Sorption of heavy metals by natural biopolymers

The sorption properties of modified hydrolysis lignin towards Cu2+, Zn2+, Ni2+, Co2+ ions in the pH range from 2 to 8 at temperature of 298.15K solution are studied. The analysis of kinetic curves of ions sorption on modified lignin at pH 7 shows that sorption equilibrium in heterogenic system ion-metal-sorbent is attained in 30-60 min. Obtained results indicate good equilibrium kinetic properties of sorbent. Supposed that reaction between sorbate and functional group of sorbent are the second-order reaction and they interact between each other in ratio 1:1. The character of the obtained electrokinetic curve suggests that the zeta potential of modified lignin strongly depends on the pH. The dependencies of cations metals sorption coefficients on the pH value of water phase are S-shaped. Maximal extraction of studied cations is observed at pH values of equilibrium solutions close to neutral ones.