Abstract:
Cement industries are the second-largest anthropogenic carbon dioxide (CO2) emitter and have gained substantial research attention to capture CO2 and minimize environmental issues. Also, the recovered carbon dioxide (CO2) can be reutilized for several applications. The adsorptive capture of CO2 appears promising as compared to absorption, membrane separations, and cryogenic distillation because it allows easy CO2 recovery. This work demonstrates the adsorptive capture of carbon dioxide on amine-functionalized styrene-divinylbenzene copolymer. Both batch and continuous adsorption data of CO2 are presented at different temperatures. The equilibrium uptake of CO2 over the polymeric adsorbent showed 2.4 mol/kg capacity at 25⁰C and near ambient pressure, which decreased by 16% with a ten-degree rise in the operating temperature. The equilibrium adsorption data are modeled with Langmuir, Nitta, Toth, Dubinin-Radushkevich, and SIPS isotherm equations to characterize the CO2-polymer adsorption system and estimate the heat of adsorption, entropy, and Gibbs free energy for CO2 adsorption. The Toth isotherm gave the best fit of the experimental data suggesting monolayer adsorption of CO2 on energetically different sites of the adsorbent. The diffusivity of CO2 within the adsorbent's interstitial space is determined as 2–9 × 10−11 m2/sec, indicating intraparticle mass transfer limitations for large-scale operations. The continuous adsorption/desorption studies of CO2 in mixtures with nitrogen were characterized via breakthrough curves. The desorption studies showed 92–94% recovery of CO2 in batch and continuous experiments at 56⁰C. A theoretical model for continuous adsorption of CO2 is also developed and validated with the experimental data. The current work could be promising for CO2 capture in the cement industry.
