Completely recyclable and reusable automatic phase-separable catalytic system for the reductive debromination of polybrominated diphenyl ethers

Abstract

An automatic phase-separable catalytic system was developed for the reductive debromination of polybrominated diphenyl ethers (PBDEs) using thiol-modified Pd nanoparticles (thiol-Pd NPs) as the catalyst, H2 as the reducing agent, and n-butanol (oil phase) and water (water phase) as solvents. This system achieved efficient and complete debromination of various PBDEs with 1–10 bromine atoms and other bromo-organic pollutants at concentrations ranging from 15 to 1500 mg L−1. Typically, this system achieved a debromination efficiency of 100 % within 15 min for all the tested bromo-organic pollutants. Importantly, the debromination reaction was conducted in a microemulsion state under stirring; upon stopping the stirring, the microemulsion automatically separated into an upper oil phase, a down water phase, and a thiol-Pd NP self-assembled membrane phase at the oil/water interface. These three phases could be easily separated from each other, allowing for their reuse across multiple debromination cycles with good reusability. The thiol modifier enhanced the stability and reusability of Pd NPs and improved the adsorption of PBDEs, facilitating their reaction with atomic hydrogen (the dominant reactive species). This method successfully eliminated PBDEs in soils by integrating with a pre-extraction process.