Biochars impregnated with Mn oxides were produced using sugarcane bagasse (SB) modified with MnCl2 (Mn(II)-BC) or KMnO4 (Mn(VII)-BC) for the removal of the herbicide 2,4-dichlorophenoxyacetic acid (2,4-D) through adsorption. The composites were structurally and functionally characterized by various techniques, revealing an irregular surface with oxide microspheres. Elemental analyses showed the presence of manganese and oxygen in distinct proportions. X-ray diffraction identified crystalline planes of MnO and Mn3O4, as well as the amorphous carbon phase. Infrared spectroscopy confirmed Mn bonded to oxygen, and its influence on BC graphitization was corroborated by Raman spectroscopy. Thermogravimetry highlighted the oxides' influence on thermal stability, while the total number of acidic and basic functions revealed notable differences in surface chemistry. Adsorptive removal of 2,4-D was optimized under conditions of pH 2.00, dosage of 2 g L−1, and particle size smaller than 100 mesh. Adsorption equilibrium was attained after 24 and 12 hours for Mn(II)-BC and Mn(VII)-BC, respectively, with experimental maximum capacities of 36.78 and 57.19 mg g−1. Freundlich and Sips isotherms fit better for Mn(II)-BC and Mn(VII)-BC, respectively, while Elovich and pseudo-second-order kinetic models were suitable. Density Functional Theory (DFT) calculations confirm that, with decreasing pH, hydrogen bonding takes place. At higher pH,binding with Mn3O4 suggests efficacy in Mn(II)-BC composite adsorption, not observed in Mn(VII)-BC due to an additional oxide, differentiating available sites. Despite Mn leaching challenges, post-acid exposure reuse showed favorable removal percentages, indicating potential for reutilization. These findings confirm the suitability of the synthesized composites as adsorbents for the remediation of water contaminated with 2,4-D.