Highly Selective Pb(II) Adsorption by DTPA-Functionalized Graphene Oxide/Carboxymethyl Cellulose Aerogel.

Abstract

Graphene oxide (GO) exhibits a strong adsorption capacity for the removal of heavy metal ions from liquids, making it a topic of increasing interest among researchers. However, a significant challenge persists in the preparation of graphene oxide-based adsorbents that possess both high structural stability and excellent adsorption capacity. In this paper, a green and environmentally friendly ternary composite aerogel based on graphene was successfully synthesized. The adsorption capacity of graphene oxide was enhanced through diethylenetriaminepentaacetic acid modification, while the incorporation of composite carboxymethyl cellulose improved the structural stability of the composite aerogel in liquid. The composite aerogel demonstrates robust interactions between its components and features a multiscale porous structure. Adsorption tests conducted with Pb(II) revealed that the GO/DTPA/CMC (GDC) composite aerogel exhibits a favorable adsorption capacity. The study of adsorption kinetics and isotherms indicated that the adsorption process follows the quasi-secondary adsorption model and Freundlich adsorption model, suggesting a chemical multilayer adsorption mechanism, and the maximum adsorption capacity for Pb(II) ions was 521.917 mg/g based on the quasi-quadratic kinetic model fitting. X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM) analyses, performed before and after adsorption, confirmed that the adsorption of Pb(II) primarily occurs through chelation, complexation, proton exchange, and electrostatic interactions between ions and active sites such as hydroxyl and carboxyl groups. This study presents an innovative strategy for simultaneously enhancing the adsorption properties of graphene oxide-based composite aerogels and ensuring solution stability.