Preparation and characterization of exfoliated graphene oxide–l-cystine as an effective adsorbent of Hg(ii) adsorption

Abstract

A facile and novel method for removal of Hg(II), based on the appealing interaction between exfoliated graphene oxide (EGO), L-cystine, and Hg(II), is reported in this paper. A thiol functional group facilitated the interaction with Hg(II), resulting in efficient adsorption. The abundant oxygen-containing functional groups on the surfaces of graphene oxide (GO) play an important role in Hg(II) sorption. Characterization of the adsorbent was performed using various characterization techniques, such as cross polarization magic angle spinning nuclear magnetic resonance, Raman spectroscopy, X-ray photoelectron spectroscopy, powder-X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscope and energy-dispersive X-ray analysis. The capability of inductively-coupled plasma mass spectrometry for Hg(II) adsorption was extensively studied under different optimal parameters and the adsorption isotherm values clearly fit with the Langmuir isotherm plot; maximum adsorption capacity was 79.36 mg g⁻¹, augmented by the thermodynamically favourable adsorption process. Second-order kinetics of the adsorption process were validated by the experimental data. Regeneration of the adsorbent was accomplished using thiourea and the potential of this novel adsorbent material was utilized in Hg(II) adsorption.