Mechanistic aspects of photocatalytic activity of metalloporphyrin–titanium mixtures in microemulsions

Abstract

Photocatalytic activity of titanium citrate and its water-in-oil microemulsions mix with zinc (II) tetraphenylporphyrin have been studied by means of adding 4-chlorophenol and following its degradation using artificial ultraviolet and visible light. 4-Chlorophenol is degraded in 71 and 86%, respectively, in 30 min with the generation of various intermediaries, whose possible formation mechanisms have been proposed based in the results of this research. The generation of benzene derivatives, different to those usually reported for this type of treatment, suggests the possibility of controlling the generation of intermediaries by simply changing the type of surfactant. In the case discussed here, we have derived a simple method for isomer generation of trimethylbenzene using a model organohalogenated compound as water contaminant and cetyltrimethylammonium bromide as surfactant.

Mechanistic Understanding of Superoxide Radical-Mediated Degradation of Perfluorocarboxylic Acids

“…Solvation is one of the most important and fundamental factors affecting the reactivity and selectivity of O 2 •– . , Acceleration of the O 2 •– -mediated transformation of PFCAs can be achieved through the choice of solvent, thus it can be of great practical importance. In addition, O 2 •– is involved in many environmentally relevant processes occurring at interfaces and other nonaqueous environments such as microemulsions and natural organic matters. , Under these conditions, its kinetics may not be adequately described with the k values measured in the aqueous solution, and solvation starts to play a pivotal role in its reactivity. Herein, we evaluated the change of O 2 •– nucleophilicity in organic solutions with different concentrations.…”

“…•− is involved in many environmentally relevant processes occurring at interfaces and other nonaqueous environments such as microemulsions and natural organic matters. 78,79 Under these conditions, its kinetics may not be adequately described with the k values measured in the aqueous solution, and solvation starts to play a pivotal role in its reactivity. Herein, we evaluated the change of O 2…”

Porphyrin-containing materials for photodegradation of organic pollutants in wastewaters: a review

“…a Best results obtained by Madriz and co-workers. 92 Fig. 11 Free-base porphyrin H 2 23, Cu23, Fe23Cl, Mn23OAc and Cu24-Cu27 used to sensitize TiO 2 .…”

“…The addition of Ti( iv ) to Zn 3 microemulsion increased the photodegradation rate of 4-CP. A few years later, the same authors 92 used the same porphyrin Zn 3 , without CTAB, and found that the best conversion percentage of 4-CP (86%) was obtained using W/O microemulsions of titanium citrate mixed with Zn 3 and irradiation with white light for 30 min.…”

“…Microemulsions can be used as "reactors" due to their unique properties like ultralow interfacial tension, sizeable interfacial area, thermodynamic stability, and, more importantly, their ability to solubilize otherwise immiscible liquids. 90 Having that in mind, Carrero, Madriz, and coworkers 91,92 reported the use of TiO 2 , Ti(IV) citrate, and Zn3 (Fig. 2) as photocatalysts in oil-in-water (O/W) and water-in-oil (W/O) microemulsions to degrade 4-chlorophenol (4-CP).…”