Currently, purification is a considerably important technology for biohydrogen (bioH(2)) production as a renewable energy resource. Adsorption methods are promising techniques for separation of CO2 from the H-2/CO2 mixture of bioH(2). In this study, the adsorbent is synthesized by impregnating activated carbon (AC) with ionic liquid (IL). The ILs were prepared using choline chloride and zinc chloride at different wt% with the AC, i.e., 0.5 wt%-3 wt%. The physical and chemical properties of the synthesized adsorbents, such as surface morphology, porosity, and structures, were investigated and characterized by using scanning electron microscopy (SEM), fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), thermogravimetric analysis (TGA), and Brunauer-Emmett-Teller analysis (BET). To investigate the actual adsorption performances, the effects of different synthesized adsorbent types and feed gas flow rates, i.e., 0.1-1.0 L min(-1), were observed. Hence, a commercial gas composed of CO2 and H-2 mixture with different compositions, i.e., 40, 50, and 60 vol%, was used as synthetic bioH(2) gas. The adsorption capacity of CO2, i.e., adsorption capacity, were determined using single adsorber column (0.6 L) at a temperature of 300 K and pressure of 1 bar. Results showed that adsorption capacity decreased with the increased feed gas flow rate. Moreover, the carbon impregnated with 1 wt% of IL showed the most excellent adsorption capacity at 84.89 mg of CO2/g of adsorbent. The present results are the initial findings generated for the bioH(2) separation technology for future high-purity hydrogen production. (C) 2018 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.