Effects of citrus pectin with different degree of esterification on adsorption of Pb²⁺ and its mechanism

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 endothermic. 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.