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Study On Removal Performance And Degradation Mechanism Of Steroidal Estrogens In Water

Posted on:2008-01-08Degree:DoctorType:Dissertation
Country:ChinaCandidate:Q S LiFull Text:PDF
GTID:1102360242458286Subject:Municipal engineering
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There is an increasing concern about the ubiquity of steroid estrogenic compounds that interfere with the function of the endocrine system. The study of steroid estrogenic compounds has become a new hotspot in drinking water treatment research.Some natural estrogens, i.e, estrone (E1), 17β-estradiol (E2), estriol (E3) and synthetic estrogens such as17α-ethynylestradiol (EE2) has previously been found to be estrogenic. Relatively minor amounts of estrogens enter the environment may bright to unpredictable risk to human and animal health.The survey results of surface water in Shanghai shows that four kinds of steroidal estrogens can be detected in raw water and finished water and their concentrations ranging from 0 to 0.10μg/L. Conventional treatment processes was ineffective in removing steroidal estrogens.In the paper, advanced oxidation processes (AOPs) (UV, UV/H2O2 and UV/TiO2), activated carbon adsorption and powder activated carbon-ultrafiltration combination process (PAC-UF) were studied. Removal characteristics, the main influencing factors and degradation mechanisms had been studied comprehensively. Experimental results showed that:UV/H2O2 can remove 17α-Ethinylestradiol and 17β-Estradiol effectively. Degradation of EE2 and E2 follows pseudo-first order. Under the conditions that the initial concentration in raw water, the intensity of UV, the dosage of H2O2 and the reaction time was 650μg/L (EE2, for E2 400μg/L), 154μw/cm2,10mg/L and 30 minutes respectively. The first order photodegradation rate constant of EE2, E2 was 0.1399min-1 and 0.0432min-1 respectively.The concentration of H2O2 had both positive and negative effects on the degradation rate of 17α-Ethinylestradiol: When the concentration of H2O2 was less than 10mg/L, first-order kinetics constant increased linearly with the increase of H2O2 dosage. When the concentration of H2O2 was more than 15mg/L, degradation of EE2 was inhibited. But to E2, its first-order kinetics constant augmented with increasing of hydrogen peroxide all along.Lower solution pH conduced to EE2 and E2 photodegradation. The photodegradation rate constant of EE2 and E2 increased with the increasing of intensity of UV radiation. The influence of some common anions such as HCO3,NO3-,Cl-,SO42 on photodegradation has been investigated, HA, HCO3-, NO3-, CO32-, Cl-and SO42- have inhibitory action on EE2 photodegradation.The degradation of steroidal estrogens in water by UV/Nano titanium suspended system, UV/TiO2 immobilization film was studied. The main influencing factors and degradation mechanism of this technology were studied. Experimental results showed that:UV/Nano titanium suspended system, UV/TiO2 immobilization film can remove 17α-Ethinylestradiol and 17β-Estradiol effectively; Degradation of EE2 and E2 follows pseudo-first order. When the dosage of TiO2 was 200mg/L,Under the same UV intensity,pH, initial concentration(400μg/L), the first order photodegradation rate constant of EE2, E2 were 0.0328min-1 and 0.018min-1 respectively.Effects of reaction pH, EE2, E2 initial concentration, applied TiO2 dose, UV light power, H2O2, O2 were investigated respectively. In the experiment concentration range, the photodegradation rate constant of EE2 and E2 increased with the increase of TiO2 dosage. Intensity of UV radiation, low or high solution pH can increase EE2 and E2 photodegradation. The photodegradation rate constant of E2 was related to the influential factors mentioned above and that it can be affected by adding H2O2,O2 The concentration of oxidant H2O2, O2 had both positive and negative effects on the degradation rate of E2.In the paper, we also invested the EE2 degradation by UV assistant with TiO2 immobilization film was made in our laboratory. It also indicates that TiO2 immobilization film has photocatalysis ability.For the first time, PAC-UF combined process was adopted to remove EE2 in drinking water. Six kinds of activated carbon were selected to be studied on adsorption isotherm, adsorption kinetics of EE2.Experimental results showed that:Freundlich adsorption isotherm model can describe the adsorption behavior of EE2 accurately. The adsorption capacity sequence was: PAC3#>GAC coco>GAC6#>PAC1#>PAC2#>GAC7#.1/n of Freundlich adsorption isotherm model was 0.1082~0.9315. In adsorption kinetics and PAC-UF experiment, we used PAC1# as tested powder active carbon. Adsorption was mainly occurred in the first 5 min.Ultrafiltration combined with PAC can remove EE2 effectivly. Remove rate increase lineally with the increasing dosage of PAC. We studied effect of SDBS and organic substance (simulate by humic acid) on EE2 removal. Both of them can decrease EE2 removal.
Keywords/Search Tags:steroidal estrogen, 17α-ethynylestradiol(EE2), 17β-estradiol (E2), ultraviolet light, hydrogen peroxide, TiO2, photodegradation rate, powder activated carbon, Powder activated carbon-ultrafiltration
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