Enhanced methylene blue degradation by graphene oxide-encapsulated nano zero-valent iron composites: Optimization, mechanistic insights, and environmental implications

Abstract

Methylene blue (MB) in textile dye wastewater poses a significant environmental challenge due to its high chemical stability and resistance to biodegradation. This study investigates the use of a novel graphene oxide-encapsulated nano zero-valent iron (GO/nZVI) composite for the efficient and sustainable degradation of MB. The GO/nZVI composite was synthesized via hydrothermal co-precipitation and self-assembly methods and characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). Under optimized conditions, the composite achieved an impressive 99.99 % degradation of MB within 40 min, demonstrating substantial improvements in stability and reusability. The composite retained over 84.5 % of its catalytic activity after five cycles, underscoring its potential for practical wastewater treatment applications. The optimization of reaction conditions through response surface methodology (Box-Behnken design, BBD) facilitated the formation of a core-shell structure, which significantly enhanced electron transfer and radical generation, crucial for MB oxidation. Radical quenching experiments confirmed hydroxyl radicals (·OH) as the primary active species, and gas chromatography-mass spectrometry (GC-MS) analysis elucidated the degradation pathway. This study presents a scalable and environmentally friendly solution for the treatment of recalcitrant organic pollutants, marking a significant advancement in water purification technologies.