High-Stable Covalent Organic Framework Towards Palladium Removal from Nuclear Wastewater

The proper management of High-Level Liquid Waste (HLLW) is essential for safeguarding the environment and human health. The presence of platinum group metals (PGMs) in HLLW can impact its disposal due to their high melting points. Therefore, it is vital to eliminate PGMs during the initial treatment phase. Thus, this research introduces an adsorption method using COF-42 as an adsorbent to target palladium (Pd). The molecular structure, integrity, and morphology of COF-42 and Pd@COF-42 are thoroughly assessed using various techniques such as PXRD, FT-IR, TGA, XPS, and SEM. The study further investigates the adsorption kinetics and thermodynamics of Pd by COF-42, revealing that the adsorption process follows a Freundlich model. The maximum adsorption capacity of COF-42 is 170.6mg/g, demonstrating a superb adsorption capacity for palladium. Additionally, the study also explores the impact of adjusting HNO3 concentration, and COF-42 dosage on the adsorption performance, highlighting the influence of acidity levels on the final outcome. Lastly, the selectivity of COF-42 towards Pd in the presence of different metal ions and its ability to be reused underscore its effectiveness in Pd(II) adsorption, attributed to the synergistic effects of its flexible ligand, framework porosity, and concentrated –NH/–NH2 groups with a strong affinity for Pd2+.