Magnetic nanofibers for remotely triggered catalytic activity applied to the degradation of organic pollutants

Abstract

This work reports on the fabrication and characterization of a noveltype of electrospun magnetic nanofibers (MNFs), and their application as a magnetically-activable catalysts for degradation of organic pollutants. The magnetic stimulation capability for the catalytic action is provided by iron-manganese oxide (MnxFe2-xO4) magnetic nanoparticles (MNPs) embedded into electrospun polyacrylonitrile (PAN), which provides stability and chemical resistance. The MNPs (average size d = 40 ± 7 nm) were first obtained by a green and fast sonochemical route, and subsequently embedded into electrospun PAN nanofibers. The final MNFs showed an average diameter of 760 ± 150 nm, providing a superhydrophobic surface with contact angle (θc = 165°), as well as a considerable amount (≈ 50 % wt.) of embedded MNPs (Mn0.5Fe2.5O4), thermally stable up to temperatures of 330 °C. The catalytic Fe2+/3+/Mn2+/3+/4+active centers on the MNPs of MNF’s surface could be remotely activated by alternating magnetic fields (AMF) to degrade the methyl blue (MB). Remarkable stability of the MNFs during heating under extreme pH conditions (3 < pH < 10) was observed along several catalytic cycles. Thedegradation kineticsin presence of hydrogen peroxide showed followed the Langmuir–Hinshelwood model with an average efficiency > 80 %, after several cycles of reusing the same sample without any regeneration process. The capacity of these materials as a catalytic material with magnetic remote activation makes them appealing for those catalytic applications under conditions of darkness or restrained access, where photocatalytic reaction cannot be achieved.