Removal of Copper and Zinc Using Biochar from Wild Sugarcane (Saccharum spontaneum L.): Sustainable Heavy Metal Removal from Aqueous Media

Water contamination by heavy metals is a major global concern resulting from anthropogenic activities and natural geological processes. Their removal and recovery are important for protecting water resources and addressing the depletion of critical metals. This study evaluated wild sugarcane (WSC) biochar as an adsorbent for Cu2+ and Zn2+ removal from aqueous media, providing a potential valorization pathway for this biomass. WSC biochars were produced at airflow rates of 8, 12, 16, and 20 L min−1 and characterized by Fourier-transform infrared spectroscopy, Raman spectroscopy, and X-ray diffraction. Cu2+ and Zn2+ adsorption data were analyzed using the Langmuir, Freundlich, and Temkin isotherm models. The characterization results indicated the presence of oxygen-, carbon-, and hydrogen-containing surface functional groups that may contribute to metal adsorption. Under the investigated batch conditions, BP12 achieved removal efficiencies of approximately 70–90% for Cu2+ and 83–94% for Zn2+. For BP12, the Langmuir expression yielded an apparent maximum Cu2+ adsorption capacity of 42.3 mg g−1, while Zn2+ uptake reached 26.9 mg g−1 and was best described by the Freundlich expression among the models evaluated; the Langmuir model did not converge for Zn2+. These results demonstrate the potential of WSC biochar for Cu2+ and Zn2+ removal from aqueous media and support the valorization of wild-sugarcane biomass as a minimally processed adsorbent.