Magnetic Carbon Quantum Dots/Iron Oxide Composite Based on Waste Rice Noodle and Iron Oxide Scale: Preparation and...

To provide an economical magnetic photocatalyst and introduce an innovative approach for efficiently utilizing discarded waste rice noodle (WRN) and iron oxide scale (IOS), we initially converted WRN into carbon quantum dots (CQDs) using a hydrothermal method, simultaneously calcining IOS to obtain iron oxide (FeO_x). Subsequently, we successfully synthesized a cost-effective, magnetic CQDs/FeO_x photocatalytic composite for the first time by combining the resulting CQDs and FeO_x. Our findings demonstrated that calcining IOS in an air atmosphere enhanced the content of photocatalytically active α-Fe₂O₃, while incorporating WRN-based CQDs into FeO_x improved the electron-hole pair separation, resulting in increased O₂ reduction and H₂O oxidation. Under optimized conditions (IOS calcination temperature: 300 °C; carbon loading: 11 wt%), the CQDs/FeO_x composite, utilizing WRN and IOS as its foundation, exhibited exceptional and reusable capabilities in photodegrading methylene blue and tetracycline. Remarkably, for methylene blue, it achieved an impressive degradation rate of 99.30% within 480 min, accompanied by a high degradation rate constant of 5.26 × 10^-3 min^-1. This composite demonstrated reusability potential for up to ten photocatalytic cycles without a significant reduction in the degradation efficiency, surpassing the performance of IOS and FeO_x without CQDs. Notably, the composite exhibited strong magnetism with a saturation magnetization strength of 34.7 emu/g, which enables efficient and convenient recovery in photocatalytic applications. This characteristic is highly advantageous for the large-scale industrial utilization of photocatalytic water purification.