Indirect photolysis of tetraphenylborate sensitized by humic acid

Tetraphenylborate (TPB) will be used in the immoblization of high-level radioactive wastes in the U.S. Department of Energyʹs Defense Waste Processing Facility. This will be the first large-scale industrial application of TPB and information regarding its behavior in the environment is needed to assess the impact of potential contamination. Previous work indicated that TPB degrades via indirect photolysis initiated by humic substances in natural waters. In this study, the contribution of selected photo-generated reactive transient compounds were evaluated. Some of the degradation products of the reaction were also identified. The results indicate that reaction paths involving the super oxide anion (O2-.) have a negligible contribution to humic acid sensitzed photolysis. Singlet oxygen (1O2), generated by sunlight irradiation of a solution containing rose bengal, rapidly degraded TPB. However, the results from experiments evaluating the role of 1O2 in TPB degradation in solutions containing humic acid were inconclusive. Triphenylboron, o-terphenyl, and bis-diphenylborinate were identified as degradation products in solvent extracts of irradiated solution using gas chromatography - mass spectrometry.