Recovering Heavy Metal Ions from Complex Solutions Using Polyethylenimine Derivatives Encapsulated in Alginate Matrix

A new sorbent was manufactured by immobilization of polyethylenimine (PEI) derivatives (glutaraldehyde-cross-linked PEI, and carbon disulfide-grafted PEI) into an alginate matrix. These composite materials take advantage of the sorption properties of both PEI and alginate, and the encapsulating properties of the biopolymer. The sorption properties of these composite materials were tested for the recovery of Cd(II), Cu(II), and Zn(II) ions from aqueous solutions. Kinetic, equilibrium, and desorption behaviors were successively investigated. Special attention was paid to competitive sorption and to the effect of inorganic ions on sorption efficiency. Sorbent morphology was observed using a scanning electron microscope (SEM) equipped with an energy dispersive X-ray microanalysis system (EDX). SEM-EDX results show a homogeneous distribution of heavy metals in beads after metal sorption. Alginate was found to have a better sorption capacity for all heavy metals studied in simple systems. Conversely, calcium and sodium salts strongly reduce the sorption of heavy metals. In complex systems, the presence of other reactive groups (amine groups from PEI) contributes to improved sorption performance.