Porous Fluorocarbon from Rice Husk for the Efficient Separation of Gases

Abstract

Abstract A porous fluorocarbon sorbent is synthesized from rice husk (RH) in a microwave reactor and then evaluated for the adsorption of different gases (CH4, CO2, and N2). The fluorocarbon is characterized by Fourier transform infrared spectroscopy (FTIR), X‐ray diffraction (XRD), Brunauer–Emmett–Teller (BET), Raman spectroscopy, Thermal gravimetric analysis (TGA), and X‐ray photoelectron spectroscopy (XPS). Significant enhancement in the surface area of activated carbon material is obtained from 29 to 531 m2 g−1 after removing naturally present silica in RH. Results reveal that rice husk fluorocarbon (RHF) has a higher adsorption affinity for CO2 (1.8 mmol g−1) than that of the sulfonated rice husk (RHS) (1.4 mmol g−1) at 298 K while the corresponding separation factor of CO2/CH4 is 4 and 3; respectively. Higher separation factors of 12 and 10 are observed for the binary system of CO2/N2, respectively. Quantum chemical density functional theory (DFT) calculations agree with the experimental observations. They reveal that RHF exhibits strong columbic interactions with considerable interaction energies of −87.85, −76.75, and −55.65 kcal mol−1 with CO2, CH4, and N2 gases; respectively. Finally, the adsorption process results are highly reproducible, with a small decrease in the adsorption capacity of less than 5% after repeated trials.

Keywords

• fluorination
• high surface area
• microwave‐assisted synthesis
• natural sorbent
• separation factor
• silica removal