Comparative Study of Ferrate, Persulfate, and Percarbonate as Oxidants in Plasma-Based Dye Remediation: Assessing Their Potential for Process Enhancement

In this study, three benign oxidants, potassium ferrate (Fe(VI)), sodium persulfate (PS), and sodium percarbonate (SPC), were combined with nonthermal plasma (NTP) to enhance the degradation of Malachite Green (MG) and Metanil Yellow (MY). Experimental factors, including dye concentration, oxidant dose, and treatment time, were optimized using Response Surface Methodology (RSM). The hybrid systems achieved markedly improved decolorization rates, with maximum efficiencies exceeding 99% within 30 min, compared to 96% for NTP alone. Kinetic analysis confirmed significantly higher rate constants for NTP-assisted oxidants, particularly NTP + Fe (VI) (kobs = 0.127 min−1), followed by NTP + PS (0.114 min−1) and NTP + SPC (0.098 min−1). Enhanced mineralization, together with stable pH and controlled conductivity variations, further substantiated the efficient breakdown of the dye molecules. Phytotoxicity assays demonstrated that untreated dyes severely inhibited germination. In contrast, effluents treated with NTP + PS and NTP + Fe (VI) restored germination and root growth to levels comparable to the deionized water (DIW) control, indicating substantial toxicity reduction. These results confirm that NTP-oxidants significantly improve oxidation performance, accelerate reaction kinetics, and yield environmentally safe effluents suitable for practical wastewater remediation.