In this study, biochar derived from pyrolysis of Mountain Ben kernel at 450°C was modified with 1 M sulfuric acid for the removal of Congo Red dye from aqueous solutions. The surface and structural characteristics of biochar before and after modification were investigated using FE-SEM, FTIR, XRD, TEM,EDX and BET techniques. Results showed that acid modification led to the formation of sulfonic functional groups, decreaing porosity, and improved surface properties. Experimental design using the Box-Behnken method indicated that the highest dye removal efficiency (95%) was achieved at pH 5, contact time of 60 minutes, temperature of 45°C, and initial concentration of 50 ppm. Kinetic and isotherm data fitted well with pseudo-second-order and Langmuir models, respectively. Thermodynamic studies revealed that the adsorption process was spontaneous and endothermic. This study demonstrates that sulfuric acid-modified biochar can be an effective and sustainable adsorbent for the removal of anionic dyes from wastewater.and showed promising performance for practical wastewater treatment applications
