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

Abstract

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.