[Degradation of Triclosan by Heat Activated Persulfate Oxidation].

Sulfate radical (SO4·-)-based advanced oxidation technologies (SR-AOPs) are widely used for remediation of contaminated groundwater and soils. This study investigated the reaction kinetics, products, and transformation pathways of triclosan, a widely used antimicrobial agent, during its degradation by heat activated persulfate oxidation. Experimental results revealed that increasing temperature or initial persulfate concentration significantly enhanced the degradation of triclosan. The reaction could be fitted in the pseudo-first-order kinetic model and the activation energy (Ea) was determined to be 142 kJ·mol-1. The presence of humic acid markedly inhibited triclosan degradation, whereas chloride (Cl-) showed a more complicated effect. Triclosan degradation was slightly accelerated in the presence of 5 µmol·L-1 Cl-, however, a higher concentration of Cl- (e.g., 10 µmol·L-1) showed an inhibitory effect. Using liquid chromatography-mass spectrometry, a total of six transformation products, including 4-chlorocatechol, 2,4-dichlorophenol, and 2-chloro-5-(2,4-dichloro-6-hydroxyphenoxy)-1,4-benzoquinone, were identified. Accordingly, the cleavage of the ether bond and hydroxylation of the phenol ring were proposed as the principal pathways of triclosan degradation upon reaction with SO4·-. The findings of this study can be used to evaluate the feasibility of decontamination of triclosan by SR-AOPs.

[Formation of Halogenated By-products in Co²âº Activated Peroxymonosulfate Oxidation Process].

Sulfate radicals (SO4·â») generated by Co²âº catalyzed activation of peroxymonosulfate (PMS) are highly oxidative and can be applied to degrade various organic pollutants. It was revealed in this research that bromide could be transformed in this process to reactive bromine species which reacted with phenol subsequently, leading to the formation of bromophenols and brominated by-products such as bromoform and dibromoacetic acid. The formation of the brominated by-products first increased and then decreased. The maximum yields of bromoform (10.3 µmol · L⁻¹) and dibromoacetic acid (14.6 µmol · L⁻¹) occurred at approximately 8 h with initial phenol, PMS, Br⁻, Co²âº, concentrations of 0.05, 1.0, 0.2, and 5 µmol · L⁻¹, respectively. Formation of the brominated by-products decreased with increasing pH. With constant total halides, increasing Cl⁻/Br⁻ ratio decreased the total formation of halogenated by- products but generated more chlorinated byproducts. The findings of this research can provide valuable information in assessing the feasibility of SO4·â» based oxidation technologies in real practice.

[Chlorination of ethynyl estradiol: a kinetic and mechanistic study].

The objective of this research is to explore the fundamentals of reactions between chlorine and ethynyl estradiol (EE2), which is expected to occur during the drinking water treatment. The first step of EE2 chlorination was shown to follow the second-order kinetics with the first order to concentrations of both target compound and chlorine, respectively. Apparent rate constants of EE2 chlorination exhibit the pH-dependent profile which indicates that the phenolic ring is the preferred site of attack by Cl. The transformation of EE2 is governed by 3 elementary reactions between different species of EE2 and HClO. The deprotonated EE2 anion is significantly more reactive than its neutral conjugate. HPLC/MS analysis revealed that several Cl atoms can be incorporated into this site via complex multi-step pathways, resulting in the formation of mono and di-chlorine substituted EE2. The incorporation of the third Cl is accompanied by immediate broken down of the ring via hydrolysis. The results of this study are helpful to fully understand the behavior of EE2 in chlorinated drinking water disinfection, provide the basis for evaluating the potential exposure of this contaminant to human. The data of this work also give insights to the formation of chlorinated drinking water disinfection by-products (DBPs).

[Removal of estrogens in laccase catalyzed oxidative processes].

The removal of 5 estrogens (bisphenol A, estradiol, ethinylestradiol, estrone and octylphenol) in laccase catalyzed oxidative processes was studied. The effects of pH and NOM on the removal of EDCs were discussed in detail, as well as the kinetics of EE2 removal and the reaction products. The results indicated that laccase was capable of removing estrogens efficiently. The optimal pH was between 4 and 6. NOM significantly inhibited the removal of estrogens at the initial stage of the reaction. However, the adverse effect of NOM was not obvious after 24 h treatment. The removal of EE2 obeyed the second-order kinetics. The activity of laccase remained stable during the reactions and the stability was higher than that of peroxidase. MS analysis demonstrated that the EE2 dimer formed through radical coupling mechanism was the main reaction product.

Effect of astaxanthin on oxidative stress of red blood cells and peroxidation damage of membrane / 中国实验血液学杂志

<p><b>OBJECTIVE</b>To explore the effect of astaxanthin (ASTA) on oxidative stress of intra- and extra- red blood cells during stored period and the protective function for cell membrane.</p><p><b>METHODS</b>The blood of volunteers was collected to prepare suspended red blood cells without leukocytes. Then the red blood cells were randomly divided into group A, group B, group C and group D. The ASTA was added into MAP preservation solution of group B, group C and group D, the final concentration of ASTA was 5, 10 and 20 µmol/L respectively. Group A was used as control group, in which only the dissolved liquid DMSO of ASTA was added. The red blood cells were stored in refrigerator at 2 °C-6 °C. On day 7, 14, 28 and day 42 of storage, the content of reactive oxygen species (ROS) in red blood cells was detected by fluorescence microplate reader. The content of malondialdehyde (MDA) was detected with TBA method. The content of hydrogen peroxide (H2O2) outside cell was detected with spectrophotometric method. The mean corpuscular volume(MCV) was detected with blood cell analyzer. The content of free hemoglobin(FHb) was detected with chemical colorimetry.</p><p><b>RESULTS</b>The ROS, MDA, FHb and H2O2 levels in B, C and D groups were lower than those in control group during the stored period. On day 7 and 14 of storage, among group B, group C, group D and group A, the MCV showed no difference in comparison with control group. On day 28 and 42 of storage, the MCV in B, C and D groups was lower than that in control group.</p><p><b>CONCLUSION</b>The ASTA can reduce the oxidative stress level of stored red blood cells inside and outside, relieve the peroxidation damage of cell membrane.</p>