Advanced phenolic foam adsorbents for CO2 capture with high capacity and selectivity via tuning the cellular structure

Abstract

This study explores the CO₂ adsorption capabilities of phenolic polymer foam (PHF) synthesized using varying concentrations of n-pentane as a blowing agent. Advanced characterization techniques, including X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and nitrogen adsorption-desorption analysis, demonstrated that an optimal concentration of the blowing agent enhances micro-mesoporosity, surface area, and cell structure, resulting in a superior CO₂ adsorption capacity of 7.34 mmol/g at 298 K and 9 bar. Response surface methodology (RSM) optimization validated these findings, showing excellent concordance between predicted and experimental results. The adsorption process was best described by the Freundlich isotherm and fractional-order kinetic models, indicating favorable multilayer adsorption characterized by both physical and chemical interactions. Thermodynamic analysis revealed an exothermic and associative adsorption process. The foam, including 2 phr blowing agent, displayed high selectivity for CO₂ over N₂, as determined by Ideal Adsorbed Solution Theory (IAST), with isosteric heat of adsorption indicating strong interactions between the adsorbate and adsorbent. Recyclability tests showed robust performance, with only an 11% reduction in capacity, underscoring its potential for industrial CO₂ adsorption. This study emphasizes the critical importance of blowing agent concentration in optimizing PHF’s cellular architecture and surface chemistry for effective CO₂ capture, offering valuable insights for the development of sustainable adsorbents.