Mechanochemical conversion of graphite to highly Cross-linked alkynyl carbon material as excellent mercury (II) sorbent

Abstract

Mechanochemical graphite oxide (MGO) was prepared by ball milling graphite, KMnO4 and KHSO4, and an alkynyl cross-linked MGO (AMGO) was obtained via its mechanochemical reaction with CaC2. Their structure and composition were characterized by various techniques, and the adsorption performance was studied for Hg (II) aqueous solution. MGO is composed of edge oxidized graphite sheets with specific area of 42.8 m2⋅g−1 along with metallic luster, higher crystallinity, more complete conjugation structure and better water dispersibility compared to commercial GO prepared via Hummers method. AMGO is a micro mesoporous material with rich alkynyl and oxygenated functional groups, high specific area (~622.1 m2∙g−1), and excellent Hg (II) adsorptivity and reusability. Its saturated adsorption is about 923 mg-Hg⋅g−1 being one of the best carbon sorbents due to its rich alkynyl and oxygenated functional groups, highly cross-linked layered structure, and micro meso-porosity. The adsorption isotherm of AMGO conforms to the Freundlich model and the adsorption rate follows the pseudo-second order kinetic model. We proposed here a novel method to reduce GO to a highly cross-linked graphite material with hierarchical pores and alkynyl cross-linked layered structure, which sheds a light to the development of 3D carbon materials by using CaC2 as an alternative reductant and cross-linker.