Riboflavin modification of zero-valent iron turns peroxydisulfate activation pathway toward dominant singlet oxygen production for targeted tetracycline resistance elimination

Targeted control of tetracycline resistance in aquatic environments is an urgent public health issue. Singlet oxygen ( 1 O 2 ) can selectively attack guanine bases in DNA sequence, offering a potential strategy for eliminating guanine-rich tetracycline resistance genes. However, conventional zero-valent iron (ZVI) activated peroxydisulfate (PDS) processes predominantly rely on non-selective free radicals (e.g. , SO 4 •- and •OH) generated via stepwise single-electron transfer. In this study, we developed a riboflavin-modified ball-milled ZVI (RF-ZVI bm ) that redirected the PDS activation pathway. The optimized RF-ZVI bm /PDS system achieved complete (6-log) inactivation of tetracycline resistant E. coli and effective degradation of the plasmid-encoded tet gene within 15 min, effectively eliminating its transformability. Mechanistic studies revealed that the surface-bound RF functioned as a bifunctional proton-coupled electron transfer (PCET) mediator, it facilitated a concerted transfer of two-electron/proton (2e − /2H + ) owing to the availability of protons in RF-ZVI bm /PDS system. This PCET pathway directly drove PDS activation toward the highly selective generation of 1 O 2 , achieving a remarkable production rate of 136.04 μM•L −1 •min −1 while substantially suppressing radical byproducts. RF-ZVI bm demonstrated excellent reusability over multiple cycles with minimal and environmentally benign modifier leaching, supporting its potential for practical application. This work elucidates a tailored PCET mechanism for dominant 1 O 2 production and provides a potent strategy for controlling the dissemination of tetracycline resistance in water environments.