Highly dispersed Fe7S8 anchored on sp2/sp3 hybridized carbon boosting peroxymonosulfate activation for enhanced EOCs elimination though singlet oxygen-dominated nonradical pathway

The synergistic effect of carbon materials with high sp2/sp3 hybridized carbon ratio and metal materials can enhance the efficiency of peroxymonosulfate (PMS) based advanced oxidation processes. In this study, a composite of highly dispersed Fe7S8 anchored on sp2/sp3 hybridized carbon (Fe7S8@HC) was developed by a facile synthesis for PMS activation. Within 10min, the removal efficiency of the target pollutant doxycycline (DOX) could reach ca. 96% in optimal Fe7S8@HC/PMS system through a 1O2-dominated non-radical pathway. Correlation mechanism analysis revealed that thiophene S, sp2/sp3 ratio and Fe(II) were critical factors for elongating of the O-O bond of PMS. Moreover, the Fe7S8@HC/PMS system exhibited favorable adaptability to interference such as common inorganic anions, humic acid and pH changes and could effectively remove various organic pollutants with low ionization potential. Moreover, the system maintained high DOX removal efficiency by running 30 cycles in a continuous flow reactor. Finally, susceptible sites of DOX and four degradation pathways were proposed by density functional theory calculation and LC-MS detection. This work not only offered new insights into the design of high-performance catalysts combining metal and biomass-based carbon materials, but also provided technical support for the remediation of water bodies containing emerging organic contaminants. With the development of science and technology, emerging organic contaminants (EOCs) have gradually entered the public's attention and were hazardous materials of great concern due to their non-degradable properties, posing a serious threat to the environment. In this work, a catalyst with Fe7S8 anchored on sp2/sp3 hybridized carbon was constructed for efficient removal of EOCs by activation of peroxymonosulfate in a non-radical pathway. The developed system had high removal performance, low ion leaching and satisfactory practical application capability, which rendered it an excellent candidate for the remediation of aqueous environmental pollution. [Display omitted] •A Catalyst of dispersed Fe7S8 anchored on hybridized carbon was prepared.•Fe7S8-2@HC800/PMS system showed great catalytic and actual application properties.•Singlet oxygen played a dominant role in the DOX removal process.•Thiophene S, sp2/sp3 carbon and Fe(II) were main active sites for PMS activation.•Possible degradation pathways of DOX were analyzed by LC-MS and DFT calculations.