Coconut shell derived activated carbon for effective separation of greenhouse gases

Abstract

The development of efficient adsorbent materials for the selective capture of greenhouse gases (GHGs) is crucial. The porosity and surface area of the materials are key factors for the GHGs separation. This study demonstrates how waste from coconut shell (CS) biomass can be used to design novel biomaterials (CS-CO2, CS-ZnCl2) with enhanced GHG selectivity. A comparison with activated carbon monoliths (ACM) and a metal-organic framework (Fe-BTC) was carried out to assess the impact of different porous matrices on GHGs capture. The adsorption equilibrium of R-32, R-125, R-134a, R-143a, CO2, and CH4 on these materials was measured between 283.15–323.15 K. The adsorption isotherms obtained were fitted using the dual-site Langmuir model. For R-32, R-125, R-134a and R-143a, the adsorption capacity follows ACM > CS-ZnCl2 > Fe-BTC > CS-CO2 due to the decrease of the surface area. The CO2 adsorption capacity is ACM > Fe-BTC > CS-ZnCl2 > CS-CO2, which is related to the micropore volume. In this case, CS-CO2 has a smaller adsorption capacity but is similar to ACM and outperforms Fe-BTC at P < 0.4 MPa. The selectivity of R-410A, R-407C, R-404A, and CO2/CH4 blends was determined with the Ideal Adsorbed Solution Theory (IAST). CS-ZnCl2 shows a higher selectivity for R-125 over R-32 in R-410A and R-407C separations due to its larger pore volume. CS-CO2 predominantly adsorbs R-134a and R-143a over R-125 in R-404A separation. ACM preferentially adsorbs CO2 over CH4 due to its large, elongated micropores. This study introduces innovative materials that improve GHGs separation and help reduce emissions.