Mercury is used in the operations of nuclear fuel processing. Much of the hazardous wastes of these processes that have been in operation since the World War II era are located at legacy sites of Department of Energy Laboratories. As a result these sites have accumulated large quantities of highly radioactive, high level mercury wastes. These legacy wastes at National Laboratories present special challenges for remediation due to contamination by radioactive elements and high organic content. They cannot be treated with normal mercury remediation methods. One widely known challenge is the V-9 tank at Idaho National Laboratory (INL).

The V-9 storage tank contains significant quantities of mixed organic solvents and other liquid wastes along with highly radioactive mercury waste from fuel processing. The mercury is at a very high concentration of 1.57% by weight (15,700 mg/kg) and may exist in several species such as elemental mercury, organic mercury and ionic, water soluble mercury. The waste in the V-9 tank that have not met Land Disposal Restriction (LDR) compliance contain chloroform, 1,1,1-trichloroethane, trichlorethene, tetrachlorethene, 1,4-dichlorobenzene, 1,2-dichlorobenzene, 1,2,4-trichlorobenzene, Aroclor-1260 and bis(2-ethylhexyl)phthalate in addition to mercury. The tank had extremely high organics and radiological content. All of the organic solvent must be removed because they fall in the F001 waste category for land disposal. Unlike a number of adsorbents that can adsorb mercury but are compromised by organic solvents, for example, activated carbon, SAMMS can adsorb mercury in this organic environment.

The adsorption isotherm was used to estimate the required mass of SAMMS to adsorb the mercury in solution to acceptable levels to pass TCLP after stabilization. An initial bench experiment to verify the isotherm used a 25 ml sample of the V-9 tank diluted with 65 ml of water. Testing was conducted on five samples with different mass loadings of SAMMS. The three samples with at least 1.6 times the predicted amount of SAMMS required to adsorb the mercury met the TCLP limits. The sample with 0.64 times the predicted amount of SAMMS and the sample with no SAMMS failed the TCLP limits.

Using the measured concentration of mercury (1.57%) INL estimated that 13.5 pounds (6.14 kg) of mercury were in the V-9 tank. Based on the bench experiment INL determined to add 1.4-1.6 times the estimated mass of adsorbent predicted by the equilibrium adsorption isotherm after the organics were sparged. According to the data from the preliminary study this ratio should yield a TCLP value of about 0.037 mg/kg, well below the limit of 0.20 mg/kg. After the V-9 tank was treated with SAMMS five samples were tested for TCLP. All five samples passed TCLP with values less than 0.032 mg/kg. INL reports that at a 90% upper confidence limit, the treatment has met the Land Disposal Restriction treatment standard and after solidification can be disposed at the ICDF (Idaho CERCLA Disposal Facility).

SAMMS is the first adsorbent to demonstrate the ability to fix mercury in this waste and meet TCLP without the use of RMERC (roasting or retorting with mercury recovery) or IMERC (incineration with mercury recovery). The SAMMS treated wastes exhibit leachable mercury below the TCLP standard and finally offers a direct and effective way to manage these highly radioactive waste products.