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In this work, a series of innovative metal oxide impregnated waste-derived activated carbons (MO/AC) was synthesized and used to purify the simulated biohydrogen based on the concept of CO2 removal from the gas stream. Effects of metal oxide types (CaO, SrO and MgO) and contents of the best metal oxides on the morphology and the CO2 adsorption capacity from the biohydrogen were investigated. It was found that both metal oxide types and contents played an important role on the adsorbent textural property and surface chemistry as well as the CO2 adsorption capacity. Among all synthesized adsorbent, the MgO-impregnated AC with 12 wt.% MgO (12MgO/AC) exhibited the highest CO2 adsorption capacity of around 94.02 mg/g. With this successive adsorbent, the biohydrogen with the H2 purity higher than 90 mol% can be achieved from the gas stream with 50 mol% CO2 for the first 2 min of adsorption period in a fixed bed reactor. The mechanism of CO2 adsorption occurred via a combined process of the physisorption and chemisorption. Besides, the 12MgO/AC exhibited a high recyclability after several repetitive adsorption/desorption cycles. [ABSTRACT FROM AUTHOR]

A series of activated carbons (ACs) derived from spent disposable wooden chopsticks was prepared via steam activation and used to separate carbon dioxide (CO2) from a CO2/hydrogen (H2) mixed gas at atmospheric pressure. A factorial design was employed to investigate the effects of the activation temperature and time as well as their interactions on the production yield of ACs and their CO2 adsorption capacity. The activation temperature exhibited a much higher impact on both the production yield and the CO2 adsorption capacity of ACs than the activation time. The interaction of both parameters did not significantly affect the yield of ACs, but did affect the CO2 adsorption capacity. The optimal preparation condition provided ACs with a desirable yield of around 23.18% and a CO2 adsorption capacity of 85.19 mg/g at 25 °C and 1 atm and consumed the total energy of 225.28 MJ/kg AC or 116.4 MJ/g-mol CO2. A H2 purity of greater than 96.8 mol% was achieved from a mixed gas with low CO2 concentration (< 20 mol%) during the first 3 min of adsorption and likewise around 90 mol% from a mixed gas with a high CO2 concentration (> 30 mol%) during the first 2 min. The CO2 adsorption on the as-prepared ACs proceeded dominantly via multilayer physical adsorption and was affected by both the surface area and micropore volume of the ACs. The adsorption capacity was diminished by around 18% after six adsorption/desorption cycles. The regeneration of the as-prepared chopstick-derived ACs can be easily performed via heating at a low temperature and ambient pressure, suggesting their potential application in the temperature swing adsorption process. [ABSTRACT FROM AUTHOR]

Sugarcane bagasse (SCB) and sugarcane bagasse ash (SCB-ash) are major agricultural residues from sugar processing industries in Thailand. In this study, SCB-derived activated carbon (SCBAC) with the optimum surface area of 489 m2/g was prepared by steam activation at 900 °C for 1 h. Hybrid granular activated carbons (GACs) were successfully developed by mixing SCBAC with bio-based polymers, alginate and gelatin, at the weight ratio of 3:1 for methylene blue (MB) adsorption. SCB-ash, which was additionally mixed in the GACs, could significantly increase compressive strength of the GACs, but decrease their surface areas and MB adsorption efficiencies. An existence of gelatin up to 30 wt% in the polymer matrix of the GACs showed a slight increase in swelling degree and iodine number, but could not enhance bead strength and MB adsorption efficiency due to its relatively lower bulk density and specific surface area. Maximum MB adsorption capacities of the GACs were found at 290–403 mg/g under this study's experimental condition. MB adsorption efficiencies at above 90 % with no deformation of all of the selected SCB hybrid GACs were finally confirmed after seven consecutive adsorption-desorption cycles using a simple regeneration with ethanol. • GACs could be developed from sugarcane bagasse residues with bio-based polymers. • Existence of gelatin in alginate enhanced swelling ratio of GACs with lower surface area. • Additional SCB-ash in GACs could significantly increase the compressive strength. • SCB hybrid GACs could be simply regenerated using ethanol without deformation. • The GACs could be reused with high MB adsorption efficiency for at least 7 cycles. [ABSTRACT FROM AUTHOR]

• H 2 -rich gas was purified by selective adsorption of CO 2 impurity via AC. • AC prepared by KOH activation at 700 °C and 90 min showed the highest CO 2 uptake of 115.5 mg/g. • Selectivity of CO 2 adsorption was 17.6 times over H 2 at 25 °C and 1 atm. • CO 2 adsorption fitted followed the Freundlich isotherm and pseudo-second-order model. • Both physical and chemical adsorptions played the role for CO 2 on the obtained AC. The production of fossil fuel-based H 2 by steam reforming and water–gas shift reactions gives the reformed gas containing both hydrogen (H 2) and carbon dioxide (CO 2). To get pure H 2 , the CO 2 must be removed. In this work, the CO 2 was selectively separated from the gas mixture of CO 2 and H 2 by adsorption process using the spent disposable wooden chopstick (SWC)-derived activated carbon (AC) synthesized by the chemical activation. An appropriate condition for biochar preparation was first explored and then the chemical activation was carried out. Two types of activation chemicals (ZnCl 2 and KOH) were employed to activate the biochar at different temperatures (500 – 800 °C). Effects of activation holding time (60 – 150 min) and activation chemical to biochar weight ratio (0.5 – 2.5) were also investigated. The optimal condition for biochar preparation was found at 500 °C and 15 min which can provide the AC yield of 29.5% and CO 2 adsorption capacity of 19.2 mg/g from the gas mixtures with 50 mol% CO 2 at 25 °C and 1 atm. The AC synthesized by the KOH activation at 700 °C using a KOH/biochar weight ratio of 1.5 for 90 min exhibited the highest CO 2 adsorption of 115.7 mg/g for the first use and dropped approximately 20% after 6 adsorption/desorption cycles. Based on the perspective Grand Canonical Monte Carlo (GCMC) simulation, the best synthesized AC exhibited the selectivity of CO 2 adsorption 17.6 times higher than that of H 2. The adsorption behavior and kinetic model of CO 2 adsorption followed the Freundlich isotherm and the pseudo-2nd order model, respectively and the CO 2 adsorption occurred via the combined physical and chemical mechanism. [ABSTRACT FROM AUTHOR]