In this study, the physicochemical properties of modified biochar using different methods, such as physical (CO₂, steam) and chemical (KOH and H₃PO₄) methods, were estimated by X-ray diffraction, N₂ adsorption-desorption, field-emission scanning electron microscopy equipped with energy-dispersive X-ray spectroscopy, and Fourier transform infrared spectroscopy. The performance of chars was evaluated using a Cr adsorption performance test. Among various chars modified in this study, CHC-P modified by H₃PO₄ showed the highest chromium adsorption efficiency. The adsorption efficiency was affected by the high nano-porosity, large surface area, and surface oxygen-containing functional groups.