Search

Mass-selective photodissociation spectroscopy and quantum mechanical calculations were combined to study the photoinduced reactions of bidenate metal complexes. The calculations approximately reproduce the action spectra of the complexes and were valuable for shaping and sorting out the fairly sophisticated reaction mechanisms in large systems.

2,4-diaminobutyric acid (DAB), a newly identified algal toxins in water, pose a great threat to human health. DAB may react with chlorine or chloramine to produce CX 3 R-type disinfection by-products (DBPs) during water treatment processes. This study mainly investigated the formation and speciation of DBPs from chlor(am)ination of DAB. The results revealed that haloacetic acids (HAAs), trihalomethanes (THMs) and haloacetonitriles (HANs) were the main kinds of CX 3 R-type DBPs generated from DAB during chlor(am)ination, of which dichloroacetic acid yielded the highest. The formation and total toxicity of four CX 3 R-type DBPs from DAB during chloramination was significantly lower than that during chlorination at each Cl 2 :N molar ratio. However, more formation of Br-THMs and I-THMs were observed during chloramination in the presence of Br - /I - . Futhermore, the effects of chlor(am)ine dosage, solution pH, reaction time, and the concentration of Br - and I - on the formation and speciation of CX 3 R-type DBPs were also evaluated during chlor(am)ination. The plausible formation pathways of CX 3 R-type DBPs from DAB were proposed and verified by theoretical calculation. The quantum chemistry calculations indicate that 1N in DAB and 8N in 2,4-diaminochlorobutyric acid (C 4 H 9 O 2 N 2 Cl) were more likely to be attacked by electrophiles, supporting the proposed pathway schemes., (Copyright © 2020 Elsevier Inc. All rights reserved.)