Removal of hydrogen sulfide from a biogas mimic by using impregnated activated carbon adsorbent

Abstract

Adsorption technology has led to the development of promising techniques to purify biogas, i.e., biomethane or biohydrogen. Such techniques mainly depend on the adsorbent ability and operating parameters. This research focused on adsorption technology for upgrading biogas technique by developing a novel adsorbent. The commercial coconut shell activated carbon (CAC) and two types of gases (H 2 S/N 2 and H 2 S/N 2 /CO 2 ) were used. CAC was modified by copper sulfate (CuSO 4 ), zinc acetate (ZnAc 2 ), potassium hydroxide (KOH), potassium iodide (KI), and sodium carbonate (Na 2 CO 3 ) on their surface to increase the selectivity of H 2 S removal. Commercial H 2 S adsorbents were soaked in 7 wt.% of impregnated solution for 30 min before drying at 120C for 24 h. The synthesized adsorbent's physical and chemical properties, including surface morphology, porosity, and structures, were characterized by SEM-EDX, FTIR, XRD, TGA, and BET analyses. For real applications, the modified adsorbents were used in a real-time 0.85 L single-column adsorber unit. The operating parameters for the H 2 S adsorption in the adsorber unit varied in L/D ratio (0.5-2.5) and feed flow rate (1.5-5.5 L/min) where, also equivalent with a gas hourly space velocity, GHSV (212.4-780.0 hour -1 ) used. The performances of H 2 S adsorption were then compared with those of the best adsorbent that can be used for further investigation. Characterization results revealed that the impregnated solution homogeneously covered the adsorbent surface, morphology, and properties (i.e., crystallinity and surface area). BET analysis further shows that the modified adsorbents surface area decreased by up to 96%. Hence, ZnAc 2 -CAC clarify as the best adsorption capacity ranging within 1.3-1.7 mg H 2 S/g, whereby the studied extended to adsorption-desorption cycle.