Modeling and Optimization of Argon-Activated Electrohydraulic Plasma Discharge Process for p-Nitrophenol Remediation

This study presents a statistical modelling and optimization of an argon-activated electrohydraulic plasma discharge (EHPD) process for the degradation and mineralization of p-nitrophenol (p-NP) in water. The EHPD reactor design incorporated dual dielectric plates to initiate plasma discharge through a central orifice. A fractional factorial design (FFD) was first employed to screen four operating variables, including argon flow rate, pH, applied power, and persulfate dosage, on the p-NP degradation efficiency and energy yield, revealing argon flow rate and applied power as two identified, significant process factors. These were then further optimized using a central composite design (CCD) and response surface methodology (RSM), with the optimal operating condition found to be 2.73 L/min and 128.6 W for argon flow rate and applied power, respectively. Under the optimal operating conditions, 10 min treatment of 50 mg/L p-NP achieved a degradation efficiency of 94.2% and 75.8% total organic carbon (TOC) removal, along with a first-order reaction rate constant of 0.296 min−1 and an energy efficiency of 0.22 g/kWh. The reaction mechanism for p-NP degradation by EHPD was proposed and confirmed with optical emission spectroscopy and radical scavengers. The optimized EHPD process proved both effective and energy-efficient in treating p-nitrophenol, highlighting its potential as a scalable and sustainable plasma-based technology for eliminating persistent organic pollutants and promoting greener water treatment practices.