Study on diffusion coefficient of benzene and ethyl benzene vapours in nanoporous silica aerogel and silica aerogel-activated carbon composites

In this study, nanoporous silica aerogel and silica aerogel-activated carbon composites have been synthesized using a water glass precursor by a cost-effective ambient pressure drying method. Equilibrium and kinetics of benzene and ethylbenzene adsorption on silica aerogel and its composites have been measured in a batch mode at three weights of adsorbent. For the first time, the experimental data have been found to fit the intra-particle diffusion model for determining diffusion coefficients. The saturation adsorption capacities of benzene and ethylbenzene vapors were 2033 mg.g-1 and 458 mg.g-1, respectively. The components uptake curves have been described by mathematical models of pseudo-first-order and pseudo-second-order models. It has been found that the pseudo-first-order model fits the experimental data better than the pseudo-second-order model. Also, the pseudo-second-order model could be used for modeling of benzene adsorption over silica aerogel and silica aerogel-2 % wt activated carbon composite at the beginning of adsorption process. The diffusion coefficients of benzene and ethylbenzene within the silica aerogel were in the range of 2.16×10^−14 - 6.66×10^−13 m^2.s^-1 and 3.65×10^−13 - 1.9^5×10^−12 m62.s^-1, respectively