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The combined extraction of cesium and strontium from caustic wastes can be achieved by adding a crown ether and a carboxylic acid to the Caustic-Side Solvent Extraction (CSSX) solvent. The ligand 4,4′(5′)-di(tert-butyl)cyclohexano-18- crown-6 and one of four different carboxylic acids were combined with the components of the CSSX solvent optimized for the extraction of cesium, allowing for the simultaneous extraction of cesium and strontium from alkaline nitrate media simulating alkaline high level wastes present at the U.S. Department of Energy Savannah River Site. Extraction and stripping experiments were conducted independently and exhibited adequate results tot mimicking waste simulant processing through batch contacts. The promising results of these batch tests showed that the system could reasonably be tested on actual waste. [ABSTRACT FROM AUTHOR]

This work emphasizes the crucial role of polar solvating molecules known as phase modifiers in solvent-extraction systems. The focus of these studies was the extraction of cesium by calix[4tarene-bis(tert-octylbenzo-crown-6) in dodecane modified with various lipophilic alcohols. Results of equilibrium modeling are consistent with aggregation of the alcohol molecules with each other and with the calixarene-cesium nitrate complexes. These modeling results are supported by electrospray mass spectrometry experiments, clearly showing the alcohol:anion adducts containing several alcohol molecules. They are also supported by crystallographic evidence showing the existence of a hexameric aggregate in the solid state for a derivative of one of the alcohol modifiers used for solvent extraction, in agreement with the species giving the best modeling results. [ABSTRACT FROM AUTHOR]

Results obtained in this work show that four calix[4]arene mono and bis(benzo-crown-6) ethers functionalized with primary amine groups feature markedly enhanced cesium stripping under acidic conditions compared with nonfunctionalized analogs. The four amine-derivatized calixarenes were surveyed in nitrobenzene diluent at 25°C, demonstrating the effect under controlled conditions, where it was seen that the amino functionalization entailed at most a mild sacrifice of cesium extraction strength or selectivity. Limited solubility of the protonated forms of the extractants appears to be a potential issue for future development, however. In the best case, calix[4]arene bis[4-(2-ethylhexyl)benzo-crown-6], possessing an aminomethyl group on the upper rim, (AMBEHB) exhibited a cesium extraction strength comparable to that of a control system containing calix[4]arene bis(tert-octylbenzo-crown-6) (BOB) under alkaline conditions, whereas stripping of the cesium from AMBEHB was 56-fold more effective than BOB. A proof-of-principle extraction, scrubbing, and stripping (ESS) cycle using AMBEHB in Isopar L modified with 0.75 M 1-(2,2,3,3-tetrafluoropropoxy)-3-(4-sec-butylphenoxy)-2-propanol (Cs-7SB) showed that a greater than three-fold more efficient stripping may be obtained with AMBEHB vs. its nonfunctionalized control BEHB. A slope analysis of systematic extraction data under caustic and acidic conditions confirmed that the extraction of cesium nitrate by AMBEHB in dodecane modified by 0.5 M Cs-7SB involves the formation of a 1:1:1 metal:ligand:nitrate organic species. [ABSTRACT FROM AUTHOR]