Dong Shen

Recovery of TiO2 nanoparticles synthesized in reverse micelles by antisolvent CO2

Abstract The possibility to recover the titanium dioxide (TiO2) nanoparticles synthesized in sodium bis(2-ethylhexyl) sulfosuccinate (AOT) reverse micelles by compressed CO2 was investigated. UV-Vis study showed that TiO2 nanoparticles could be deposited from the reverse micelles by the dissolved CO2. The nanoparticels were prepared and characterized by the transmission electron microscopy (TEM). The results showed that the TiO2 nanoparticles of very small size could be obtained. The effect of the operation conditions on the particle size is discussed.

Solvatochromic behavior of phenol blue in CO2+ethanol and CO2+n-pentane mixtures in the critical region and local composition enhancement

The UV-Vis spectra of probe phenol blue in CO(2)+ethanol and CO(2)+n-pentane binary mixtures were studied at 308.15 K and different pressures. The experiments were conducted in both supercritical region and subcritical region of the mixtures by changing the compositions of the mixed solvents. On the basis of the experimental results the local compositions of the solvents about phenol blue were estimated by neglecting the size difference of CO(2) and the cosolvents. Then the local composition data were corrected by a method proposed in this work, which is mainly based on Lennard-Jones sphere model. It was demonstrated that the local mole fraction of the cosolvents is higher than that in the bulk solution at all the experimental conditions. In the near critical region of the mixed solvents the local composition enhancement, defined as the ratio of cosolvent mole fraction about the solute to that in the bulk solution, increased significantly as pressure approached the phase boundary from high pressure. The local composition enhancement was not considerable as pressure was much higher than the critical pressure. In addition, in subcritical region the degree of composition enhancement was much smaller and was not sensitive to pressure in the entire pressure range as the concentration of the cosolvents in the mixed solvents was much higher than the concentration at the critical point of the mixtures.