(42a) Oxime-Based Adsorbents for Selective Separation Among Rare Earth Elements

Van T. C. Le,¹ Hong Minh Tran,¹ Ngoc T. Bui^1,2,*

¹School of Sustainable Chemical, Biological, and Materials Engineering, The University of Oklahoma, Norman, Oklahoma 73019, USA

²School of Civil Engineering and Environmental Science, The University of Oklahoma, Norman, Oklahoma 73019, USA

It is inevitable to augment metal stocks with diverse resources and methods to ensure an undisrupted supply of critical metals. Recovering metals from wastewater and brine through separating and recycling is, therefore, important energetically, economically, and environmentally. This work demonstrates the design and use of oxime-based crystal adsorbents for efficient and selective separation of rare earth elements (REEs) from aqueous environments. A family of oxime-based coordination complex adsorbents, hereafter referred to as oCCAs, was synthesized. The selection of oxime ligands was found to play a crucial role in the resulting morphologies and structures of oCCAs, varying from rhombic dodecahedra, cube, and hexagonal sheet to sphere when benzamide oxime, 4-methylbenzamide oxime, 4-aminobenzamide oxime, and 2-chlorobenzaldehyde oxime are used as metal chelators correspondingly in the reactions. The selective REEs capture behaviors of the oCCAs are fine-tuned by adjusting the functional groups in the oxime ligands. Notably, the adsorbent constructed from 4-aminobenzamide oxime displayed the most effective REEs adsorption capacity and separation factor. In addition, effects of background sodium chloride, often encountered in several wastewater streams, morphological transformation, and membrane integration on REE separating performances were investigated. The design approach used in this study offers a promising strategy to accelerate the discovery of new materials that can be synthesized efficiently and with ease toward augmenting REEs for various industrial applications.