Manipulation of carbon dioxide adsorption and desorption via CO₂-philic fibrous polyethyleneimines under alternating current electric fields by frequency tuning.

Abstract

When subjected to an alternating current (AC) electric field, the frequency of the field introduces an extra degree of control over electrokinetic phenomena, as well as molecular alignment and structural conformation that facilitate the binding of adsorbate onto the recognition sites to enhance the performance of adsorption. Herein, Nylon-6 fibrous membrane were coated with a CO2-philic layer of molecularly imprinted polyethyleneimines (MIP) for CO₂ capture using coaxial electrospinning. The MIP-coated Nylon6 fibrous membrane (6/MIP) was place in a electric polarization (EP) device consisting of two mesh electrodes. An EP was generated with an alternating current electric field (ACEF) between the mesh electrodes to induce the protonation of MIP layer during the CO₂ adsorption. The maximum adsorption capacities of CO₂ (q_CO2) on 6/MIP were 1.26 and 1.91 mmol/g in the absence and presence of ACEF at 225 kHZ and 15 V. The adsorption rate constant of CO₂ on the 6/MIP in the presence of the ACEF was ca. 45 % higher than that in the absence of the ACEF. At 1200 kHz, the maximum q_CO2 on 6/MIP decreased to 0.31 mmol/g due to energy dissipation, which facilitated desorption. For CO₂/N₂ gas mixture (15/85 by volume), the CO₂/N₂ selectivity and purity of the gas stream after regeneration reached to 71.1 and 92.6 % in the presence of the ACEF. The 6/MIP is reused up to 12 cycles using EP method and thermal methods, respectively. Consequently, recycling adsorbents via the EP method minimizes their degradation and enhances their stability upon reuse.