Comparative study on the effect of ZnCl2, a 60:20:20 mol % eutectic of ZnCl2-NaCl-KCl and CO2 during activation of pinewood

Chemical activation in molten salts is a recent development in the field of tailoring activated carbon, where a combination of activating agents is used rather than a single compound. However, a comprehensive understanding of differences in catalytic activity is lacking. So, the question remains which chemical activation method is more beneficial. This research compares the catalytic effect of ZnCl2 as a single activating agent and its eutectic mixture of ZnCl2-KCl-NaCl (60:20:20 mol %). Pinewood shavings were chemically activated at 400 degrees C in a mass ratio of 5 to 1 (salt to biomass) and then washed to remove the activating agent. Obtained materials were subsequently physically activated using CO2 at 800 degrees C in an attempt to further increase their surface area. Properties of obtained carbons were characterized by elemental and proximate analyses, ICP-AES, FTIR, gas adsorption (N-2, CO2), and adsorption (iodine, methylene blue, and molasses). Chemical activation with ZnCl2 and the eutectic mixture resulted in a surface area of respectively 910 m(2)/g and 917 m(2)/g with significant differences in porosity. The eutectic mixture created a greater proportion of micropores. ZnCl2 was more beneficial for mesoporosity which was formed over a broad range, whereas the eutectic mixture created mesopores in a narrower size range (19-27 nm). Subsequent CO2 gasification widened the pores and lowered the surface area, decreasing the adsorption capacity. This study illustrates that employing mixtures of molten salts has several advantages over a single activating agent and might lead to further development of tailor-made activated carbons.