Smooth pore surface in zeolites for krypton capture under humid conditions

Abstract

Efficient trace radioactive krypton isotopes (⁸⁵Kr) capture from air under humid conditions is a critical challenge for nuclear safety and environmental protection. Commercial zeolites suffer from low Kr/N₂ selectivity due to cation-induced interactions that strengthen nitrogen (N₂) adsorption, while their hydrophilicity triggers severe water competition. Herein, we proposed utilizing the smooth pore surface in pure-silica zeolites to weaken the N₂ adsorption and mitigate water competition. The pure silica ZSM-11 exhibited significant Kr/N₂ selectivity (4.8) and Kr uptake of 12.8 cm³/g at 298 K and 1 bar, superior to the commercial zeolites. Its intersecting ten-membered ring (10-MR) channels facilitated optimal Kr interactions and distribution, as corroborated by Grand Canonical Monte Carlo (GCMC) simulations, which revealed preferential multisite Kr···O interactions with significantly higher Kr densities than N₂. Dynamic breakthrough experiments demonstrated that pure silica zeolites, particularly ZSM-11, achieved superior Kr capturing performance and cycling stability under humid conditions (relative humidity (RH) = 72.6%), realizing a leap from ppm levels to high purity (> 80%) Kr. This work demonstrated the rational design of pore surface and topologies in zeolite for inert gases capture provided an effective technological route for radioactive krypton isotopes separation under humid conditions.