正烷基亚氨二乙酸与铜(Ⅱ)离子络合平衡的研究

来源期刊：中南大学学报(自然科学版)1985年第2期

论文作者：殷群生 张祥麟 陈超球

文章页码：107 - 113

关键词：亚氨二乙酸； 混合溶剂； 生成常数； 金属离子络合物； 络合平衡； 水溶液； 十四烷基； 络合能力； 电子构型； 配位体

摘    要：本文在25±0.1℃,表观离子强度0.1(KNO₃)条件下,用pH电位法测定了五种正烷基亚氨二乙酸(C_nH_2n+1N(CH₂COOH)₂,n=6,8,10,12,14)在混合溶剂中及水溶液中与Cu²⁺形成的络合物的生成常数。结果表明:在硅孔雀石和黑钨矿的浮选中,当捕收剂C_nH_2n+1N(CH₂COOH)₂的n小于12时,其捕收能力大幅度下降的原因不在络合能力的衰减,而在水溶性等方面的差异;正烷基亚氨二乙酸与金属离子络合物的生成常数在混合溶剂(75vol%二氧已环、25vol%水)中比水溶液中增加的值与该金属离子的外层电子构型,广义软硬酸碱度等因素有关。

Abstract: The complex equilibria between n-hexyl iminodiacetic acid and Cu(Ⅱ) have been studied pH-potentiometrically by the method of excess metal ion both in the aqueous solution and in the mixed solvent water-dioxane (75vol%). It was shown by our experiments that no protonated complexes had been formed. Because of the close similarities between n-hexyl iminodiacetic acid and the other four long-chain n-alkyl iminodiacetic acids, it is reasonable to suppose that no protonated complexes would be formed between these acids and Cu(Ⅱ). Then we restricted our investigation to the normal complexes by applying the method of excess ligand. The successive stability constants K₂’s for the systems mentioned above have been obtained by Bjerrum’s half n method. The successive stability constants K₁’s, however, have not yet been obtained using the same method. So a formula has been derived to evaluate K₁ from the data in the neighbourhood of n=0.8, thereby K₁’s have been obtained, which S. Chaberek and A. E. Martell deemed impossible with the experiments like ours (T_A: T_M=2: 1) but on the system Cu(Ⅱ)-iminodiacetic acid. The stability constants evaluated at 25±0.1℃ and apparent ionic strength 0.1(KNO₃) are shown in the following table. The reasons for the absence of complex CuriA (A stands for C_nH_2n+1N(CH₂COO)₂^2-), the relative complexing abilities of Ni²⁺, Cu²⁺ and Zn²⁺ with the n-alkyl iminodiacetie acids, and the influences of the solvents on complex stabilities have been discussed.