Treatment of ethylmercury chloride by heterogeneous photocatalysis over TiO2

Abstract

Ethylmercury chloride (C2H5HgCl) was treated by UV/TiO2 photocatalysis in the presence of O2 and under N2 at pH 4.2. No report exists on C2H5Hg+ degradation by heterogeneous photocatalysis. The adsorption of C2H5Hg+ over TiO2 (no irradiation) was studied and fitted to the Freundlich isotherm. The photocatalytic evolution of C2H5Hg+ was adjusted to a two parameter Langmuir-Hinshelwood model, modified to include a third parameter attributed to the deactivation caused by the deposition of Hg(0). Hg(II) in solution, Hg(0) and Hg2Cl2 (detected only under N2) were the products of the photocatalytic degradation; the organic moiety was degraded but no organic by-product could be detected. Experiments in the absence of O2 showed a higher conversion rate, indicating that C2H5Hg+ is removed both by oxidative and reductive pathways, being this last step partially inhibited by O2. A degradation mechanism considering both oxidative and reductive one-electron transfer steps is proposed.