Establishing soil adsorption testing methods for gaseous mercury and evaluating the distribution coefficients of silica sand, decomposed granite soil, mordenite, and calcium bentonite

Abstract This study investigated the soil adsorption characteristics against gaseous mercury. A method for the adsorption tests using gaseous mercury was established, and the distribution coefficients for silica sand, decomposed granite soil, mordenite, and calcium bentonite were evaluated. Glass vials with polytetrafluoroethylene (PTFE) plugs were suitable for the adsorption tests as gaseous mercury did not adsorb onto the glass vials, indicating that the effects of the gaseous mercury adsorbed onto the glass vials are negligible. Although the PTFE plug could not completely seal a vial containing gaseous mercury, the leakage could be corrected using the damping time constant. The soil adsorption tests revealed changes in the gaseous mercury concentrations, which were fitted to the Langmuir nonequilibrium adsorption model. Assuming gaseous mercury did not leak from the vial, numerical simulations were conducted using the fitted parameters of the maximum adsorption amount, adsorption rate, and desorption rate. The evaluated distribution coefficients at equilibrium conditions were 56.3 mL/g for silica sand, 2070 mL/g for decomposed granite soil, 3490 mL/g for mordenite, and 7140 mL/g for calcium bentonite.