Enhancement of CO2 absorption and heat transfer properties using amine functionalized magnetic graphene oxide/MDEA nanofluid

Amino-functionalized magnetic graphene oxide is added to MDEA solution to improve the CO2 absorption. Graphene oxide (GO) was synthesized and functionalized by amine groups and magnetic materials (NH2-mGO). NH2-mGO was fully characterized using XRD, FTIR, SEM, EDS, TEM, and BET techniques. The presence of O, Fe, and N elements with weight percentages of 21.51, 9.43, and 5.61 indicated that graphene surfaces were well functionalized with ethylenediamine and magnetic Fe3O4 nanoparticles. 0.1 wt.% NH2-mGO was added to the 40 wt.% aqueous MDEA solution to obtain a novel absorption solution known as nanofluid. CO2 absorption experiments were conducted at different temperatures and pressures and the results showed that the absorption has been improved by 19% compared with the base fluid (40 wt.% aqueous MDEA solution). Thermal conductivity of the nanofluid was examined and results revealed an increase of about 17% in the thermal conductivity of the nanofluid compared to the base fluid. Convective heat transfer investigations also showed an average improvement of 15% after the addition of nanoparticles into the fluid. NH2-mGO had the ability to effectively recovered and retain its active sites on the surface throughout the repeated cycles and thermal treatment. The magnetic property of the as-prepared nanostructure allowed recovering the spent nanoparticles for using in the subsequent absorption process.