Treatment of phenylmercury salts by heterogeneous photocatalysis over TiO2.

E.M. DE LA FOURNIÈRE; A.G. LEYVA; E.A. GAUTIER; M.I. LITTER

CHEMOSPHERE

PERGAMON-ELSEVIER SCIENCE LTD

Lugar: Oxford; Año: 2007 vol. 69 p. 682 - 688

0045-6535

UV/TiO2 photocatalysis of phenylmercury salts in aqueous solutions has been performed starting from both acetate(C6H5HgCH3CO2, PMA) and chloride (C6H5HgCl, PMC) salts, in the presence or the absence of oxygen at acidic pH. Removal ofHg(II) in solution took place with the simultaneous deposit of dark or pale gray solids on the photocatalyst, identified as metallicHg (when starting from PMA) or mixtures of Hg(0) and Hg2Cl2 (when starting from PMC). Partial mineralization of the organic partof both compounds has also been achieved. Hg(II) removal and mineralization were enhanced in the absence of oxygen. PMA photocatalysisfollowed a saturation kinetics, going from first order at low concentrations to zero order at higher concentrations (>0.5 mM).For PMA, reaction was faster at high pH (11) with formation of mixtures of Hg and HgO. Phenol was detected as a product of thereaction in both cases, PMA and PMC, and no formation of dangerous methyl- or ethylmercury species was observed in the first case.A mechanism for the photocatalytic reaction has been proposed. The fact that calomel was found as a deposit when starting from PMCunder nitrogen suggests that the mechanism of Hg(II) transformation proceeds through successive one-electron transfer reactions passingby mercurous forms.