Organoarsenicals are regularly used as feed additives in the poultry industry, although use of these compounds has been phased out in some countries. This study investigated treatment of wastewater containing organoarsenicals, such as roxarsone (ROX) and nitarsone (NIT), using the photochemical UV-H2O2 system. Experiments were conducted using a batch recycle reactor equipped with a low pressure mercury lamp (253.7 nm). The photon flux of the UV reactor was 1.14 (�0.18)�10-5 Einstein/L-s, as determined by potassium ferrioxalate actinometry. Organoarsenicals were quantified using liquid chromatography with electrospray ionization tandem mass spectrometry (LC-ESI-MS/MS). Transformation of these compounds was modelled using a fluence-based kinetic model. The apparent rate constant showed a linear relationship up to a molar ratio of 50 mol H2O2 /mol organoarsenical. The second order rate constant for organoarsenical transformation by hydroxyl radicals was determined using a competition kinetics model that employed para-chlorobenzoic acid (pCBA); the corresponding rate constants for ROX and NIT were found to be 3.33(�0.78)�109 and 8.28(�0.49)�108 M-1s-1, respectively. While solution pH (4.9-8.6) and nitrate (0-0.5 mM) did not significantly affect transformation efficiency, 10 mM bicarbonate reduced the pseudo-first order rate constant by 2.5 times. The presence of organic matter from chicken litter also reduced transformation efficiency. An arsenic mass balance between initial and transformed samples showed that organoarsenicals released arsenate upon transformation. In conclusion, the UV-H2O2 process can be effectively employed to treat wastewater containing organoarsenicals; however, the resulting inorganic arsenic must also be considered.

Photochemical UV-H<sub>2</sub>O<sub>2</sub> system for oxidation of organoarsenicals in agricultural wastewater

248th National Meeting (2014)

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Photochemical UV-H2O2 system for oxidation of organoarsenicals in agricultural wastewater

Photochemical UV-H₂O₂ system for oxidation of organoarsenicals in agricultural wastewater