Porous g-C3N4 modified with phenanthroline diamide for efficient and ultrafast adsorption of palladium from simulated high level liquid waste

Abstract

The efficient recovery of palladium from high level liquid waste (HLLW) is of growing importance for achieving sustainable development and resolving challenges in radioactive waste treatment. Nonetheless, the hunt for strong materials for the selective adsorption of palladium ion (Pd(II)) at high acidity remains a formidable obstacle. In this work, hierarchically porous g-C₃N₄ with high specific surface area was synthesized as a matrix of adsorbent that provides a rapid transport channel for Pd(II). Subsequently, N,N′-diethyl-N,N′-ditolyl-2,9-diamide-1,10-phenanthroline (DAPhen) was modified for integration into g-C₃N₄ to create CN-DAPhen for obtaining an adsorbent with excellent selectivity and efficient adsorption for Pd(II). The adsorption of Pd(II) in HNO₃ medium was examined using batch experiments. CN-DAPhen displayed quick adsorption kinetics, and equilibrium was reached within 5 min. By fitting the data using the Langmuir model, the maximum adsorption capacity of CN-DAPhen was calculated to be 390.63 mg g⁻¹. In practice, the functionalized nanomaterial was employed to recover Pd(II) from simulated HLLW containing competing metal ions. The adsorption selectivity of CN-DAPhen for Pd and Ru was also explored by combining adsorption experiments and DFT calculation. On this basis, a continuous process was developed for separating Pd and Ru from HLLW. Furthermore, the excellent radiation resistance and reusability of CN-DAPhen endowed it with great practical potential for the treatment of HLLW. This study not only introduces a novel species with superior adsorbent capability in selectively recovering palladium but also reveals a potential strategy for the development of robust nanomaterials for nuclear waste cleanup.