Asnan Rinovian, Winda Sastria, Demi Dama Yanti, Reyhan Puji Putranto, Sudibyo Sudibyo, Miftahul Huda, Heryanto Heryanto, Himawan Tri Bayu Murti Petrus, Ahmad Tawfiequrrahman Yuliansyah, Hana Safitri, Yudha Gusti Wibowo
This study presents the development of a multifunctional magnetite-AC-RM composite for efficient methyl orange (MO) removal through combined adsorption and photocatalytic processes. The composite was prepared at a 2:2:1 wt ratio (AC:RM:Fe₃O₄) via co-precipitation. XRD and FTIR analyses confirmed the coexistence of Fe–O, Al–O, and Si–O functional groups, while BET results showed a surface area of 558.58 m² g⁻¹, higher than AC-RM (442.780 m²/g), indicating partial pore reopening after Fe₃O₄ incorporation. SEM–EDS analysis revealed a uniform nanoparticle distribution, and VSM confirmed strong ferromagnetic behavior, allowing rapid magnetic recovery. The magnetite-AC-RM composite exhibited superior adsorption performance with over 90% MO removal within 50 min at pH 2. The adsorption equilibrium followed the Langmuir isotherm, suggesting monolayer adsorption on a homogeneous surface, while kinetic data fitted well to the pseudo-second-order model (R² > 0.99), indicating chemisorption as the dominant mechanism. Thermodynamic parameters (ΔG° = −3954 to −1499 J/mol, ΔH° = −41.15 kJ/mol, ΔS° = −122.75 J/mol K) confirmed that the process was spontaneous and exothermic. Overall, the synergistic integration of activated carbon, red mud, and Fe₃O₄ produced a highly reactive, magnetically recoverable, and thermodynamically favorable adsorbent. The magnetite-AC-RM composite offers a low-cost, efficient, and sustainable solution for removing anionic dyes such as methyl orange from aqueous solution. © 2026 The Author(s). Published by Elsevier Ltd. This is an open access article under the CC BY license. http://creativecommons.org/licenses/by/4.0/
Research Center for Mineral Technology, National Research and Innovation Agency (BRIN), Lampung Selatan, 35361, Indonesia; Department of Chemistry, Institut Teknologi Sumatera, Lampung, 35365, Indonesia; Department of Physics, Hasanuddin University, Makassar, 90245, Indonesia; Department of Chemical Engineering (Sustainable Mineral Processing Research Group), Faculty of Engineering, Universitas Gadjah Mada, Jl. Grafika 2, Yogyakarta, 55281, Indonesia; Department of Chemistry, Universitas Islam Negeri Raden Inten Lampung, Lampung, 35131, Indonesia; Sustainable Mining and Environmental Research Group, Department of Mining Engineering, Institut Teknologi Sumatera, Lampung, Indonesia