The Extraction of Am(III) and Eu(III) from Aqueous Ammonium Thiocyanate by Dihexyl-<i>N,N</i>-diethylcarbamoylmethylphosphonate and Related Compounds

Abstract

Abstract The extraction behavior and separation factors of Am(III) and Eu(III) from low acid ammonium thiocyanate solutions were studied using dihexyl-N,N-diethylcarbamoylmethylphosphonate (DHDECMP) and related compounds. It was found that very dilute (<0.1 M) solutions of ammonium thiocyanate were sufficient to allow quantitative extraction of Am(III) with DHDECMP. Significant differences between DHDECMP and dibutylbutylphosphonate (DB[BP]) in the extraction of Am(III) and Eu(III) from thiocyanate were found and indicate chelation is occurring with DHDECMP, unlike the situation in the low acid lithium nitrate system. Infrared spectroscopy of the extracted complexes of La(III) and extraction studies with dihexyl-N,N-diethylcarbamoylethylphosphonate (DHDECEP), dihexyl-N,N-diisobutylcarbamoylmethylphosphonate (DHDIBCMP), and di-(2-ethylbutyl)-N,N-diethylcarbamoylmethylphosphonate (DEBDECMP) confirm that chelation occurs with thiocyanate complexes of Am(III) and Eu(III). Separation factors, α, for Am(III) and Eu(III) were the lowest with DB[BP] (α = 5.84) and the highest with DHDIBCMP (α = 10.8).