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New materials and processes for metal-ion separation and extraction based on selective transport of ions across membranes have been developed. Using molecular simulations, porphyrin-based ionophores (molecular ion-carriers) were designed for selectivity in complexing metal ions and other transport properties, such as solubility in organic or aqueous solution. Selectivity was designed into the carriers by controlling basicity, shape, and size of the ionophore specifically for extraction of heavy metals and radionuclides. Promising ionophores were synthesized and tested for application in two different extraction systems. In the first, a supported liquid membrane (SLM) separates two liquid phases--one containing waste and the other a liquid to which the specified metal ions are extracted. The ionophores selectively transport a specified metal ion through the intervening liquid layer to give a pure solution of the metal ion that is easily concentrated. In the second, metal ions were photoreduced to insoluble compounds or elemental metal particles. Separation of the metal particles leaves a pure metal precipitate. These extraction technologies offer convenient new means of separation and extraction for processing Mo-99, decontamination and decommissioning, radioactive waste remediation, and heavy metal waste stream treatment. The initial focus area was on high-level waste tank remediation of heat and gamma emitters (137Cs and 90Sr), long-lived radionuclides (99Tc), and other metal ions contained in highand low-level waste. Ion-extraction technology with designed ionophores and photoreducers provides increased sustainability and lower cost and complexity of manufacturing processes. Adaptation to pump/treat methods for use at sites such as the White Sands Experimental Test Station and Tuba City were also considered. The technology is differentiated from other efforts (1) by use of molecular simulation to engineer high-performance ionophores and photoreducers, uniting Sandia's chemical, computational, and materials science expertise in a rational, iterative approach, (2) by applying Sandia's recognized expertise in the molecular design of porphyrin-based materials, and (3) by the use of new liquidmembrane and photoreduction technologies. Designed Ionophores for Liquid-Membrane Separation and Extraction of Metal Ions 2

LDRD Final Report on Designed Ionophores for Liquid-Membrane Separation and Extraction of Metal Ions