Novel core-shell structural nZVI@Fe₂P for sulfadiazine (SDZ) degradation: Accelerated Fe(III)/Fe(II) dynamic cycling, boosted Fenton performance and stability

Nano zero valent iron (nZVI) is widely used in traditional hydrogen peroxide (H₂O₂)-based Fenton reactions for the degradation of persistent organic pollutants in aqueous environments. How to restrain the blocked electron transfer aroused from thickening of the iron oxide passivation layer and reinforce the Fe(III)/Fe(II) dynamic cycling is essential for Fenton reactions. In this work, a novel core–shell structural nZVI@Fe₂P was fabricated and employed for the degradation of sulfadiazine (SDZ). Compared to nZVI, the nZVI@Fe₂P demonstrated a significant performance and stability in the degradation of SDZ. Completed SDZ removal is achieved in less than 15 min and the SDZ removal kept over 60% even in the ninth consecutive cycles. Although the SDZ removal decreased dramatically to only 27.4% in the tenth cycle, the value could be restored to 80.6% after a facile re-phosphorization process. Both experimental and density function theory (DFT) calculation revealed the dominant role of Fe₂P in promoting H₂O₂ activation and strengthening the Fe(III)/Fe(II) dynamic cycling. In the nZVI@Fe₂P/H₂O₂ system, the low impedance and high proton conductivity of the Fe₂P shell layer played a dual function, i.e., accelerating electron transfer and donating electrons for the continuous Fenton reaction. This implication of these findings provides a novel strategy by integrating the state-of-the-art material science, advanced oxidation process, and mechanism elucidation for practical environmental wastewater remediation.