Strontium hydroxide-modified nanoclay montmorillonite for CO₂ capture: response surface methodology and adsorption mechanism

ABSTRACT

In this work, the effects of surface activation and modification of nanoclay adsorbent on CO₂ adsorption capacity were investigated. SEM analysis showed that after activation, the nanoclay layer structure has been retained and did not lose crystallinity as a layer structure. FTIR analysis concludes that structural changes occur even in the early stages of surface treatment with HCl. BET analysis showed that during surface activation, the MMT-4 sample had the highest specific surface area of 144.35 m².g⁻¹ and pore volume of 0.18 cm³·g⁻¹. Besides, for the modified sample, mesoporous-microporous gradually decrease during surface modification with SH. In the optimisation, the effect of operating conditions including temperature, pressure, acid concentration for adsorbent surface activation, and the weight percent (wt. %) of strontium hydroxide were investigated using RSM. Optimal adsorption capacity of 102.21 mg/gwas obtained at temperature of 25°C, pressure of 9 bar, the acid concentration of 4.03 Mol/L, and SH of 16.25 wt.%. Investigation of adsorption isotherm models indicates a well-fitting correlation between the Sips isotherm model and experimental data. The best fit of the CO₂ adsorption experimental data with Elovich model indicates the connection of CO₂ to the modified sample by forming the chemical bonds due to the high surface energy. Thermodynamic parameters showed that the adsorption process is spontaneous and exothermic.

KEYWORDS:

• CO₂
• nanoclay
• structure modification
• adsorption mechanism
• optimisation
• response surface methodology
• strontium hydroxide

Disclosure of potential conflicts of interest

No potential conflict of interest was reported by the author(s).