Fabrication of porous carbon nanofiber webs from polyacrylonitrile and cellulose acetate for NaCl removal from water using capacitive deionization

Abstract

Capacitive deionization (CDI) has shown potential in addressing freshwater scarcity. CDI's electrode design is a key to better performance as it determines the extent of water purification. For carbon electrodes, the pore structure is an important factor influencing removal kinetics and ion storage. Herein, porous carbon nanofibers with diameters ranging from 277 to 348 nm were fabricated from blends of polyacrylonitrile (PAN) and cellulose acetate (CA) through electrospinning and carbonization. Surface area and pore properties were adjusted by varying the proportions of the precursors while ensuring no adverse alteration to the products' tangible properties. Enhanced pore structure and specific surface area were evident in the blend-based carbon nanofibers. The blend ratio of 2:8 (CA:PAN) had a high specific surface area of 925.47 m2/g and a pore volume of 0.7884 cm3/g. Correspondingly, a high specific capacitance of 177.5 F/g was attained. Desalination performance was determined in batch mode using 500 mg/L NaCl solution. A salt adsorption capacity of 6.57 mg/g and charge efficiency of 0.46 was obtained for the blend that had 20% CA. The carbon nanofibers demonstrated good desalination stability when used repetitively indicating their excellent potential for practical application.