Isotherm, kinetics and thermodynamics of adsorption of Bisphenol A onto modified and unmodified corn cob: A comparative study

This study investigated the adsorption characteristics of bisphenol A (BPA) onto unmodified corn cob (UMCC) and hydrogen peroxide-modified corn cob (MCC) to evaluate their efficiency as adsorbents. The UMCC and MCC were synthesized using standard procedures, and characterized using SEM (Phenom Pro X) and FTIR (Cary 630 Agilent Technologies). Batch adsorption experiments were conducted to determine the effects varying contact time, adsorbent dosage, pH, temperature, and initial BPA concentration on the adsorbent performances. Scanning electron microscopy (SEM) images revealed that MCC had a more porous and irregular surface morphology than UMCC, contributing to its higher adsorption efficiency. The maximum BPA removal occurred at pH 6. Adsorption equilibrium was attained at contact time of 40 min at 86.25 and 60.30 % removal for both MCC and UMCC respectively. Adsorption also increased with increased temperature from 25 ⁰C to 65 ⁰C. Adsorption isotherms were analyzed using Langmuir, Freundlich, and Temkin models, with the Langmuir model providing the best fit. Kinetic studies using pseudo-first-order and pseudo-second-order, indicated that the pseudo-second-order model best described the adsorption process. Thermodynamic analysis (ΔG°, ΔH°, and ΔS°) confirmed that the adsorption was spontaneous and endothermic. These results suggest that corn cob biochar, particularly MCC, is a promising adsorbent for BPA removal from aqueous solutions.