Mitigating the passivation of zero-valent iron: the role of diatom frustules in activating peracetic acid for organic pollutant degradation

This study represents the first attempt to employ underutilized diatom frustules (DF) as a scaffold to enhance the dispersion and formation of zero-valent iron (ZVI), aiming to overcome the rapid passivation of ZVI in conventional zero-valent iron–activated peracetic acid (ZVI/PAA) system. Through use of a liquid-phase reduction method, a novel material, ZVI@DF, was synthesized. By adjusting the DF doping amount, the physicochemical properties of ZVI@DF can be modified. Under optimal conditions, the ZVI@DF/PAA system achieved over 98% methylene blue (MB) removal within 30   minutes, demonstrating a 30% efficiency improvement compared to conventional ZVI/PAA. The research also examined common water quality parameters, confirming that typical anions have minimal impact on the performance of the ZVI@DF/PAA system, resulting in stable pollutant removal efficiency. Electron paramagnetic resonance (EPR) experiments confirmed that HO•, R-O•, and •O 2 − radicals induced by ZVI activating PAA via silanol groups on DF are the main species for MB degradation. After four cycles, ZVI@DF maintains over 85% MB degradation efficiency. The amorphous silica nanoflower structure formed by doping with a small amount of DF significantly delays passivation, providing active sites for generating radicals to degrade pollutants. This study provides a new strategy for purifying emerging pollutants, recovering underutilized diatom materials, and activating PAA.