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Bai X.,Institute of Chemical Technology | Ye Z.-f.,Key Laboratory of Water and Sediment science | Li Y.-f.,Institute of Chemical Technology | Zhou L.-c.,Institute of Chemical Technology | Yang L.-q.,Institute of Chemical Technology
Process Biochemistry | Year: 2010

In this work, a new and economical way to prepare macroporous poly(vinyl alcohol) (PVA) foam was explored by adding calcium carbonate as a pore-forming agent and using epichlorhydrin as a chemical crosslinking agent to improve foam stability. The mixture for foam formation has been optimized to obtain macroporous PVA foam carriers with uniform apertures, narrow distribution of pore sizes, and good elasticity. The crosslinked PVA foam (CPVAF) carrier demonstrated better chemical and thermal stability, as well as larger specific surface area and diffusion coefficients than the traditional PVA (TPVA) carrier. Nitrifying bacteria were used to test the suitability of CPVAF and TPVA carriers for immobilized microorganisms. CPVAF carriers supported higher biomass density and microbial activity than TPVA carriers. At the same biomass density, the higher nitrification rate of CPVAF carriers was attributed to excellent mass transfer of the substrate (and oxygen) between the bulk solution and the immobilized microorganisms. © 2009 Elsevier Ltd. All rights reserved. Source


Ji G.,Key Laboratory of Water and Sediment science | Guo F.,The Key Laboratory of Urban Human Residential Environmental Science and Technology
Chemosphere | Year: 2010

An ultrasound-enhanced elution system using water at a temperature of 70 °C was employed to remove severely biodegraded heavy oil (SBHO) from weathered soil. The effect of varying the ultrasonic power density from 0 to 100 W L-1 on the elution of SBHO and three characteristic biomarkers (C26-34 17α 25-norhopanes, C26-28 triaromatic steroids (TAS), and C27-29 methyl triaromatic steroids (MTAS) was analyzed using GC/MS, scanning electron microscopy (SEM), and X-ray diffraction (XRD). The amount of SBHO and biomarkers present in the treated soils and eluent had significant negative correlation with increasing ultrasonic power density. Elution of the three biomarkers was closely related to the number of C atoms in the marker: C26-34 17α 25-norhopanes with more carbon numbers and MTAS homologs with less carbon numbers were more readily eluted at higher power densities. The smaller TAS species were more readily eluted at a power density of less than 60 W L-1, while larger TAS species displayed improved elution at power densities greater than 60 W L-1. SEM images of samples treated at higher power densities revealed a more compact SBHO accumulation layer at the water-soil interface. The results of XRD and energy spectroscopy experiments indicated that ultrasound at a power density of 20 W L-1 was helpful for the formation and sedimentation of calcite, although this effect disappeared at higher power of greater than 60 W L-1. © 2010 Elsevier Ltd. All rights reserved. Source


Zhu Y.,Key Laboratory of Water and Sediment science | Zhu Y.,Peking University | Ni J.,Key Laboratory of Water and Sediment science | Ni J.,Peking University | Huang W.,University of Sichuan
Bioprocess and Biosystems Engineering | Year: 2010

Based on the response surface methodology, an effective microbial system for diosgenin production from enzymatic pretreated Dioscorea zingiberensis tubers with Trichoderma reesei was studied. The fermentation medium was optimized with central composite design (35) depended on Plackett-Burmann design which identified significant impacts of peptone, K 2HPO4 and Tween 80 on diosgenin yield. The effects of different fermentation conditions on diosgenin production were also studied. Four parameters, i.e. incubation period, temperature, initial pH and substrate concentration were optimized using 45 central composite design. The highest diosgenin yield of 90.57% was achieved with 2.67% (w/v) of peptone, 0.29% (w/v) of K2HPO4, 0.73% (w/v) of Tween 80 and 9.77% (w/v) of substrate, under the condition of pH 5.8, temperature 30 °C. The idealized incubation time was 6.5 days. After optimization, the product yield increased by 33.70% as compared to 67.74 ± 1.54% of diosgenin yield in not optimized condition. Scale-up fermentation was carried out in a 5.0 l bioreactor, maximum diosgenin yield of 90.17 ± 3.12% was obtained at an aeration of 0.80 vvm and an agitation rate of 300 rpm. The proposed microbial system is clean and effective for diosgenin production and thus more environmentally acceptable than the traditional acid hydrolysis. © Springer-Verlag 2009. Source


Yang Q.-Z.,Peking University | Yang Q.-Z.,Shandong Polytechnic University | Chang Y.-Y.,Peking University | Chang Y.-Y.,Key Laboratory of Water and Sediment science | And 2 more authors.
Water Research | Year: 2013

It is necessary to develop "green" disinfection technology which does not produce disinfection by-products. Lysozyme-layered double hydroxide nanocomposites (LYZ-LDHs) were prepared by intercalating LYZ in LDH for the first time. Their antibacterial activity was evaluated using staphylococcus aureus as a target. The bacteria removal mechanism was also studied. Characterization of LYZ-LDHs by X-ray diffraction and Fourier transform infrared spectroscopy indicated that LYZ was successfully intercalated in LDH, compressed and deformed without secondary structural change. LYZ-LDHs showed excellent bactericidal effectiveness against staphylococcus aureus. The antibacterial performance of LYZ-LDHs was found to be affected by the LYZ/LDH ratio and the pH of the bacteria-containing water. The bacteria removal efficiency of LYZ-LDHs with LYZ/LDH mass ratio of 0.8 was consistently above 94% over the pH range of 3-9. LYZ-LDHs adsorbed bacteria to their surface by LDH and then killed them by the immobilized LYZ. This new material integrated the bactericidal ability of LYZ and adsorption ability of LDH. Moreover, the antibacterial ability of LYZ-LDHs was persistent and not limited by the adsorption capacity. © 2013 Elsevier Ltd. Source


Sui X.,Key Laboratory of Water and Sediment science | Sui X.,Stockholm Environment Institute | Ji G.,Key Laboratory of Water and Sediment science
Journal of Hazardous Materials | Year: 2010

An ultrasound-enhanced elution system employing Triton X-100 solutions was used for remedying aging soils contaminated with super heavy oil. The effect of varying the ultrasonic power density on the elution of the oil and three characteristic biomarkers was analyzed using GC/MS and FTRS. The oil and biomarkers remaining in treated soils decreased as a similar first-order function of increasing ultrasonic power density. Elution of the three biomarkers in the absence of ultrasound was closely related to carbon numbers in the marker: smaller molecules were more readily eluted. This trend was reversed upon application of ultrasound at higher power densities, with improved elution of molecules containing a greater carbon numbers. The two ratios, both 22S/(22S + 22R) of C 26-34 17α 25-norhopanes and 20S/(20S + 20R) of C 26-28 triaromatic steroids, in treated soils decreased with increasing power density from 20 to 100 W L -1. The results of SEM, FTRS, XRD, and energy spectroscopy experiments indicated that the mineral and chemical compositions of soils eluted at power densities greater than 60 W L -1 closely resembled clean soils. © 2009 Elsevier B.V. All rights reserved. Source

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