FeOγ/S-g-C ₃ N ₄ catalyzed PMS oxidation for Rhodamine B degradation from aqueous solution: performance assessment and mechanism

Synthetic dyes persist in industrial effluents, posing serious ecological and health risks due to their high stability and toxicity. Conventional treatments fail to eliminate such dyes fully, necessitating advanced oxidation strategies. This study investigates the degradation of Rhodamine B (RhB) using a sulfate radical–mediated advanced oxidation process activated by FeOγ/S‑g‑C3N4, a heterogeneous catalyst prepared through co‑doping graphitic carbon nitride with iron and sulfur. Characterization using FTIR, XRD, SEM, EDX, VSM, and XPS confirmed the successful incorporation of dopants and catalyst stability. Optimal degradation occurred at PMS and catalyst dosages of 0.2 g/L each, at 20 °C, and pH 6.33 for 10 mg/L RhB, achieving 99.09% removal within 90 min. A slightly higher degradation efficiency (99.55%) was obtained at pH 3, indicating the catalyst’s robustness across a wide pH spectrum. Kinetic analysis conformed to a pseudo‑first‑order model with a rate constant of 0.046 min−1. Radical scavenging experiments revealed singlet oxygen as the predominant reactive species, accompanied by hydroxyl radicals, superoxide anions, and sulfate radicals. High‑resolution mass spectrometry indicated the formation of oxidative intermediates, validating molecular degradation. The catalyst maintained excellent reusability, minor iron leaching, and structural stability across five cycles, emphasizing its high activity, operational reliability, and economic feasibility for dye removal applications.