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 120°C 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.

Hydrogen sulfide (H2S) should be removed in the early stage of biogas purification as it may affect biogas production and cause environmental and catalyst toxicity. The adsorption of H2S gas by using activated carbon as a catalyst has been explored as a possible technology to remove H2S in the biogas industry. In this study, we investigated the optimal catalytic preparation conditions of the H2S adsorbent by using the RSM methodology and the Box–Behnken experimental design. The H2S catalyst was synthesized by impregnating commercial activated carbon (CAC) with zinc acetate (ZnAc2) with the factors and level for the Box–Behnken Design (BBD): molarity of 0.2–1.0 M ZnAc2 solution, soaked temperature of 30–100 °C, and soaked time of 30–180 min. Two responses including the H2S adsorption capacity and the BET surface area were assessed using two-factor interaction (2FI) models. The interactions were examined by using the analysis of variance (ANOVA). Hence, the optimum point of molarity was 0.22 M ZnAc2 solution, the soaked period was 48.82 min, and the soaked temperature was 95.08 °C obtained from the optimum point with the highest H2S adsorption capacity (2.37 mg H2S/g) and the optimum BET surface area (620.55 m2/g). Additionally, the comparison of the optimized and the non-optimized catalytic adsorbents showed an enhancement in the H2S adsorption capacity of up to 33%.

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Metal-based adsorbents with varying active phase loadings were synthesized to capture hydrogen sulfide (H2S) from a biogas mimic system. The adsorption–desorption cycles were implemented to ascertain the H2S captured. All prepared adsorbents were evaluated by nitrogen adsorption, Brunauer–Emmett–Teller surface area analysis, scanning electron microscopy–energy-dispersive X-ray spectroscopy, and Fourier transform infrared spectroscopy. From the results, modified adsorbents, dual chemical mixture (DCM) and a core–shell (CS) had the highest H2S adsorption performance with a range of 0.92–1.80 mg H2S/g. After several cycles of heat/N2 regeneration, the total H2S adsorption capacity of the DCM adsorbent decreased by 62.1%, whereas the CS adsorbent decreased by only 25%. Meanwhile, the proposed behavioral model for H2S adsorption–desorption was validated effectively using various analyses throughout the three cycles of adsorption–desorption samples. Moreover, as in this case, the ZnAc2/ZnO/CAC_OS adsorbents show outstanding performances with 30 cycles of adsorption–desorption compared to only 12 cycles of ZnAc2/ZnO/CAC_DCM. Thus, this research paper will provide fresh insights into adsorption–desorption behavior through the best adsorbents’ development and the adsorbents’ capability at the highest number of adsorption–desorption cycles.

In this work, the performance of anion exchange membrane (AEM) electrolysis is evaluated. A parametric study is conducted, focusing on the effects of various operating parameters on the AEM efficiency. The following parameters—potassium hydroxide (KOH electrolyte concentration (0.5–2.0 M), electrolyte flow rate (1–9 mL/min), and operating temperature (30–60 °C)—were varied to understand their relationship to AEM performance. The performance of the electrolysis unit is measured by its hydrogen production and energy efficiency using the AEM electrolysis unit. Based on the findings, the operating parameters greatly influence the performance of AEM electrolysis. The highest hydrogen production was achieved with the operational parameters of 2.0 M electrolyte concentration, 60 °C operating temperature, and 9 mL/min electrolyte flow at 2.38 V applied voltage. Hydrogen production of 61.13 mL/min was achieved with an energy consumption of 48.25 kW·h/kg and an energy efficiency of 69.64%.

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.

This study focuses on the synthesis, characterization, and evaluation of the performance of core shell nanostructure adsorbent for hydrogen sulfide (H2S) capture. Commercial coconut shell activated carbon (CAC) and commercial mixed gas of 5000 ppm H2S balanced N2 were used. With different preparation techniques, the CAC was modified by core shell impregnation with zinc oxide (ZnO), titanium oxide (TiO2), potassium hydroxide (KOH), and zinc acetate (ZnAC2). The core structure was prepared with CAC impregnated by single chemical and double chemical labelled with ZnAC2-CAC (single chemical), ZnAC2/KOH-CAC, ZnAC2/ZnO-CAC, and ZnAC2/TiO2-CAC. Then, the prepared core was layered either with KOH, TiO2, NH3, or TEOS for the shell. The synthesized adsorbents were characterized in physical and chemical characterization through scanning electron microscopy (SEM), thermal gravimetric analysis (TGA), and Brunauer-Emmett-Teller (BET) analyzers. Operation of the adsorber column takes place at ambient temperature, with absolute pressure at 1.5 bar. The H2S gas was fed into the column at 5.5 L/min and the loaded adsorbents were 150 g. The performance of synthesized adsorbent was analyzed through the adsorbent’s capability in capturing H2S gas. Based on the results, ZnAc2/ZnO/CAC_WOS shows a better adsorption capacity with 1.17 mg H2S/g and a 53% increment compared to raw CAC. However, the degradation of the adsorbents was higher compared to ZnAc2/ZnO/CAC_OS and to ZnAc2/ZnO/CAC_WS ZnAc2/ZnO/CAC_OS. The presence of silica as a shell has potentially increased the adsorbent’s stability in several cycles of adsorption-desorption.