Highly Selective Capture of ReO4– by a Conjugated Amine-Based Polymer Synthesized via a One-Pot Strategy

Abstract Given the highly dispersed occurrence of rhenium in the natural environment, it is commonly encountered in conjunction with other minerals and primarily occurs as perrhenate ions (ReO4–) in the acidic waste solutions produced by nonferrous metallurgical operations. The advancement of techniques for the efficient, economical, and selective extraction of rhenium from metallurgical waste acids holds significant socio-economic value. In the present study, a functional polymer designated CY-PPZ, characterized by a conjugated amine structure, was synthesized via a one-pot reaction employing cyanuric chloride and piperazine as monomeric precursors, designed for the targeted adsorption of ReO4– ions. Experimental investigations revealed that CY-PPZ exhibited superior adsorption performance for ReO4– across a broad pH range (2–8), achieving adsorption equilibrium within 480 min and demonstrating a maximum adsorption capacity of 350.92 mg/g. The polymer also displayed remarkable selectivity and resistance to interference from competing ions, as evidenced by a distribution coefficient (Kd) of 14.34 L/g. Notably, in simulated metallurgical waste acid solutions characterized by elevated concentrations of competing anions, specifically with a molar ratio of ReO4– to NO3–, SO42–, and Cl– of 1:3000, the removal efficiency of ReO4– consistently exceeded 88.52%. Additionally, CY-PPZ exhibited excellent recyclability, retaining a removal efficiency of 90.20% after 8 successive adsorption–desorption cycles. Economic analysis indicated that each gram of CY-PPZ could yield an approximate socio-economic value of $26.866. Mechanistic insights obtained from XPS and DFT calculations confirmed that the primary adsorption mechanisms involved synergistic electrostatic interactions and chemical coordination between CY-PPZ and ReO4– ions. In summary, CY-PPZ emerges as a highly promising material for the selective, efficient, and cost-effective extraction of rhenium from metallurgical waste acid streams.