Magnetic nanoreactor Fe₃O₄@HNTs as heterogeneous Fenton-like catalyst for acid fuchsin degradation: Efficiency, kinetics and mechanism

Compared with traditional heterogeneous Fenton catalysis, iron-based catalysts with nano-confinement effect could significantly improve the effectiveness for organic pollutants degradation, due to the shorter migration distance and longer half-life of reactive oxygen species (ROS). Here, we encapsulated the Fe3O4 nanoparticles in the lumen of halloysite nanotubes (HNTs) by means of the electrostatic interactions to fabricate the Fe3O4@HNTs nanoreactor with an outstanding Fenton-like catalytic performance. The instrumental characterizations indicated that the Fe3O4 NPs successfully loaded on the inner wall of HNTs. An active dye acid fuchsin (AF) was chosen as the target pollution to evaluate the Fenton-like catalytic performance of Fe3O4@HNTs nanoreactor. The experimental results showed that the degradation efficiency of 50 mg L-1 AF could approach 100% in 120 min reaction time under almost neutral pHs. To have an insight into the Fenton-like mechanism of Fe3O4@HNTs nanoreactor, the comparisons of AF degradation in different systems, dominant free radicals, iron leaching concentration, H2O2 decomposition efficiency, and (OH)-O-center dot production efficiency were investigated in details. In addition, the degradation pathways of AF were also predicted based on the density functional theory, frontier orbit theory, and high performance liquid chromatography-quadrupole-time of flight mass spectrum (HPLC-QTOF-MS) technique.