Photoinduced reduction of divalent mercury by quinones in the presence of formic acid under anaerobic conditions

The laser flash photolysis technique (λexc = 355 nm) was used to investigate the mechanism of the HgCl2 reduction mediated by CO2- radicals generated from quenching of the triplet states of 1,4-naphthoquinone (NQ) by formic acid. Kinetic simulations of the experimental signals support the proposed reaction mechanism. This system is of potential interest in the development of UV-A photoinduced photolytic procedures for the treatment of Hg(II) contaminated waters.The successful replacement of NQ with a commercial fulvic acid, as a model compound of dissolved organic matter, showed that the method is applicable to organic matter-containing waters without the addition of quinones.

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► We investigate the mechanism of Hg(II) photo-reduction mediated by naphthoquinone.
► We show that mercury can be eliminated from the solutions as Hg2Cl2.
► A commercial fulvic acid can also promote the photo-reduction of Hg(II).