Preparation of self-supporting flexible NiFe2O4 fibers and their adsorption performance for Pb(II)

Abstract

Magnetic fibers are ideal adsorbent material, the fibers have large aspect ratio, entangled with each other, do not agglomerate in water, magnetic materials can be magnetically separated, so magnetic fibers have the advantage of not agglomerating in water, easy to separate, more suitable for use as an adsorbent. The most commonly used methods for preparing NiFe₂O₄ fibers were direct electrospinning and surface loading. Whether using NiFe₂O₄ as a filler for direct electrospinning or loading it onto fibers, there are issues with limited NiFe₂O₄ content and uneven loading. Compared to commonly used direct electrospinning and surface loading, we developed a simple sol–gel method to prepare the precursor spinning solution, then prepared the magnetic NiFe₂O₄ fibers with excellent flexibility through electrospinning, and applied it to the adsorption of Pb (II) for the first time. The spinning solution was synthesized using iron sources, nickel sources and citric acid, the iron and nickel ions coordinated with carboxyl group according to the monodentate coordination. The flexible NiFe₂O₄ fibers exhibited a saturation magnetization of 18.2 emu/g. Specific surface area of the flexible NiFe₂O₄ fibers was 13.443 m²/g and total pore volume of the magnetic NiFe₂O₄ fibers was 0.074 cm³/g. In the adsorption experiment, The NiFe₂O₄ fibers demonstrated a maximum Pb(II) adsorption capacity of 49.53 mg/g. Due to the self-supporting and non-agglomeration advantages of the fiber structure in solution and the maximum adsorption capacity of the NiFe₂O₄ fibers synthesized in this study for Pb(II) exceeded that of most previously reported NiFe₂O₄ adsorbents. Flexible magnetic fibers provided a new solution for simultaneously improving the adsorption capacity of pollutant and achieving rapid magnetic separation, becoming another new material for expanding applications in the field of wastewater treatment.