Mordenite zeolite synthesized hydrothermally for treatment of real petroleum refinery effluent: RSM optimization, kinetics, and isotherm studies

Abstract

Petroleum refinery wastewater is one of the most challenging industrial effluents due to its high chemical oxygen demand (COD), biochemical oxygen demand (BOD), and turbidity. In this study, mordenite zeolite was successfully synthesized via the hydrothermal method and applied as an adsorbent for the treatment of real petroleum refinery wastewater from Kermanshah refinery, Iran. The synthesized zeolite was characterized using XRD analysis. Central Composite Design (CCD) under Response Surface Methodology (RSM) was employed to investigate and optimize the effects of operational parameters, including pH (4–10), contact time (30–150 min), and adsorbent dosage (2–10 g/L) on the removal efficiencies of COD, BOD, and turbidity. The quadratic models showed high accuracy with R² values of 0.98, 0.97, and 0.99 for COD, BOD, and turbidity removal, respectively. Under optimum conditions (pH = 6.2, contact time = 114 min, adsorbent dosage = 8.3 g/L), the removal efficiencies reached 78.4% for COD, 84.6% for BOD, and 92.1% for turbidity. Adsorption kinetics followed the pseudo second order model, and equilibrium data were well described by both Langmuir and Freundlich isotherms, with maximum adsorption capacity (qₘₐₓ) of 68.5 mg/g for COD. The results demonstrate that hydrothermally synthesized mordenite zeolite is a cost-effective and efficient adsorbent for real petroleum refinery wastewater treatment.