Kinetic modeling of the removal of phenolic compounds from olive mill wastewater by hierarchical zeolite/carbon nanotubes: Isotherm, kinetics, and thermodynamic

Abstract

ABSTRACT In this study, plain zeolite (ZSM5) and hierarchical zeolite (H-ZSM5) were synthesized as efficient adsorbents for the removal of polyphenolic/antioxidant compounds from olive mill wastewater (OMW). The XRD and FTIR results confirmed the successful synthesis of ZSM5 zeolites. SEM images and BET demonstrated that H-ZSM5 possessed a markedly greater surface area of 337.99 m2/g in contrast to ZSM5 (162.84 m2/g). For H-ZSM5, the values determined for pore volume, total volume, and pore diameters are 77.655 cm3 g−1, 0.1844 cm3 g−1, and 2.1826 nm. The absolute zeta potential values varied between 5.36 ± 1.21 and − 46.41 ± 1.32 mV, with the peak absolute value of − 46.41 ± 1.32 mV occurring at pH 4. The optimal conditions for the removal of phenolic compounds, achieving an efficiency exceeding 90%, were identified as a pH of 4, an adsorbent dosage of 50 mg, and a contact duration of 90 minutes. The adsorption isotherm was found to align with the Langmuir model rather than the Freundlich model, indicating a monolayer adsorption capacity of 48.7 mg/g. Kinetic studies were consistent with a pseudo-first-order model (R2 >0.99). Ultimately, the thermodynamic analysis suggested that the adsorption of OMW onto ZSM5 is both spontaneous and governed by a physisorption mechanism.