Photocatalytic UV-degradation of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) in the presence of silver doped zeolite

Abstract

Silver incorporated into the Y zeolite framework was prepared and characterized. Low temperature luminescence analysis indicates the formation of silver-silver excimers (excited state dimers) and exciplexes (excited state trimers) that were found to be activated at 250 nm and 300 nm, respectively. The catalytic activity of the modified material was tested toward the photodecomposition of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). The site selective activity was evaluated using two sources of UV irradiation at 254 and 302 nm. The catalyst was found to effectively decompose TCDD in a methanol/tetrahydrofuran solution to reach 86% after 5 h. In the presence of the catalyst, a hydroxyl derivative was identified as an intermediate for the 302 nm catalytic pathway. This was not observed for the 254 nm process. Furthermore, irradiating of TCDD under 254 nm UV source for 6 h resulted in the formation of three products with molecular ion peaks of 113, 128, and 158 amu. On the other hand, the 302 nm gives two major products with molecular ion peaks of 220 and 252 amu. The study also indicates that the hydroxyl derivative could be potentially more toxic than the parent TCDD while all other isolated products were found to be less toxic than TCDD. Keywords: Silver, Zeolite, Catalyst, Photodegradation, UV light, TCDD