The role of Fe(III) on phosphate released during the photo-decomposition of organic phosphorus in deionized and natural waters.

The photo-decomposition of organic phosphorus is an important route for the phosphorus cycle by which phosphate is regenerated in the aquatic environment. In this study, the role of Fe as a natural photosensitizer toward the decomposition of organic phosphorus to release phosphate was examined in deionized and natural waters under UV and sunlight irradiation using glyphosate as the organic phosphorus model. The results showed that the concentration of glyphosate decreased with irradiation time in the Fe/UV and Fe/sunlight systems and TOC gradually decreased, which confirmed that glyphosate was degraded by Fe. The amount of phosphate released from the photo-decomposition of glyphosate was higher in the presence of Fe than that of the control experiment under UV and sunlight irradiation conditions, and the generation rate of phosphate also increased with increasing Feconcentrations. The formation of hydroxyl radicals (·OH) in the Fe/UV and Fe/sunlight systems was identified according to the photoluminescence spectra (PL) using coumarin as the trapping molecule, and the steady-state concentrations of ·OH for the Fe/UV and Fe/sunlight systems were 1.06 × 10 M and 0.09 × 10 M, respectively. When natural water was spiked with glyphosate and Fe, the phosphate that was released in the Fe was higher than that of the control, and the phosphate that was released was inhibited when isopropanol was added to the reaction. All of these results demonstrate that the photochemical activity of Fe has significantly impact in the release of phosphate from the photo-decomposition of organic phosphorus.