Activation of H2O2 via sulfide-modified nanoscale zero-valent iron for tetracycline removal: Performance and mechanism

Tetracycline (TC) is widely detected in various environments and promotes bacterial resistance. In the present research, sulfide-modified nanoscale zero-valent iron (S-nZVI) was fabricated and used as activator of hydrogen peroxide (H2O2) for TC degradation. Sulfidation could improve the hydrophobicity of nZVI and its reactivity for TC degradation by up to 260 %. The reaction rate constant of the S-nZVI/H2O2 system was 16 times faster than that of the S-nZVI system. The quenching experiments results proved that •OH was the predominant radical involved in TC degradation. •OH played a significant role in ferryl ion (Fe(IV)) formation under acid conditions, while TC plays crucial roles under neutral pH condition in Fe(IV) formation by accelerating Fe(III) oxidation into Fe(IV). The possible degradation pathways were analyzed, and the toxicity analysis confirmed that the S-nZVI/H2O2 system is an effective method for degrading, and thus reducing the toxicity of TC. Therefore, this study suggests the possibility of an S-nZVI/H2O2 system for the efficient degradation of TC.