Biosorption of Heavy Metals from Water onto Phenolic Foams Based on Tannins and Lignin Alkaline Liquor

Abstract

In this study, easy to manufacture and ecological solid free-formaldehyde phenolic foams were prepared by a mechanical foaming process from mixtures of tannins and lignin alkaline liquor. The resulting biosourced phenolic foams were characterized and examined as bio-adsorbents for heavy metals (Cu2+, Cd2+, Zn2+ and Pb2+) removal from aqueous solutions. Many experimental parameters were investigated to optimize metals adsorption such as solution pH, temperature, initial metal concentration, and metals-foams contact time. The adsorption capacities of studied metals onto biosourced foams reached 46.5, 41, 29.1, and 100.9 mg/g for Cu2+, Cd2+, Zn2+ and Pb2+, respectively. Their adsorption isotherms and kinetics isotherms were simulated using nonlinear regression to determine the best fit to the experimental data. The study of the obtained isotherms proved that the adsorption process on biosourced phenolic foams follows the Sips isotherm for Zn2+ and Redlich-Peterson isotherm for Cu2+, Cd2+ and Pb2+. The kinetics adsorption study showed that the Elovich model for Cd2+, the Avrami model for Pb2+ and the general order model for Cu2+ and Zn2+ fits more to experimental data. These porous materials could be used as low cost and efficient bio-adsorbents for heavy metals removal from polluted water.