Engineering GO@Zn–Hap@CA porous heterostructure for ultra-fast and ultra-high adsorption efficacy: investigation towards the remediation of chromium and lead

Abstract

In the contemporary era, research into the structures involving emerging 2D materials, inorganic components, and polymers has evolved at a tremendous pace for environmental protection and sustainability. Herein, this study reports the design and fabrication of a GO@Zn–Hap@CA porous heterostructured adsorbent using 2D graphene oxide (GO), inorganic zinc-doped hydroxyapatite (Zn–Hap) and cellulose acetate (CA) via a crosslinking approach for the removal of Cr(VI) and Pb(II) ions. The synthesized raw material and the developed heterostructured adsorbent were intensely characterized by X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectroscopy, X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), field emission scanning electron microscopy (FE-SEM), and N₂ gas adsorption–desorption analysis. The fabricated GO@Zn–Hap@CA heterostructure exhibited high roughness, high surface area and mesoporous texture and thereby has shown an enhanced capture of Cr(VI) and Pb(II) ions. Importantly, it possessed an ultrahigh maximum adsorption capacity of 384 mg g⁻¹ and 400 mg g⁻¹ for Cr(VI) and Pb(II) at pH = 2 and pH = 5, respectively. Investigation of the adsorption isotherm and kinetics indicate that both Cr(VI) and Pb(II) adsorption fitted well with the Freundlich isotherm model and pseudo-second-order kinetic model. While probing the kinetics, the equilibrium was observed to reach at an ultrafast duration, for instance, 50 min for chromium and 60 min for lead. A study on the effect of the co-existing ions revealed that the cations and anions had a less significant effect on Cr(VI) and Pb(II) adsorption. Such results offer insights into the intriguing potential of GO@Zn–Hap@CA for the elimination of hazardous pollutants from the aquatic environment.