Enabling technologies for the rapid dechlorination of polychloroarenes and PCBs.

Dielectric heating and acoustic cavitation (ultrasound or high-performance disperser) may all dramatically enhance conversion rates and yields in heterogeneous metal-assisted organic reactions even when low reagent excesses are used. These so called "enabling technologies" bring with them process intensification, safer protocols, cost reduction and energy savings. We herein describe a series of rapid polychlorinated aromatic and PCBs dechlorinations (15min) carried out in a moderate excess of metallic sodium and using non-conventional techniques. We compared the results with those obtained for reactions carried out under conventional heating and with those performed with less reactive metals such as magnesium and zinc. In this comparison, high-intensity ultrasound stands out as the technique of choice.

Catalytic properties of catechol 1,2-dioxygenase from Acinetobacter radioresistens S13 immobilized on nanosponges.

Catechol 1,2-dioxygenases are iron containing enzymes able to convert catechol into cis,cis-muconate, a precursor of the industrially important compound adipic acid. Catechol 1,2-dioxygenase from Acinetobacter radioresistens S13 was immobilized on beta-cyclodextrins cross-linked with carbonate groups (nanosponges) with a yield of 29 mg of enzyme per gram of support. This support was chosen for its low cost and its ability to offer different types of interactions with the enzyme. The activity profiles at different pH and temperatures showed a shift of the optimal pH from 8.5, for the free protein, to 9.5, for the immobilized protein and, similarly, a shift in optimal temperature from 30 degrees C to 50 degrees C. The Michaelis-Menten constant, KM, increased from 2.0 +/- 0.3 microM, for the free form, to 16.6 +/- 4.8 microM for the immobilized enzyme, whereas the rate constant, k(cat), values were found to be 32 +/- 2 s(-1) and 27 +/- 3 s(-1) for the free and immobilized forms respectively. The immobilization process also increased the thermostability of the enzyme with 60% residual activity after 90 min at 40 degrees C for the immobilized protein versus 20% for the free enzyme. A residual activity of 75% was found after 15 min at 60 degrees C for the immobilized enzyme while the free form showed a total loss of activity under the same conditions. The activity toward other substrates, such as 3- and 4-methylcatechol and 4-chlorocatechol, was retained by the immobilized enzyme. A small scale bioreactor was constructed and was able to convert catechol into cis,cis-muconic acid with high efficiency for 70 days.

Decontamination of soil containing POPs by the combined action of solid Fenton-like reagents and microwaves.

The effect on halogenated aromatics of solid, non-toxic oxidants such as sodium percarbonate and the urea/hydrogen peroxide complex (Fenton-like reagents) was investigated. A microwaves-assisted, solvent-free method for soil decontamination is presented. It marks a considerable advance in the search of more efficient, environment-friendly procedures for the degradative oxidation of persistent organic pollutants. Residual pollutants in treated soil samples were determined by GC/MS analysis after solvent extraction or direct thermal desorption. Results showed that 4-chloronaphthol, 2,4-dichlorophenoxyacetic acid and p-nonylphenol had been degraded completely, 2,4-dibromophenol to a large extent.