Americium Separation from Rare Earths via Segmented Extraction
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Solution Overview
Problem
Current methods for separating americium from rare-earth elements in radioactive waste processing often result in incomplete separation, contamination, and complications in further processing due to simultaneous extraction or low extraction efficiency, especially at high nitric acid concentrations.
Innovation Solution
A method involving a neutral organic extraction agent in a polar fluorinated solvent, using N,N,N',N'-tetraalkyl-amide of diglycolic acid for initial extraction and a solution with specific concentrations of complexone, nitrogen-containing organic acid, and salting-out agent for selective back extraction of americium, optimizing the separation process to achieve complete separation of americium from all rare-earth elements in one cycle.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If collective extraction of americium and rare-earth elements is used, then extraction efficiency is improved, but separation effectiveness deteriorates
Solution Approach 1:
The extraction process is divided into two distinct stages: (1) collective extraction of americium and rare-earth elements together using a neutral extractant, and (2) selective back-extraction of americium from the organic phase using an acid solution containing complexing agents. This segmentation allows both high extraction efficiency and complete separation to be achieved at different stages of the process.
Solution Approach 2:
The method performs preliminary collective extraction of both americium and rare-earth elements into the organic phase, creating a concentrated mixture that is then subjected to selective back-extraction. This preliminary action ensures that no target elements are left behind in the aqueous phase, while the subsequent selective step achieves complete separation.
2Manufacturing precision
If TALSPEAK method is used for separation, then separation effectiveness is improved, but extraction effectiveness at high nitric acid concentrations deteriorates
Solution Approach 1:
The method changes the chemical parameters of the back-extraction solution by using acid solutions containing specific complexing agents (such as oxalic acid, hydroxamic acids, or carboxylic acids) at controlled concentrations. This parameter change enables selective back-extraction of americium from the organic phase even when the feed solution contains high concentrations of nitric acid (up to 6-8 mol/L), overcoming the limitation of the conventional TALSPEAK method.
3Manufacturing precision
If ALSEP extraction mixture is used, then separation effectiveness is improved, but extraction ability towards americium deteriorates
Solution Approach 1:
The method employs a composite extraction system combining a neutral extractant (such as di(2-ethylhexyl)phosphoric acid or mono(2-ethylhexyl)-2-ethylhexyl phosphonate) for initial collective extraction with an acid back-extraction solution containing complexing agents. This composite approach leverages the strengths of different chemical systems to achieve both high extraction ability and complete separation effectiveness.
4Productivity
If binary extraction mixture of neutral and acid extractant is used, then extraction ability is improved, but device complexity deteriorates
Solution Approach 1:
The method segments the extraction process into two distinct operational stages using different chemical systems: (1) a neutral extractant stage for collective extraction, and (2) an acid back-extraction stage for selective separation. This segmentation simplifies the overall process design compared to attempting to combine both functions in a single mixed extractant system, while maintaining high extraction ability and separation effectiveness.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The method effectively separates americium from all rare-earth elements in a single extraction cycle, improving the purity of the re-extract and simplifying further processing by reducing contamination and the need for additional separation steps.
Implementation Method 1
simultaneous (collective) extraction of americium and the rare-earth elements from radioactive nitro-acid (nitric) solution with solution of neutral organic extraction agent in polar fluorinated organic solvent
Implementation Method 2
selective back extraction of americium with solution containing 5-20 g/L of a complexone, 5-60 g/L nitrogen-containing organic acid and 60-240 g/L salting-out agent
Implementation Method 3
solution containing 5-20 g/L of a complexone, 5-60 g/L nitrogen-containing organic acid and 60-240 g/L salting-out agent
Data Source
AI summary
The proposed invention relates to processes of extraction and concentration of radio nuclides and can be used in radiochemical technologies when processing liquid radioactive wastes. A method for extraction of americium from liquid radioactive wastes and its separation from rare-earth elements comprises simultaneous extraction of americium and rare-earth elements from radioactive nitrate solution with neutral solution of organic extracting agent in polar fluorinated organic solvent, washing of saturated with metals organic phase, selective re-extraction of americium. N,N,N',N'- tetraalkyl-amide of diglycolic acid is used as an extracting agent and solution containing 5-20 g/L of complexon, 5-60 g/L of nitrogen-containing organic acid and 60-240 g/L of salting-out agent is used as a solution for re-extraction of americium. Technical effect is the extraction of americium from acidic liquid radioactive solutions and its separation from all rare-earth elements in a single extraction cycle.