80 - Applications of Graphene Sand Composites in Water Treatment

Water scarcity and the occurrence of chemicals of emerging concern (CECs) are making the world in need of renewable water resources. The implementation of low-cost, environmentally friendly, and effective treatments represents a valuable solution. Slow sand filtration is an affordable and easy method to filter water with a few weaknesses such as clogging and the inability to remove CECs. To overcompensate these limited weaknesses, graphene-coated sand was studied. Ottawa, concrete, and masonry sand were used, using a reduction method to transform a coating of sugar into elemental carbon in N2 atmosphere at temperatures reaching 750°C. The synthesized materials were activated using sulfuric acid. To verify the effectiveness of the coating process used, a digital microscope, Raman spectroscopy, scanning electron microscope, and energy-dispersive X-ray spectroscopy were implemented. Flow-through columns were used to evaluate the ability of the different materials to remove turbidity, bacteria, COD, nitrate, and CECs using treated municipal wastewater (pre-UV). Due to the additional expense related to the activation process, columns packed with graphene sands were tested alongside the non-activated ones as well as columns containing the raw sands. Digital microscopy indicated Ottawa sand's inferior coating to concrete and masonry sands. Raman spectroscopy showed complete sugar graphitization. SEM highlighted 10 nm carbon sheets. Total coliforms and E. coli were consistently removed (up to 99%). COD saw moderate removal ( <65%), while nitrate and CECs exhibited limited removal ( <30% and <20% respectively).