Solid-photosensitized Methylation of Inorganic Mercury in Aqueous Acetic Acid Solutions

Abstract

Photochemical methylation of inorganic mercury in the presence of such colored solids as mercury(II) oxide, solid sulfur and mercury(II) sulfide has been investigated in aqueous acetic acid solutions of mercury(II) acetate.
The yields of methylmercury photo-produced in the systems of mercury(II) oxide, solid sulfur and mercury(II) sulfide when irradiated with a 20 W blacklight lamp were about 1O³, 1O² and 1O⁴ times, respectively, higher than that in the control solution without any supended solids. It was confirmed that in the mercury(II) oxide system mercury(II) oxide acted as the photosensitizer for the production of methylmercury, while in the solid sulfur system basic mercury(II) sulfate formed during the photo-reaction acted as an additional photosensitizer. In the mercury(II) sulfide system, mercury(II) sulfide solubilized rapidly in the dark coupled with the reduction of mercury(II) ions, and the resulting sulfur atoms photo-polymerized to give a milky white solid, "photosulfur", which acted as the primary photosensitizer. The"photo-sulfur"was converted further into basic mercury(II) sulfate through a similar process as in the case of solid sulfur system.
The phc4osensitized, methylation in these heterogeneous systems was supposed to occur via energy transfer from solids to the mercury(II) acetate molecule.