Studies on Methods of Mercury Vapor Collection and Analysis.

There is a tremendous need for the determination of a highly selective and specific method for the collection and analysis of mercury vapor in industrial atmospheres. Whenever mercury vapor sampling is done a number is usually generated, but there has been some concern as to whether the actual concentration level is indicated by this number because of the effects of interferences. These interferences include chemicals and relative humidity. This research was, therefore, designed to test these variables and search for a more selective and specific collecting medium for mercury vapor with emphasis on solid sorbents. Six solid sorbing materials were evaluated to determine their mercury vapor collecting capabilities. Elemental mercury vapor was collected with Silver wool, Silver Chromosorb P, silver membrane filters, Hopcalite, ferrous sulfide, and charcoal impregnated with iodine. Different mercury concentrations were generated and exposed to the six sorbing materials simultaneously, and their collecting efficiencies were determined. Chlorine, sulfur dioxide, and hydrogen sulfide were introduced into the mercury vapor steam and their effects on the collecting abilities of the monitors were determined. Different levels of humidity were tested and the effect on the sorbing materials noted. Thermal desorption of the collected mercury from the sorbing materials was employed. The subsequent analysis was done by flameless atomic absorption spectrophotometry using a quartz cell. The non-destructive use of the sorbing materials was employed with the monitors being reused for mercury collection after repeated thermal desorption. Silver wool, Silver Chromosorb P, and silver membrane filters retained their collecting efficiencies after repeated use. However, there was a severe loss in the collecting ability of Hopcalite and ferrous sulfide after initial thermal desorption. The sorbing materials exhibited the ability to collect mercury vapor under various conditions. The monitors exhibited varying collecting efficiencies. Silver wool and Silver Chromosorb P averaged about 88% collecting efficiency with 100% efficiency occurring at low mercury concentrations. Silver membrane filters averaged about 68% efficiency while Hopcalite and ferrous sulfide averaged about 60% efficiency. The use of charcoal impregnated with iodine was discontinued when problems developed during the thermal desorption process. Chlorine had about 25% negative effect on the sorbing materials; sulfur dioxide, 14%; hydrogen sulfide, 35%; and humidity, 35%. There was a general decrease in the amount of mercury collected by the monitors when the chemical interferences and humidity were present. The extent of this effect varied with each monitor. Humidity and some of the chemical interferences normally found in industrial atmospheres affected the efficient collection of mercury vapor by the monitors. Silver wool and Silver Chromosorb P are highly selective and specific for mercury vapor collection. Ascarite and Mg(CLO(,4))(,2) could be used to minimize the effect of chemical interferences and humidity on the sorbing materials.PhDPublic healthUniversity of Michiganhttp://deepblue.lib.umich.edu/bitstream/2027.42/157968/1/8025742.pd