Separation and capture of CO2 from ambient air using TEPA-functionalized PAN hollow fibers

Solid amine sorbents have potential application in direct air capture of CO2 due to the advantages of low generation energy-demanding, and high adsorption capacity. Although the powdery solid amine sorbents exhibit high CO2 adsorption capacity, large pressure drop still limits their applicability. Structured solid amine are considered as good alternatives to solve this problem, but they still have the bottle-neck of insufficient CO2 adsorption capacity. To this end, we proposed solid amine hollow fiber to address these problems. In this work, tetraethylenepentamine (TEPA)-functionalized polyacrylonitrile (PAN) hollow fibers were fabricated via hydrolyzing nitrile groups on hollow fiber surface and then chemically grafting TEPA on it. The as-prepared PAN-TEPA hollow fiber was characterized by Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), and Brunauer-Emmett-Teller (BET). In CO2 capture experiment, PAN-TEPA hollow fiber achieved high adsorption capacity under low CO2 concentration (5.07 mmol g−1, 5000 ppm, CO2-N2) source. The adsorption kinetics were studied, and Avrami fractional-order kinetics model fitted best with experimental curve. The adsorption capacities under low concentrations fitted well with Langmuir isotherm. Temperature-vacuum swing (TVS) desorption process was employed to rengenerate PAN-TEPA hollow fiber, and the regeneration conditions were screened. In direct air capture, PAN-TEPA hollow fibers had an adsorption capacity of 2.02 mmol g−1. CO2 Saturated PAN-TEPA hollow fibers could be efficiently regenerated by TVS desorption process. After 11 adsorption–desorption cyclic experiments, the decrease of breakthrough CO2 adsorption capacity is not obvious. Due to their characteristics in CO2 adsorption and desorption processes, PAN-TEPA hollow fiber is a potential sorbent for separation and capture of CO2 from ambient air.