Effect of impregnated activated carbon on carbon dioxide adsorption performance for biohydrogen purification

Abstract

The challenge in biohydrogen (bio-H2) production is the presence of low hydrogen purity, which contains a high concentration of carbon dioxide (CO2). Bio-H2 purification systems are required to produce high-purity hydrogen for industrial applications, such as adsorption for CO2 removal. This study tested the effect of impregnated activated carbon (AC) and feed gas flow rate on CO2 adsorption performance. Different types of adsorbents were synthesized by impregnating the chemical on AC, such as potassium iodide, potassium hydroxide, copper (II) sulfate, sodium carbonate, and zinc acetate. The feed gas flow rate was varied in the range of 0.25–1.0 L min−1 by using synthetic bio-H2 gas, that is, mixing the gas with 50 vol.% H2 and 50 vol.% CO2. The CO2 adsorption performances of the synthesized adsorbents were evaluated in terms of breakthrough time and adsorption capacity. To evaluate the reusability of the adsorbents, adsorption–desorption cycles were conducted for several times. For desorption, atmospheric air was used to remove the adsorbed CO2 from the adsorbents. The effect of air flow rate on CO2 desorption was assessed by setting the air flow rate to be between 100 and 350 L min−1. The impregnated AC with zinc acetate displayed the highest adsorption capacity of 63.61 mg CO2/g adsorbent and the longest breakthrough time of 25.7 min. The optimum feed gas flow rate was 0.25 L min−1, thereby demonstrating that the lowest feed gas flow rate resulted in the highest adsorption capacity. Moreover, desorption was faster at higher air flow rates.