AROMATIC SUBSTITUTED METALLACARBORANES AS EXTRACTANTS OF CS-137 AND SR-90 FROM NUCLEAR WASTES

Phenyl- and 1,2-diphenyl-1,2-dicarba-closo-dodecaborane have been synt hesized and deboronated to yield [7-C6H5-7,8-C2B9H11](-) and [7,8-(C6H 5)(2)-7,8-C2B9H10](-). Reaction of the monophenyl with KOBut and CoCl2 in 1,2-dimethoxyethane (dme) led to [3,3'-Co(1-C6H5-1,2-C2B9H10)(2)]( -) 1(-). This has been fully characterized by X-ray analysis. A simila r reaction with [7,8-(C6H5)(2)-7,8-C2B9H10](-) did not yield the expec ted sandwich compound. On the contrary, reaction of [7,9-(C6H5)(2)-7,8 -C2B9H10]- with KOBut and CoCl2 in a mixture of dme and diethylene gly col dimethyl ether led to [3,3'-Co{1,7-(C6H5)(2)-1,7-C2B9H9}(2)] 2(-). The two sandwich complexes were tested for liquid-liquid extraction a nd transport through supported liquid membranes of Cs-137, Sr-90 and E u-152. Extractions for Cs-137 were very good at pH 3 but decreased con siderably at pH 1 for H[1], while H[2] showed good efficiency even at this pH. The extraction of Sr-90 was performed with the incorporation of a synergistic linear polyether and was good at pH 3 and 1. For the extraction of Eu-152, compound H[2] displayed good efficiency. Transpo rt experiments of Cs using supported liquid membranes were performed w ith H[1] and H[2] and o-nitrophenyl hexyl ether as the membrane solven t. The permeability of Cs-137 for compound H[2] was 30.9 cm h(-1) whil e for H[1] it was 7.95 cm h(-1). These permeabilities are much higher than those of usual carriers under comparable conditions.