重金属离子与典型离子型有机污染物的络合效应研究

采用自动电位滴定法,研究了水环境中4种常见的重金属离子Cu2+、Pb2+、Zn2+、Cd2+与环丙沙星、磺胺甲基嘧啶和全氟辛酸的络合效应.测定了3种有机物与4种金属离子的络合常数logK值,计算了各种络合物在不同pH值下的形态分布. 结果表明,Cu2+与环丙沙星能形成较为稳定的络合物Cu(cip±)2+、Cu(cip±)22+、Cu(cip-·cip±)+,其络合能力要远强于Pb2+、Zn2+、Cd2+,前者形成的络合常数要比后三者高出3个数量级.4种金属离子与磺胺甲基嘧啶均有一定的络合能力,但稳定常数差别不大.全氟辛酸分子中由于带有较多的电负性强的F,表现出强酸的性质,与4种金属离子未见明显的络合作用.

Study on complexation effect between heavy metal cations and typical ionic organic pollutants

The complexation effect between ciprofloxacin (CIP), sulfamerazine (SMR) and perfluorooctanoic acid (PFOA) and typical heavy metal cations (Cu2+, Pb2+, Zn2+, Cd2+) was investigated by automatic potentiometric titration method and the titration curves were used to derive the binding constants logK between the metals and ligands. Aqueous speciation distribution of various metallic complexes at different pH values were then calculated. Results showed that Cu2+ could form stable complexes Cu(cip±)2+、Cu(cip±)22+、Cu(cip-·cip±)+ with CIP and the binding affinity of Cu2+ was much stronger than that of Pb2+, Zn2+ and Cd2+. Four metal cations all could complex with SMR, while with little difference. Since PFOA molecule carried a lot of F atoms, it behaved like strong acid and no significant complexation effect was observed between PFOA and four metal ions.