Biosorption of Pb and Cd onto Polygonum sachalinense

Abstract

Adsorption of Pb and Cd onto a biosorbent, carbonized Polygonum sachalinense (CPS) was investigated. The carbonization condition was 1 h at 350ºC. The adsorption behaviors of Pb and Cd onto CPS could be explained by a proposed adsorption model based on the monodentate binding of the divalent metal ions with two types of adsorption sites. The adsorption sites were considered as carboxylic and phenolic groups based on the results of Boehm titration and FT-IR analysis. The maximum adsorption capacity of CPS for the divalent metal ions was determined as 1.22 mmol/g, and it was much larger than the values reported in the previous reports. The binding affinities of Pb of the adsorption sites were considered as much higher than those of Cd based of the adsorption constants. The adsorption constants of Pb and Cd with carboxylic group were about 200–2000 times larger than the of the adsorption constants with phenolic group. The kinetics of Pb and Cd onto CPS were also investigated. It was found that the adsorption of the divalent metal ions onto the phenolic group was a rate limiting step.