Department of Chemistry, University of Calgary, 2500 University Drive NW, Calgary, AB, Canada T2N 1N4.
Environ Sci Technol. 2010 Dec 1;44(23):9075-9. doi: 10.1021/es1019993. Epub 2010 Nov 3.
Photocatalytic routes to dechlorinate polychlorinated biphenyls (PCBs) have considerable potential for development. This paper describes efficient dye-photocatalyzed processes which can be driven by long wavelength light sources including light-emitting diodes (LEDs), fluorescent lamps, and quite probably sunlight. The reduced form of methylene blue (MB), leuco-methylene blue (LMB), has previously been found to photoinduce dechlorination of chloroaromatics with an electron transfer from its triplet excited state. Sodium borohydride, used in this case is an efficient sacrificial reductant, which can maintain LMB as the major species in competition with air oxidation of LMB to MB. There is also evidence that it plays a further (chain reaction) role in promoting the LMB photodechlorination process as well. The generality of the photoelectron transfer from reduced members of the phenothiazine dye family is demonstrated with phenothiazine and leuco-methylene green when a wavelength (UV) is chosen to produce the highly reductive triplet. It is likely that dechlorination can be initiated by many triplet excited states with adequate reduction potential.
光催化路线脱除多氯联苯（PCBs）具有很大的发展潜力。本文描述了高效的染料光催化过程，这些过程可以由长波长光源驱动，包括发光二极管（LED）、荧光灯，并且很可能包括阳光。亚甲基蓝（MB）的还原形式（LMB）之前已被发现可以通过其三重态激发态的电子转移来光诱导氯代芳烃脱氯。在这种情况下，使用的硼氢化钠是一种有效的牺牲还原剂，可以将 LMB 维持为主要物质，与 LMB 被空气氧化为 MB 竞争。也有证据表明，它在促进 LMB 光脱氯过程中还起到了进一步的（链反应）作用。当选择波长（UV）产生高还原性三重态时，用吩噻嗪和无色亚甲基绿证明了从吩噻嗪染料家族的还原成员中光电子转移的通用性。具有足够还原电位的许多三重态激发态很可能引发脱氯。
