Rapid, photocatalytic, and deep debromination of polybrominated diphenyl ethers on Pd-TiO2: intermediates and...

Titanium dioxide with surface-loaded palladium (Pd-TiO2) was able to easily remove all ten bromine atoms from decabromodiphenyl ether (BDE209) within 1 h under the irradiation of sunlight or an artificial light source. By contrast, fewer than three bromine atoms were eliminated on the pristine TiO2 even with prolonged irradiation (5 h). During the photocatalytic debromination, moreover, the formed BDE intermediates exhibited a significant difference between the Pd-TiO2 and pristine TiO2 systems, and much less position selectivity for the debromination on Pd-TiO2 was observed than that on the pristine TiO2 surface. For another polybrominated diphenyl ether (BDE15), pristine TiO2 was incapable of its photocatalytic reduction, whereas the loading of Pd enabled its debromination to diphenyl ether within 20 min. In addition, an evident induction period appeared in the photocatalytic debromination of BDE15 on Pd-TiO2. The experiments imply that the Pd-cocatalyzed effect changes significantly the photocatalytic reductive debromination pathways.