黑荆树单宁与金属离子络合性质的研究

Study on Complexation Properties of Black Wattle Tannin with Metals Ions

采用pH电位滴定法测定了不同温度下,离子强度(I)0.1 mol/L的NaCl溶液中单宁酸、橡椀单宁、黑荆树单宁的加质子常数和若干金属络合物稳定常数,考察了单宁结构单元对Fe3+、Cu2+、Zn2+、Ni2+的离子络合选择性的影响,讨论了影响加质子常数和稳定常数的因素。研究结果表明,实验温度下单宁对Fe3+、Cu2+的络合稳定常数大小为:黑荆树单宁>橡椀单宁>单宁酸,对Zn2+、Ni2+的络合稳定常数大小为:橡椀单宁>黑荆树单宁>单宁酸。升高温度有利于酚羟基的解离但不利于单宁-金属络合物的形成。用柱层析提纯的黑荆树单宁对其金属络合物的稳定常数的影响不大。

Protonation constants and metal-complex stability constants of tannic acid, valonea tannin and black wattle tannin were determined by pH potentiometric titration under different temperatures in ionic strength Ⅰ= 0.1 mol/L NaCl solution. The complexation selectivities of different structures of tannins with Fe^3＋ , Cu^2＋ ,Zn^2＋ , Ni^2＋ ions were investigated and factors affecting protonation constant and stability constant were discussed. The results showed that the order of stability constants of the tannins complexed with Fe^3＋ , Cu^2＋ ions was ：black wattle tannin 〉 valonea tannin 〉 tannic acid, and that of tannins with Zn^2＋ , Ni^2＋ ions was ：valonea tannin 〉 black wattle tannin 〉 tannic acid. The rise of temperature was favorable for disassociation of phenol hydroxyl but unfavorable for the formation of complex, The purification of black wattle tannin by gel column chromatography showed little effect on the complex stability constants.