Novel carbon based Fe-Co oxides derived from Prussian blue analogues activating peroxymonosulfate: Refractory drugs degradation without metal leaching

To meet the current challenges of removing refractory drugs from wastewater and groundwater, an efficient and environmentally friendly treatment process is desired. Herein, a novel magnetic composite of carbon-based Fe-Co oxide (MCFC) was fabricated from a Prussian blue analogue and graphene oxide by pyrolysis in nitrogen and then re-sintering in air. MCFC showed good performance for several kinds of refractory drugs (including 4-aminobenzoic acid ethyl ester (ABEE), sulfamethoxazole and acyclovir) degradation by activation peroxymonosulfate (PMS), without any detectable metal leaching, as an important green environmental remediation technology. A slight performance decrease of MCFC observed during the reuse, was able to be recovered by a simple thermal process. No metal ions dissolution and thermal regeneration was an important development on PMS activation catalyst. Degradation intermediates of a refractory drug, ABEE, were identified by liquid chromatography quadrupole time-of-flight mass spectrometry. The degradation pathways of ABEE were established, with intermediates being generated by the electrophilic/radical addition and the hydrogen abstraction. At last, PMS activation pathways was proposed as that PMS was activated by Co²⁺ and Fe²⁺ on the surface of MCFC, pyrrolic-N, pyridinic-N, and carbonyl groups, to form singlet oxygen (¹O₂), hydroxyl radicals (^[rad]OH) and sulfate radicals (SO₄^[rad]−). The synergistic effects between the metal nanocrystals and nitrogen-doped carbon promoted the regeneration of the surface Fe²⁺ and Co²⁺, which resulted in F4C6G5-6N-4a showing excellent catalytic activity for PMS activation. Through the above combination of non-radical (¹O₂) and radical (SO₄^[rad]− and ^[rad]OH) processes, ABEE was degraded and mineralized. This work presents a promising green heterogeneous catalyst for the degradation of refractory drugs in municipal wastewater/groundwater by PMS activation.