A singlet oxygen non-radical pathway for Rhodamine B dye degradation: Study on its stability, mechanism of degradation, and detoxification

This study examined the degradation pathway of used face mask-derived carbon (UFMC) as a catalyst to activate peroxymonosulfate (PMS) without light sources and metal for Rhodamine B (RhB) dye degradation. The structural changes in the UFMC catalyst resulting from RhB degradation reduced its oxygen functionality and so reduced the rate of RhB dye degradation with each usage. The structural changes of UFMC catalysts were confirmed by Fourier transform infrared, Raman, and X-ray photoelectron spectroscopy. The oxygen functionalities were involved in the generation of reactive oxygen species (ROS), in terms of singlet oxygen (1O2), which are involved in the RhB dye degradation mechanism. This was confirmed using paramagnetic resonance (EPR) spectroscopy and scavenging analyses. Re-useability and stability investigations revealed the UFMC catalyst reached a minimum degradation percentage (38.8%) in the 5th cycle, confirming the complete utilization of UFMC functional groups for RhB dye degradation. Finally, the ability to detoxify the RhB dye water was assessed using zebrafish (Danio rerio) with different RhB dye concentrations (2 to 6 mg/L), and 0 to 72 h of incubation at 26 °C and the yeast cells (Saccharomyces cerevisiaetests) harvested about 107 cells per mL for 24 h under shaking at 160 rpm at 30 °C. Based on these results, the animal models were exposed to the RhB dye water, the significant changes in their growth were evident. However, treated with the RhB degraded water as a control, no developmental deformity was observed. This research employed the UFM derived carbon conveniently supported with PMS for dye removal application.