Magnetically recoverable Fe 3 O 4 @polydopamine nanocomposite as an excellent co-catalyst for Fe 3+ reduction in advanced oxidation processes.

Advanced oxidation processes are widely applied to removal of persistent toxic substances from wastewater by hydroxyl radicals (·OH), which is generated from hydrogen peroxide (HO) decomposition. However, their practical applications have been hampered by many strict conditions, such as iron sludge, rigid pH condition, large doses of hydrogen peroxide and Fe, etc. Herein, a magnetically recyclable FeO@polydopamine (FeO@PDA) core-shell nanocomposite was fabricated. As an excellent reducing agent, it can convert Fe to Fe. Combined with the coordination of polydopamine and ferric ions, the production of iron sludge is inhibited. The minimum concentration of hydrogen peroxide (0.2 mmol/L and Fe (0.18 mmol/L)) is 150-fold and 100-fold lower than that of previous reports, respectively. It also exhibits excellent degradation performance over a wide pH range from 3.0 to 9.0. Even after the tenth recycling, it still achieves over 99% degradation efficiency with the total organic carbon degradation rate of 80%, which is environmentally benign and has a large economic advantage. This discovery paves a way for extensive practical application of advanced oxidation processes, especially in environmental remediation.