Proceedings of the 2022 Mississippi Water Resources Conference

Year: 2022 Authors: Nusair A., Alkhateb H., D'Alessio M.

Water scarcity and the occurrence of chemicals of emerging concern (CECs) are making the world in need of safe and renewable water resources. Slow sand filtration (SSF) represents an affordable but effective method to filter water. However, SSF has a few weaknesses such as clogging and the inability to effectively remove CECs. The goal of this study was to investigate the ability of graphene-coated sand to overcompensate these limitation. Three types of sand, Ottawa, concrete, and masonry, were used. Graphine-coated sand was obtained using a reduction method to transform a coating of sugar into elemental carbon in N2 atmosphere at temperatures reaching 750℃ followed by activation with sulfuric acid. Vertical flow-through columns were used to evaluate the ability of the different materials to remove turbidity and bacteria. Due to the additional expense related to the activation process, columns packed with graphene-coated sands were tested alongside the non-activated ones as well as columns containing the raw sands. A digital microscope as well as Raman spectroscopy, scanning electron microscope (SEM), and energy-dispersive X-ray spectroscopy were implemented to verify the effectiveness of the coating process.

The digital microscope revealed that rounded (Ottawa sand) particles were coated less efficiently than sub-angular and angular particles (concrete and masonry sand). The Raman spectroscopy revealed the formation of G and D bands in all three graphitized sands suggesting complete graphitization of the sugar and the presence of defect site necessary for the adsorption of contaminants. Furthermore, the peak intensity was 30% higher in concrete and masonry graphitized sands compared to Ottawa graphitized sand. SEM revealed the formation of carbon sheets 10 nm thick and EDS results backed up the geological identification of the sands with quantification of the elements. In the presence of high turbidity (average: 250 NTU), graphene-coated Ottawa sand, not only achieved higher turbidity removal than the raw Ottawa sand but also experienced less severe clogging. Higher bacterial removal was achieved with graphene-coated sands, in particular Ottawa and masonry, compared to the corresponding non-coated sands.