Biomedical subjects
Publications and source records attributed to E Pelizzetti.
A zeolitic material containing Ti chains activated by light allows a shape-selective transformation of organic compounds; the molecules that can enter into the zeolitic cavities are protected from the light-induced processes, while the other are degraded.
The formation of nitrophenols was studied as a consequence of ultra violet (UV) irradiation of aqueous solutions of phenol and nitrate in the range of pH 1-12. The study was performed both in homogeneous phase and in the presence of water-suspended TiO2. The effects of pH, dissolved oxygen and 2-propanol as .OH scavenger have been evaluated. A reaction mechanism is proposed, based on the experimental results.
Nitrophenols are formed in aqueous solution upon UV irradiation of phenol and nitrite. The formation of nitrophenols is enhanced by dissolved oxygen and inhibited by the addition of 2-propanol. The mechanism of phenol photonitration involves both .NO2 (or N2O4, reacting with phenol, and 4-nitrosophenol, which is oxidised to 4-nitrophenol. A reaction scheme is proposed based on experimental results.
Phenol photonitration and photonitrosation were studied both in homogeneous and in heterogeneous phase in the presence of TiO2 particles. The effect of pH as well as of the semiconductor particles on the kinetics and products of the reaction was observed. Formation of nitrophenols is enhanced at acidic pH, due to thermal processes initiated by nitrous acid, as well as in the presence of TiO2, due to the photocatalytic oxidation of nitrite.
The photocatalytic transformation of dexamethasone and the formation of its intermediate compounds have been studied using titanium dioxide as a photocatalyst. The degradation of dexamethasone occurs easily through the formation of several hydroxy derivatives whose characterization has been made by HPLC/MS/MS. Even if both oxidative and reductive processes can be operating, only oxidative products have been identified in air saturated aqueous suspensions. A pattern of reaction pathways accounting for the observed intermediates is proposed. The obtained experimental evidence may be rationalized postulating the existence of a double initial mechanism. A single oxidation step resulting from the attack by one *OH radical leading to the formation of five hydroxy-derivatives and a concomitant attack involving two *OH radicals leading to the hydroxylation of the quinoid moiety of the molecule.
We report a thermodynamic study of the aqueous solutions of 1-(3,3,4,4,5,5,6,6,6-nonafluorohexyl) pyridinium chloride, bromide, and iodide and N-octyl pyridinium iodide. Dilution enthalpies and osmotic coefficients of the aqueous solutions of these cationic surfactants have been measured at 313 K as a function of the concentration. The experimental data are expressed in terms of apparent and partial molar quantities. The changes in thermodynamic properties upon micellization have been obtained from the experimental data by using a pseudo phase transition approach. The cmc at 313 K have been evaluated from the plot of the milliosmolality, the measured quantity, vs molality. From the comparison with the trends of the enthalpies at 298 K of the same set of compounds, the effect of temperature on the energetics of their solutions can be derived. The trends of thermodynamic properties vs molality and the micellization parameters confirm that the effect of the counterions, however strong and inversely proportional to the radius of the hydrated counterion, seems to be reduced with respect to the hydrogenated analogs. The curves of the apparent and partial molar enthalpies vs m for the bromide and the iodide are lowered, with respect to the curve of the chloride, by an amount comparable to that at 298 K. This observation suggests that the changes in the absolute trends of the curves and in the micellization enthalpies are due to the modification of the more mobile hydrophobic hydration shell of the perfluoroalkyl chain, whereas the hydration sphere of the counterions is practically unaffected. The heat capacity data and the comparison with the behaviour of hydrogenated analogs is in agreement with the above observation. The trends of the free energies confirm that the degree of counterion binding, beta, and the aggregation number, n, increase with the increasing of the radius of the hydrated counterion.
The paper reviews the theoretical models and equations used for the interpretation of weak acid dissociation equilibria in the presence of micellar systems. The models and the equations of the literature can be rewritten and reinterpreted in terms of the generalized pseudophase model, for which the basic equations are reported. Some new relationships for the titration of weak acids in micellar systems are presented.
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