Collection and thermal evolution behaviors of different mercury species captured with gold

The effects of temperature on the collection and evolution of different mercury (Hg) species captured with gold were investigated to help determine if temperature control could be used to provide Hg speciation information in gaseous effluents. Elemental mercury, dimethyl mercury, and mercuric chloride were loaded onto a gold trap (one Hg species per test) at temperatures of 25-375 degrees C. The Hg was then evolved (in argon) at 900 degrees C. in other tests, Hg was loaded onto the trap at 25 degrees C and then heated (in argon) at 50-1000 degrees C to release Hg. The argon streams were analyzed using cold vapor atomic fluorescence to obtain information on Hg collection and evolution as a function of temperature. The Hg was released from the gold entirely as elemental mercury, regardless of the Hg species collected. Temperatures of about 250 degrees C were required to release the Hg, and there were no differences among Hg species with respect to the temperatures necessary to evolve the Hg. Results of the tests on Hg collection efficiency versus the temperature of the gold trap indicated that proper selection of the collection temperature could potentially be used to provide Hg speciation information-However refinements in the technique are necessary before it can be put into practical use.