Effect of Temperature on Maximum Polymerization Rate of Silicic Acid in Supersaturated Silicic Acid Solutions

Abstract

Experiments on the polymerization reaction of silicic acid were carried out at pH7 and the effect of temperature (nearly 313, 333 and 353 K) was experimentally examined on the polymerization of silicic acid, particularly on the maximum polymerization rate, in supersaturated silicic acid solutions (the initial silicic acid concentration was approximately 500, 700 and 900 mg/l). In the case of 700 and 900 mg/l of the initial silicic acid concentration, the polymerization rate increased with increasing temperature. In the case of 500 mg/l, the polymerization rate decreased with increasing temperature and the polymerization reaction did not occur at 353 K. At the fixed temperature, the polymerization rate of silicic acid was higher as the initial silicic acid concentration was higher. Regardless of both initial silicic acid concentration and temperature, the polymerization rate of silicic acid became maximum when the supersaturated silicic acid concentration decreased by 20∼30%. The maximum polymerization rate of silicic acid Rmax is represented by the following equation:log R_max=k₁·pH+k₂·log{(C₀-C_e)/C_e}+k₃T+k₄where R_max, pH and T are the maximum polymerization rate of silicic acid [mg 1^-1 min^-1], the pH and the temperature of solution [K], respectively. C₀ and C_e are the initial concentration and the equilibrium concentration of silicic acid [mg/l]. From the experimental results in this study and Sugita and Yamamoto (1999), the above equation will be able to be useful at the range of the following conditions : pH=6.4∼7.9, (C_o-C_e) /C_e=1.25∼4.59 and T=308∼353 K. Then, k₁=0.632±0.002, k₂=3.73±0.01, k₃=0.0385±0.0014, k₄=-17.1±0.5.