Enhanced Photocatalytic Degradation of Methyl OrangeUsing N-Doped Carbon Quantum Dots/TiO₂ NanocompositeDerived from Orange Peel

Abstract

The release of azo dyes such as Methyl Orange (MO) from the textile industry poses serious environmental problems due to their toxic, stable, and difficult-to-degrade properties. Conventional treatment methods such as adsorption, coagulation, and chemical oxidation have not been able to effectively degrade dyes, so a more efficient and environmentally friendly alternative approach is needed. Photocatalysis technology is a potential solution because it can mineralize organic compounds into harmless products. However, conventional photocatalysts such as TiO₂ NPs have limited activity in visible light due to their large band gap and high electron-hole recombination rate. This study aims to improve the photocatalytic performance of TiO₂ NPs through the integration of nitrogen-doped carbon quantum dots (NCQDs) synthesized from orange peel waste using a one-step hydrothermal carbonization method, then composited with TiO₂ NPs through a low-temperature hydrothermal reaction. Characterization was performed using SEM and SEM-EDX to analyze the morphology and elemental composition. Photocatalytic activity was tested against MO degradation under UV irradiation using a UV-Vis spectrophotometer. The results showed that the NCQDs/TiO₂ composite had a homogeneous morphology and strong chemical interaction between NCQDs and TiO₂ NPs. Degradation efficiency reached 32.5% in 90 minutes, higher than pure TiO₂ NPs by 2.5%, with an increase in the reaction rate constant from 2.81×10⁻⁴ to 4.37×10⁻³ min⁻¹ and a decrease in half-life from 41.1 h to 2.65 h. Thus, the NCQDs/TiO₂ nanocomposite based on orange peel has potential as a sustainable photocatalyst for the treatment of MO.