Selective removal of organic contaminants and ascorbic acid enhancement effect based on the magnetic Fe⁰/FeS₂-doped carbon nanolayer

Developing highly effective iron-based catalyst to selectively remove organic contaminants has garnered considerable attention. Herein, a magnetic Fe⁰/FeS₂-doped carbon nanolayer (S-Fe@NC) was synthesized through a straightforward one-step pyrolysis method, pyrolyzing a mixture composed of 4,6-dihydroxypyrimidine, trithiocyanuric acid, and FeCl₃·6H₂O. With the presence of PMS, S-Fe@NC demonstrated the ability to remove almost 100% bisphenol-A (50 μM) within 3 min, attributed to its excellent graphitization degree and high FeS₂/Fe⁰ content. Furthermore, the S-Fe@NC catalyst demonstrated an impressive k_obs value of 1.476 min⁻¹, which surpassed the traditional Fenton system by 77 times and even exceeded the commercial Fe⁰ catalyst by 127 times. More importantly, the S-Fe@NC/PMS system succeeded in selectively removing organic contaminants based on the hydrophobic interaction between catalyst and contaminants. Besides, the result of electron paramagnetic resonance and the radical quenching experiments indicated that ·OH, SO₄^·−, ¹O₂, and O₂^·− were involved in the organic contaminants removal. Interestingly, after adding ascorbic acid (AA) to the S-Fe@NC/PMS system, more ROS could be generated to result in the k_obs augmenting by 4.16 times (6.133 min⁻¹), completely different from the common sense that AA was usually used as a radical quencher. Additionally, the magnetically separable catalyst also exhibited excellent reusability and broad pH adaptability (2.0–12.0). This study provided a valuable insight for developing highly selective and effective Fe-based catalyst for practical wastewater treatment.