Effect of TiO2 nanoparticles on the mass transfer process of absorption of toluene: Experimental investigation and molecular dynamics simulation

Toluene is a typical representative of aromatic volatile organic compounds, and its elimination makes an important contribution to combating air pollution. In this work, the effect of TiO2 nanoparticles on the mass transfer process during the removal of toluene by deep eutectic solvent (tetraethylammonium chloride and oleic acid) was investigated experimentally and theoretically. First, the removal effect of different nanofluids was evaluated by dynamic bubble absorption experiments. The concentration and particle size of TiO2 nanoparticles have a significant effect on the toluene removal performance of nanofluids. Toluene removal performance was improved with the increase of TiO2 concentration until the concentration increased to 0.1 wt %. However, However, when the concentration of TiO2 nanoparticles increases further to 0.5 wt %, the toluene removal performance is weakened. It was also found that the mass transfer effect decreases as the size of the nanoparticles increases. In addition, the microscopic mechanism of mass transfer of toluene before and after the addition of TiO2 nanoparticles is investigated by molecular dynamics simulations. The interaction energy, radial and spatial distribution functions, and self-diffusion coefficient were calculated to provide molecular insights into the mass transfer mechanism. The results show that TiO2 nanoparticles improve the mass transfer performance of toluene without changing the mechanism of interaction between toluene and deep eutectic solvent. TiO2 nanoparticles increase the area of gas-liquid mass transfer or the diffusion rate of gas in the liquid phase to improve the mass transfer process.