Sequential improvement of activated carbon fiber properties for enhanced removal efficiency of indoor CO2

Abstract

For effective capture of low-level indoor CO2, a polyacrylonitrile (PAN) solution was doped with potassium hydroxide (KOH) before electrospinning to increase the specific surface area and microporosity of the resulting activated carbon nanofiber (ANF). Additionally, the KOH-doped ANF was treated with tetraethylenepentamine (TEPA) in ethanol to introduce nitrogen functionalities favorable for CO2 adsorption on the surface. The sequential improvements of the physical and chemical properties of ANF were carried out at a PAN: KOH mass ratio of 1:0−0.05 and TEPA solution concentrations of 1, 2, and 3%. The effects of KOH and TEPA on the structure and chemical properties were investigated using a Monosorb instrument, a field-emission scanning electron microscope, a thermogravimetric analyzer, and an x-ray photoelectron spectrometer. In terms of the textural improvements resulting from KOH doping, a sample of 0.03-ANF showed a significant increase in specific surface area: from 94.59 for pristine ANF to 469.09m2/g after treatment. The XPS(X-ray photoelectron spectroscopy) examinations also showed a large increase in the content of the nitrogen-containing functional groups on the sample treated with TEPA, thereby increasing the selective adsorption capacity of 0.3% CO2 by 21-fold. The combination of textural enhancement by KOH impregnation and surface chemistry enhancement provided by the TEPA doping improved the low-level CO2 capture capability of ANF.