腐植酸中不同分子量组分与As(Ⅲ)的络合性能

采用超滤方法将腐植酸（HA）分成5个不同分子量组分，利用平衡透析法研究HA中不同分子量组分与As（III）的络合特征和作用机理，计算络合过程的条件分配系数、表观稳定常数.结果表明，腐植酸组分的分子量对HA与As（III）的络合过程有显著的影响，当分子量小于10kDa时，HA与As（III）络合能力明显强于其他条件.其中羧基和酚羟基在HA与砷络合中起重要作用，为主要络合位点.采用Scatchard分析和双位点配体模型对络合结果进行拟合，发现HA中不同分子量组分和As（III）的络合过程中均存在强和弱2种络合位点.

Complexation of As(III) with different molecular weight fractions of humic acid

Humic acid (HA) was divided into five fractions with different molecular weights by ultrafiltration. The complexation behaviours and mechanism of different HA fractions with As (III) were investigated by the method of equilibrium dialysis. The conditional distribution coefficients and apparent stability constants were calculated and analysed to evaluate the complexation process. The results showed that the molecular weight of HA had significant influences on the complexation of HA with As (III). The complexing capability of HA with molecular weight less than 10kDa was better than others. The carboxyl and phenolic hydroxyl groups in HA played an important role in the complexation of HA with arsenic, and they were the main complexation sites. Based on Scatchard analysis and a two-site ligand model fitting with the complexation results, it was found that there were two types of binding sites (strong and weak) in the complexation process between different HA fractions and As (III).