ω-THIOCAPROLACTAM AS AN EXTRACTING REAGENT FOR Hg(II) FROM CHLORIDE, NITRATE, AND PERCHLORATE MEDIA.

Solvent extraction of Hg(II) from chloride, nitrate, and perchlorate media using ω-thiocaprolactam (R) dissolved in chloroform was studied. In all media the extraction equilibria are reached very fast, less than a 5 minute period of shaking time is needed. At high metal: extractant ratio (1:10) the percent of extraction of Hg(II) decreases in the order chloride > nitrate = perchlorate and in the pH range studied ( 0-3 ) is independent of this variable. At low metahextractant ratios (1:50, 1:100) the percent of extraction does not depend on the media used. In the latter case a dependence with the acidity in the chloride media is observed. The dimerization constant of the extractant in CHCI3 was determined to be 109±15 by UV measurements. Graphical and numerical analysis of the data with the LETAGROP-DISTR program allowed to propose the extraction reactions involved and evaluate their equilibrium constants. Organic phase species of the type HgX2R and HgX2R2 ( where X = CI, NO3, or CIO4) were found to explain better the experimental results obtained. However, in concentrated HCI the extraction of Hg(II) is explained by the formation of HgCI3RH and HgCI4(RH)2 species.