Chemical versus physical activation of coconut shell: A comparative study

Granular activated carbons with high porosity were produced from dried endocarp of coconut shell using both physical activation with CO2 and chemical activation with H3PO4 or ZnCl2. Efforts were focused on the elucidation of the activation processes and on the establishment of correlations between these and the properties of the synthesized materials. The results show that the physical process permits to tailor the pore size distribution more accurately. However, the resulting materials present relatively low packing densities due to the occurrence of empty spaces that originate, at least partially, from the structure of conductor vessels present in the botanical structure of the precursor. On the other hand, chemical activation with H3PO4 or ZnCl2 permits to reduce drastically the occurrence of such empty spaces, leading to materials with higher packing densities, which positively affect the volumetric adsorption capacity. Further, chemical activations leads to lower weight losses during the activation processes and permits the synthesis of carbons with higher mechanical resistance and elevated proportion of mesopores.

Graphical abstractFigure optionsDownload full-size imageDownload as PowerPoint slideHighlights► Biomass based activated carbons were produced by physical (CO2) and chemical (H3PO4 or ZnCl2) activation. ► Physical process permitted to tailor the pore size distribution more accurately. ► Physical activation generates carbons with empty spaces originated from the botanical structure of the precursor. ► Chemical activation redistributes the botanical structure, minimizing the occurrence of empty spaces. ► Chemical activation leads to carbons with higher packing densities, which favors the volumetric adsorption capacity.