ABSTRACT

H2S Adsorption Characteristics of Adsorbent Made by Coffee Grounds

H2S adsorption characteristics of adsorbent made by coffee grounds were investigated. The manufacturing method of adsorbent used in this experiment is to activate the carbonized coffee grounds with steam and carbon dioxide after carbonization of dried coffee grounds. For analyses of the manufactured adsorbent, various methods such as chemical composition analysis, particle size analysis, scanning electron microscope(SEM), BET analysis, measurement of pH and iodine adsorptivity were adopted.
The major experimental results are as follows. The pH of coffee ground samples were 4.5 to 10.4 and the iodine adsorptivities were 263 to 582 mg/g. The BET surface area of activated coffee grounds was 160 times higher than carbonized coffee grounds, which indicates that the activation process is significant for manufacturing adsorbent using coffee grounds.
In both activation methods for coffee grounds, the specific surface area increased with increasing activation temperature. In case of steam activation at 600~700℃, the specific surface area is increased in the range of 310.4~639.2 m2/g, but in the case of complex activation, it shows a larger increase in the range of 348.7~780 m2/g.
The hydrogen sulfide equilibrium adsorption capacity of the adsorbents made by coffee grounds showed the adsorption capacity of 150.1~201.6mg H2S/g adsorbent in steam activation and 164.3~234.1mg H2S/g adsorbent in complex activation. It has been found that the optimal combination of activation temperature, steam injection rate, and activation time is required because the reduction of specific surface area or the reduction of various functional groups that can induce physical adsorption results in reduced equilibrium adsorption capacity.
In addition, the hydrogen sulfide equilibrium adsorption capacity of the coffee adsorbent was proportional to the partial pressure, and the hydrogen sulfide equilibrium adsorption capacity was able to simulate the experimental values for Langmuir, Freundlich, and Langmuir-Freundlich model equations.
Adsorption monitoring experiments for single odor(hydrogen sulfide) and complex odors(hydrogen sulfide and ammonia mixture) showed that adsorbents made by coffee grounds had very good odor adsorption capacity due to relatively fast adsorption rate and high removal efficiency. Based on the results of this study, if more technical and economic optimization studies on the active treatment of coffee grounds are conducted, the practical applicability of existing coffee grounds is expected to be greatly improved.


Key words: Coffee grounds, Steam activation, Complex activation, Hydrogen sulfide, Equilibrium adsorption capacity, Adsorption monitering