Insights into the role of hydroxyl group on carboxyl-modified MWCNTs in accelerating atenolol removal by Fe(III)/H2O2 system

[Display omitted] •MWCNTs promote the removal of ATL mediated by Fenton-like system.•–OH and –COOH on MWCNTs cooperate to facilitate the cycling of Fe(III)/Fe(II).•·OH directly attacked ATL, while O2·– promoted the cycling of Fe(III)/Fe(II).•Theoretical calculations revealed Fe(III) interacts with –OH by H-bond and O–H···π. The effects of multi-walled carbon nanotubes (MWCNTs) on the removal of contaminants mediated by Fenton reactions and how the functional groups on MWCNTs cooperate to modulate the cycling of Fe(III)/Fe(II) remain unclear. Here, we showed that MWCNTs significantly enhanced the removal of atenolol (ATL) in Fenton-like system by facilitating the generation of ·OH and O2·–, in which ·OH directly attacked ATL, while O2·– promoted the cycling of Fe(III)/Fe(II). Moreover, we found that in addition to –COOH, –OH on MWCNTs played an important role in ATL removal, that is, Fe(III) was likely to interact with –OH by H-bond and O–H···π interactions, which significantly reduced the reduction potential of Fe(III)/Fe(II), thus promoting the removal of ATL. Our findings revealed the role of –OH and –COOH on MWCNTs in promoting the removal of ATL in Fe(III)/H2O2 system, which is helpful to rationally design the CNTs-based materials applied for wastewater treatment.