In this study, we delve into the synthesis of Conocarpus (pruning waste) biochar (C.biochar) and its composite with Iron/Manganese (Fe/Mn-C.biochar) through a modified wet impregnation method. Batch adsorption experiments were conducted to evaluate the methylene blue (MB) removal efficiency of C.biochar and Fe/Mn-C.biochar composite from aqueous solution. Several key factors were analyzed, namely, contact time, adsorbent dose, pH level, and MB concentration. Fe/Mn-C.biochar composite showcased remarkable MB removal efficiency, exhibiting a 100% removal rate, whereas C.biochar alone removed 25% MB. Adsorption capacity peaked at 97.41 mg g-1 within 60 minutes of contact time. pH values significantly influenced the adsorption process, indicating improved removal efficacy at both acidic and alkaline conditions. This improvement is potentially attributed to surface complexation and the interaction between metal ions in the composite. A kinetic study was conducted, favoring the pseudo-second-order model. MB dye removal data exhibited best fit to Temkin and D–R models that showcased chemisorption, reinforcing the suitability of the composite for successful adsorption. FTIR analysis revealed the presence of diverse functional groups in the synthesized nanocomposites. For Fe/Mn-C.biochar composites, the IR analysis exhibited peaks associated with metal-oxygen vibrations, emphasizing the incorporation of Fe and Mn. However, the peak intensities related to Fe and Mn reduced after the adsorption of MB, suggesting the creation of complexes between the dye molecules and metal oxides. Additionally, morphological studies and EDS analysis further confirmed that the weight ratio of Fe and Mn decreased in the MB-adsorbed nanocomposites. These mechanisms provide a sustainable and optimistic solution for the elimination of MB dye.