Crystalline boron-boosted Fenton-like activation of persulfate by carbon-coated nano zero-valent iron for efficient degradation of tetracycline.

Nano zero-valent iron (nZVI)-based advanced oxidation processes (AOPs) have broad application prospects in environmental remediation, but the surface passivation of nZVI severely limits their performance. Although carbon coating can inhibit the oxidative passivation of nZVI in air, the deposition of iron ions on its surface during the reaction still leads to its rapid deactivation. In this study, crystalline boron was introduced as a novel co-catalyst to activate peroxydisulfate (PDS) in conjunction with carbon-coated nZVI (Fe⁰@C) for the degradation of tetracycline (TC). The results showed that the Boron/Fe⁰@C/PDS system achieved complete removal of TC within 1 min. Free radical scavenging and chemical probe experiments confirmed the generation of multiple reactive oxygen species, with singlet oxygen being primarily responsible for the degradation of TC. Mechanism investigations revealed that crystalline boron can accelerate the redox cycle of iron ions by donating electrons, thereby inhibiting the deposition of iron ions on the Fe⁰@C surface and achieving the stable release of ferrous ions and the continuous activation of PDS. Furthermore, crystalline boron gradually undergoes surface oxidation during the electron donation process, but its surface self-cleaning effect can continuously expose new active sites. The synergistic effect of crystalline boron and carbon coating prevents passivation of nZVI throughout its lifecycle, thereby ensuring excellent catalytic efficiency and long-term stability. This study provides a practical anti-passivation strategy and offers new insights into the rational design of nZVI-based AOPs.