Non-thermal plasma and Fe2+ activated persulfate ignited degradation of aqueous crystal violet: Degradation mechanism and artificial neural network modeling

Degradation of aqueous crystal violet (CV) by non-thermal plasma combined with Fe2+ activated persulfate (PS) was investigated. Compared with single Fe2+ activated PS system and single non-thermal plasma system, 54% and 42% enhancement for the degradation rates of CV were observed in the non-thermal plasma combined with Fe2+ activated PS (NTP/Fe2+/PS) system, respectively. The effects of initial pH, discharge power, Fe2+ concentration and PS addition on the degradation of CV were reported. The degradation of CV by NTP/Fe2+/PS followed pseudo-first-order reaction kinetics. The concentrations of generated H2O2, O3 and OH in the NTP/Fe2+/PS system achieved 0.36 mg/L, 1.36 mg/L and 3.2 × 10−6 mol/L at 1 min, respectively. In the NTP/Fe2+/PS system, the absorbance of the aqueous solution at 584 nm, the pH value and TOC decreased with increasing reaction time. Intermediate products and the degradation mechanism of CV were proposed according to the analysis of gas chromatography mass spectrometry. The acute toxicity of the solution showed a decreasing trend with the reaction time. The artificial neural network (ANN) models of NTP/Fe2+/PS system were established, and the ANN model could simulate the CV degradation process effectively. In the NTP/Fe2+/PS system, pH value had the greatest effect on the degradation of CV.