多胺功能化介孔炭对Pb(Ⅱ)的吸附动力学与机制

Adsorption Kinetics and Mechanism of Lead(Ⅱ) on Polyamine-Functionalized Mesoporous Activated Carbon

采用硝酸氧化和乙二胺聚合在微波辅助磷酸活化中孔蔗渣基介孔炭孔道内修饰了含氮多胺基团,制备了多胺功能化生物质炭材料AC-EDA,分析了溶液pH、初始浓度和吸附时间等参数对材料吸附Pb(Ⅱ)影响,探讨了其动力学吸附行为与吸附机制.结果表明,多胺功能化炭材料AC-EDA对Pb(Ⅱ)有较好的吸附效率,5 min内可达饱和吸附量的70%;酸性条件下,增大溶液pH有利于Pb(Ⅱ)吸附;材料AC-EDA对Pb(Ⅱ)的吸附位能量存在差异化,在吸附初始阶段,吸附速率由颗粒内扩散控制,中后期主要由膜扩散控制;准二级方程能很好地描述多胺功能化炭材料对Pb(Ⅱ)的吸附动力学行为.AC-EDA对Pb(Ⅱ)的吸附是自发的吸热反应过程,提高温度对铅(Ⅱ)离子吸附有促进作用;D-K-R吸附能>11 kJ·mol-1,表明化学反应在Pb(Ⅱ)吸附过程中起主导作用;吸附Pb(Ⅱ)前后的AC-EDA材料XPS图谱表明,多胺基团参与了吸附反应,是材料高效吸附Pb(Ⅱ)的重要因素.

Bagasse mesoporous carbon was prepared by microwave assisted H3PO4 activation. Amido and imido groups were modified with ethanediamine on the channels＇ surface of mesoporous carbon through nitric oxidation and amide reaction. The influence of Pb（Ⅱ） concentration,adsorption time on Pb（Ⅱ） adsorption on the ethanediamine-modified mesoporous carbon（AC-EDA） was investigated. The adsorption kinetics and mechanism were also discussed. The results showed that AC-EDA had a great performance for Pb（Ⅱ） adsorption,and more than 70% of Pb（Ⅱ） was adsorbed in 5 minutes. The adsorption amount of Pb（Ⅱ） on the carbon increased with the increase of solution pH in acidic conditions. It was found that AC-EDA had different binding energies on different adsorption sites for Pb（Ⅱ） separation. The Pb（Ⅱ） adsorption process on AC-EDA was controlled by intra-particle diffusion in the first 3 min,and then film diffusion played the important pole on the adsorption. The adsorption amount increased with the increase of temperature,indicating the adsorption was an endothermic reaction. The high adsorption energy（ 11 kJ·mol^-1） implied that the adsorption was a chemical adsorption. The XPS of AC-EDA before and after Pb（Ⅱ） adsorption showed that the polyamine group was involved in the adsorption,and should be a main factor of the high efficient adsorption.