MgZnAl-EDTA柱撑水滑石吸附Pb(Ⅱ)的热力学和动力学

Thermodynamics and kinetics for Pb(Ⅱ) adsorption with MgZnAl-EDTA LDHs

采用共沉淀法合成了Mg2 ZnAl-CO3水滑石,以其为前体运用离子交换法进行插层组装,制备了Mg2 ZnAl-EDTA柱撑水滑石,并用XRD和IR对样品进行表征.以Mg2 ZnAl-CO3水滑石和Mg2 ZnAl-EDTA柱撑水滑石为吸附剂,用于水中Pb2+的吸附.吸附热力学研究表明该吸附过程符合Langmuir等温吸附,其ΔGθ、ΔHθ和ΔSθ均为负值,是自发、放热且熵减小的过程;吸附动力学研究表明,该吸附过程符合准二级动力学模型,同时包含物理吸附和化学吸附.

The Mg2ZnAl-CO3 LDHs was synthesized by coprecipitation method and ED-TA pillared Mg2ZnAl-LDHs was successfully synthesized by the ion exchange method with Mg2ZnAl-CO3 LDHs as precursor.The prepared samples were characterized by XRD and IR.Mg2ZnAl-CO3 LDHs and Mg2ZnAl-EDTA LDHs were used as adsorbent for the adsorption of Pb^2＋ from water.The results showed that equilibrium isotherms were well fitted to the Langmuir equation,and thermodynamic parameters such as ΔG^θ,ΔH^θand ΔS^θ were calculated from Langmuir constants.Three kinetics models were used to fit the experimental data,and it was found that the pseudo-second order kinetics model could be used to describe the adsorption process appropriately,which including physical adsorption and chemical adsorption.