Characterization and upgrading of a new Mozambican graphite ore for the production of graphene materials

Abstract

This study investigates the mineralogical characteristics of Mozambique graphite, with a particular focus on the Ancuabe deposit, located in the Cabo Delgado Province of northern Mozambique. Analysis of the mineralogy of the ore shows the presence of large flakes of graphite in parallel veinlets that follow the strike of the main foliation and in a disseminated form with structures that feature massive, highly foliated schists. The ore's mineral composition, as determined by XRF is dominated by SiO₂ (∼75 %), containing <0.5 wt% of critical raw materials as Ti, V_, Ni, and Cr. Approximately 30 % of the ore is carbon, which is attributed to graphite as determined by XRD, Raman spectroscopy and optical microscopy.

The potential of these graphite deposits to serve as a raw material in the production of graphene was examined. For that, the graphite ore was purified through size fractionation, employing standard graphite purification methods. The total graphite, along with the graphite fractions, were utilised as raw material for the preparation of graphene oxide (GO) via standard chemical oxidation and exfoliation methods. The monolayers of GO obtained from the whole graphite fraction exhibited the typical oxidation of basal planes and edges but were obtained at a low yield. However, this yield was enhanced by subjecting the three graphite fractions to an optimized procedure, which involved employing longer reaction times with the larger-sized graphite fractions. Consequently, the overall process yield was significantly increased, and it was also possible to obtain GO sheets of controlled lateral size, ranging from very large to small.