Green One-Step Approach to Prepare Sulfur/Reduced Graphene Oxide Nanohybrid for Effective Mercury Ions Removal

Abstract

A one-step, eco-friendly strategy is developed to prepare sulfur/reduced graphene oxide nanohybrid (SRGO) (sulfur nanoparticles of average size ∼20 nm) using the combined effect of the polyphenolic compounds and acids present in Citrus limon juice. The prepared nanohybrid is characterized with Fourier transform infrared, Raman spectroscopy, X-ray diffraction, and transmission electron microscopy. The detailed plausible mechanism of the simultaneous reduction of graphene oxide and formation of sulfur nanoparticles is also established. The nanohybrid demonstrated a fast and efficient Hg2+ removal at around pH 6–8. The adsorption kinetics followed pseudosecond-order and the isotherm could be well described by the Langmuir model. The thermodynamic parameters (ΔG0, ΔS0, and ΔH0) are calculated from the temperature-dependent isotherms and indicate that the adsorption process is endothermic and spontaneous. The nanohybrid also has excellent reusability and high selectivity of Hg2+. Therefore, this nanohybrid has use as a promising toxic Hg2+ adsorbent.