Highly selective adsorption of rhenium by amyloid-like protein material

Rhenium separation from molybdenum in molybdenite minerals and waste leachate has become an emerging challenge. Addressing this challenge, we prepared a set of protein-based alkylamine/alkylammonium salts complexes as extradants for selective uptake of rhenium from molybdenum, where the protein component turned into the insoluble amyloid-like structure when its internal disulfide bonds were reduced, namely phase-transition process. Among them, the phase-transited lysozyme and methyletrioctyleammonium chloride complex (PTL-N263) exhibited the most efficient adsorption at the alkaline condition for the electrostatic interaction between negatively charged metal ions with positively charged center (R4N+) in N263, where negatively charged protein residues hindered the ion exchange of Cl− in N263 for larger size Mo species (Mo7O246−) than smaller size Re species (ReO4−). The adsorption follows the Freundlich model and pseudo-second-order kinetics, which exhibits top-level adsorption performance with a maximum adsorption capacity of 124 mg/g and a separation factor (βRe/Mo) of 2.78 × 103 for Re. The adsorption capacity per unit area (57.2 mg/(g m2)) is 1.6–41 times higher than previously reported adsorbents, and the cost for adsorbing 1 g of Re (VII) is $1.07, indicating its industrial capability. This adsorption strategy can be applied to separating Re from Mo in binary solutions and industrial wastewater with other competing ions.