Degradation of Methylene Blue in Water via Peroxymonosulfate Activation Using Exfoliated Banana Peel Hydrochar as Catalyst

ABSTRACT The increasing discharge of synthetic dyes such as methylene blue (MB) into aquatic systems poses serious environmental and public health risks due to persistence, toxicity, and resistance to conventional treatment methods. Peroxymonosulfate (PMS)‐based advanced oxidation processes have gained attention for dye degradation, yet practical use depends on catalysts that are active, sustainable, and cost‐effective. This study reports the synthesis and application of exfoliated banana peel hydrochar (E‐BPHC) as a metal‐free catalyst for PMS‐driven MB degradation. Banana peel waste was converted into hydrochar via hydrothermal carbonization, followed by microwave‐assisted chemical exfoliation to generate a porous carbon framework. Field emission scanning electron microscopy and Fourier transform infrared spectroscopy revealed a transition from a dense morphology to an open, sponge‐like network enriched with aromatic surface functionalities. A response surface model showed strong agreement with experimental results ( R 2 = 0.9905). Under optimized conditions, 99.45% MB removal was achieved. PMS activation on the E‐BPHC surface likely generates sulfate and hydroxyl radicals that degrade MB through N‐demethylation and chromophore cleavage. Kinetic analysis followed second‐order behavior ( k 2 = 0.1477 L mol − 1 min − 1 ). Relative to metal‐based catalysts, E‐BPHC offers high activity without metal leaching, demonstrating the promise of waste‐derived porous carbons for sustainable wastewater treatment.