OMEGA-THIOCAPROLACTAM AS AN EXTRACTING REAGENT FOR HG(II) FROM CHLORIDE, NITRATE, AND PERCHLORATE-MEDIA

Solvent extraction of Hg(II) from chloride, nitrate, and perchlorate m edia using omega-thiocaprolactam (R) dissolved in chloroform was studi ed. In all media the extraction equilibria are reached very fast, less than a 5 minute period of shaking time is needed. At high metal: extr actant ratio (1:10) the percent of extraction of Hg(II) decreases in t he order chloride > nitrate a perchlorate and in the pH range studied (0-3) is independent of this variable. At low metal:extractant ratios (1:50, 1:100) the percent of extraction does not depend on the media u sed. In the latter case a dependence with the acidity in the chloride media is observed. The dimerization constant of the extractant in CHCl 3 was determined to be 109+/-15 by UV measurements. Graphical and nume rical analysis of the data with the LETAGROP-DISTR program allowed to propose the extraction reactions involved and evaluate their equilibri um constants. Organic phase species of the type HgX2R and HgX2R2 ( whe re X- = Cl-, NO3- or ClO4-) were found to explain better the experimen tal results obtained. However, in concentrated HCl the extraction of H g(II) is explained by the formation of HgCl3RH and HSCl4(RH)(2) specie s.