Performance of nano zero-valent iron activated peroxydisulfates prepared by carbothermal reduction using various bagasse components

Biomass has been utilized in the carbothermal reduction method to reduce iron cations, thereby synthesizing nano zero-valent iron (nZVI). The effect of the biomass components on the regulation of the performance of prepared nZVI is not clear and the mechanism of action remains to be explored. Biomass components such as cellulose, hemicellulose, lignin, and amylum were used to prepare carbon-loaded nano zero-valent iron. It was demonstrated that increasing the cellulose content of the mixture led to higher Fe⁰ content by 2–6 times and a greater activation efficiency of peroxydisulfate (PDS) by 2–5 times. nZVI prepared by carbothermal reduction using bagasse (Fe⁰/CB) removed 99.8 % of metronidazole in 60 min. The bagasse’s cellulose content was found to be 59.5 % and the results demonstrated that the composites prepared with the cellulose content exceeded 60 % had unusual properties. The pyrolysis process of the mixtures showed that cellulose promotes the production of nZVI by generating more reducing gases (e.g. CO, CH₄). Furthermore, the efficiency of activated PDS in removing metronidazole was confirmed, with cellulose-prepared nZVI (c-Fe⁰/C) proving to be the most effective activator. Its removal rate was 1.3 times higher than that of Fe⁰/CB. Physical characterization and mechanistic investigations demonstrated that c-Fe⁰/C has the same active sites as Fe⁰/CB and produces the same type and amount of reactive oxygen species. These demonstrates that cellulose is a critical component in the preparation of nZVI during carbothermal reduction. This study provides guidelines for preparing carbothermal reduced nZVI and establishes a theoretical basis for its engineering application.