to stand without agitation for 1 minute, then, a 2 mL sample was taken from the supernatant layer at a position of 2 cm under the liquid surface of the suspension. The absorbance of the sample was measured at 700 nm spectrophotometrically.
