草炭水溶解态有机质与金属离子络合稳定常数的测定

Determination of the stability constants of complexing between the water-soluble-organic-matter of peat and the metal ions

采用离子交换平衡法测定草炭水溶解态有机质与 Cu2 +、Pb2 +、Zn2 +、Cd2 + 4种金属离子 ,在 2种 p H条件下的络合稳定常数 .结果表明 ,金属离子与草炭水溶解态有机质通常形成混合或多核络合物 ;2种 p H条件下的络合配位数和稳定常数序列均为 :Cu2 + >Pb2 + >Zn2 + >Cd2 + ,高 p H条件下 。

Ion exchange equilibrium method was used to determine the stability constants of the complexes formed by the water soluble organic matter (WSOM) of peat and four different ions under two pH conditions. When I=0.1, pH=3.5, the order of the coordination numbers x was Cu 2+ (0.92)>Pb 2+ (0.59)>Zn 2+ (0.33)>Cd 2+ (0.18), and the order of stability constants was Cu 2+ ( 3.31)> Pb 2+ (1.57)>Zn 2+ (0.73)>Cd 2+ (0.37). When I=0.1, pH=5.0, the order of the coordination numbers x was Cu 2+ (1.42)>Pb 2+ (0.65)>Zn 2+ (0.34)>Cd 2+ (0.25), and the order of stability constants was Cu 2+ (4.71)>Pb 2+ (1.26)>Zn 2+ (0.79)>Cd 2+ (0.47). Metal ions and WSOM usually formed mixed or polynuclear complexes. Under high pH condition, there was a remarkable increase in coordination numbers and stability constants.