‪Preparation an‎d modification of phenolic foams for optimal carbon dioxide adsorption‬

10/12/2026 12:00:00 AM

In this study, the improvement of CO₂ adsorption performance in phenolic polymer foams (PHF) was investigated through two approaches: (1) optimizing the percentage of the normal-pentane foaming agent an‎d (2) chemically modifying the foam by adding polyethylene glycol (PEG). Structural investigations using XRD, FTIR, BET, SEM, an‎d TGA methods showed that the prepared foams have a hierarchical structure an‎d suitable specific surface area, making them efficient for CO2 adsorption. In the first part, the effect of the foaming agent percentage on the CO₂ adsorption capacity was eva‎luated. The sample containing 2 phr normal-pentane (PHF-2) showed an adsorption capacity of 2.4 mmol/g at a temperature of 25°C an‎d a pressure of 1 bar. Using the response surface methodology (RSM) an‎d central composite design, optimal conditions were determined, an‎d the adsorption capacity increased to 7.34 mmol/g at a pressure of 9 bar. The adsorption isotherm analysis showed that the Freundlich model has the best fit, an‎d the adsorption is physical, multilayer, an‎d on a heterogeneous surface. The fractional-order kinetic model also had the best fit with the data, indicating the complexity of the adsorption process an‎d multiple reaction pathways of adsorption. Thermodynamic studies showed that the adsorption process is exothermic an‎d spontaneous. In the selec‎tivity test, PHF-2 foam showed a higher tendency to adsorb CO₂ compared to N₂, which was due to the higher polarizability an‎d quadrupole moment of CO₂. After 10 adsorption an‎d regeneration cycles, only an 11% decrease in adsorption capacity was observed, indicating the high stability of the foam. In the second part, chemical modification was performed by adding 4% by weight of PEG, which led to a significant increase in adsorption capacity; such that at a temperature of 25°C an‎d a pressure of 1 bar, the capacity increased from 3.31 to 8.43 mmol/g (approximately 40% improvement). The Freundlich model still had the best fit, an‎d multilayer physical an‎d chemical adsorption was confirmed. The fractional-order kinetic model an‎d thermodynamic analysis also showed the complex an‎d exothermic behavior of the process, respectively. In addition, the modified foams had high thermal stability an‎d recyclability. In the selec‎tivity test, the PHF/4%PEG sample showed a selec‎tivity of 10.23% at a temperature of 25°C an‎d a pressure of 1 bar, which was 17.25% higher than the unmodified foam, an‎d improved by up to 23% with increasing pressure. After 10 cycles, the decrease in adsorption capacity for PHF an‎d PHF/4%PEG samples was 11% an‎d 9.6%, respectively, which confirms the excellent stability of these adsorbents. Overall, the results show that optimizing the structure of phenolic foam an‎d modifying it with PEG effectively improves the adsorption performance, selec‎tivity, an‎d cyclic stability of the foams, making them a suitable option for industrial applications in CO₂ adsorption.

واژه‌هاي كليدي: جذب سطحيCO2، فوم فنوليك، پلي اتيلن گليكول، ساختار مزو-ميكرو، روش سطح پاسخ

Keywords: Adsorption, Carbon dioxide, Phenolic foam (PHF), Polyethylene glycol (PEG), Meso-micro porous structure, Response Surface Methodology (RSM)

Rezvaneh Eshraghi

Mohammad fasihi, Ahad ghaemi