Efficient catalytic degradation of p-nitrophenol using a novel 2D nanoflake array MWCNTs/PPy/PDA-nZVI catalyst

[Display omitted] •A 2D nanoflower-like MWCNTs/PPy/PDA-nZVI catalyst was constructed on stainless steel mesh.•The catalyst exhibited highly efficient catalytic performance and excellent stability.•An unprecedented catalytic activity for the continuous flow reactor was obtained, outperforming batch reactor with 2–3 orders of magnitude.•It represents a promising design of nZVI catalytic reactor toward environmental applications. Heterogeneous Fenton-like catalyst, nano zero-valent iron (nZVI) is being increasingly investigated as an environmental-friendly and low-cost reagent for water purification. However, low utilization ratio of reactive sites and poor stability make its application in realistic scenario challenging. Herein, a unique two-dimensional (2D) nanoflower-like catalyst via anchoring nZVI on multiwalled carbon nanotubes/polypyrrole/polydopamine (MWCNTs/PPy/PDA) was successfully constructed on the surface of stainless steel (SS) mesh for p-nitrophenol (PNP) degradation. The 2D nanoflake array structure with ultrathin thickness (about 50 nm) inhibited nZVI agglomeration and promoted the exposure of active sites. PNP can be degraded with the modified kinetic rate constant (K-value) up to 76.02 μmol g−1 s−1, surpassing other Fenton-like systems by factors of 158.4–1267. And the removal rate maintained 90.6 % in the 6th cycle. Notably, a continuous flow reactor was established and exhibited an unprecedented K-value of 14.57 mmol g-1 s-1, outperforming batch reactor with 2–3 orders of magnitude. The PDA-modified substrate reshaped the nZVI morphology, acted as a valid media to promote the electron transfer and enhance utilization ratio of reactive sites, and stabilized nZVI. This study verified the crucial roles of the catalyst morphology and reductive functional groups of substrate for the enhancement of catalytic performance. This study provides necessary inspiration and guidance for rational designing of efficient nZVI catalytic reactor toward environmental applications and more.