Ultrafast degradation of organic pollutants in an Fe3O4-CoS2-x activated persulfate catalytic system with an Fe-Co catalytic cycle involving oxygen and sulfur vacancies

Processes that ensure the rapid degradation of organic pollutants are urgently required in wastewater treatment. Heterogeneous catalysts in sulfate radical-based advanced oxidation processes (SR-AOPs) have a low catalytic efficiency, long reaction time, and are difficult to recover. Rationally designed magnetically separable Fe3O4-CoS2-0.4 that was rich in sulfur and oxygen vacancies was used as an efficient catalyst for peroxymonosulfate (PMS) activation to rapidly degrade various dyes and antibiotics. The synergistic effect of Fe, Co and S on the activation of PMS and the sulfur and oxygen vacancy generated by the composite greatly promoted the catalytic performance, in which the singlet oxygen (1O2) generated was the main active species in the degradation process. Fe3O4-CoS2-0.4 is easily separated from the reaction solution by magnets and shows good recyclability and stability in removing MB, achieving removal rates of 100%, 100% and 96.07% in the first, second and third cycles, respectively. Fe3O4-modified CoS2 also greatly reduces the ion leaching of cobalt ions and the secondary pollution. In addition, for several other typical dyes and antibiotics (metronidazole, phenol, tetracycline, levofloxacin, crystal violet, malachite green, and rhodamine B), high removal rates (100%, 100%, 88.3%, 90.3%, 100%, 100%, and 100%, respectively) were achieved in a short time.