Analysis of an open-air argon plasma driven photo-Fenton reaction for degradation of synthetic dyes: Optical emission spectroscopy and statistical design optimization

Abstract

This research was designed to treat synthetic dyes in aqueous solutions using an atmospheric pressure argon plasma-driven photo-Fenton process. Optical emission spectroscopy and statistical optimization of the argon plasma-driven photo-Fenton process parameters were performed to efficiently degrade synthetic dyes. Lab-scale experiments were performed utilizing an argon plasma jet coupled with a Fenton reagent mixture of hydrogen peroxide (H2O2) and ferrous ions (Fe2+). Based on the response surface methodology, a statistical Box-Behnken design (BBD) was used to optimize the photo-Fenton process by changing Fe2+ concentration, H2O2 concentration, and plasma treatment time as the control factors. Optical emission spectroscopy was conducted to understand the reactive plasma species in the jet. Boltzmann plot was used to study the plasma temperature. The argon plasma jet contained OH, Ar, N2, and atomic oxygen (O) reactive species and radiations in the visible and ultraviolet range. According to BBD, the maximum dye removal efficiency of 97.01% was possible with 40 mg/l of Fe2+ ions, 200 mg/l of H2O2, and 17.5 min of plasma exposure. The statistical model is well-fitted to a second-order polynomial equation. The optimum conditions for dye degradation were Fe2+ (40 g/l), H2O2 (200 g/l), and a plasma treatment time 23.18 min obtained from the optimizer plot. The statistical model showed a 99.76% fit to the experimental data of dye degradation.