Polydopamine-mediated grafting polyethylenimine on blended polystyrene/dopamine electrospun nanofibrous adsorbent for removal Congo red from water

In this work, the water-soluble polyethyleneimine (PEI) was grafted onto the blended polystyrene (PS) and dopamine (PS/DA) electrospun fiber by using poly-dopamine (PDA) as an intermediate layer (PS/DA@PDA@PEI) to develop the water purification material toward Congo red (CR) dye removal. The morphology and structure of the obtained fibers were characterized by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS). Batch adsorption experiments were performed to investigate pH impacts, comparative adsorption, kinetics, isotherms, and thermodynamics. In comparison with PS/DA fibers and (PS/DA)@PDA fibers, the PS/DA@PDA@PEI fibers exhibited much higher CR adsorption capacity. The adsorption results also showed that the adsorption process toward CR by PS/DA@PDA@PEI fibers followed the Langmuir isotherm model and pseudo-second-order model. Meanwhile, the thermodynamic study revealed that CR removal was both spontaneous and endothermic. Further, the PS/DA@PDA@PEI loaded with CR can be recycled with HCl solution, which can be used repeatedly for CR adsorption. This work indicates that PS/DA@PDA@PEI fibers have great potential to be used as promising adsorbents for CR removal from water.