The decontamination of organophosphate flame retardants from aqueous solution has received considerable interest recently because of their potential threat to human health and the environment. We report herein the TiO2 photocatalytic oxidation of the flame retardant, tris-(2-chloroethyl) phosphate (TCEP), from aqueous solution. GC-NPD were used to monitor the disappearance of TCEP concentration during photocatalytic degradation. Our results demonstrate more than 90% of TCEP ([TCEP] &lt;100 µM) is degraded within 1 hour upon irradiation at 350 nm in oxygen-saturated aqueous suspension of TiO2 at ambient temperature. The degradation follows pseudo first order kinetics with rate constants varying from 0.22 to 0.04 min-1 depending on the initial concentrations over the range of 48.2 – 192.7 µM. The rate constant for the degradation decreases with increasing initial TCEP concentration, implying the process may be controlled by mass transfer (adsorption&lt;-&gt;desorption) at the surface of TiO2. The solution pH does not have a major impact on the degradation from pH 4-9. Mineralization to chloride and phosphate were monitored by ion chromatography over 5 hours of extended irradiation and a good mass balance was observed for both anions. The degradation decreases by ~ 50% with the addition of an equal amount of the hydroxyl radical scavenger, coumarin, indicating hydroxyl radicals are the main species participating in the degradation mechanism. The monoester and diester TCEP adducts are the primary products identified by NMR. Extensive product studies are ongoing to develop a detailed understanding of the pathways of the degradation mechanism. These results suggest that photocatalytic oxidation will be useful for the decontamination of aqueous solutions contaminated with recalcitrant organophosphate compounds.

TiO2 Photocatalytic degradation of the flame retardant, tris (2-chloroethyl) phosphate: Kinetic and mechanistic studies

253rd National Meeting (2017)

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