Solar-driven photocatalytic degradation of methylene blue and hydrogen production using an eco-friendly HAp/Fe2O3 heterojunction

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Recycling steelmaking by-products and organic waste remains a major environmental challenge. In this study, iron oxide (Fe 2 O 3 ) was recovered from blast furnace dust waste (BFDW), while hydroxyapatite (HAp) was produced from seashell waste. HAp/Fe 2 O 3 heterojunctions containing different Fe 2 O 3 loadings (20%, 40%, and 60%) were then prepared to evaluate their photocatalytic performance under sunlight. The resulting materials were characterized by XRD, FE-SEM/EDS, TEM, N 2 adsorption-desorption, UV-Vis, PL, XPS, and electrochemical analyses. Photocatalytic degradation tests using methylene blue (MB) showed that the heterojunction containing 40% Fe 2 O 3 exhibited the best performance, removing nearly 75% of the contaminant while retaining its structural stability after five reuse cycles. Hydrogen production exceeded 25 μmol g −1 . Charge-carrier density and bandgap energy were key factors governing MB degradation, whereas the band positions of HAp and Fe 2 O 3 within the heterojunction played a critical role in photocatalytic hydrogen production.