This study reports on the impregnation of bi-metallic adsorbents based on commercial coconut activated carbon (CAC), surface-modified with metal acetate (ZnAc2), metal oxide (ZnO and TiO2), and the basic compound potassium hydroxide (KOH). The morphology of the adsorbents was then characterized with SEM-EDX, the microporosity was determined using Brunauer-Emmett-Teller (BET) analysis, the thermal stability was investigated via thermogravity analysis (TGA), and functional group analysis was undertaken with Fourier-transform infrared (FTIR) spectroscopy. These modified adsorbents were subjected to a real adsorption test for H2S capture using a 1 L adsorber with 5000 ppm H2S balanced for N2, with temperature and pressure maintained at an ambient condition. Adsorption-desorption was carried out in three cycles with the blower temperature varied from 50 °C to 150 °C as the desorption condition. Characterization results revealed that the impregnated solution homogeneously covered the adsorbent surface, effecting the morphology and properties. Based on this study, it was found that ZnAc2/TiO2/CAC_DCM showed a significant increase in adsorption capacity with the different temperatures applied for the desorption in the second cycle: 1.67 mg H2S/g at 50 °C, 1.84 mg H2S/g at 100 °C, and 1.96 mg H2S/g at 150 °C. ZnAc2/ZnO/CAC_DCM seemed to produce the lowest percentage of degradation in the three cycles for all the temperatures used in the adsorption-desorption process. Therefore, ZnAc2/ZnO/CAC_DCM has the potential to be used and commercialized for biogas purification for H2S removal.
Keywords: H2S removal; adsorbent; adsorption–desorption; biogas purification.