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3M Selective Separation Cartridge

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Tech ID: 1543
Project Overview
 At Department of Energy (DOE) sites where radioactive materials were processed for weapons development and production there is waste which needs to be remediated. Much of the waste occurs in the form of aqueous solutions. Separating radionuclides and other contaminants from these solutions is necessary before they can be discharged to the environment. Often, contaminants must be removed to below EPA drinking water standards. 3M has developed particle-loaded membranes that contain ten to thirty micron-sized particles. There is great flexibility in particle selection and it is possible to fabricate membranes from just about any particle provided it is properly sized. These membranes have been fabricated into cartridges which can be installed in the same vessels used for filters. Captured radionuclides are immobilized on cartridges which can be easily handled and packaged for storage or further processing.

Technology Description
Particle-loaded membranes have been developed that contain ten to thirty micron-sized particles. There is great flexibility in particle selection and it is possible to fabricate membranes from just about any particle provided it is properly sized. These membranes have been fabricated into cartridges which can be installed in the same vessels used for filters. In practice they function just like columns albeit ones with very large diameter compared to height. The photo shows a nominal ten-inch cartridge but much larger ones can be manufactured. Benefits: Effluent from cartridge-based separation systems has lower concentrations of wastes than effluent from columns (i.e. a superior level of decontamination can be achieved), Volume of secondary wastes including material that must be stored is reduced, Flow rate at which waste streams can be processed is much higher for cartridge-based systems because the kinetics of exchange is much more rapid due to the small particle size, Captured radionuclides are immobilized on cartridges which can be easily handled and packaged for storage or further processing, The footprint of a cartridge-based system is small compared to columns making it easier to protect workers from radiation, Through selection of the proper particle, wastes can be captured selectively avoiding generation of mixed wastes. Technology development has been evolutionary starting with the EMPORETM membrane that was made from tiny fibrils of poly-tetrafluoroethylene (PTFE) and small particles. Because PTFE is embrittled by radiation, a different fibrous matrix was introduced which resists radiation. Since the process for fabricating each of these membranes is quite different, considerable effort was expended in developing WWL, the term used for the radiation-resistant web. Converting WWL into cartridges involved additional development that is still ongoing. In parallel, systems for carrying out separations have also been developed along with a pilot-scale device. It includes filters for removing particulates that would otherwise clog absorber cartridges, vessels that house the absorbers, and controls with everything mounted on a portable drip tray/support.

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