Green Synthesis and Catalytic Characterisation of Iron Oxide Nanoparticles from Banana Peel Extract for Wastewater Remediation

Green synthesis routes using plant extracts offer an environmentally benign alternative to conventional chemical precipitation methods for producing metal oxide nanoparticles, and banana peel is an abundant agro-waste in South West Nigeria. This study reports the green synthesis of iron oxide nanoparticles using banana peel extract from plantain sourced in Ogun State as the reducing and capping agent. Iron (III) chloride solution at varying concentrations was mixed with banana peel aqueous extract at different volume ratios, and the reaction was conducted at pH 8 to 11. The synthesised nanoparticles were characterised by XRD, FESEM-EDS, TEM, FTIR, VSM, and UV-Vis spectrophotometry. Catalytic performance was evaluated by heterogeneous Fenton oxidation of methylene blue and tetracycline antibiotic in aqueous solution at varying hydrogen peroxide concentration, catalyst dose, initial pollutant concentration, pH, and temperature. XRD and TEM confirmed the formation of maghemite and magnetite phases with average particle size of 14.7 nm. The catalyst achieved 96.4% methylene blue degradation within 60 minutes at pH 3, 50 mg/L hydrogen peroxide, and 0.5 g/L catalyst. Tetracycline degradation of 87.3% was achieved within 90 minutes under optimised conditions. Reactive hydroxyl radical was identified as the dominant oxidant by radical quenching experiments. Catalyst stability over five consecutive runs showed less than 8% activity loss, with minimal iron leaching (0.4 mg/L) confirming heterogeneous reaction dominance. The study supports banana peel-derived nanoparticles as a sustainable catalyst for advanced wastewater treatment in Nigeria. Keywords: green synthesis, iron oxide nanoparticles, Fenton oxidation, wastewater, banana peel