Carbon Dioxide Adsorption in Nanopores of Coconut Shell Chars for Pore Characterization and the Analysis of Adsorption Kinetics

Abstract EN

The uptake data of CO2 adsorption at 273 K by coconut shell chars prepared at various carbonization temperatures from 250 to 550°C were used for characterizing pore texture of chars as well as the analysis of CO2 adsorption kinetics.

The equilibrium isotherms were used to determine the porous texture of chars, employing the DR equation and GCMC simulation.

It was found that all the test chars contain micropores of a size range from 0.8 to 2.2 nm with the pore size distribution becoming wider for char prepared at a higher carbonization temperature.

Porous properties of chars, including surface area, total pore volume, and the average pore size, appear to increase with an increasing carbonization temperature.

The analysis of CO2 uptake during the transient measurement of isotherms revealed that the kinetics of CO2 adsorption is governed by the internal diffusional transport of the adsorptive molecules.

The effective pore diffusivity characterizing this transport process increases with increasing CO2 loading and passes through a maximum at a certain loading.

This maximum pore diffusivity shifts to a higher value as the carbonization temperature is increased.

A semiempirical equation was developed to correlate the effective pore diffusivity of CO2 with the equilibrium adsorption loading and its predictive capability is satisfactory.