Coal-Based Graphene Oxide for Applications in Drilling Fluids and Water Treatment

The large-scale application of existing graphene oxide (GO) is mainly limited by its high production cost and environmental problems caused by the use of a large amount of concentrated acid in the synthesis process. Optimized coal-based GO (CGO) was produced with an acid consumption reduced by 60%, yet it exhibited a comparable size (0.7 μm) and composition to samples synthesized with 100% acid usage. The material was further evaluated as a fluid loss additive in water-based drilling fluids and as an adsorbent for removal of hexavalent chromium [Cr(VI)] from aqueous solutions. In American Petroleum Institute (API) brine at 70 °C, CGO reduced filter cake thickness by 60% compared with bentonite, demonstrating superior filtration control. When functionalized with polyethylenimine (PEI) and polyanionic cellulose (PAC), CGO achieved a Cr(VI) adsorption capacity of 716 mg/g under acidic conditions. These findings establish the dual functionality of CGO in drilling fluid filtration and wastewater treatment, highlighting its promise for energy and environmental applications.