Determination of Critical Micelle Concentration of Bayberry Tannin via pH Method and Its Influence Factors

Critical micelle concentration (CMC) was a vital physical character of bayberry tannin (BT). In this paper, CMC of BT was determined by pH method. The jump of H⁺ concentration before and after the formation of BT micelle was investigated to obtain the CMC by plotting a graph of pH against C_BT. Furthermore, influence factors of CMC were also investigated. The result showed that CMC of BT was 1067.9mg/L at the temperature of 303.0K, and the CMC was influenced by solution temperature, kind and usage of inorganic ions. Along with the rise of solution temperature, CMC decreased first and then increased. A minimum value of 1062.0mg/L was determined at 313.0K. Meanwhile, CMC also decreased after additions of Na⁺ and Ca²⁺ into BT solution, respectively. And the CMC was 891.4 mg/L after adding Ca²⁺ which was lower than that of Na⁺ for the higher charge of Ca²⁺. The CMC of BT was 897.5 mg/L and 891.4 mg/L respectively after adding Na⁺ and Ca²⁺ with the same amount. (10 mmol/L, the temperature of 303.0K).