Surface Functionalization of Graphene Oxide with Hyperbranched Polyamide-Amine and Microcrystalline Cellulose for Efficient Adsorption of Heavy Metal Ions

Abstract Graphene oxide (GO)-based adsorbents have received attention in the removal of heavy metal ions in wastewater due to its large specific surface area and oxygen-containing functional groups, which can enhance the interaction between GO and heavy metal ions. Many researchers are seeking economical and effective strategies to further improve the adsorption capacity of GO. Different from other studies, this study proposed to introduce more active groups with hyperbranched polymer and construct micro/nano 3D bumps with cellulose on the surface of GO to improve the adsorption performance of GO. First, hyperbranched polyamide-amine (HPAMAM) functionalised GO was fabricated by the formation of amide bond between the carboxyl group of GO and the amino group of HPAMAM to endow GO more active groups and increase the affinity of adsorbent with heavy metal ions. Then, dialdehyde cellulose (DAC) obtained through the oxidation of microcrystalline cellulose was grafted onto GO/HPAMAM by forming a Schiff-based structure between the amino group of HPAMAM and aldehyde group of DAC; it is used to fabricate micro/nano 3D bumps on the surface of GO to increase the contact area between the adsorbent and pollutants. The obtained GO/HPAMAM/DAC adsorbent exhibited strong adsorption capacity and good cycle stability for heavy metal ions. The maximum adsorption capacities of Pb(Ⅱ), Cd(Ⅱ) and Cu(Ⅱ) were 680.3, 418.4 and 280.1 mg/g at 298 K, which were better than those of most adsorbents reported. Pseudo-second-order kinetic model and Langmuir isotherm model could describe this adsorption process. The adsorption of Pb(Ⅱ), Cd(Ⅱ) and Cu(Ⅱ) contributed to the chelation or complexation of nitrogen- and oxygen-containing groups on GO/HAPAMAM/DAC adsorbent. This study may provide a novel strategy for improving the adsorption performance of GO with hyperbranched polymer and cellulose.