Highly efficient CO_(2)capture on acid-treated sepiolite impregnated with mixed polyethyleneimine and diethanolamine

Amine-functionalized solid adsorbents exhibit broad prospects in CO_(2)capture from flue gases due to their high adsorption capacity and selectivity.However,reported adsorbents are still facing challenges,including high costs,the easy agglomeration of polyamines,and limited adsorption temperature ranges.In this study,sepiolite-based mixed amine adsorbents are prepared by synergistically impregnating acid-treated sepiolite with a mixture of polyethyleneimine(PEI)and diethanolamine(DEA).Results show that at a PEI/DEA loading ratio of 1:1 and a mixture loading of 60wt%,the CO_(2)adsorption capacity of the resulting adsorbent increases from 0.58 mmol/g for acid-treated sepiolite to 2.89 mmol/g at 60℃,and remains above 2.50 mmol/g after 10 cycles.Meanwhile,the optimized adsorbent maintains a capacity of over 2.44 mmol/g within the temperature range of 30-70↓.Additionally,the CO_(2)selectivity and maximum heat of adsorption for the optimized adsorbent are calculated to be 1184 and 60.08 kJ/mol,respectively.An improved CO_(2)adsorption capacity is obtained,an increase from 0.052 mmol/g for acid-treated sepiolite to 1.60 mmol/g.Furthermore,an in-situ diffuse reflectance infrared Fourier-transform spectroscopy(DRIFTS)analysis reveals that the introduction of DEA into PEI helps in polyamine dispersion,thereby enhancing CO_(2)adsorption capacity.The CO_(2)capture mechanism follows a zwitterionic reaction,where CO_(2)is ultimately converted into carbamate and carbamic acid.Overall,the as-prepared sepiolite-based mixed amine adsorbents,which are characterized by high CO_(2)adsorption capacity and selectivity,low cost,broad adsorption temperature range,moderate heat of adsorption,and good cycle stability,show promising potential for industrial applications.