Development of membranes from coal-derived Graphene Oxide for organic dye removal in wastewater treatment

Abstract

Coal, though abundant, faces increasing restrictions due to its environmental impact as a fossil fuel. However, its carbon-rich nature presents opportunities for sustainable valorisation. This study explores the transformation of Botswana’s coal fines, an underutilized waste product, into valuable carbon nanomaterials, specifically graphite and graphene oxide (GO). Graphitization of coal fines was followed by GO synthesis using an optimized version of the improved Hummers’ method, producing highly hydrophilic GO with an oxygen content of up to 40.7 %. Comprehensive characterization techniques, including FTIR, Raman spectroscopy, and SEM-EDX, confirmed the compositional and morphological integrity of the graphite and GO. The synthesized GO was then used to fabricate membranes via a dead-end filtration method, with varying GO concentrations. These membranes demonstrated exceptional performance in removing Methylene Blue dye, achieving up to 99.8 % rejection, porosity of 13.2 %, and flux ranging from 0.62 to 17 L/m2.hr. Additionally, a fouling resistance of 0.087 m2.hr.bar/L indicated strong potential for long-term application. The findings highlight a cost-effective, environmentally friendly pathway for converting coal waste into purposeful GO membranes, designed for advanced water purification applications through selective dye removal mechanisms such as π-π interactions.