Crosslinked Chitosan-Sulfonated Polyphenylsulfone Electrospun Nanofibers: A Highly Water-Stable and Versatile Adsorbent for Organic Dye Removal

Abstract

The dissolubility of electrospun chitosan nanofibers in aqueous environments is a matter of concern for the long-term water treatment application. In this study, chitosan was ionically crosslinked with a highly chemical stable polymer, sulfonated polyphenylsulfone (sPPSU), with aim of developing water stable electrospun nanofibers adsorbent for removal of an anionic dye, Congo red (CR). The morphology was characterized by electron microscopies, which showed high longitudinal uniformity nanofiber and fibrous orientation with no characteristic flaws on the surface of nanofibers. Additional studies for detecting changes in the surface wettability of the electrospun chitosan fibers by contact angle were performed, while TGA and DSC were used for determining the thermal stability and crosslinking phenomenon, respectively. To demonstrate the efficiency of the adsorbents, the dye removal rate is investigated as a function of pH, adsorbent dosage, and dye concentration. The optimal experimental conditions for achieving the best adsorptive behavior were 150 min for optimal time, 5 mg adsorbent dose, 10 ml dye solution volume, and 180 rpm shaker speed. The crosslinked chitosan nanofibers were regenerated over adsorption–desorption cycles to validate the favorable reusability. The obtained results revealed that the sPPSU crosslinked chitosan had excellent water-stability, and maximum anionic dye adsorption capacity (531.56 mg/g) according to the Langmuir model, and 371 mg/g was the actual adsorption ability. Additionally, the developed nanofibers showed an excellent reusability, exhibiting removal efficiency (~ 70%) after three consecutive adsorption–desorption cycles.