Attenuation of decabromodiphenyl ether (BDE209) using Ag/Fe0 complexed with citrate in various environmental and toxicity assessments by evaluating ryegrass

Abstract

In this research, a bimetallic compound of silver-modified nano zero-valent iron (Ag/Fe⁰) was synthesized and utilized to degrade pentabromophenyl ether (BDE209) under various environmental conditions with the presence of citric acid (CA). Liquid chromatography-mass spectrometry (LC-MS) analysis revealed twelve intermediate products formed during the degradation of BDE209. Both the Fe⁰–CA system and 0.2% Ag/Fe⁰–CA system showcased a degradation efficiency of 68.7% and 72.7% respectively in a liquid solution after 24 hours of treatment, along with a 9.1% and 18.2% total organic carbon (TOC) removal. Amid soil conditions, degradation rates reached 66.4%, 54.1%, and 50.5% respectively for initial BDE concentrations of 5 ppm, 10 ppm and 15 ppm in the presence of a degradation system comprising 30 g kg⁻¹ Ag/Fe⁰ and sodium citrate/CA (NaCA/CA) over 45 days. The potential environmental impacts of this process were assessed using ryegrass as a phytotoxicity marker in soil, wherein the measured chlorophyll and malondialdehyde (MDA) contents indicated that the addition of Ag/Fe⁰ successfully mitigated stress damage caused by BDE209. Furthermore, Ag/Fe⁰ has the capability to permeate the cell wall of ryegrass roots and establish interconnections. STEM-EDS patterns revealed that Ag was more readily accumulated inside of the cells compared to Fe. In conclusion, this study introduces an innovative approach for the safe and efficient oxidative degradation of BDE209 under both aquatic and terrestrial environmental conditions.