河水可溶性有机物与Cu^(2+)络合常数的确定

Determination of conditional stability constant of copper with river water DOC

分别采用单配位体、双配位体离散模型与连续分配模型对水体中可溶性有机物与金属铜离子的络合行为进行描述 .单配位体模型的使用中可采用不同拟合手段 ,对拟合结果有一定影响 .单纯以可决系数与误差平方和为判断依据 ,非线性拟合的拟合效果最佳 ,拟合结果为条件稳定常数logk =2 2 6 ,络合容量C =6 70mol·g-1.检测窗口的变化在极大程度上影响络合常数的计算结果 .双配位体模型的非线性拟合结果为logk1=7 2 9、logkn=1 90、C1=0 0 2 3mol·g-1、Cn=13 74 6mol·g-1,与单配位体模型相比没有明显改善 .连续分配模型可用来描述不同络合位饱和度下条件稳定常数的连续变化 ,并从曲线的外推计算出最强络合位的络合常数logkmax=4

Single site, multi site discrete ligand model and continuous distribution model were applied for determining stability constant and binding capability of dissolved organic carbon from natural water with copper. A number of methods available for titration data manipulation were evaluated. Based on final loss and determinative coefficient, the parameters obtained using nonlinear estimation (log k =2 26, C=6 70 mol·g -1 ) fitted to the experimental data best, which were affected by the variation in detection window. Two site model was also used to calculate the binding parameters (log k 1=7 29,log k n =1 90, C 1=0 023?mol·g -1 , C n =13 746?mol·g -1 ), showing no obvious improvement compared to single site model. A modified continuous distribution model based on the Scatchard plot was introduced to reflect the variations in binding energies with the increase in saturation of binding sites. Constant for binding at the strongest site, with greatest significance from an environmental standpoint, was obtained from intercept values and the result was log k max =4 71.