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ABSTRACT: The mechanisms of simultaneous photocatalytic hydrogen production and estrogenic activity (EA) removal from secondary effluent were investigated by evaluating the effects of initial dissolved oxygen (DO), organic matter, and inorganic ions on the process. The photocatalytic process was enhanced and can be divided into two phases according to the availability of DO. In aerobic phase, the humic/fulvic-like compounds in hydrophilic substances fraction were preferentially decomposed by aerobic photo-formed reactive oxygen species (i.e. O2(-), h(+), and OH) with generation of electron donors (i.e. formaldehyde, acetaldehyde, acetate, and formate). Approximately 41% of dissolved organic carbon and 90% of EA were reduced in the aerobic phase. In the following anoxic phase, the hydrogen production was significantly improved (apparent photonic efficiency 3.04 × 10(-3)) by the generated electron donors and accompanied with completely EA removal by the anoxic photo-formed OH. Hydrogen production was enhanced with the presence of low concentrations of [Formula: see text] (below 0.1 mmol/L) and [Formula: see text] (below 0.2 mmol/L) through accelerating electrons accumulation while it was inhibited at high concentrations since the formed ion-radicals could not decompose humic/fulvic-like compounds. EA removal was inhibited by [Formula: see text] and [Formula: see text] through scavenging h(+)/$OH. The presence of [Formula: see text] (below 1 mmol/L) only resulted in minor impacts since [Formula: see text] was almost unreactive toward electronor OH in neutral conditions.
Water Research 03/2013; · 4.86 Impact Factor
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ABSTRACT: In the present paper, the TiO nanorod arrays electrode was developed as a sensor for the determination of chemical oxygen demand (COD) based on a photoelectrochemical degradation principle. Effects of common parameters, such as applied potential, light intensity and pH on its analytical performance were investigated. Under the optimized conditions, the nanorod arrays electrode was successfully applied in the COD determination for both synthetic and real samples. In the COD determination, the proposed method can achieve a practical detection limit of 18.3mgL and a linear range of 20-280mgL. Furthermore, the results obtained by the proposed method were well correlated with those obtained using the conventional (i.e., dichromate) COD determination method. The main advantages of this COD determination method were its simplicity, long term stability and environmental friendly (corrosive and toxic reagents not consumed). This work would open a new application area (COD determination) of the TiO nanorod arrays.
Analytica chimica acta 03/2013; 767:141-7. · 4.31 Impact Factor
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ABSTRACT: Simultaneous estrogenic activity removal and hydrogen production from secondary effluent were successfully achieved using TiO(2) microspheres modified with both platinum nanoparticles and phosphates (P-TiO(2)/Pt) for the first time. The coexistence of platinum and phosphate on the surface of TiO(2) microspheres was confirmed by transmission electron microscope, energy-dispersive X-ray and X-ray photoelectron spectroscopy analyses. P-TiO(2)/Pt microspheres showed a significantly higher photocatalytic activity than TiO(2) microspheres and TiO(2) powders (P25) for the removal of estrogenic activity from secondary effluent with the removal ratio of 100%, 58.2% and 48.5% in 200 min, respectively. Moreover, the marked production of hydrogen (photonic efficiency: 3.23 × 10(-3)) was accompanied by the removal of estrogenic activity only with P-TiO(2)/Pt as photocatalysts. The hydrogen production rate was increasing with decreased DO concentration in secondary effluent. Results of reactive oxygen species (ROS) evaluation during P-TiO(2)/Pt photocatalytic process showed that O(2)(-)and OH were dominant ROS in aerobic phase, while OH was the most abundant ROS in anoxic phase. Changes of effluent organic matter (EfOM) during photocatalysis revealed that aromatic, hydrophobic, and high molecular weight fractions of EfOM were preferentially transformed into non-humic, hydrophilic, and low MW fractions (e.g. aldehydes and carboxylic acids), which were continuously utilized as electron donors in hydrogen production process.
Water Research 12/2012; · 4.86 Impact Factor
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ABSTRACT: A flat plate serpentine reactor modified from ultraviolet disinfection pool in municipal wastewater treatment plants was developed for the removal of 17-ethinylestradiol (EE2) for the first time. The photocatalytic degradation performance of EE2 was investigated in this serpentine reactor under different conditions such as inlet concentrations, loaded catalyst concentrations, incident radiations fluxes, and flow velocities. More than 98 % of EE2 was removed under certain conditions within 120 min. An integrated model including a six-flux adsorption-scattering model and a modified flow diffusion model was established to investigate the effect of radiation field and flow velocities, respectively. A satisfactory agreement was observed between the model simulation and experimental results, showing a potential for design and scale-up of photocatalytic reactor for wastewater treatment.
Environmental Science and Pollution Research 08/2012; · 2.65 Impact Factor
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ABSTRACT: The removal of estrogenic chemicals during wastewater reclamation has been a great concern. Current advanced treatment processes are inefficient for the removal of estrogenic chemicals from secondary effluents of municipal wastewater treatment plants (WWTPs) due to the coexistence of other pollutants with less environmental significance which are also removed simultaneously. The search for highly selective and low-cost removal methods is warranted. Therefore, surface-molecular-imprinted polymer-modified TiO(2) nanotube (S-MIP-TiO(2) NT) photocatalysts were fabricated, characterized, and tested for the removal of estrogenic pollutants from wastewater in this study for the first time. Scanning electron microscopy and Fourier-transform infrared spectroscopy studies showed that the TiO(2) NTs (with an average diameter of 60 nm) were successfully imprinted with functional groups (i.e., carboxyl). The adsorption selectivity and photocatalytic activity of the S-MIP-TiO(2) NTs towards template compound (17β-estradiol, E2) were improved, compared with neat TiO(2) NTs. Interestingly, S-MIP-TiO(2) NTs exhibited higher adsorption intensity and photocatalytic selectivity at low concentrations (from 10 ng/L to 100 μg/L, as normal estrogenic chemical concentrations in secondary effluents) of E2 than that at high concentrations (from 10 to 1,000 mg/L). It was also found that some representative estrogenic chemicals and estrogenic activity could be selectively and rapidly removed from secondary effluents of municipal wastewater treatment plants using S-MIP-TiO(2) NTs as photocatalysts. In addition, S-MIP-TiO(2) NT photocatalysts exhibited excellent regeneration characteristics. Photocatalytic treatment using S-MIP-TiO(2) NTs could be a promising approach for the effective removal of estrogenic chemicals from secondary effluents of municipal WWTPs.
Environmental Science and Pollution Research 05/2012; · 2.65 Impact Factor
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ABSTRACT: Aquatic ecosystems are often polluted with more than one type of contaminant, and information on the combined toxic effects
of mixed pollutants on aquatic organisms is scarce at present. Acute toxicity of aromatic compounds and their ternary mixtures
to the alga (Scenedesmus obliquus) was determined by the algae growth inhibition test. The median effective concentration (EC
50) value for a single aromatic compound and EC
50mix values for mixtures were obtained. the logarithm of n-octanol/water partition coefficient (logP
mix) and the frontier orbital energy gap (ΔE
mix) for mixtures were calculated. Based on the quantitative structure-activity relationship model for single chemical toxicity
log(1/EC
50)=0.426logP−1.150ΔE+12.61 (n=15, R
2=0.917 and Q
2=0.878), the following two-descriptor model was developed for the ternary mixture toxicity of aromatic compounds: log(1/EC
50mix)=0.682logP
mix−0.367ΔE
mix+4.971 (n=44, R
2=0.869 and Q
2=0.843). This model can be used to predict the combined toxicity of mixtures containing toxicants with different mechanisms
of action.
Chinese Science Bulletin 04/2012; 54(19):3521-3527. · 1.32 Impact Factor
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ABSTRACT: Graphene-titania composite film electrodes have been fabricated by a dip-coating method. Transmission electron microscopy (TEM) images show that the titania nanoparticles were dispersed uniformly, with only a little aggregation on the surface and edges of the graphene sheets. XRD analysis showed that the composite electrodes comprised the anatase phase of titania with just a little rutile phase. The photoelectrocatalytic activities of the as-prepared samples were investigated by studies of the degradation of Reactive Brilliant Red dye X-3B (C.I. reactive red 2). An enhancement of the photocurrents was observed using the graphene-titania composite electrodes, compared with pure titania film electrodes, under UV light irradiation. This improvement is attributed to the following two reasons: enhanced migration efficiency of the photo-induced electrons and enhanced adsorption activity of the dye molecules. In addition, we investigated the effects of graphene content and pH values on the photoelectrocatalytic activity of the as-prepared composite film electrodes. Results showed that there was an optimal amount of 5% (initial graphite oxide content).
Journal of hazardous materials 04/2012; 223-224:79-83. · 4.14 Impact Factor
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ABSTRACT: The effects of Pb on photosynthetic pigments, oxidative stress and antioxidant response were assayed using biochemical and histochemical methods in leaves of Vallisneria natans (Lour.) Hara treated with 0-100 μM Pb(2+) for 0-6d. The Pb content increased with the increase of exposure duration and a highest Pb uptake value (about 9.4 mg Pbg(-1) dry weight) was obtained at 6d. Pb induced the accumulation of H(2)O(2) and O(2)(-). The increase of malondialdehyde content and the decrease of total chlorophyll and carotenoids were detected in V. natans under Pb stress. Activities of NAD(P)H oxidase, guaiacol peroxidase, glutathione reductase and ascorbate peroxidase increased at 75 μM Pb(2+) for 2-6 days, while activities of superoxide dismutase and catalase and the content of ascorbic acid increased within two days in plants exposed to 75 μM Pb(2+) and decreased thereafter. The Pb uptake and accumulation mechanism were discussed.
Ecotoxicology and Environmental Safety 12/2011; 78:28-34. · 2.29 Impact Factor
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ABSTRACT: In this study, the alterations in nutrient elements content, reactive oxygen species level and antioxidant response were studied in leaves of Vallisneria natans (Lour.) Hara exposed to salicylic acid (SA, 10 or 100 μM), or Pb (50 μM) or their combinations for 4d. No significant alterations in Mn and Ca content were observed but content of Cu, Zn, Fe and P decreased in plants exposed to SA alone. SA application inhibited the uptake of Pb and partially reversed Pb-induced the alterations in Mn, Ca and Fe content in leaves of V. natans exposed to 50 μM Pb. The decreased chlorophyll (a+b) and increased malondialdehyde and O(2-) and H(2)O(2) content were detected in plants exposed to 100 μM SA, 50 μM Pb, 10 μM SA+50 μM Pb or 100 μM SA+50 μM Pb. Application SA partially inhibited Pb-induced the increase of malondialdehyde, O(2-) and H(2)O(2) content. 100 μM SA decreased the activity of NADH oxidase and the content of non-protein thiols, carotenoids and ascorbic acid and increased the content of dehydroascorbate in plants treated with or without Pb. SA alone decreased the ascorbate peroxidase activity and increased the catalase and peroxidase activity, while SA application increased catalase activity but had no significant effect on ascorbate peroxidase and peroxidase activity in V. natans exposed to Pb. The results indicate that SA involves in the regulation of Pb uptake, nutrient balance and oxidative stress.
Chemosphere 03/2011; 84(1):136-42. · 3.21 Impact Factor
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ABSTRACT: For better understanding the metabolic adaptations to Pb stress in submerged plants, the alterations in mineral elements uptake and in secondary metabolism were studied in leaves of Vallisneria natans (Lour.) Hara exposed to 0-100μM Pb for 0-7d. Pb content increased in leaves in a dose-dependent way. The increase of calcium, magnesium and iron content and the decrease of phosphorus, potassium and manganese content were detected in leaves of V. natans under Pb stress, while no significant changes were detected in copper and zinc concentration. Meanwhile, there was an increase in the concentrations of total phenolic and flavonoids. Pb treatment caused an increase in the catalytic activities of shikimate dehydrogenase, phenylalanine ammonialyase and polyphenol oxidase. The results suggest that nutrient uptake and secondary metabolism were actively regulated by V. natans plants in response to Pb stress.
Ecotoxicology and Environmental Safety 03/2011; 74(5):1297-303. · 2.29 Impact Factor
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ABSTRACT: In the present work, a novel composite photocatalyst ceria-coated activated carbon (CCAC) was prepared by a facile method. The composite photocatalyst was characterized by X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET), scanning electron microscopy (SEM) and photocatalytic degradation of 4-chlorophenol (4-CP). A synergy effect for 4-CP degradation was observed because the activated carbon (AC) with strong adsorbent activity provided sites for the adsorption of 4-CP. Then, the adsorbed 4-CP can migrate continuously onto the surface of ceria particles and then degraded at there. Hydroquinone (HQ) and benzoquinone (BQ) were found to be the main intermediates of the photocatalytic 4-CP degradation with ceria or CCAC by HPLC measurement. The results suggested that the same reaction mechanism occurred in the presence of ceria or titania.
Journal of hazardous materials 12/2010; 184(1-3):1-5. · 4.14 Impact Factor
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ABSTRACT: To investigate the effect of exogenous Nitric oxide (NO) on submerged plants, Hydrilla verticillata (L.f.) Royle was treated with 25 -400 sodium nitroprusside (SNP, a NO donor) for 0.5 -4 d. The alterations in plant growth, H 2 O 2 , total chlorophyll and malondialdehyde (MDA) content and the antioxidant response were assayed. The results showed that 25 -100 SNP increased the plant growth and total chlorophyll content and reduced the level of H 2 O 2 . However, an increase in H 2 O 2 and MDA content and a decrease in total chlorophyll were detected in plants exposed to 200 -400 SNP. The activity of catalase and peroxidase decreased in plants exposed to 25 -400 SNP; and for superoxide dismutase, its activity was suppressed by the 25 and 50 M SNP. The content of ascorbic acid and dehydroascorbate were also determined. The results provided the evidence that 25 -100 M SNP increased the growth of H. verticillata by alleviating the oxidative stress and 200 -400 M SNP might enhance the oxidative stress in plant cell. The results suggested that NO has dual role on the growth and ROS metabolism of Hydrilla verticillata (L.f.) Royle.
AFRICAN JOURNAL OF BIOTECHNOLOGY 12/2010; 9:7470-7476. · 0.57 Impact Factor
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ABSTRACT: This study investigated the growth kinetics of a psychrotroph, Pseudomonas putida LY1, while growing on phenol as a sole carbon and energy source. This bacterium could completely biodegrade 200mg/L phenol across a temperature range from 2.5 to 35 degrees C, with an optimum temperature of 25 degrees C. High initial phenol concentrations (800 mg/ml) were inhibitory to bacterial growth. At lower concentrations of phenol, the growth kinetics correlated well with the Haldane model. The Haldane parameters of psychrotrophic P. putida LY1 were almost within the range reported for other organisms in previous literature. This information on a psychrotrophic organism is of great importance for low temperature bioremediation of contaminated environments.
Bioresource technology 04/2010; 101(17):6740-4. · 4.25 Impact Factor
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ABSTRACT: Ce-doped titania hollow spheres were prepared using carbon spheres as template and Ce-doped titania nanoparticles as building blocks. The Ce-doped titania nanoparticles were synthesized at low temperature. The prepared hollow spheres were characterized by X-ray diffraction (XRD), transmission electron microscope (TEM), X-ray photoelectron spectroscopy (XPS) and UV-vis diffuse reflectance spectrum (DRS). The effect of Ce content on the physical structure and photocatalytic properties of doped titania hollow sphere samples was investigated. Results showed that there was an optimal Ce-doped content (4%) for the photocatalytic activity of X-3B degradation. The apparent rate constant of the best one was almost 31 times as that of P25 titania. The mechanism of photocatalytic degradation of dyes under visible light irradiation was also discussed.
Journal of hazardous materials 01/2010; 178(1-3):517-21. · 4.14 Impact Factor
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ABSTRACT: In the present study, the in vivo effects of commercial propoxur alone and in combination with isoprocarb and chlorpyrifos on acetylcholinesterase and glutathione S-transferases activities in goldfish (Carassius auratus) were investigated. Brain and muscle AChE activity was significantly inhibited (88% and 85% at most, respectively) by propoxur after 5 d of exposure at concentrations between 141 and 2263μg/L, bell-shaped concentration-response curves were obtained. In most cases, time dependence was apparent. Under insecticide mixture exposure (binary mixture propoxur/isoprocarb and ternary mixture propoxur/isoprocarb/chlorpyrifos), the inhibition of AChE activity was significant in all cases and linear concentration-response relationships were observed. Propoxur (alone and in combination) significantly inhibited gill GST activity, and both mixtures also induced significant inhibition of liver GST activity. However, concentration and time dependence were not apparent. AChE is likely to be more informative than GST and seems to be a good biomarker to diagnose exposure to anticholinesterase pesticides in wild populations of this species.
Environmental toxicology and pharmacology. 11/2009; 28(3):414-9.
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ABSTRACT: Natural attenuation, biostimulation and bioaugmentation of nitrobenzene (NB) contaminated sediments were investigated and compared. The removal rate of NB from contaminated environments with bioaugmentation was much faster than with biostimulation and natural attenuation. Within 10 days, 6 mg/kg and 53 mg/L nitrobenzene in sediment and water, respectively, was degraded with the augmentation of Pseudomonas putida isolated from the contaminated sediment. There was no distinct performance difference between natural attenuation and biostimulation, demonstrating that addition of nutrients had no effect on the bioremediation process. The information on the current phase is a crucial step in making policy decisions for the application of bioremediation.
Bulletin of Environmental Contamination and Toxicology 08/2009; 83(6):865-8. · 1.02 Impact Factor
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ABSTRACT: Nd-doped titania hollow spheres were prepared using carbon spheres as template and Nd-doped titania nanoparticles as building blocks. The Nd-doped titania nanoparticles were synthesized at low temperature. The prepared hollow spheres were characterized by X-ray diffraction (XRD), transmission electron microscope (TEM), scanning electron microscope (SEM), X-ray photoelectron spectroscopy (XPS) and UV–vis diffuse reflectance spectrum (DRS). The effects of Nd content on the physical structure and photocatalytic activities of doped titania hollow sphere samples were investigated. Results showed that there was an optimal Nd-doped content (3.9 at.%) for the photocatalytic degradation of dye X-3B (C.I. Reactive Red 2). The apparent rate constant of the best one was almost 9 times as that of P25 titania. The mechanism of photocatalytic degradation of dyes under visible light irradiation was also discussed.
Applied Surface Science.
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ABSTRACT: The photocatalytic degradation kinetics of rhodamine B (RhB) by TiO2-coated activated carbon (TiO2/AC) catalyst under different reaction conditions (light intensity, TiO2 content in TiO2/AC and initial content of contamination) was elucidated by modeling. The kinetics of Rhb photodegradation was found to follow the first-order rate law and could be described in terms of a modified Langmuir–Hinshelwood model. The value of the apparent rate constant kapp was proposed on the basis of intrinsic element reactions, such as light intensity, reaction intermediates and the photo-induced hole (h±) formation. The apparent rate constant kapp first increased with increasing TiO2 content of the TiO2/AC catalyst and then decreased. The optimal value of the TiO2 content could be obtained through the model; the apparent rate constant was linear with respect to the square of the intensity. The validity of the model was also proved with other researchers’ results.
Desalination.
