Selective protein-based separation of critical elements from mine wastes

Abstract Critical elements underpin clean-energy, electronics and catalysis, yet conventional extraction from mine waste is chemically intensive, poorly selective, and increasingly infeasible as ore/waste grades decline. Bioleaching is gaining traction, but purification from leachates remains difficult, especially for chemically similar ions such as rare-earth elements (REE) and platinum group elements (PGE). Proteins offer an alternative: they recognise metals via programmable binding pockets and can be engineered for affinity, selectivity, and process compatibility. This review outlines coordination principles relevant to separation; compiles case studies for REE, gallium (Ga), rhodium (Rh) and arsenic (As); surveys discovery and engineering pipelines; compares protein deployment formats; and assesses challenges and routes to scale. Progress varies widely across elements. REE binding is comparatively mature: lanmodulin (LanM) and derivatives deliver high affinity and have enabled separation prototypes. Ga lags, with few binders reported to date. Rh remains poorly grounded in biology, with most evidence coming from interactions of synthetic organorhodium complexes with proteins rather than direct Rh-binders. The exception is As, where binding is well mapped, but mainly in the context of remediation rather than resource recovery. Scale is the main bottleneck: kilogram-scale production at acceptable cost is difficult, capacities often lag synthetic resins, and performance can decline in liquors with high ionic strength, competing ions, low pH, fouling, and repeated regeneration. Progress will require higher-capacity, longer-lived formats and expanded binder repertoires for underexamined elements such as Ga, Ge, Rh, Nb/Ta, In and Pd/Pt via speciation-aware discovery, engineering, and de novo or machine-learning design under mine-relevant conditions.