Reusable Silk-Based Mesoporous Membranes for Recovery of Rare-Earth Elements

The extraction of rare-earth elements (REEs) from low-grade sources, including electronic waste (E-waste), has garnered significant interest as a means to supplement current REE manufacturing, which is primarily through unsustainable mining. REEs have proven invaluable in countless industries, from electronics to defense, but their supply is failing to keep up with demand. Herein, we demonstrate an important step toward environmentally friendly, biobased REE extraction using silk nanofibril (SNF) and SNF/silk-elastin-like protein (SELP) membranes functionalized with two lanthanide binding tags (LBT1 and LBT2). These membranes offer facile fabrication with clear scale-up potential while enabling highly specific REE binding and, crucially, reusability. Additionally, through specific protein engineering, we were able to improve the binding efficiency of terbium onto the SELP membranes. The bound REEs can then be recovered by simple acid leaching, after which the membrane can be reused for additional cycles. This membrane-based approach avoids environmentally harmful solvents used in traditional liquid–liquid extraction and could enable the recycling of REEs that would otherwise be disposed of as industrial or e-waste.