Engineering Fe-modified corncob biochar for the removal of methylene blue by adsorption

Iron-impregnated corncob biochar (Fe-MCCB) was synthesized from corn cob waste using FeCl 3 impregnation followed by high-temperature pyrolysis to develop a cost-effective and sustainable adsorbent to eliminate methylene blue (MB) from water. The successful integration of iron oxides (Fe 2 O 3 /Fe 3 O 4 ) onto the biochar was confirmed by XRD, SEM-EDS, and FTIR characterization. Batch adsorption experiments demonstrated that Fe-MCCB exhibited a distinct adsorption performance compared with corncob derived carbon (CCB), the Fe-MCCB removed ∼100% of MB within 5 minutes at a low dosage (100 ppm MB eliminated with 30 mg of Fe-MCCB), whereas the CCB removed only 58% under similar conditions. However, the adsorption capacity of Fe-MCCB is about 233 mg/g, which is ∼ 3 times greater than that of CCB. This increase might be due to the surface heterogeneity and the existence of active adsorption sites on Fe-MCCB. The Langmuir isotherm and pseudo-second-order kinetics were employed to explain the adsorption process. Furthermore, the thermodynamic analysis confirmed that the adsorption process is both spontaneous and endothermic. Therefore, the adsorbent, Fe-MCCB could be suggested as a viable adsorbent for the elimination of cationic dyes, especially MB, from water. • Iron impregnation increased active sites in corn cob derived biochar, Fe-MCCB • Fe-MCCB shows ultrafast methylene blue removal (100% within 5 min) • Fe-MCCB outperforms pristine CCB • Adsorption follows the Langmuir isotherm and pseudo-second-order kinetics • Fe-MCCB offers a sustainable solution for dye-contaminated wastewater