Eco-friendly CO₂ adsorption by activated-nano-clay montmorillonite promoted with deep eutectic solvent

ABSTRACT

In this work, an innovative and environmentally friendly adsorbent for CO₂ capture is synthesized by Choline Chloride-Urea (ChCl: U) functionalization of the acid-activated montmorillonite (MMT) for the first time. The surface area enhancement was achieved by acid activation at 3 Molarity, which resulted in 7.1 and 10.9 times increase in the specific area and pore volume, respectively. In fact, the highest reported value of the surface area of montmorillonite has been achieved. The characterization was carried out by FTIR, BET, XRD, and SEM to ensure the qualification of the modified acid-activated and then impregnated with the solvent. The optimum condition for the input variable was 30 ºC, 9 bar, and 50% of the solvent to MMT, where the response was 252 mg/g. The evaluation of the heterogeneous and mono-multilayer adsorption indicated the experimental data well-fitted to the Hill isotherm model with n higher than 1, indicating the desirability of the adsorbent (n was also 1.59 for the Freundlich isotherm model). The Elovich kinetic model was observed to be in the best agreement with the experimental data. Eight cycles of adsorption-desorption results indicated an excellent reversible adsorbent with low-temperature regeneration (90ºC) is attained.

KEYWORDS:

• Deep eutectic solvent
• montmorillonite
• Nano-clay
• CO₂ adsorption
• RSM
• isotherm

Disclosure statement

No potential conflict of interest was reported by the authors.

Statement of novelty

• Synthesizing a green adsorbent for CO₂ capture by Choline Chloride-Urea (ChCl: U) functionalization of montmorillonite (MMT) for the first time.

• The specific surface area of MMT increased 10 times at an optimum value of 3 M. HCl.

• HCl effect on adsorbent porosity, and consequently CO₂ adsorption capacity was investigated.

• The CO₂ uptakes of bare MMT, acid-activated MMT, and DES impregnated MMT were investigated.

• Heterogeneous and mono-multilayer adsorption indicated the experimental data well fitted to the Hill isotherm, and the Elovich kinetic model.

• A low-temperature regeneration adsorbent during 8 cycle adsorption-desorption.

• This paper has informed a complete characterization for DES-based adsorbent in the view point of kinetic, thermodynamic, and isotherm for any possible scale-up study.