Study of H2S Adsorption and Water Regeneration of Spent Coconut-Based Activated Carbon

A coconut shell-based activated carbon was studied as hydrogen sulfide adsorbent in four subsequent adsorption/regeneration cycles. The regeneration of exhausted carbon was done using washing with cold and hot water with a defined ratio of water volume to the unit weight of carbon. The observed changes in the capacity were linked to such surface features of activated carbons as pH and porosity. The cold and hot water washing result in the similar capacity for H 2 S adsorption. After the first adsorption run the capacity of carbon for hydrogen sulfide adsorption significantly decreased (around 60%). The subsequent runs revealed more or less constant capacity with similar efficiency for the removal of sulfur species. The results indicate that after the first run the most active adsorption cites located in small pores are exhausted irreversibly. The sulfur adsorbed on those sites is strongly bound as elemental sulfur and sulfuric acid. Despite this, the carbon surface was found to have other adsorption/oxidation sites which can be regenerated using cold or hot water washing. Besides sulfuric acid being removed from the pore volume of activated carbon a significant percentage of elemental sulfur was also removed.