Modified biomass is a green and renewable sorbent to remove organic pollutants in water. In this study, an efficient bio-based adsorbent was obtained by Fenton-like pretreatment of peanut hull with FeOCl, which can be used to efficiently remove methylene blue from water. The adsorption experiment showed that under the conditions of 25°C, pH 6.0, MB concentration of 100 mg·L⁻¹ and adsorbent dosage of 1.0 g·L⁻¹, the adsorption equilibrium could be achieved within 6 min, with MB removal rate of 85.1% and maximum adsorption capacity of 132 mg·g⁻¹, which was much higher than that of untreated peanut hull (64 mg·g⁻¹). Material characterization showed that Fenton-like pretreatment resulted in the surface morphology change and pore structure formation of peanut hull, and the specific surface area increased significantly, which was an important reason for rapid adsorption. The adsorption mechanism showed that the adsorption of methylene blue followed pseudo second-order models, and conformed to Redlich-Peterson and Langmuir models. According to the thermodynamic analysis results, it is concluded that the adsorption process is endothermic and spontaneous. Adsorption mechanism includes hydrogen bonding, static electricity and van der Waals force. GRAPHICAL ABSTRACT