Highly
toxic iodinated products would form in oxidation and disinfection
of iodine-containing water. Variation of iodinated aromatic products
in ferrate [Fe(VI)] oxidation of phenolic compounds (phenol, bisphenol
A (BPA), and p-hydroxybenzoic acid (p-HBA)) in iodine-containing water was investigated. At pH 5.0, oxidation
of phenolic compounds was inhibited by competitive reaction of ferrate
with I–, and no formation of iodinated aromatic
products was detected. Almost all I– was converted
into nontoxic IO3
–. At pH 7.0, 8.0, and
9.0, HOI formed in ferrate oxidation of I– and further
reacted with phenols, with the formation of iodinated aromatic products.
Mass spectrometry analysis showed that both kinds and contents of
iodinated aromatic products were raised with the increase in solution
pH and the content of I–, and these iodinated aromatic
products were further oxidized by ferrate. Ferrate deprived iodine
from iodinated aromatic products and transferred highly toxic organic
iodine into nontoxic IO3
–. An electron-donating
substituent (alkyl) increased the reactivity of phenol with ferrate
and HOI and facilitated ferrate oxidation of iodinated phenols. An
electron-drawing substituent (carboxyl) decreased the reactivity of
phenol with ferrate and HOI and hindered the further oxidation of
iodinated aromatic products. A kinetic model about the variation of
phenol, BPA, and p-HBA in reaction with ferrate in
iodine-containing water was developed, and the oxidation profile of
phenolic compounds could be satisfactorily predicted at various iodide
concentrations.
Abstract1‐2‐2‐type Zintl phase compounds have promising thermoelectric properties because of their complex crystal structures and multiple valence‐band structures. In this work, a series of single phase (Yb0.9Mg0.1)MgxZn2−xSb2 (x = 0, 0.2, 0.4, 0.6, 0.8, and 1) compounds are prepared by alloying YbZn2Sb2 with 10 at% MgZn2Sb2 and different amounts of YbMg2Sb2. The incorporation of Mg at the Yb site, as well as at the Zn site, not only leads to an effective orbital alignment confirmed by the dramatically enhanced density of states effective mass and Seebeck coefficients, but also increases the point defect scattering, contributing to a low lattice thermal conductivity ≈0.54 W m−1 K−1 at 773 K. Combined with the optimization of the carrier concentration by Ag doping at the Zn site, a highest ZT value ≈1.5 at 773 K is achieved in (Yb0.9Mg0.1)Mg0.8Zn1.2Ag0.002Sb2, which is higher than that of all the previously reported 1‐2‐2‐type Zintl phase compounds.
In this work, it was found that the most widely used brominated flame retardant tetrabromobisphenol A (TBrBPA) could be transformed by free chlorine over a wide pH range from 5 to 10 with apparent second-order rate constants from 138 to 3210 M(-1)·s(-1). A total of eight products, including one quinone-like compound (i.e., 2,6-dibromoquinone), two dimers, and several simple halogenated phenols (e.g., 4-(2-hydroxyisopropyl)-2,6-dibromophenol, 2,6-dibromohydroquinone, and 2,4,6-tribromophenol), were detected by high-performance liquid chromatography tandem mass spectrometry (HPLC-MS/MS) using a novel precursor ion scan (PIS) approach. A tentative reaction pathway was proposed: chlorine initially oxidized TBrBPA leading to the formation of a phenoxy radical, and then this primary radical and its secondary intermediates (e.g., 2,6-dibromo-4-isopropylphenol carbocation) formed via beta-scission subsequently underwent substitution, dimerization, and oxidation reactions. Humic acid (HA) considerably inhibited the degradation rates of TBrBPA by chlorine even accounting for oxidant consumption. A similar inhibitory effect of HA was also observed in permanganate and ferrate oxidation. This inhibitory effect was possibly attributed to the fact that HA competitively reacted with the phenoxy radical of TBrBPA and reversed it back to parent TBrBPA. This study confirms that chlorine can transform phenolic compounds (e.g., TBrBPA) via electron transfer rather than the well-documented electrophilic substitution, which also have implications on the formation pathway of halo-benzoquinones during chlorine disinfection. These findings can improve the understanding of chlorine chemistry in water and wastewater treatment.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.