Application of Graphene and Graphene Compounds for Environmental Remediation

Graphene is a sp(2) hybridised single atom thick carbon material that has attracted enormous scientific attention over the years due to its unique mechanical, thermal and electronic properties. Its outstanding ability for excellent mobilisation of charge carriers combined with the presence of carboxyl, hydroxyl and other functional groups after oxidation or reduction reactions has equipped it with the means to tackle environmental pollutants. Over the years, graphene has been hybridised with metals and metal compounds such as magnetite, calcium alginate, silicon dioxide, zinc oxide, zinc sulphide, titanium dioxide, silver phosphate and zeolites. Such hybrids have proved useful for removing organic dyes from aqueous solutions under a range of pH and temperatures values. Pollutants such as methylene blue (MB), methyl orange (MO), rhodamine B, rhodamine 6G and 1-naphthol have either been adsorbed or photodegraded under UV or visible light spectrums. Inorganic pollutants such as chromium, arsenic, uranium, mercury, fluoride, antimony, zinc, perchlorate and copper have also been remediated by graphene and graphenic oxide. They have also been reported to simultaneously remove organic and inorganic contaminants from water. Desorption studies have proved favourable for almost all cases testifying to the reusability of graphene. In addition to the usefulness of graphene as an adsorbent, a case of membrane filtration involving polysulfone membranes mixed with graphene has been discussed. From the viewpoint of environmental chemistry this paper delineates various approaches that have been successfully utilised over the years to modify and enhance graphene's potential to aid in the clean-up of water along with a close look at its underlying mechanisms.