MERCURY EXTRACTION BY THE TRUEX PROCESS SOLVENT .2. SELECTIVE PARTITIONING OF MERCURY FROM CO-EXTRACTED ACTINIDES IN A SIMULATED ACIDIC ICPP WASTE SYSTEM

The TRUEX process is being evaluated at the Idaho Chemical Processing Plant (ICPP) as a means to partition the actinides from acidic sodium-bearing waste (SEW). The mercury content of this waste averages 1 g/l. Because the chemistry of mercury has not been extensively evaluated in the TRUEX process, mercury was singled out as an element of interest. Radioactive mercury, Hg-203, was spiked into a simulated solution of SBW containing 1 g/l mercury. Successive extraction batch contacts with the mercury spiked waste and successive scrubbing and stripping batch contacts of the mercury loaded TRUEX solvent (0.2 M CMPO-1.4 M TBP in dodecane) show that mercury will extract into and strip from the solvent. The extraction distribution coefficient for mercury, as HgCl2, from SEW having a nitric acid concentration of 1.4 M and a chloride concentration of 0.035 M was found to be 3. The stripping distribution coefficient was found to be 0.5 with 5 M HNO3 and 0.077 with 0.25 M Na2CO3. Because experiments described here show that mercury can be extracted from SEW and stripped from the solvent, a process has been developed to partition mercury from the actinides in SEW.