Fenton Catalytic Degradation of Rhodamine B by Zero-Valent Iron/Alumina Catalyst

Rhodamine B (RhB) is a typical xanthene-based cationic dye. Its widespread application has brought serious safety and environmental risks. Heterogeneous Fenton systems based on zero-valent iron (Fe⁰) are promising for RhB degradation. However, bare Fe⁰ suffers from severe agglomeration and surface passivation. In this study, alumina with a large pore volume and high specific surface area was employed as a support to enhance Fe⁰ dispersion and stability. The catalyst was prepared via a glucose-assisted carbothermal reduction method, and the formation of Fe⁰ was confirmed by X-ray diffraction and electron microscopy analyses. Under optimal conditions (pH = 3.58, catalyst dosage = 0.8 g·L^-1, H₂O₂ = 10 mM), 10 mg·L^-1 RhB was completely degraded within 25 min, with a pseudo-first-order rate constant of 0.432 min^-1. This exhibits a faster degradation rate and efficiency advantage. Radical quenching experiments indicated that hydroxyl radicals (•OH) were the dominant reactive species, while singlet oxygen (¹O₂) also contributed to the degradation process. Two primary degradation pathways, including N-deethylation and hydroxylation, were identified. The catalyst showed moderate reusability with slight deactivation after repeated cycles. This study demonstrates that tailoring the pore structure of alumina supports is an effective strategy to enhance Fe⁰ dispersion, mass transfer, and catalytic performance in heterogeneous Fenton systems.