Efficient removal of Pb(II) and Cd(II) from water by polyethyleneimine-amidated sepiolite-sodium alginate composite microspheres: Characterization and mechanistic analysis

In order to improve the physicochemical properties of heavy metal adsorbents, researchers developed a novel composite microsphere material (SEI) by incorporating Sepiolite (Sep) and cross-linked polyethyleneimine (PEI) with sodium alginate (SA) as a carrier. The stability of the SEI under normal use conditions was high by thermogravimetric analysis, and COOH, OH, and NH functional groups were detected by FTIR, which were confirmed to be involved in adsorption. It was found that the adsorption rate of SEI on Pb(II) and Cd(II) obeyed a pseudo-second-order kinetic model, while the adsorption pattern was closely related to the Langmuir equation. Notably, the maximum adsorption capacity of SEI for Pb(II) and Cd(II) was 1099.93 mg/g and 112.89 mg/g, respectively, at 30 °C. In addition, thermodynamic analyses showed that the adsorption process was spontaneous, with entropy increase along with heat absorption. After six adsorption and desorption cycles, the removal of Pb(II) and Cd(II) by SEI remained above 90 %. These findings suggest that SEI is a promising and environmentally friendly material for the removal of Pb(II) and Cd(II).