离子强度和阴离子特性对聚丙烯酸螯合稀土元素的影响,Macromolecular Chemistry and Physics

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离子强度和阴离子特性对聚丙烯酸螯合稀土元素的影响
Macromolecular Chemistry and Physics ( IF 2.5 ) Pub Date : 2023-08-14 , DOI: 10.1002/macp.202300235
Connor M.B. Gallagher ₁ , Michael D. Schulz ₁

Affiliation

稀土元素 (REE) 是许多现代技术的关键组成部分，但其有效分离和纯化仍然面临重大挑战。金属结合聚合物可能有助于开发传统分离技术（例如溶剂萃取）的有前景的替代方法，而深入了解溶液中金属离子和聚合物之间的相互作用对于这种开发至关重要。在这项工作中，使用等温滴定量热法 (ITC) 测量金属结合热力学，研究了离子强度对聚丙烯酸与 REE 螯合的影响。ITC 实验表明，当离子强度因醋酸钠缓冲强度的增加而增加时，聚合物-REE 结合变得越来越不利。然而，当通过添加氯化钠来增加离子强度时，结合再次变得越来越不利，但程度小于当离子强度因增加缓冲强度而增加时。此外，当用氯化钠提高离子强度时，结合亲和力的降低是由焓驱动的，而当用乙酸钠缓冲液提高离子强度时，结合亲和力的降低是由熵驱动的，这表明乙酸根离子存在竞争性结合。这些结果强调了离子强度在聚合物-金属结合热力学中的重要性，并将指导关键金属纯化新工艺的开发。

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Effect of Ionic Strength and Anion Identity on Rare-Earth Element Chelation by Poly(acrylic acid)

Rare-earth elements (REEs) are critical components of many modern technologies, but their efficient separation and purification continue to pose significant challenges. Metal-binding polymers may enable the development of promising alternative approaches to conventional separation techniques (e.g., solvent extraction), and insights into the interactions between the metal ions and polymers in solution are crucial to such development. In this work, the effect of ionic strength on the chelation of REEs by poly(acrylic acid) is investigated using isothermal titration calorimetry (ITC) to measure the metal-binding thermodynamics. ITC experiments revealed that when ionic strength increases from increasing the sodium acetate buffer strength, polymer-REE binding becomes increasingly disfavored. However, when ionic strength is increased by the addition of sodium chloride, binding again becomes increasingly disfavored, but to a lesser extent than when ionic strength increases from increasing the buffer strength. Additionally, the reduction in binding affinity is enthalpically driven when ionic strength is raised with sodium chloride, while it is entropically driven when raised with sodium acetate buffer, suggesting competive binding by the acetate ions. These results highlight the importance of ionic strength in polymer-metal binding thermodynamics and will guide the development of new processes for the purification of critical metals.

更新日期：2023-08-14

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