Willyan Machado Giufrida

High-Pressure Vapor-Liquid Equilibrium Data for Ternary Systems CO2+ Organic Solvent + Curcumin

In the present work phase equilibrium data for the ternary systems CO2 + ethanol + curcumin and CO2 + ethyl acetate + curcumin, at different concentrations of curcumin in the organic solvent (0.01 g cm -3 , 0.005 g cm -3 for ethanol and 0.01 g cm -3 , 0.0025 g cm -3 for ethyl acetate) are reported. The static synthetic method, using a variable-volume view cell was employed for obtaining the experimental data in the temperature range of (303 to 333) K and pressures up to 11 MPa. Vapor-liquid phase transitions were observed as bubble and dew points for the overall compositions investigated. The phase equilibria of the ternary systems were fitted to the Peng-Robinson equation of state (PR-EoS) using only binary system information. Experimental data together with modeling results may constitute relevant information for the precipitation of curcumin using the supercritical antisolvent process.

Effect of phase composition on the photocatalytic activity of titanium dioxide obtained from supercritical antisolvent

Photocatalytic activity of TiO2 nanoparticles is highly dependent on their phase composition. The coexistence of anatase and rutile phases in a single nanoparticle eases the electron transfer process between the phases, and favors the separation of photogenerated pairs. In this work, highly photoactive mixed-phase TiO2 nanostructures were prepared by supercritical antisolvent precipitation (SAS), an environmentally friendly technology. It is shown here that this methodology has the remarkable ability to produce highly porous (515 m2/g) and crystalline TiO2 nanoparticles. The phase composition of as-prepared TiO2 samples can be tailored through annealing process. Several mixed-phase TiO2 samples were tested to assess the correlation between photocatalytic activity and phase composition. The photocatalytic performance is strongly affected by the anatase-rutile ratio, since the synergism between phases enhances the charge separation, reducing the recombination effect of the photogenerated pairs (e-/h+). It was found that the nanocatalyst composed by 7.0 wt% of rutile phase and 93.0 wt% of anatase phase, named as TiO2_650, presented the highest photodegradation for both methyl orange (MO) and methylene blue (MB) dyes. Interestingly, TiO2 samples prepared by SAS have superior photoactivity than the benchmark photocatalyst names as P25, which is a widely used TiO2 material composed of anatase and rutile phases.