A novel amino acid functionalized biosorbent (almond shells) for the removal of phenol from aqueous solutions: linear and nonlinear kinetic models and thermodynamic studies

In this work, phenol was adsorbed from an aqueous solution using a novel and natural adsorbent that was made from the wastes of almonds and functionalized with amino acids. FTIR, SEM, XRD, and BET methods were used to ascertain the modified biosorbent’s structural and physical properties. The effective factors on phenol removal, which include pH (2–12), adsorption dose (0–1 to 0–35 g/l), contact time (5–180 min), initial concentration (30–180 mg/l), and temperature (20–40 °C), were investigated and optimized. It was found that phenol adsorption was highly pH-dependent, reaching 90% at pH 6–8. Because of the rapid rate of adsorption, the system reached equilibrium after 90 min. The thermodynamic study discovered that the adsorption of phenol onto the biosorbent was an exothermic and spontaneous process. The pseudo-second-order model’s linear and non-linear forms both fit the kinetic data well, and the Langmuir isotherm, with a good adsorption capacity of 174.95 mg/g, had the best match with experimental data for both forms. The findings reveal that non-linear forms better describe the experimental data. After five cycles of adsorption and desorption, the biosorbent’s potential for reuse demonstrated a 90% adsorption efficiency. The results demonstrate that the adsorbent under study has a high capacity to extract phenol from water environments and can be suggested as an effective green adsorbent for removing phenol and phenolic compounds from water environments.