Terahertz-Intra-Particle Diffusion Model for Adsorption of Ethanol in Graphene-Based Materials

In this article, the terahertz-intraparticle diffusion model (THz-IPD) based on the intraparticle diffusion model and terahertz amplitude is established to assess diffusion adsorption rates and describe the mass transfer mechanism controlled by intraparticle diffusion. The diffusion adsorption process for four graphene-based materials with ethanol was analyzed by terahertz time-domain spectroscopy. Diffusion adsorption rates for four graphene-based materials were evaluated using a terahertz-pseudo second-order kinetic model and a terahertz-double-exponential model, revealing that intraparticle diffusion is one of the rate-limiting factors for adsorption. THz-IPD fitting found that intraparticle diffusion is not the only controlling factor. Hydrophobic interaction and hydrogen bonds are the decisive factors for the adsorption rates of hydrophobic and hydrophilic graphene-based materials. The results were supported by Brunner--Emmet--Teller (BET) surface area analysis, scanning electron microscope/energy spectrometer, and Fourier transform infrared methods.