Study of regeneration of activated carbons used as H2S adsorbents in water treatment plants

Regeneration of unmodified activated carbons used in New York City sewage treatment plants was carried out using cold water washing and thermal treatment at 300degreesC. The efficiency of the regeneration process was evaluated using adsorption of nitrogen, thermal analysis and dynamic measurement of hydrogen sulfide breakthrough capacity. Although differences in the behavior of samples from different locations exist, the results showed that thermal treatment is more efficient than cold water washing. The latter process was able to remove only a small percentage of sulfur species in the form of sulfuric acid, leaving the deposit of elemental sulfur intact. However, treatment at 300degreesC resulted in the removal of a significant amount of deposited sulfur species. The hydrogen sulfide adsorption capacity of regenerated samples was low due to the alterations in surface chemistry, which occurred during the treatment. The efficient regeneration of the carbon. surface was not achieved due to the presence of significant amounts of volatile organic compounds adsorbed from effluent air. (C) 2002 Elsevier Science Ltd. All rights reserved.