Preparation and Cr (VI) adsorption of functionalized polyimide fibers

In order to overcome the shortcomings of nanofiber membranes such as low mechanical properties and poor acid resistance, amino-rich functionalized polyimide (PI)-polyethyleneimine (PEI) fibers were successfully prepared in the study. The structure and morphology in each functionalization step were characterized by scanning electron microscopy (SEM), atomic force microscopy (AFM), static contact angle, attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR), and X-ray photoelectron spectroscopy (XPS) measurements. The adsorption kinetics analysis showed that the adsorption process followed a pseudo-second-order model, and the adsorption isotherm could be described better by the Langmuir model indicating the adsorption process was mainly chemical and homogeneous monolayer adsorption. Furthermore, the maximum adsorption capacity based on the Langmuir model was about 50 mg g(-1), and the calculated thermodynamic parameters demonstrated an endothermic process. Meantime, the PEI-grafted PI fibers also exhibited good regeneration performance and stable tensile strength during recycling tests process. In the first 3 adsorption-desorption cycles, the removal efficiency and tensile strength of PI-PEI fibers could be maintained up to 60.44% and 89.29% of the initial adsorption, respectively. This work achieved the function of removing Cr (VI) by combining the excellent high temperature resistance, acid resistance, and mechanical properties of PI fibers.