Carbonization of hydrothermally modified spent coffee grounds and tea leaves and the ethene adsorption properties of the resulting carbons

Abstract

Spent coffee grounds and tea leaves were hydrothermally treated and carbonized to investigate the structure of the resulting carbons and their potential for ethene adsorption. After the hydrothermal treatments, the carbonized yield and the porosity in the carbons were increased. The increases in ultra-micropores and micropore/mesopore volumes which were respectively calculated by CO₂ and N₂ adsorption varied depending on the kind of feedstock. Hydrothermal treatment using ethanol washing to remove crystalline fatty acids, prior to carbonization, considerably increased the BET specific surface area, particularly in coffee grounds. In all carbons studied, ultra-micropores were also developed mainly by the thermal decomposition of cellulose components in the hydrochars. These narrower pores in the carbons were found to be effective for ethene adsorption because of strong correlation between ethene and CO₂ adsorptions.