Enhanced reductive dechlorinization

Enhancement of PCB photodegradation also is observed in the presence of t r i f luoroace t i c acid (40), presumably via the protonated intermediates (ArClH ). Dienes, such as 1,3-cyclohexadiene, accelerate haloaromatic photoreactions (41.) and modify chloronaphthalene photochemistry by enhancing reductive dechlorination and suppressing dimerization (42). The mechanism is believed to involve exciplex formation with the diene or protonation by the olefin (43). 

At the site of chemical laundry, a project with an electrokinetic biofence (EBIS ) started in April 2001. This fence has been installed to disperse nutrients in the ground and groundwater in order to enhance reductive dechlorinization of present perchloroethene (PCE), trichloroethene (TCE), cw-l,2-dichloroethene (C-DCE),... 

Dechlorination occurred in parts of the soil column where reducing conditions (Eh-pH conditions) are dominant. The most significant reductive dechlorination of TCE occurred near the cathode, a source of electrons during electroosmosis. Results show the need to include a decay term in the transport equations. The results show that potential chemical transformation of chlorinated organic compounds could enhance the remediation efficiency during EO. 

Although reductive dechlorination is modelled either based on an empirical approach or a single site model, TCE dechlorination in the presence of cysteine apparently requires the use of a two-site model. The simulation as shown in Figure 3b indicates that quantitatively, the two-site model proposed here is sufficient for the interpretation of the experimental results. To enhance the predictive capability of the model, further research is needed to determine adsorption parameters independently. 

Figure 19.9. Electrochemically enhanced microbial reductive dechlorination of perchloro-ethene (PCE) and oxidative degradation of vinyl chloride (VC). Stimulated biodegradation is indicated by a chloride increase during electrochemical treatment.

The formation of reaction products such as ferric oxide or ferric hydroxides on the ZVI surface will decrease the activity of the ZVI, therefore Umiting the operational life of ZVI (Li and Farrell, 2000). As shown in Eqs. 23.14 and 23.15, the proton (H+) is not only beneficial to the reductive dechlorination reactions but it can also eliminate the formation of precipitates (ferric oxide or ferric hydroxide) to maintain the ZVI activity. Chang and Cheng (2006) have made an important note that the electrolysis reaction in the EK system would act as a proton (H ) provider when incorporating ZVI into the system. Therefore, the higher the voltage gradient that was applied to the process, the more production at the anode enhanced PCE... 

Semkiw ES, Barcelona MJ (2011) Field study of enhanced TCE reductive dechlorination by a full-scale whey PRB. Ground Water Monit Remed 31(l) 68-78... 

PCP is rapidly metabolized in rats, resulting in rapid elimination from the liver, kidney, and blood. The dechlorination mediated by liver chromosal enzymes is enhanced by pretreatment with inducing agents such as phenobarbitol. Initially, hydrolytic dechlorination takes place, yielding tetrachloro-/7-hydroquinone, which reductively dechlorinates further to... 

The dechlorination of the C-3 and C-5 position of the pyrazinone system was described to be fast under microwave irradiation [29]. Contrary to the reported de-chlorination [26] via palladium-catalyzed reaction with sodium formate 100 °C for 2-4 h and at the C-5 position in 2-3 days, a dramatic rate enhancement was observed under microwave irradiation (Scheme 12). The mono-reduction at C-3 was performed at 190 °C in DMF in merely 5 min, and the reduction of C-5, starting from the mono-reduction product, was performed in n-butanol in 55 min to afford the fois-reduction product in good overall yield. 

T0237 ElectrokineticaUy Enhanced Bioremediation—General T0238 Electrokinetics, Inc., Electrokinetic Soil Cleaning T0239 Electro-Petroleum, Inc., Electrokinetic Treatment T0248 ENERGIA, Inc., Reductive Photo-Dechlorination (RPD)... 

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