Phytogenic rGO@ZnCo2O4 spinel nanoarchitecture for solar-induced detoxification of endocrine disruptors: interface engineering and charge carrier modulation

Abstract

Phthalate esters (PAEs), such as dibutyl phthalate (DBP) and benzyl butyl phthalate (BBP), are ubiquitous plasticizers that persist in aquatic environments, posing severe endocrine-disrupting and carcinogenic risks. This work reports a sustainable approach for solar-driven detoxification of PAEs using a phytogenically synthesized rGO@ZnCo₂O₄ nanocomposite. The composite, fabricated via a green co-precipitation method employing Azadirachta indica leaf extract, integrates reduced graphene oxide with a ZnCo₂O₄ spinel framework to enhance light absorption, surface reactivity, and charge carrier mobility. Structural, surface and optical analyses confirmed the formation of a crystalline spinel phase with rGO incorporation, yielding a high surface area and a narrowed band gap. Electrochemical studies revealed low charge transfer resistance, while radical quenching experiments identified ˙OH and O₂˙^– as the primary oxidative species. Under natural sunlight, the optimized system achieved 97% DBP and 96% BBP degradation within 180 min in model solutions and over 75% removal in industrial wastewater, with substantial mineralization confirmed by TOC analysis. LC-MS and GC-MS investigations elucidated the degradation pathways, indicating transformation into low-toxicity intermediates. The catalyst exhibited excellent stability and reusability over nine cycles without structural degradation. These results establish rGO@ZnCo₂O₄ as a next-generation, solar-active photocatalyst that unites green synthesis, exceptional stability, and real-water applicability, paving the way for sustainable, large-scale remediation of endocrine-disrupting pollutants.