不同酯化度的柑橘果胶对Pb^(2+)的吸附作用影响及其机理研究

Effects of citrus pectin with different degree of esterification on adsorption of Pb^(2+) and its mechanism

制备四种不同酯化度(82.32%、75.57%、64.56%、55.88%)的柑橘果胶,并研究其对Pb^(2+)吸附的影响及吸附机理。结果表明,四种不同酯化度的果胶均在温度为30℃,铅离子溶液pH=5.0时吸附效果好。高酯化度的柑橘果胶对Pb^(2+)吸附作用更强。四种不同酯化度的果胶对Pb^(2+)吸附的速度都很快,经过40 min后基本达到平衡。各热力学参数表明四种不同酯化度果胶对Pb^(2+)的吸附是一个自发、吸热的过程。经四种动力学模拟发现四种不同酯化度果胶对Pb^(2+)的吸附动力学符合准二级动力学方程,吸附速率受化学吸附控制;而且Pb^(2+)的吸附发生在果胶表面,并未进入内部。

Citrus pectin with four different degree of esterification （ 82.32% , 75.57% , 64.56% , 55.88% ） were prepared, then their adsorption effect and mechanism towards lead were studied.It was found that all the pectins showed good adsorption when the solution temperature was 30 ℃ and pH was 5.0.It indicated that high esterified pectin had good effect on the adsorption. Citrus pectin with different degree of esterification could adsorb lead at a fast rate, they almost achieved adsorption equilibrium after 40 minutes.Various thermodynamic parameters was evaluated and it was found that the adsorption process was spontaneous and endothermie.The kinetic data were analyzed using four adsorption kinetic models, and kinetics of Pb2＋ adsorption by pectin with four different degree of esterification was better described by the pseudo-second-order equation, The adsorption rate was controlled by chemisorption.The Pb2＋ was adsorbed by transferring to the pectin surface and it did not move into the interior.