Polypyrrole deposited electrospun PAN/PEI nanofiber membrane designed for high efficient adsorption of chromium ions (VI) in aqueous solution

Chromium (Cr (VI)) is one of the heavy metals that seriously endanger human health and the environment. It is a huge challenge to develop high-efficiency adsorbents with low cost, simple preparation method and green production technique and zero pollution to the environment. In this work, electrospinning technology was used to prepare polyacrylonitrile/polyethyleneimine (PAN/PEI) electrospinning nanofiber membranes (ENM), and then polyacrylonitrile/polyethyleneimine/polypyrrole (PAN/PEI/Ppy) composite nanofiber membrane (CNM) was successfully synthesized by chemical depositing polypyrrole (Ppy) on the surface of PAN/PEI ENM. PAN/PEI ENM provided a larger specific surface area, which facilitated better and more uniform deposition of Ppy on the surface of nanofiber membranes. Scanning electron microscope (SEM) and transmission electron microscope (TEM) images showed that the prepared PAN/PEI/Ppy CNM looked like "balsam pear", and had high adsorption capacity of Cr (VI), with a maximum adsorption capacity of 368 mg g-1. After five times of adsorption-desorption, the removal of Cr (VI) reached more than 95%. More importantly, compared to the current complex chemical synthesis of Cr (VI) ion adsorbents and secondary pollution to the environment, electrospinning fully demonstrates the huge technical advantages of industrial applications, including high efficiency, simple preparation, and green (no harmful chemical by-products), low cost, no secondary pollution. PAN/PEI/Ppy CNM will be promising solid adsorbent candidates for the removal of Cr (VI) ions in wastewater.