Kinetic and isothermal insights on phenol removal via biochar from vicia Faba stems

Phenol contamination in water poses serious risks to human health and ecosystems, necessitating low-cost and sustainable treatment options. This study investigates the preparation of biochar from Vicia Faba Stems (VFS) through direct pyrolysis at 600 °C and evaluates its efficiency in phenol removal from aqueous solutions. The produced VFS biochar (VFSB) was characterized using Brunauer-Emmett-Teller (BET) analysis for surface area, Fourier Transform Infrared (FTIR) spectroscopy for functional groups, X-ray Diffraction (XRD) for structural features, and pHPZC for surface charge. VFSB exhibited a high carbon content (83.1%), porous sheetlike structure, and surface area of 144.34 m²/g, with a pHPZC of 6. Batch adsorption experiments showed rapid equilibrium within 3 h and a maximum removal efficiency of 88.86% at pH 6. The adsorption capacity increased by 45.82% across pH 2-12, with an average uptake of 19.30 ± 3.61 mg/g. Adsorption followed pseudo-second-order kinetics, while equilibrium data fit the Freundlich isotherm, indicating multilayer adsorption. Thermodynamic analysis revealed the process is spontaneous and endothermic. Reusability tests confirmed four adsorption cycles, with efficiency decreasing from 88.86% to 47.31%. The findings establish Vicia faba stem biochar as effective for phenol removal and highlight its potential to guide future studies on affordable, reusable, and practical solutions for organic contaminant treatment.