The microbial immobilization method using polyvinyl alcohol （PVA） gel as an immobilizing material was improved and used for entrapment of activated sludge. The oxygen uptake rate （OUR） was used to characterize the...The microbial immobilization method using polyvinyl alcohol （PVA） gel as an immobilizing material was improved and used for entrapment of activated sludge. The oxygen uptake rate （OUR） was used to characterize the biological activity of immobilized activated sludge. Three kinds of PVA-immobilized particles of activated sludge, that is, PVA-boric acid beads, PVA-sodium nitrate beads and PVA-orthophosphate beads were prepared, and their biological activity was compared by measuring the OUR value. The bioactivity of both autotrophic and heterotrophic microorganisms of activated sludge was determined using different synthetic wastewater media （containing 250 mg/L COD and 25 mg/L NH4^＋ -N）. The experimental results showed that the bioactivity and stability of the three kinds of immobilized activated sludge was greatly improved after activation. With respect of the bioactivity and the mechanical stability, the PVA-orthophosphate method may be a promising and economical technique for microbial immobilization.展开更多
The influence of relative humidity( RH) on the properties of electrospun polyvinyl alcohol( PVA) nanofibers that might determine the application of nanofibers in high-efficiency air filters is not clear. PVA nanofiber...The influence of relative humidity( RH) on the properties of electrospun polyvinyl alcohol( PVA) nanofibers that might determine the application of nanofibers in high-efficiency air filters is not clear. PVA nanofiber mat was prepared between two hot airthrough ES( polyethyene( PE) and polypropylene( PP) composite fiber) non-woven substrates as a sandwich structure nanofiber composite filter using an electrospinning technique combining with an ultrasonic sewing process. The filtering mechanism of the composite was discussed in detail. The effects of nanofiber diameters,nanofiber layer thickness and RH in environment on the properties of PVA nanofibers were investigated by scanning electron microscopy( SEM), X-ray diffraction( XRD), automatic filter tester and universal strength tester. The results showed that the PVA nanofiber composite fabrics had high filtration efficiency with lowpressure drop and there was a negative correlation between filtration efficiency and nanofiber diameter. After keeping in a high RH environment for several hours, the mechanical property of PVA nanofiber composites was deteriorated but the high filtration efficiency was increased.展开更多
A mass flow matching model(MFMM)was established for studying the stable status of solution electrospinning.The study of the solution droplet status at the needle tip focused on various combinations of applied voltages...A mass flow matching model(MFMM)was established for studying the stable status of solution electrospinning.The study of the solution droplet status at the needle tip focused on various combinations of applied voltages and injection rates to figure out their influence on steadily fabricating polyvinyl alcohol(PVA)nanofibers prepared from PVA spinning solutions with two different mass fractions(10%and 16%).The results revealed that during the stable electrospinning,the influence resulted from the change of the injection rate approximately canceled out the impact brought by adjusting the applied voltage,leading to almost the same morphology as that of the PVA nanofibers.And the mass fraction of PVA in the spinning solution dominated the structure and the diameter distribution of the electrospun nanofibers.Under stable electrospinning conditions,the composite membrane was produced by depositing PVA nanofibers on the polyethylene terephthalate(PET)nonwoven substrate for an air filtration test.Furthermore,the prepared composite membrane exhibited a high air filtration efficiency(99.97%)and a low pressure drop(120 Pa)for 300-500 nm neutralized polystyrene latex(PSL)aerosol particles,demonstrating its potential as an alternative for a variety of commercial applications in air filtration.展开更多
Using polysulfone （PSF） hollow fiber ultrafiltration membranes as the substrate, sodium alginate （SA） and polyvinyl alcohol （PVA） blend solutions as the coating solution, and maleic anhydride （MAC） as the cros...Using polysulfone （PSF） hollow fiber ultrafiltration membranes as the substrate, sodium alginate （SA） and polyvinyl alcohol （PVA） blend solutions as the coating solution, and maleic anhydride （MAC） as the cross-linked agent, SAPVA/PSF hollow fiber composite membranes were prepared for the dehydration of ethanol-water. The effects of different sodium alginate concentration in the coating solutions and different operating temperatures on pervaporation performance were investigated. The experimental results showed that pervaporation performance of the SA-PVA/PSF composite membranes for ethanol-water solution exhibited a high separation factor although they had a relatively low permeation flux. As SA concentration in SA-PVA coating solution was 66.7% and the operating temperature was 40 ℃, SA-PVA/PSF hollow fiber composite membrane （PS4） had a separation factor of 886 and flux of 12.6 g/（m^2·h）. Besides, SA-PVA/PSF hollow fiber composite membranes （PS3 and PS4） were used for the investigation of the effect of ethanol concentration in the feed solution on pervaporation performance.展开更多
Pure and doped Polyvinylidene difluoride (PVDF) films, for the detection of infrared radiation, have been well documented using the mechanism of pyroelectricity. Alternatively, the electrical properties of films made ...Pure and doped Polyvinylidene difluoride (PVDF) films, for the detection of infrared radiation, have been well documented using the mechanism of pyroelectricity. Alternatively, the electrical properties of films made from Polyvinyl Alcohol (PVA) have received considerable attention in recent years. The investigation of surface resistivities of both such films, to this point, has received far less consideration in comparison to pyroelectric effects. In this research, we report temperature dependent surface resistivity measurements of commercial, and of multiwall carbon nanotubes (MWCNT), or Ag-nanoparticle doped PVA films. Without any variation in the temperature range from 22°C to 40°C with controlled humidity, we found that the surface resistivity decreases initially, reaches a minimum, but rises steadily as the temperature continues to increase. This research was conducted with the combined instrumentation of the Keithley Model 6517 Electrometer and Keithley Model 8009 resistivity test fixture using both commercial and in-house produced organic thin films. With the objective to quantify the suitability of PVDF and PVA films as IR detector materials, when using the surface resistivity phenomenon, instead of or in addition to the pyroelectricity, surface resistivity measurements are reported when considering bolometry. We found that the surface resistivity measurements on PVA films were readily implemented.展开更多
基金Project supported by the National Natural Science Foundation of China(No.50327802,50325824,50678089).
文摘The microbial immobilization method using polyvinyl alcohol （PVA） gel as an immobilizing material was improved and used for entrapment of activated sludge. The oxygen uptake rate （OUR） was used to characterize the biological activity of immobilized activated sludge. Three kinds of PVA-immobilized particles of activated sludge, that is, PVA-boric acid beads, PVA-sodium nitrate beads and PVA-orthophosphate beads were prepared, and their biological activity was compared by measuring the OUR value. The bioactivity of both autotrophic and heterotrophic microorganisms of activated sludge was determined using different synthetic wastewater media （containing 250 mg/L COD and 25 mg/L NH4^＋ -N）. The experimental results showed that the bioactivity and stability of the three kinds of immobilized activated sludge was greatly improved after activation. With respect of the bioactivity and the mechanical stability, the PVA-orthophosphate method may be a promising and economical technique for microbial immobilization.
基金National Natural Science Foundation of China(No.51573133)Foundation for the Author of National Excellent Doctoral Dissertation of China(No.201255)+2 种基金Program for New Century Excellent Talents in University of China(No.NCET-12-1063)Tianjin Natural Science Foundation of China(No.14JCYBJC17600)The Science and Technology Plans of Tianjin,China(No.15PTSYJC00230)
文摘The influence of relative humidity( RH) on the properties of electrospun polyvinyl alcohol( PVA) nanofibers that might determine the application of nanofibers in high-efficiency air filters is not clear. PVA nanofiber mat was prepared between two hot airthrough ES( polyethyene( PE) and polypropylene( PP) composite fiber) non-woven substrates as a sandwich structure nanofiber composite filter using an electrospinning technique combining with an ultrasonic sewing process. The filtering mechanism of the composite was discussed in detail. The effects of nanofiber diameters,nanofiber layer thickness and RH in environment on the properties of PVA nanofibers were investigated by scanning electron microscopy( SEM), X-ray diffraction( XRD), automatic filter tester and universal strength tester. The results showed that the PVA nanofiber composite fabrics had high filtration efficiency with lowpressure drop and there was a negative correlation between filtration efficiency and nanofiber diameter. After keeping in a high RH environment for several hours, the mechanical property of PVA nanofiber composites was deteriorated but the high filtration efficiency was increased.
文摘A mass flow matching model(MFMM)was established for studying the stable status of solution electrospinning.The study of the solution droplet status at the needle tip focused on various combinations of applied voltages and injection rates to figure out their influence on steadily fabricating polyvinyl alcohol(PVA)nanofibers prepared from PVA spinning solutions with two different mass fractions(10%and 16%).The results revealed that during the stable electrospinning,the influence resulted from the change of the injection rate approximately canceled out the impact brought by adjusting the applied voltage,leading to almost the same morphology as that of the PVA nanofibers.And the mass fraction of PVA in the spinning solution dominated the structure and the diameter distribution of the electrospun nanofibers.Under stable electrospinning conditions,the composite membrane was produced by depositing PVA nanofibers on the polyethylene terephthalate(PET)nonwoven substrate for an air filtration test.Furthermore,the prepared composite membrane exhibited a high air filtration efficiency(99.97%)and a low pressure drop(120 Pa)for 300-500 nm neutralized polystyrene latex(PSL)aerosol particles,demonstrating its potential as an alternative for a variety of commercial applications in air filtration.
基金Project supported by the National Basic Research Program of China (Grant No.2003CB615705)
文摘Using polysulfone （PSF） hollow fiber ultrafiltration membranes as the substrate, sodium alginate （SA） and polyvinyl alcohol （PVA） blend solutions as the coating solution, and maleic anhydride （MAC） as the cross-linked agent, SAPVA/PSF hollow fiber composite membranes were prepared for the dehydration of ethanol-water. The effects of different sodium alginate concentration in the coating solutions and different operating temperatures on pervaporation performance were investigated. The experimental results showed that pervaporation performance of the SA-PVA/PSF composite membranes for ethanol-water solution exhibited a high separation factor although they had a relatively low permeation flux. As SA concentration in SA-PVA coating solution was 66.7% and the operating temperature was 40 ℃, SA-PVA/PSF hollow fiber composite membrane （PS4） had a separation factor of 886 and flux of 12.6 g/（m^2·h）. Besides, SA-PVA/PSF hollow fiber composite membranes （PS3 and PS4） were used for the investigation of the effect of ethanol concentration in the feed solution on pervaporation performance.
文摘Pure and doped Polyvinylidene difluoride (PVDF) films, for the detection of infrared radiation, have been well documented using the mechanism of pyroelectricity. Alternatively, the electrical properties of films made from Polyvinyl Alcohol (PVA) have received considerable attention in recent years. The investigation of surface resistivities of both such films, to this point, has received far less consideration in comparison to pyroelectric effects. In this research, we report temperature dependent surface resistivity measurements of commercial, and of multiwall carbon nanotubes (MWCNT), or Ag-nanoparticle doped PVA films. Without any variation in the temperature range from 22°C to 40°C with controlled humidity, we found that the surface resistivity decreases initially, reaches a minimum, but rises steadily as the temperature continues to increase. This research was conducted with the combined instrumentation of the Keithley Model 6517 Electrometer and Keithley Model 8009 resistivity test fixture using both commercial and in-house produced organic thin films. With the objective to quantify the suitability of PVDF and PVA films as IR detector materials, when using the surface resistivity phenomenon, instead of or in addition to the pyroelectricity, surface resistivity measurements are reported when considering bolometry. We found that the surface resistivity measurements on PVA films were readily implemented.
