Thermal Regeneration of Activated Carbon Used as an Adsorbent for Hydrogen Sulfide (H₂S)

The treatment of gaseous contaminants, such as hydrogen sulfide (H₂S), is often carried out with adsorbent materials that are disposed of after saturation. The reuse of such materials promotes sustainability and the reduction in unnecessary waste. Granular activated carbon (GAC) is a well-known adsorbent used to capture gaseous H₂S which can be reused. It is hypothesized that it can also concentrate contaminants for future treatment, thereby reducing secondary treatment costs. Cyclic adsorption/desorption experiments were completed with samples of GAC to investigate the feasibility of implementing the concept of repeated H₂S adsorption/desorption in the construction of a pilot odor control device. A column filled with GAC was exposed to a stream of H₂S gas and then heated to 500 °C to regenerate the carbon. The concentration of H₂S at the inlet and outlet of the column was measured at regular intervals. Three samples of GAC had an average adsorption efficiency of 82% over the course of three cycles and were regenerated to 70% of initial adsorptive capacity after one cycle, and 60% after two cycles. These results indicate that after being saturated with H₂S, GAC can be regenerated at high temperatures, evidence that H₂S may become concentrated during the process. Additional characterization experiments confirmed that the sulfur content of the carbon increased after adsorption and decreased after thermal regeneration. The procedures demonstrated in this experiment were further utilized with a pilot device designed to provide a low-cost method for reducing odors in landfill gas.