风化煤富啡酸、红壤富啡酸及胡敏酸与Eu(Ⅲ)配合物的稳定常数测定

DETERMINATION OF STABILITY CONSTANTS OF WEATHERED COAL FULVIC ACID,RED EARTH FULVIC ACID AND HUMIC ACID WITH Eu(Ⅲ)

以15 2 ,15 4Eu作示踪剂 ,用改进的斯蒂文森 (Stevenson)阳离子交换平衡法 ,测定了河南巩县风化煤富啡酸、广东大亚湾红壤富啡酸和胡敏酸与Eu(Ⅲ )生成的配合物稳定常数。实验结果表明 ,在离子强度为 0 0 1mol/kg、pH值为 5时 ,在实验所用的腐殖质浓度和Eu(Ⅲ )浓度范围内 ,主要生成了配位比为 1∶1的配合物。相应配合物稳定常数的对数值lgβ11的平均值分别为 :4 76± 0 1 2 ,3 78± 0 1 1和 4 48± 0 1 7。

Stability constants of weathered coal fulvic acid,red earth fulvic acid and humic acid with Eu(Ⅲ) are determinated by the modified Stevenson’s cation exchange method.It is found that 1∶1 type complexes of the three humic substances with Eu(Ⅲ) are mainly formed, respectively under the experimental conditions (pH=5±0.2, I =0.01 mol/kg,the concentrations of three humic substances range from 10 -4 mol/L to 10 -3 mol/L and free Eu(Ⅲ) concentrations range from 10 -7 mol/L to 10 -6 mol/L).The averages of stability constants of Eu(Ⅲ) complexes with the weathered coal fulvic acid,the red earth fulvic acid and the humic acid are 4.76±0.12,3.78± 0.11 and 4.48 ±0.17,respectively.tabilityc