NSRRC Activity Report 2022

070 NSRRC ACTIVITY REPORT 2022 Fig. 1 : (a) XRD pattern of Cu–Fe BNPs before and after reaction (b) Fe K-edge XANES spectra of Cu–Fe BNPs before and after reaction. [Reproduced from Ref. 4] Nano-Iron Rapidly Degrades Toxic Pollutants Nanoscale bimetallic zerovalent iron particles rapidly degrade halogenated contaminants in water. K nown and emerging persistent organic pollutants (POPs) have garnered attention due to their presence in environmental matrices and their adverse health and ecological effects; this is primarily true for POPs with halides, such as pentachlorophenol (PCP), polybrominated diphenyl ethers (PBDEs), and tetrabromobisphenol A (TBBPA). Yang-Hsin Shih and his collaborators (National Taiwan University) developed several nanomaterials and investigated the ability of specific microbes to effectively degrade POPs and several emerging organic contaminants. 1,2 PBDEs and TBBPA are applied to polymeric materials in the production of brominated flame retardants (BFRs). Studies have reported PBDE contamination in several sites in Taiwan; furthermore, crops growing in contaminated soil uptake PBDEs. This novel study utilized the debromination mechanism and absorptive capacity of nanoscale zerovalent iron (NZVI) to rapidly remove PBDEs. However, NZVI cannot dechlorinate PCP. The modification of the NZVI surface with a second metal enhances the reactivity of particles, causing them to behave as electron transferrers. Pd and Fe nanoparticles (NPs) effectively remove PCP. For common cations, the enhancement of Cu 2+ and Ni 2+ ions was achieved by doping the reduced forms of Cu and Ni on the Pd and Fe surfaces using X-ray Near Edge Spectrometry (XANES) analysis. Ni–Fe and Cu–Fe NPs were later developed to enhance PCP removal. 3,4 For Cu–Fe bimetallic nanoparticles (Cu–Fe BNPs), the TBBPA removal rate and debromination efficiency increased with higher Cu doping content, higher temperature, and lower pH. One study analyzed the complete debromination pathway and the time evolution of intermediate byproducts at different pH values. 4 Cu–Fe BNPs can be used more than six times and thus serve as stable and reusable catalysts. Genotoxic test results of the treated solution indicated no notable hazardous potential. Moreover, the Fenton reaction can be employed to degrade byproducts using additional H 2 O 2 . Spectra obtained from an analysis of the particles with X-ray diffraction at 2θ = 44.1° and 43° at TLS 13A1 revealed zerovalent states of Fe and Cu, respectively ( Fig. 1(a) ). 4 After the reaction, the researchers discovered peaks of FeO x instead of Fe 0 . Shih’s team used XANES at TLS 17C1 to further analyze the particles. 4 The normalized Fe K-edge spectra of the bimetallic nanoparticles ( Fig. 1(b) ) revealed an obvious absorbance feature from 7112 to 7115 eV, which also corresponds with zerovalent Fe. Cu transferred electrons from Fe to pollutants to promote dehalogenation. Cu–Fe BNPs with a Cu content of 4% had the best reactivity. Cu–Fe BNPs are promising as a means to treat BFRs. Furthermore, compared with several surfactants, cetyl trimethylammonium bromide (CTAB) was observed to markedly enhance the removal of PCP with Ni–Fe NPs. 3 The small particle size of Ni–Fe CTAB and the electrostatic interaction between electronegative phenolate groups of PCP and electropositive Ni–Fe CTABs increased the