Yttrium-90 Purification via Nitric Acid Precipitation
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Solution Overview
Problem
Current methods are inadequate for producing multi-curie quantities of chemically and radiochemically pure Yttrium-90 (Y-90) on a weekly basis, with insufficient separation from Strontium-90 (Sr-90) and other metal ions, which are essential for cancer treatment applications.
Innovation Solution
A semi-continuous method involving the dissolution of radioactive strontium nitrate salts, evaporation, treatment with high concentrations of nitric acid to precipitate strontium, and subsequent use of selective membranes and resins to remove Sr-90 and Zr decay products, resulting in purified Y-90.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional separation methods are used to extract Y-90 from Sr-90, then Y-90 can be obtained, but the separation purity is insufficient with Sr-90 contamination above acceptable levels
Solution Approach 1:
The separation process is divided into multiple sequential stages: initial dissolution, first precipitation with nitric acid, filtration, second precipitation, and final purification. Each stage progressively removes different levels of Sr-90 contamination, achieving the required separation factor of less than 1×10−6 through cumulative purification effects.
Solution Approach 2:
The method utilizes changes in chemical parameters, specifically acid concentration (nitric acid at greater than 80-wt %) and pH levels, to control the precipitation and dissolution behavior of Sr-90 and Y-90 compounds. By adjusting these parameters at different stages, the process achieves selective separation and high-purity Y-90 recovery.
2Manufacturing precision
If multiple purification steps are implemented to achieve Sr-90 separation factor less than 1×10−6, then purity improves, but production time and process complexity increase
Solution Approach 1:
The method employs a semi-continuous production approach where Y-90 is extracted from Sr-90 in sequential batches without complete interruption. The Sr-90 source remains in place and is repeatedly processed through dissolution and precipitation cycles, allowing continuous Y-90 production while maintaining high separation purity through multiple passes.
Solution Approach 2:
The process includes preliminary dissolution of Sr-90 salts and pre-adjustment of acid concentrations before the actual precipitation steps. These preparatory actions ensure that when the purification steps are executed, they proceed efficiently with optimal conditions already in place, reducing overall processing time while maintaining purity requirements.
3Productivity
If high concentrations of nitric acid are used to precipitate Sr-90, then separation efficiency improves, but handling and safety complexity increase
Solution Approach 1:
Nitric acid serves as an intermediary chemical that facilitates the separation process. By using controlled concentrations of HNO3 (greater than 80-wt %), the method achieves selective precipitation of Sr-90 as nitrate salts while keeping Y-90 in solution. The acid acts as a mediator that enables high separation efficiency without requiring more hazardous conditions.
Solution Approach 2:
The method carefully controls the concentration parameter of nitric acid, using greater than 80-wt % HNO3 specifically for the precipitation step. This parameter optimization achieves maximum separation efficiency while managing the hazards associated with high-concentration acid handling through precise control and appropriate engineering controls.
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 efficiently produces high-purity Y-90, reducing Sr-90 and Zr contamination to below detectable levels, meeting stringent purity requirements for cancer research and treatment, while allowing for the reuse of Sr-90.
Implementation Method 1
contacting the solids with greater than 80-wt % HNO3, whereby Y-90 is dissolved in the acid solution and strontium is precipitated as a solid
Implementation Method 2
evaporating the solution to incipient dryness to leave solids
Data Source
AI summary
The present invention provides a method of separating and purifying Yttrium-90 (Y-90) from Strontium-90 (Sr-90). In addition, a zirconium (Zr) clean-up step for the Y-90 is provided. Uses of the Y-90 purified by the method include cancer research and treatment. Y-90 is particularly useful in cell directed therapy, e.g., where the Y-90 is attached directly or indirectly to a targeting molecule such as an antibody.