Enhanced degradation of organic dyes by peroxymonosulfate with Fe3O4-CoCO3/rGO hybrid activation: a comprehensive study

Background: Peroxymonosulfate (PMS) activation emerges as a very promising technology for the decomposition of recalcitrant in wastewater and it is necessary to understand the mechanisms of PMS activation and organic decomposition for the development of effective catalysts. Methods: Fe3O4-CoCO3/rGO was synthesized through a one-step solvothermal method, characterized by various surface analyses (e.g., XRD, SEM, EDX, TGA, FTIR, BET, VSM, and Raman), and applied for Rhodamine B (RhB) removal via PMS activation. Several degradation products were identified by mass spectrometry, and the degree of mineralization was estimated through total organic carbon analysis. Significant findings: The Fe3O4-CoCO3/rGO/PMS system exhibits excellent RhB removal efficiency of 98.69% within a short time of 180 s, where the rate constant (1.427 min−1) was much higher than that of Fe3O4 (0.0241 min−1), CoCO3 (0.626 min−1), and rGO (0.01726 min−1). The synergistic effect of Fe3O4, CoCO3, and rGO effectively enhanced the removal of RhB due to its efficient generation of reactive oxygen species (ROS). In which, 1O2 and SO4•− were identified as the predominant ROS in the Fe3O4-CoCO3/rGO/PMS system via radical quenching experiments. The presence of rGO reduced the leaching of Fe and Co about 2 times (0.38 and 0.54 mg/L, respectively) after 4 consecutive cycling tests with the RhB removal efficiency of above 90%. This study shows that Fe3O4-CoCO3/rGO is an effective catalyst over a wide pH range from 3 - 10 for PMS activation to degrade organic pollutants. © 2022 Taiwan Institute of Chemical Engineers