Oxidative degradation of Rhodamine B solution with nZVI persulfate activation

Abstract

In this study, the researchers evaluated the use of nano-zero-valent iron (nZVI) activated persulfate (PS) for the degradation of Rhodamine B (RhB). The effects of various operating parameters such as initial pH, and dosages of PS, nZVI and citric acid (CA) on the removal rate of RhB were investigated. The results demonstrated that at a PS dosage of 5 mmol·L<sup>-1</sup>, nZVI dosage of 0.3 g·L<sup>-1</sup>, 0.1 mmol·L<sup>-1</sup> CA, and pH of 5, the degradation rate of RhB was 94.970%. The degradation and kinetic analysis of RhB using micron-scale zero-valent iron (mZVI) and nZVI revealed that nZVI exhibited higher activity with PS due to its smaller particle size. The activation of PS by nZVI is higher compared to mZVI, and the ineffective consumption is half that of the mZVI/PS system, the TOC removal rate increased by 18.65%. Kinetic analysis indicated that under the mentioned reaction conditions, the degradation process followed a pseudo-second-order reaction model, with the highest apparent reaction rate constant (kobs). The researchers also identified active radical species in the nZVI/PS system. Additionally, Gas Chromatography-Mass Spectrometry (GC-MS) analysis was used to detect reaction intermediates and propose a possible degradation pathway for RhB.