Sol-gel synthesized CuO nanoparticles supported on reduced graphene oxide nanocomposite for sunlight-catalytic methylene blue degradation and nanofluid applications.

The presence of organic dye contaminations has been a major concern in recent years. Metal oxides and their composite have created a huge interest in the degradation of organic pollutants utilizing particularly direct sunlight has been investigated recently. This study demonstrated a facile sol-gel-assisted synthesis of copper oxide (CuO) nanoparticles (NPs) dispersed on reduced graphene oxide (rGO) composite for solar light-assisted removal of methylene blue (MB) dye and nanofluids applications. Transmission electron microscopic images displayed that the CuO NPs, which had a mean diameter of 30 nm, were dispersed on the rGO surface. The composite photocatalyst demonstrated a 92% degradation rate for MB dye. In addition, the study examined the impact of photocatalyst quantity, concentration of MB, and pH on MB degradation. A study on radical scavenging demonstrated that the generation of superoxide radicals was the main factor responsible for the degradation of MB. The stability test demonstrated that the degradation efficiency of the MB did not exhibit a substantial reduction after four consecutive cycles. Furthermore, the thermal conductivity of CuO/rGO nanofluids depends on the particle concentration and temperature. The thermal conductivity enhancement of the nanofluids with a 0.07% volume fraction at 65 °C in deionized water and ethylene glycol was found to be 47.5% and 30.3%, respectively. Highlights: Sol-gel synthesis of CuO/rGO composite for photocatalysis and nanofluids. The composite photocatalyst degraded 92% of MB dye in 90 min under sunlight. The ROS study confirmed that O₂^–• was the reason for MB dye degradation. The highest thermal conductivity was observed with a volume fraction of 0.07%. [ABSTRACT FROM AUTHOR]