Modeling and optimizing phenol degradation in aqueous solution using post discharge DBD plasma treatment

The present study was carried out to optimize the treatment process of phenol in aqueous solution using dielectric barrier discharge (DBD) plasma and experiments were designed by using response surface methodology and central composite design (RSM-CCD). The study explores the efficacy of a DBD plasma system that mainly generates ozone in the degradation of phenol in standard aqueous solutions at concentrations simulating those found in industrial wastewater from operating units in Iraqi oil refineries. The study investigates the influence of key operating factors, namely, applied voltage (Volt), air flow rate (L/min), initial phenol concentration (ppm), and treatment time (min) aiming to identify the removal efficiency optimal conditions. According to the analyzed results of RSM, the experimental data is best fitted with a model of the quadratic polynomial with regression coefficient values of more than 0.9. After 10 minutes, almost 50% of phenol with an initial concentration of 4 ppm was eliminated. Optimal degradation of phenol was achieved by elevating the voltage from 10,000 to 30,000 V. The % phenol degradation increased from 0 to 82%. With the right conditions—an initial phenol concentration of 2.47 ppm, a flow rate of 0.50 L/min, a time of 14.53 min, and an applied voltage of 29,986.38 volts—under these optimal conditions, a phenol removal efficiency of 97.5% was achieved. The Pareto chart confirmed that the time and the applied voltage have the greatest influence on the % phenol degradation. Additionally, we showed that DBD had the highest removal efficiency with hydroxyl radical playing the major role in the degradation while O 3 -DBD also gave rise to relatively high efficiency with ozone making an important contribution. The findings of this study underscore the immense potential of non-thermal discharge plasma technology and the utilization of RSM in enlightening the optimization of advanced oxidation processes for effective wastewater treatment.