3D superhydrophilic polypyrrole nanofiber mat for highly efficient adsorption of anionic azo dyes

Abstract

The demand for cost-effective, easy-handling, and recyclable adsorbents with high performance for removal of organic dyes is gaining prominence. Although polypyrrole (PPy) has proven to be promising for adsorption of anionic azo dyes (AADs), the use of PPy-based particles and fibers still faces limitations such as challenging separation and undesirable mass transfer. In this work, a superhydrophilic polypyrrole nanofiber mat (PPy NFM) with a 3D fluffy porous structure was developed via in situ polymerization of pyrrole monomers with electrospun PAN@PVP NFM as the substrate and followed by freeze-drying. The 3D PPy NFM exhibited a fast adsorption rate (within 3 h) and high adsorption capacity (up to 234.62 mg g−1) towards AADs, remarkably superior to those of 2D lamellar PPy NFM. After five times of reuse, the reduction of adsorption capacities for AADs was less than 10%. Another striking advantage of the 3D PPy NFM lies in the integration of dispersibility and integrity, making it easy to use and recycle without centrifugation or filtration. Moreover, the adsorption behaviors of three dye models, Metanil Yellow (MY), Acid Orange 7 (AO7), and Acid Yellow 9 (AY9), were thoroughly discussed, suggesting that the adsorption of AADs by the PPy NFM involves multiple mechanisms, including electrostatic attraction, π–π interaction and hydrogen bonding, thus ensuring high adsorption efficiency. These attractive characteristics make 3D PPy NFM be a potential eco-friendly adsorbent in dye wastewater treatment.