<![CDATA[Water pollution caused by synthetic dyes such as Congo red (CR) and methylene blue (MB) is a serious environmental problem. This study developed magnetic activated carbon based on siwalan peel (Fe3O4/AC) as a sustainable adsorbent for removing CR and MB and enabling convenient magnetic separation. The Fe3O4/AC material was synthesized by chemically activating siwalan peel biomass, followed by in situ co-precipitation of magnetic particles. We characterized the materials using BET, XRD, FT-IR, and SEM-EDX. Batch adsorption experiments evaluated dye removal under varying operational parameters: adsorbent dose (0.25–1.25 g), contact time (10–100 minutes), and pH (2, 6, and 10). We analyzed dye concentrations before and after adsorption using UV-Vis spectrophotometry. The maximum removal efficiencies for CR and MB were 95.3% and 94.8%, respectively, at a contact time of 80 minutes and an adsorbent dose of 1.25 g. Adsorption data were fitted to linear kinetic (pseudo-first-order, pseudo-second-order, and intraparticle diffusion) and isotherm (Freundlich, Langmuir, and Temkin) models, which confirmed pseudo-second-order kinetics and the Langmuir isotherm model. These models confirmed pseudo-second-order kinetics and the Langmuir isotherm. Characterization results before and after adsorption indicated a chemisorption mechanism, complemented by electrostatic attraction. The results demonstrate that the biomass-derived Fe3O4/AC is an effective and promising adsorbent for dye wastewater treatment.]]>
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