A comprehensive study to evaluate absolute uptake of carbon dioxide adsorption onto composite adsorbent

In this study, new composite adsorbent with enhanced thermal conductivity and adsorption capacity was synthesized and analyzed comprehensively for the development of compact CO2 based adsorption cooling system. The consolidated composite was prepared employing activated carbon, graphene nanoplatelets and hydroxyl cellulose as a parent adsorbent, thermal conductivity enhancer, and binder, respectively. The surface area and pore volume of the composite were found to be 1778 +/- 13 m(2)g(-1) and 1.014 cm(3)g(-1), respectively. In addition, the composite showed 233% higher thermal conductivity compared to the parent activated carbon. Adsorption characteristics of CO2 were measured at temperature ranging from 20 to 70 degrees C and pressures up to 5 MPa. Absolute uptake was evaluated from excess adsorption based on the following two methods: (i) the adsorbed phase volume is equal to the pore volume of the adsorbent; and (ii) the adsorbed phase volume is almost zero under low pressure and/or high temperature conditions. Furthermore, the averaging of above two methods was also taken for avoiding these two extreme assumptions. Obtained absolute adsorption uptake data were fitted with modified Dubinin-Astakhov and Toth models. Results indicated good approximation between data points and models. The average isosteric heats of adsorption estimated using modified D-A and T6th model were found to be 19.742 kJ mol(-1) and 19.023 kJ mol(-1), respectively. The obtained characteristics of composite adsorbent are prerequisites for designing compact CO2 based adsorption cooling systems. (C) 2019 Elsevier Ltd and IIR. All rights reserved.