Freundlich Isotherm-Based Biosorption of Pb(II) and Cu(II) Using Agro-Industrial Waste-Derived Biochar: Influence of Optimum Operational Parameters and Surface Functionalities Aninda Tifani Puari*
Department of Agricultural and Biosystem Engineering, Faculty of Agricultural Technology, Universitas Andalas, West Sumatera, Indonesia.
*anindapuari[at]ae.unand.ac.id
Abstract
This study evaluated the biosorption performance of biochar (ECH-BC), synthesized from agro-industrial waste, for the removal of Pb(II) and Cu(II) ions from aqueous solutions. The biochar was characterized using Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM-EDX), and surface area analysis to determine its structural and chemical properties. FTIR spectra revealed prominent hydroxyl, carbonyl, and carboxyl functional groups, which exhibited notable shifts and intensity changes after biosorption, indicating their involvement in metal ion binding through complexation and electrostatic interactions. SEM images displayed a highly porous structure with irregular cavities, while EDX analysis confirmed the presence of Pb and Cu peaks post-biosorption, accompanied by a reduction in the relative abundance of native elements such as C and O. Batch adsorption experiments were conducted at varying initial metal concentrations, and the equilibrium data were fitted to Langmuir and Freundlich isotherm models. The Freundlich model exhibited a higher correlation coefficient for both Pb(II) and Cu(II), indicating that adsorption occurred predominantly on a heterogeneous surface with multilayer coverage. The optimum condition of Pb(II) were 6, 0.15 g, and 180 minutes, while the conditions of Cu (II) were 6.9, 0.05, 134.92, respectively. The enhanced performance is attributed to the biochar^s abundant functional groups and porous morphology, which collectively promote metal ion uptake. These findings highlight the potential of ECH-BC derived from agro-industrial residues as an efficient, cost-effective, and environmentally sustainable biosorbent, aligning with circular economy principles and providing a viable approach for heavy metal remediation in wastewater treatment.
