Nanoscale Alanine-Modified Zero-Valent Iron for Fenton-Like Degradation of the Mixed Organic Solvents of Tributyl Phosphate and n-Dodecane

Abstract

During the reprocessing of spent nuclear fuel, mixed organic solvents of tributyl phosphate (TBP) and n-decane (DD) after extraction may encounter treatment difficulties. This study synthesized nanoscale alanine-modified zerovalent iron (Ala@Fe⁰) as a Fenton-like catalyst. Various characterization techniques were employed to analyze the surface morphology, structure, and properties of Ala@Fe⁰. The results showed that alanine was successfully grafted onto Fe⁰, increasing the Fe(0) content and enhancing the specific surface area and surface hydrophobicity. The catalytic performance of Ala@Fe⁰ in degradable organic solvents was evaluated. Under the optimal reaction conditions, the oxidation efficiency could exceed 60%, and the volume reduction rate of organic solvents could exceed 95%. Electron spin resonance (ESR) analysis indicated that the active oxygen species in the Ala@Fe⁰–H₂O₂ system were mainly hydroxyl radicals (·OH). The interaction mechanism was analyzed by using density functional theory (DFT) calculations and interaction region indicator (IRI) isosurface maps. The proposed catalytic degradation mechanism indicated that Ala@Fe⁰ could avoid oil-phase encapsulation and undergo Fenton reactions through two possible interface mechanisms to oxidize TBP and DD. This study provides a theoretical basis for the modification of iron-based materials and their application in treating organic solvents derived from spent nuclear fuel reprocessing.