Hemp Stem Activated Carbon for Fermentative Hydrogen Enhancement

Hemp stem was used as a raw material to make available activated carbon as it contains high carbon and adsorption capacity. It was synthesized by a chemical activation using H₃PO_4. The effect of activation temperature within a range of 350-500°C was explored. The obtained hemp stem activated carbons (H-ACs) were used for biohydrogen enhancement. Treated activated carbon (TAC) from the National Nanotechnology Center, Thailand was used for a comparative study. The results showed that H-AC with activation temperature of 500°C obtained the maximum hydrogen yield of 2.64 ± 1.16 mol of H₂/mol of sucrose. Determination of specific surface area based on the Brunauer-Emmet-Teller (BET) theory, showed that H-AC (500°C) possessed the highest mesopore volume of 0.3650 cm³/g with specific surface area of 1,219.24 m²/g. A greater porosity of H-AC (500°C) as compared to TAC and other H-ACs led to a greater adsorption ability, particularly for volatile fatty acids, thus enhanced fermentative hydrogen production.