Halloysite nanotube confined interface engineering enhanced catalytic oxidation of photo-Fenton reaction for aniline aerofloat degradation: Defective heterojunction for electron transfer regulation

Aniline aerofloat (AAF), as a major flotation reagent widely employed in beneficiation process, has been ignored with persistent toxicity and unsatisfied smell to environment. Herein, a spatial confinement of HNTs@MoS2/Fe was constructed by in situ growth of defects-rich MoS2/FeOOH in-and-out of halloysite nanotubes (HNTs) for completely degradation of AAF. The results showed that similar to 99 % of AAF was degraded within 60 mins photo-Fenton reaction and the K-obs was calculated 0.223 min(-1) which is much higher than recent reports. Interestingly, HNTs@MoS2/Fe can adjust the pH of reaction system to maintain it within a suitable range for highly efficient AAF degradation even at the initial pH 7. TEM images showed that the particle size of MoS2/FeOOH hybrids was 10-50 nm which is very beneficial to decrease the diffusion distance of ROS to avoid self-consumption. XPS and EPR results confirmed that the catalyst with unsaturated S edges and defects effectively promoted the active sites and electron transfer. More importantly, the separated electrons regulated the Mo4+/Mo6+ and Fe3+/Fe2+ cycle which maintained H2O2 decomposition for stable ROS generation. The regenerated Fe2+ and Mo4+ played dual role for H2O2 decomposition to generate ROS. The DFT calculation proved the S defects and FeOOH heterojunction facilitate photogenerated electrons to fast migrate from MoS2 to FeOOH and achieve e(-)/h(+) separation, this is the major driving force for maintaining the generation of ROS in photo-Fenton system. This work will provide an ingenious idea to prepare HNTs confined catalyst with low cost and high durability for removal refractory organic pollutants.