Experimental investigation of carbon dioxide absorption by amine-based nanofluids containing two-dimensional hexagonal boron nitride nanostructures

Abstract

In this research, the influence of the two-dimensional hexagonal boron nitride nanostructures (hBNNs) upon the process of carbon dioxide (CO2) absorption into the aqueous solution of methyl diethanolamine (MDEA) was investigated. The absorption tests were performed using the pressure drop technique in a stirred thermostatic reaction chamber. The hBNNs were synthesized through the sonication-assisted hydrolysis method and characterized by FTIR, XRD, FESEM, EDX, and TGA techniques. After synthesis and characterization, the nanostructures were dispersed in an aqueous MDEA solution at different concentrations via ultrasonication and without surfactants. The stability of the nanodispersions was measured by the zeta potential analysis. The effect of hBNNs loading, MDEA concentration in the base fluid, and amount of nanofluid on the absorption process was also studied. The results revealed that the addition of hBNNs into the base fluids up to a concentration of 0.025 wt% improves the initial CO2 absorption rate and the total amount of absorbed CO2, yet, by further increasing the concentration, the mentioned values are decreased. According to the absorption measurements, for the 5 wt% aqueous solution of MDEA containing 0.025 wt% hBNNs, the highest enhancement of the initial CO2 absorption rate and the total absorbed CO2 into the nanofluid were 5.1 and 3.98%, respectively. The results also indicated that higher MDEA concentrations weaken the enhancement effect of the nanofluids. Furthermore, it was observed that the effect of the nanofluids on the absorption process is independent of their amount. According to the experiments, hBNNs could be reused for at least five consecutive cycles, without a significant drop in the nanofluid efficiency. The results of this study indicated that the use of the two-dimensional hBNNs at very low concentrations improved the CO2 absorption process.