Solvent extraction of selenate and chromate using a diaminocalix[4]arene

The extraction of Se(VI) and Cr(VI) using a diammoniumcalix[4]arene was inv estigated. A study of parameters such as ligand concentration, pH or diluen t was carried out and allowed to specify the stoichiometry of the extracted species. It was shown that Se(VI) is extracted into CHCl3 as (LH22+, Cl-, HSeO4-)and ((LH22+)(2), 2Cl(-), SeO42-) species at pH 2.6. An increase of p H or an addition of 5% or 10% decanol in CHCl3 favors the extraction of SeO 42- over HSeO4- but leads to a drastic decrease of selenium extraction. Cr( VI) was shown to be extracted as (LH22+, Cl-, HCrO4-) at pH 2.6 and probabl y as (LH+, HCrO4-) for higher pH.