Degradation\nof Remazol Brilliant Blue Dye Using Persulfate\nActivated by Fe<sub>3</sub>O<sub>4</sub>@PDA Nanoparticles: Kinetic\nStudies, Radical Determination, and Phytotoxicity Test

In the current research work, an advanced oxidation process\nwas\napplied to the degradation of Remazol brilliant blue dye (RBBD) using\na sulfate radical. Fe<sub>3</sub>O<sub>4</sub>@PDA nanoparticles were\nsynthesized using coprecipitation and self-polymerization techniques.\nNanoparticle formation was confirmed by XRD, FTIR, FESEM-EDX, VSM,\nand XPS analyses. The crystalline nature of the material showed that\nit possessed a spherical shape with an <i>M</i><sub>s</sub> value of 58 emu/g. The elemental composition and binding energy\nfrom EDX and XPS analyses showed successful doping. Batch studies\nwere conducted, and experimental studies showed that the optimum condition\nfor degradation of 90 ppm of RBBD was 0.3 g/L of nanomaterial, 20\nmM PS at pH 3, achieving 91.35% degradation. The kinetic model suitable\nfor this study was a pseudo-second-order kinetic model with <i>R</i><sup>2</sup> value >0.9. From the radical identification\ntests, sulfate radicals played a dominant role in degradation, and\nto confirm it, EPR analysis was conducted using DMPO. A stability\ntest was performed for 5 cycles in which the degradation efficiency\nwas reduced appreciably. From XPS, XRD, and EDX analyses, the elemental\ncomposition and oxidation state of the recycled material used in the\nfifth cycle showed variation in a negligible manner when compared\nto the fresh catalyst used in the first cycle of the degradation experiment.\nIntermediate identification was done by GCMS analysis, and it disclosed\nthe formation of aliphatic products from the degradation of RBBD with\nless toxicity. Phytotoxicity analysis was conducted using green grams\nfor 10 days, and it proved that intermediates formed in the solution\nwere nontoxic to the plants. Additionally, TOC and COD removal % were\nattained to be 80.021 and 80.903%, respectively, which confirm the\nmineralization efficacy. Hence, this research work proved the efficient\nperformance of the catalyst for RBBD degradation with less formation\nof intermediates, and therefore, this technique is most suitable for\nthe reduction of water pollution.