Warrior's armor: Study on the aging of sulfidated micro-sized zero valent iron in air and its subsequent reactivity for chloramphenicol degradation in different acid systems

In the practical application process, the reactivity and performance of ZVI-based materials when being placed in the air for a few days, weeks or months was worth studying. Most studies on the aging of ZVI were carried out in solution, only considering the reactivity of ZVI in aqueous solution. In this work, we investigated the degradation of chloramphenicol (CAP) in sulfuric acid (SA) and citric acid (CA) systems by sulfidated micro-sized zero-valent iron (S-mZVI) in air with different aging days. The results showed that with the increase of aging days in the air, the degradation effect of S-mZVI on CAP in different acid systems showed a similar trend (first increasing and then decreasing), the removal effect of S-mZVI on CAP reached the best within the aging time of 5–9 days. The degradation path of CAP could be divided into oxidation path and reduction path. The XPS and XRD characterization results of the materials on different aging days indicated that the characteristic peak of Fe 3 O 4 was detected on the surface of the materials with the increase of aging days, which may be the reason for changing degradation efficiencies of CAP by S-mZVI for different aging days. In addition, in different systems of SA and CA, the degradation curves of CAP differed. This might be caused by two reasons: (1) CA could adsorb on S-mZVI while SA could not; (2) The initial pH of the CA system played a more significant effect on CAP degradation compared to that of the SA system.