adsorptive removal of sunset yellow dye using magnetic biochar

Synthetic azo dyes are among the major pollutants found in industrial wastewater and are difficult to remove due to their chemical stability. sunset yellow (sy), widely used in food products, raises environmental concerns because of its persistence and potential adverse effects. in this study, lemon pulp waste was converted into biochar through pyrolysis at 300 °c and further modified with fe3o4 to improve its adsorption ability. batch experiments were performed at an initial dye concentration of 50 mg/l, an adsorbent dosage of 0.1 g, neutral ph, and room temperature. the modified biochar reached a maximum adsorption capacity of 25 mg/g, while the unmodified sample showed only 1.74 mg/g. fe-sem images revealed the transformation from a dense surface in the raw biochar to a more open and textured structure after activation. ftir results confirmed the presence of oxygen-containing functional groups and fe-o vibrations involved in dye binding. these findings show that magnetically modified lemon-based biochar can serve as a low-cost adsorbent for removing sy from aqueous solutions.