Rational design of a cationic polymer network towards record high uptake of 99TcO4- in nuclear waste

Tc-99 is a long-lived radionuclide present in large amounts as TcO4 anion in used nuclear fuel. Its removal from the waste stream is highly desirable because of its interference capability with actinide separation and its volatile nature during the nuclear waste vitrification process. Despite the progress achieved in the past few years, the design of anion-exchange materials with optimized Tc uptake property and improved stability under the extreme condition, is still a research goal beneficial for reducing the volume of secondary radioactive solid waste generated during the waste partitioning process. However, their design philosophy remains elusive, with challenges coming from charge repulsion, steric hindrance, and insufficient reactive sites within the materials. Herein, we present a design philosophy of cationic polymer network materials for TcO4- separation by systematic precursor screening and structure prediction. This affords an optimized material, SCU-CPN-2 (SCU=Soochow University), with extremely high positive charge density while maintaining high radiation resistance. SCU-CPN-2 exhibits a record high adsorption capacity (1,467 mg/g towards the surrogate ReO4-) compared to all anion-exchange materials reported up to date. In addition to ultrafast adsorption kinetics, SCU-CPN-2 has remarkable selectivity over nitrate and sulfate, and facile recyclability.

Automated summary

Tc-99 is a long-lived radionuclide present in large amounts in used nuclear fuel. Designing anion-exchange materials with optimized Tc uptake property is a research goal beneficial for reducing the volume of secondary radioactive solid waste. However, challenges exist in the design philosophy with difficulties such as charge repulsion, steric hindrance, and insufficient reactive sites.