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

Abstract

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.

Mesostructural study on graphenic-based carbon prepared from coconut shells by heat treatment and liquid exfoliation

“…It can be used to estimate the thermal decomposition behavior of biomass as a function of weight reduction (TGA curve) and its first derivative (DTG -derivative thermogravimetric curve). A minor peak was observed in the DTG curve at temperatures below 100 C, which corresponds to the release of intrinsic water [30,31], resulting in an approximate mass loss of 5.7%. A significant amount of mass loss (~45.26 %) occurs between 200 and 400 C. Generally, heat degradation of biomass occurs as a result of hemicellulose, cellulose, and lignin decomposition [32,33].…”

Physico-chemical and combustion analyses of bio-briquettes from biochar produced from pyrolysis of groundnut shell

“…Pyrolysis causes substantial transformation to the surface morphology of the chars, this is probably caused by the increased rupture of the biomass structure due to release of more volatile matter as the heating temperature was increased [37]. Pyrolysis distorted the fine collagen fiber network [38]. The finer the particle size, the easier the compaction processes during densification and the better the quality of the briquette [39].…”

Optimization of pyrolytic oil production from coconut shells by microwave-assisted pyrolysis using activated carbon as a microwave absorber

“…Owing to its amorphous structure and low activation energy, hemicellulose could decompose at lower temperatures, over a wider temperature range between 190°C and 380°C (Escalante et al, 2022). At the same time, cellulose could decompose in a slightly narrow temperature range between 250°C and 400°C (Tangsathitkulchai, Junpirom, & Katesa, 2016). Thus, it could be inferred that the appearance of the overlapping peaks of the TGA/DTG curves was mostly related to the breakdown of the cellulose and hemicellulose components.…”