Enhanced removal of petroleum pollutants from petrochemical wastewater using ferric sulfate nano-coagulants: experimental evaluation and modeling

Oil pollution in wastewater poses a significant environmental threat due to its toxicity to aquatic ecosystems and potential risks to human health. This study explores the use of ferric sulfate nanoparticles as an advanced coagulant for treating effluents from the Shiraz Petrochemical Complex. A two-stage reactor system was employed to optimize treatment conditions, focusing on mixing speed, coagulant dosage, and the use of coagulant aids (NaOH and Na₂CO₃). Optimal performance was observed at a mixing speed of 120 rpm in the primary reactor, reducing chemical and biological oxygen demand (COD and BOD) to 19 mg/L and 6.5 mg/L, respectively. Removal efficiencies for petroleum hydrocarbons, oily compounds, and aromatic substances improved with increased coagulant dosage, achieving up to 62.8%, 4%, and 5.2% improvement, respectively. Zeta potential analysis revealed decreased electrostatic repulsion at higher dosages, with values reaching − 13.4 mV. A second-order polynomial regression model demonstrated excellent predictive accuracy (R² = 0.9999), validating the experimental findings. These results underscore the potential of nano-enhanced coagulation for industrial wastewater treatment.