A Fe 3 O 4 /FeAl 2 O 4 composite coating via plasma electrolytic oxidation on Q235 carbon steel for Fenton-like degradation of phenol

Abstract

The Fe₃O₄/FeAl₂O₄ composite coatings were successfully fabricated on Q235 carbon steel by plasma electrolytic oxidation technique and used to degrade phenol by Fenton-like system. XRD, SEM, and XPS indicated that Fe₃O₄ and FeAl₂O₄ composite coating had a hierarchical porous structure. The effects of various parameters such as pH, phenol concentration, and H₂O₂ dosage on catalytic activity were investigated. The results indicated that with increasing of pH and phenol content, the phenol degradation efficiency was reduced significantly. However, the degradation rate was improved with the addition of H₂O₂, but dropped with further increasing of H₂O₂. Moreover, 100 % removal efficiency with 35 mg/L phenol was obtained within 60 min at 303 K and pH 4.0 with 6.0 mmol/L H₂O₂ on 6-cm² iron oxide coating. The degradation process consisted of induction period and rapid degradation period; both of them followed pseudo-first-order reaction. Hydroxyl radicals were the mainly oxidizing species during phenol degradation by using n-butanol as hydroxyl radical scavenger. Based on Fe leaching and the reaction kinetics, a possible phenol degradation mechanism was proposed. The catalyst exhibited excellent stability.

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