Rs. Herbst et al., MERCURY EXTRACTION BY THE TRUEX PROCESS SOLVENT .1. KINETICS, EXTRACTABLE SPECIES, AND DEPENDENCE ON NITRIC-ACID CONCENTRATION, Solvent extraction and ion exchange, 13(3), 1995, pp. 431-446
Mercury extraction from acidic aqueous solutions by the TRUEX process
solvent (0.2 M CMPO - 1.4 M TBP in n-dodecane) has not extensively bee
n examined. Research at the Idaho Chemical Processing Plant (ICPP) is
currently being conducted to evaluate the TRUEX process for actinide r
emoval from several acidic waste streams, including liquid sodium-bear
ing waste (SEW), which contains significant quantities of mercury. Pre
liminary experiments were performed involving the extraction of Hg-203
, added as HgCl2, from 0.01 to 10 M HNO3 solutions. Mercury distributi
on coefficients (D-Hg) range between 3 and 60 from 0.01 M to 2 M HNO3.
At higher nitric acid concentrations, i.e. 5 M HNO3 or greater, D-Hg
significantly decreases to values less than 1. These results indicate
mercury is extracted from acidic solutions less than or equal to simil
ar to 2 M HNO3 and stripped with nitric acid solutions less than or eq
ual to similar to 5 M HNO3. Experimental results indicate the extracta
ble species is HgCl2 from nitrate media, i.e., chloride must be presen
t in the nitrate feed to extract mercury. Extractions from Hg(NO3)(2)
solutions indicated substantially reduced distribution ratios, typical
ly D-Hg < 1, for the range of nitric acid concentrations examined (0.0
1 to 8 M HNO3). Extraction of mercury, as HgCl2, by the individual com
ponents of the TRUEX solvent was also examined from 2 M HNO3. The dilu
ent, n-dodecane, does not measurably extract mercury. With a 1.4 M TBP
/n-dodecane solvent, D-Hg similar to 3.4 compared with D-Hg similar to
7 for the TRUEX solvent. Finally, the kinetics of Hg-203 extractions
were examined. For contact times varying from 15 seconds to 10 minutes
, the distribution coefficient of (HgCl2)-Hg-203 was essentially const
ant at D-Hg approximate to 18 from 1 M HNO3 solutions. Consequently, m
ercury extraction by the TRUEX solvent is kinetically rapid.