[Lead adsorption by the root cell wall of tea plant]

A research was done to study the Pb adsorption by the root cell wall of tea plant extracted from Longjing 43. It was indicated that the amount of Pb adsorbed by the root cell wall increased with augment of the initial pH of the solution under acidic condition, dramatically as the pH ranged from 2.0 to 4.5. The amount of Pb increased with the Pb concentration in the solution at pH 4.5, which could be well fitted by the Freundlich adsorption model. The adsorbed Pb reached 9.7 mg x g(-1) under equilibrium condition, 90% of which was adsorbed in 320 minutes, while 50% was desorbed in 60 minutes based on the desorption dynamic curve. The kinetics of both adsorption and desorption could be well described by a second-order rate equation. The amount of absorbed Pb by the root cell wall varied after modified treatments, reducing by 51.1% after esterifing, 41.3% with pectinase, and 10.8% via aminomethylation, suggesting that carboxyl, galacturonic acid, pectin and amino, to some extent, all took part in the Pb adsorption by the root cell wall.