Edmondo Pramauro

A Critical Review of Surfactant-Mediated Phase Separations (Cloud-Point Extractions): Theory and Applications

Abstract The general concept of using the unique phase separation behavior of some surfactant micelle solutions as a means for extractive separation is outlined and described. Next, the specific micellar parameters and phase separation behavior of nonionic and zwitterionic charge-type surfactant solutions are summarized. In addition, the phase behavior of some derivatized B-cyclodextrin solutions is briefly described. The specific applications of such systems and their phase behavior for the extractive preconcentration, separation, and/or purification of metal chelates, biomaterials, and organic compounds are summarized and discussed. The potential use of affinity ligands in conjunction with the cloud-point approach for selective bioextractions is also mentioned. The experimental protocols, advantages, and limitations of the different cloud-point extraction techniques are outlined. The use of zwitterionic as opposed to nonionic surfactant media in such separations is compared and contrasted. In addition, ...

Analytical applications of organized molecular assemblies

Abstract Organized molecular assemblies have great potential utility in many types of analytical method. This review is concerned with recent of micelles, reversed micelles and micro-emulsions in shifting acid-base equilibria, and in electrochemical measurements, ultraviolet-visible spectrophotometry, micellar-echanced phosphorimetry and fluorimetry, liquid-liquid extraction, flame and plasmas atomic spectrometry, and high-performance and thin-layer liquid chromatography.

Characterization of methyl orange and its photocatalytic degradation products by HPLC/UV–VIS diode array and atmospheric pressure ionization quadrupole ion trap mass spectrometry

Abstract HPLC/UV–VIS diode array and HPLC/MS techniques were successfully applied to the analysis of sulfonated molecules present in samples coming from the photocatalytic degradation of the azo dye indicator, methyl orange. The substrate was chosen as a simple model for the study of reactions involving the more complex commercial products used for the dyeing of textile fibers. Unexpected MS fragmentation path was observed, due to the very stable methyl orange molecular structure. The chromatographic information were combined with the obtained MS, MS/MS data and the UV–VIS diode array spectra and allowed to rationalize the molecular structures attributable to the various degradation products.

Photodegradation of pentachlorophenol catalyzed by semiconductor particles

Abstract The heterogeneous photocatalytic degradation of pentachlorophenol (PCP) in aqueous solutions containing a suspension of TiO2 leads to the quantitative formation of CO2 and HC1. The photodegradation has also been studied in other semiconductor dispersions such as ZnO, CdS, WO3, and SnO2. TiO2 appears the most efficient. Oxygen and water are essential ingredients in the complete mineralization of this pollutant found near pulp and paper industries. Experiments with sunlight show a promising route for the water treatment processes; the half life of PCP (initial concentration 4.5 × 10−5M) is about 8 minutes, in the presence of 2 g/l of TiO2.

Photocatalytic degradation of polychlorinated dioxins and polychlorinated biphenyls in aqueous suspensions of semiconductors irradiated with simulated solar light

Abstract The complete photocatalytic degradation of two polychlorinated dibenzo-p-dioxins and one polychlorinated biphenyl to CO 2 and HC1 has been investigated in aerated aqueous suspensions of several semiconductors (TiO 2 , ZnO, CdS, TiO 2 Pt 5% by weight, and Fe 2 O 3 ) irradiated by simulated solar light. The particular compounds were the 2-chlorodibenzo-p-dioxin (CDD), the 2,7-dichlorodibenzo-p-dioxin (DCDD), and the 3,3′-dichlorobiphenyl (DCB). TiO 2 shows the highest photo-activity for the degradation process studied; platinization seems to have little effect. The presence of conduction band electron scavengers such as Ag + and Fe 3+ ions increase the activity of TiO 2 .

Photocatalytic and photolytic transformation of chloramben in aqueous solutions

The photocatalytic degradation of chloramben (3-amino-2,5-dichlorobenzoic acid) was investigated in aqueous solutions containing TiO2 suspensions under irradiation with simulated solar light. The primary degradation of the herbicide, the mineralisation of the organic carbon to CO2 and the formation of chloride ion from organic chlorine proved to be relatively fast, whereas the conversion of organic nitrogen into ammonium and nitrate ions took place only at delayed irradiation times. Photolytic degradation processes proved also to be active in the examined time interval, but they were far from producing complete mineralisation, leaving considerable amounts of residual organic products. Various aromatic intermediates that originated from chloramben during the photocatalytic treatment were detected and identified using GC-MS. Similarly, the main aromatic products arising from photolytic decomposition were also identified, and, in turn, they proved to undergo complete mineralisation upon addition of TiO2.

Sunlight Photodegradation of 2,4,5-Trichlorophenoxy-acetic Acid and 2,4,5-Trichlorophenol on TiO2. Identification of Intermediates and Degradation Pathway

The photocatalytic degradation of 2,4,5-trichlorophenoxyacetic acid and 2,4,5-trichlorophenol has been investigated in oxygenated aqueous suspensions of TiO2. Complete mineralization to CO2 and HC1 occurs with half-lives of 30–90 minutes. The effect of loading and thermal pre-treatment of the semi-conductor catalyst, as well as the influence of added chloride ions have been examined. In the degradation of the 2,4,5-trichlorophenoxyacetic acid, several intermediates were detected by gas-chromatographic/mass-spectrometric techniques. A scheme for the photodegradation is formulated.

Solubilization in micellar systems. Analytical and environmental applications

Surfactant-based separation techniques largely exploit the solubilization power of micelles and other amphiphilic aggregates towards a great variety of hydrophilic and hydrophobic solutes. Micellar extraction, based on the cloud-point phenomenon, and micellar ultrafiltration have been succesfilly applied for preconcentration and removal of organic and inorganic analytes of environmental concern from aqueous media. In particular, the recent development of chelating surfactant aggregates allows to perform very selective demetallation treatments. The factors which control the separation efficiencies of these methods are examined and discussed.

Identification of photocatalytic degradation pathways of 2-Cl-s-triazine herbicides and detection of their decomposition intermediates

Abstract the photocatalytic degradation of three 2-chloro-s-triazine herbicides (simazine, propazine, atrazine) over TiO 2 particles under simulated solar light has been investigated. In the early steps, the degradation progresses through competitive reactions such as oxidation of the side alkyl chain and substitution of chlorine with hydroxyl groups, the last process occurring for less than 10% of degradation. Further oxidative processes give rise to the formation of dealkylated products. Several intermediates have been detected by GC-MS and comprehensive degradation schemes are proposed. The three herbicides, bearing different alkyl groups, exhibit relevant differences in the relative role of the competitive degradation pathways.

Photochemical degradation of chlorinated dioxins, biphenyls phenols and benzene on semiconductor dispersion

Abstract The degradation of various aromatic pollutants present in aqueous media was performed using suspensions of semiconductor particles under illumination. The efficiency of the process has been shown to be dependent on the nature of the catalyst. The complete mineralization of halophenols has been observed after long term experiments.