Studies on adsorption behavior of Pb(II) onto a thiourea-modified chitosan resin with Pb(II) as template

In order to find an effective absorbent material based on chitosan which has good adsorption selectivity for heavy metals, we prepared thiourea-modified chitosan resin with Pb(II) as template (TMCR template). TMCR template was synthesized by using O-carboxymethylated chitosan to absorb Pb(II) ions first and then being cross-linked with a polymeric Schiff's base of thiourea/glutaraldehyde. The effects of parameters such as pH, contact time, initial concentration and temperature on the adsorption of TMCR template were studied. The result showed the maximum uptake of Pb(II) was found to be 2.02 mmol/g at pH 6.0, 25 °C. Adsorption experiments showed the TMCR template had high selectivity for Pb(II) in solution containing binary mixtures with Cu(II), Zn(II), Cd(II) and Ni(II). The experimental data also indicated that the adsorption process was exothermic spontaneous and fit well with Lagergren's pseudo-second-order model in comparison to pseudo-first-order kinetic.