Capturing Acidic CO₂ Using Surface-Active Difunctional Core–Shell Composite Polymer Particles via an Aqueous Medium

Abstract

Multifunctional surface-active polymeric composites are attractive materials for the adsorption of various small molecules. Herein, dual-functionalized micron-sized surface-active composite polymer particles were prepared by a three-step process for CO2 adsorption. First, polystyrene (PS) seed particles were prepared via the dispersion polymerization of styrene. PS/P­(MMA-AAm-EGDMA) composite polymer particles were then synthesized by aqueous seeded copolymerization of methyl methacrylate (MMA) and acrylamide (AAm) in the presence of an ethylene glycol dimethacrylate (EGDMA) cross-linker. Finally, the amide moieties of PS/P­(MMA-AAm-EGDMA) composite particles were converted into an amine-functionalized composite by using the Hofmann degradation reaction. The presence of primary amine groups on the surface of aminated composite particles was confirmed by some conventional chemical routes, such as diazotization and Schiff’s base formation reactions. The formation and functionality of the PS seed, PS/P­(MMA-AAm-EGDMA), and aminated PS/P­(MMA-AAm-EGDMA) composite polymer particles were confirmed by Fourier transform infrared (FTIR) spectra analyses. Scanning electron microscopy (SEM) analysis revealed spherical shape, size, and surface morphologies of the PS seed, reference composite, and aminated composites. The elemental surface compositions, surface porosity, pore volume, pore diameter, and surface area of both composite particles were evaluated by energy-dispersive X-ray (EDX) mapping, X-ray photoelectron spectroscopy, and Brunauer–Emmett–Teller (BET) and Barrett–Joyner–Halenda (BJH) analyses. Dynamic light scattering (DLS) and ζ-potential measurements confirmed the pH-dependent surface properties of the functionalized particles. The amount of the adsorbed anionic emulsifier, sodium dodecyl sulfate (SDS), on the surface of aminated PS/P­(MMA-AAm-EGDMA) is higher at pH 4 than that at pH 10. A vice versa result was found in the case of cationic surfactant, hexadecyltrimethylammonium bromide (HTABr), adsorption. Synthesized aminated composite particles were used as an adsorbent for CO2 adsorption via bubbling CO2 in an aqueous medium. The changes in dispersion pH were monitored continuously during the adsorption of CO2 under various conditions. The amount of CO2 adsorption by aminated composite particles was found to be 209 mg/g, which is almost double that of reference composite particles.

Facile Fabrication and Characterization of Amine-Functional Silica Coated Magnetic Iron Oxide Nanoparticles for Aqueous Carbon Dioxide Adsorption

“…An aqueous CO 2 absorption study was performed in a four-necked round bottomed flask according to our established procedure with some modifications, which is schematically shown in Figure . Our real experimental set up used for aqueous adsorption of CO 2 is illustrated in Figure S2.…”

“…An aqueous CO 2 absorption study was performed in a four-necked round bottomed flask according to our established procedure with some modifications, which is schematically shown in Figure 1 . 40 Our real experimental set up used for aqueous adsorption of CO 2 is illustrated in Figure S2 . The modified protocol for aqueous adsorption of CO 2 is described here in brief: a certain amount of distilled deionized water was taken in the flask.…”

“…In our previous investigation, we developed potentially active difunctional core–shell composite polymer particles and used them as a recyclable adsorbent for capturing acidic CO 2 in an aqueous medium. 40 This research endeavor provided valuable insights into the applicability of composite polymer particles for CO 2 capturing; however, several significant limitations were identified. One of the major drawbacks of our previous approach was the intricate and time-consuming multistep synthesis process required to fabricate the composite polymer particles.…”

“…Figure 1. (a) A typical schematic experimental set up, and (b) graphical representation of the pH variations for the adsorption of aqueous CO 2 by magnetic Fe 3 O 4 /SiO 2 -NH 2 nanoparticles 40. …”