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This investigation aims to implement the fixed bed column method to eliminate methylene blue (MB) by H₃PO₄ treated eucalyptus leaves (PEUL). PEUL is characterized using SEM, XRD, FTIR, solid-state NMR, and BET surface areas. Initially, the batch experiments revealed that the maximum percentage removal of MB is obtained at pH 8. The column experiments are performed at pH 8 and 25 °C with a varying bed height (5–9 cm), rate of flow (10–20 ml min⁻¹), and MB concentration (10–50 mg L⁻¹). The column experimentation shows that the breakthrough and exhaustion times rise with the bed's height but decrease with the increasing rate of flow and MB concentration. Different well-known kinetic models are tested with the experimental results, which display that the Thomas model (R² = 0.9969, χ² = 0.0005) fits better than others, so it is appropriate for the scale-up design. The Langmuir isotherm model (R² = 0 …