The agglomeration of nanoparticles reduces the surface area and reactivity of nano zero-valent iron (NZVI). In this paper, highly dispersive and reactive NZVI immobilized in mesoporous silica microspheres covered with FeOOH was synthesized to form reactive mesoporous silica microspheres (SiO 2 @FeOOH@Fe). The characteristics of SiO 2 @FeOOH@Fe were analyzed by transmission electron microscopy, Fourier transform infrared spectroscopy simultaneous thermal analysis, X-ray photoelectron spectroscopy, and Brunnaer–Emmett–Teller surface area analysis. The mean particle size of the reactive mesoporous silica microspheres was 450 nm, and its specific surface area was 383.477 m 2 g −1 . The degradation of dcabromodiphenyl ether (BDE209) was followed pseudo-first-order kinetics, and the observed reaction rate constant could be improved by increasing the SiO 2 @FeOOH@Fe dosage and by decreasing the initial BDE209 concentration. The stability and longevity of the immobilized Fe nanoparticles were evaluated by repeatedly renewing the BDE209 solution in the reactor. The stable degradation of BDE209 by SiO 2 @FeOOH@Fe was observed within 10 cycles. Agglomeration-resistance and magnetic separation of SiO 2 @FeOOH@Fe were also performed. The improved dispersion of SiO 2 @FeOOH@Fe in solution after one-month storage and its good performance in magnetic separation indicated that SiO 2 @FeOOH@Fe has the potential to be efficiently applied to environmental remediation.
Jianyu Gong,Ruiyuan Xue,Yake Xu,Hao Lv,Nan Wang,Xiaoming Su
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.
Polybrominated diphenyl ethers have been identified as a new class of organic pollutants with ecological risk due to their toxicity, bioaccumulation, and global distribution. Proper remediation technologies are needed to remove them from the environment. In this paper, Ni/Fe bimetallic nanoparticles were synthesized by chemical deposition and used to degrade decabromodiphenyl ether (BDE209). The characteristics of Ni/Fe nanoparticles were analyzed by transmission electron microscopy, X-ray diffractometry, X-ray photoelectron spectroscopy, and Brunnaer–Emmett–Teller surface area analysis. Ni/Fe bimetallic nanoparticles with diameters in the order of 20–50 nm could effectively degrade BDE209 in the solvent (tetrahydrofuran/water). Influence factors, such as Ni/Fe nanoparticle dosage, initial BDE209 concentration, and Ni loading, on the removal of BDE209 were studied. The results indicated that the degradation of BDE209 followed pseudo-first-order kinetics, and the degradation rate of BDE209 increased with increasing the amount of nano Ni/Fe particles, Ni/Fe ratio, and decreasing the initial concentration of BDE209. Through analyzed the mass balance of the BDE209 removal, degradation was the main process of BDE209 removal. The mechanism of debromination was deduced by analyzing the reaction products using gas chromatography–mass spectrometry, the bromide ion in the solution and varying the solvent conditions. Stepwise hydrogen reduction is the main process of debromination, and the hydrion play an important role in the reaction. Moreover, the experiment of long term performance and leaching of Ni were also carried out to test the stability and durability of Ni/Fe nanoparticles in BDE209 degradation.
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