Immobilization of activated sludge using improved polyvinyl alcohol (PVA) gel

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.

Influence of Relative Humidity on Polyvinyl Alcohol (PVA) Nanofibers for High-Efficiency Air Filter

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.

Sodium alginate-polyvinyl alcohol/polysulfone (SA-PVA/PSF) hollow fiber composite pervaporation membrane for dehydration of ethanol-water solution

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.

Temperature Dependent Surface Resistivity Measures of Commercial, Multiwall Carbon Nanotubes (MWCNT), and Silver Nano-Particle Doped Polyvinyl Alcohol (PVA) Films

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.

高温后钢-PVA混杂纤维高性能混凝土与变形钢筋黏结性能试验

为研究高温后钢-聚乙烯醇(polyvinyl alcohols,PVA)混杂纤维高性能混凝土(hybrid fiber high performance concrete,HFHPC)与变形钢筋的黏结性能退化规律,以200、400、600、800℃为目标温度,选取钢纤维体积率、PVA纤维体积率、矿粉掺量为正交试验因素设计并制作25组HFHPC试件,完成了单调荷载下的中心拉拔试验。结果表明:高温后各组HFHPC试件黏结破坏形态均表现为钢筋拔出破坏;试验温度范围内,对HFHPC试件黏结强度的影响程度均为:钢纤维体积率最大、矿粉掺量次之、PVA纤维体积率最小;随着温度的升高,HFHPC试件黏结强度逐渐下降,且在相同温度条件下,HFHPC试件黏结强度和峰值滑移相比于未掺纤维的混凝土试件均有所提升,其中,200℃时HFHPC试件的黏结强度提升最为显著,分别提升了33.69%、35.76%、37.54%和46.03%;混杂纤维能显著提高高温后高性能混凝土与钢筋的峰值界面能,明显改善黏结延性和耗能能力;提出的考虑温度作用后的混杂纤维混凝土与钢筋黏结-滑移模型与试验实测结果吻合较好,可为火灾后混杂纤维高性能混凝土结构损伤评估及加固方案提供参考。

RTP-PVA混杂纤维的工程水泥基复合材料干缩性能试验研究

为研究回收轮胎聚合物(recycled tyre polymer,RTP)和聚乙烯醇(polyvinyl alcohol,PVA)混杂纤维对工程水泥基复合材料(engineered cementitious composites,ECC)干缩性能的影响,对RTP-PVA混杂纤维总体积分数为2.0%的ECC进行流动性、直接拉伸和干缩试验,并分析混杂纤维作用机理和干缩计算模型.结果表明:RTP纤维替代率为12.5%~50%对ECC流动性影响不大,比单掺PVA纤维的ECC流动性降低1.09%~3.69%.ECC的抗拉强度随RTP纤维替代率的增加而降低,不同比例的混杂纤维比单掺PVA纤维的ECC抗拉强度降低了23.6%~56.6%.不同比例混杂纤维ECC干缩率曲线趋势相近,7 d时干缩率为28 d时的80.92%~82.77%.ECC的干缩率随RTP纤维替代率的增加而降低,28 d时不同RTP纤维替代率的混杂纤维比单掺PVA纤维的ECC干缩率降低了0.80%~2.09%.RTP-PVA混杂纤维可在ECC中协同发挥作用抑制基体干缩,结合试验结果得到适合RTP-PVA混杂纤维ECC的指数型干缩预测模型.

Preparation and Properties of Chitosan/Polyvinyl Alcohol Blended Fiber Membrane for Medical Dressing

The antibacterial dressing prepared by the electrospinning can play a role in protecting the wound,preventing infection and promoting wound healing,and have broad application prospects.Chitosan(CS)/polyvinyl alcohol(PVA)blended fiber membrane was successfully prepared by electrospinning.The fiber morphology,thermal properties and material composition of CS/PVA blended fiber membrane were studied,and the interaction between CS and PVA was analyzed,and the optimum blend ratio was also determined.Then glutaraldehyde(GA)steam cross-linking of the blended fiber membrane was carried out in order to improve the water resistance of the fiber membrane.At the same time,the effect of different cross-linking time on the water resistance of fiber membrane was investigated.The apparent morphology of the fiber membrane was observed by a scanning electron microscope(SEM).The results showed that with the increase of spinning solution concentration,the morphology of the fiber became more and more regular,and the fiber diameter increased gradually.The intermolecular interaction between CS and PVA was found by Fourier transform infrared(FTIR)spectroscopy and thermal properties,which improved the spinnability of CS electrospinning.After cross-linking,the water resistance of the fiber membrane was greatly improved,among which the effect of 4 h cross-linking was the best,and the water resistance of the fiber membrane increased by 64.89%.

Fabrication of High-Efficiency Polyvinyl Alcohol Nanofiber Membranes for Air Filtration Based on Principle of Stable Electrospinning

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.

玉米秸秆-PVA复合气凝胶的制备及其吸附性能研究

以玉米秸秆为原料,用溴化锂和聚乙烯醇(PVA)溶液将其溶解,制备玉米秸秆-PVA复合气凝胶。采用正交试验法对制备工艺进行优化,并通过FT-IR、吸附率等手段对气凝胶的相关性能进行表征。结果表明:复合气凝胶的优化制备工艺条件为:固液质量比(秸秆∶混合溶液)为1∶100,PVA添加量与秸秆的质量比为100∶15,PVA浓度为5%,溴化锂浓度为66%,溴化锂溶液和PVA的质量比为13.85∶1。该工艺下所制得的复合气凝胶密度低至0.0268 g/cm^(3),比表面积为175.00 m^(2)/g,对废弃机油的最大吸附倍率为35.01 g/g。制备过程中,纤维素的氢键被破坏,PVA与纤维素之间通过氢键连接。复合气凝胶的密度越小,其吸油率越大。复合气凝胶具有全范围内的孔径,且大部分孔径处于介孔范围内,因此有利于对大分子污染物的吸附。

GO-PVA注浆材料的制备及其强度特征研究

由于瓦斯抽采钻孔周围稳定性较差,受扰动影响易致钻孔周围煤岩体产生新的裂隙,进而降低瓦斯抽采效率,为填补现有材料颗粒大、胶结能力差的缺陷,引入纳米材料和高分子聚合物材料改善瓦斯抽采钻孔封孔材料的性能,并分析纳米材料氧化石墨烯(Graphene Oxide,GO)、高分子聚合物聚乙烯醇(Polyvinyl Alcohol,PVA)纤维复掺于水泥基注浆材料中的宏微观强度特征。采用单因素试验探究GO最佳质量分数及PVA纤维最佳长度和质量分数,确定最优值后再与普通水泥注浆材料进行复合对比试验,并通过单轴压缩测试不同养护龄期下的强度变化规律,结合蠕变特性、相似模拟和扫描电子显微镜(Scanning Electron Microscope,SEM)图像,探讨复合材料的增强机理。研究结果表明:两类添加剂均对水泥基注浆材料抗压强度展现出有效的提升作用,尤其是当氧化石墨的质量分数为0.04%,PVA质量分数和长度分别为0.2%和3 mm时,其抗压性能达到顶峰,密封性能提升,抵抗外界应力变化的能力得到增强。研究结果可为封孔注浆材料的研发提供基础。

Degradation Performance and Biodiversity of an Anaerobic Polyvinyl Alcohol-Degrading Microbial Community

Polyvinyl alcohol( PVA) is a water-soluble synthetic polymer that is hard to biodegrade. PVA-degrading microorganisms were previously reported as unitary bacteria and most of them have been identified as aerobes. In this work,a microbial community was cultured anaerobically and its degradation performance and biodiversity were analyzed. The microbial community was cultured for more than 40 d,which represents a highly efficient degradation performance with a chemical oxygen demand removal efficiency of 88. 48%. Operational taxonomic unit-based analysis of the sequences revealed a highly diverse community in the reactor. To note,metagenome 16s rDNA sequencing delineated 19 phyla and 41 classes. Specifically, proteobacteria, chlamydiae, bacteroidetes,firmicutes,and planctomycetes play key roles in the biodegradation processes. Moreover,the betaproteobacteria class belonging to the proteobacteria phylum was the predominant bacterial members in this community. Our results demonstrated that anaerobic treatment of PVA wastewater is feasible and confers degradation by a highly diverse microbial community.

Preparation and Characterization of pH-Sensitive Polyvinyl Alcohol Hydrogel for Cancer Therapy

Hydrogel has emerged as an excellent carrier platform for smart drug delivery and effective cancer treatment due to its high water content, good biocompatibility and sufficient mechanical properties. In this work,the DOX-loaded polyvinyl alcohol( PVA)hydrogel was prepared by freeze-thawing technique. The swelling test and the mechanical properties of the pure PVA hydrogels were performed. In addition, the in vitro drug release profiles were examined and the in vitro antitumor efficiency against He La cells was also estimated. The results indicated that the resulting PVA hydrogels contained significant amounts of water and possessed good mechanical properties,and DOX-loaded PVA hydrogel exhibited a sustained and p H-responsive DOX release. The MTT assays also demonstrated that the released DOX could effectively inhibit the proliferation of He La cells. Thus,the cross-linked PVA hydrogel can be further developed as a promising platform for cancer therapy.

THE MECHANISM OF SURFACE METALLIZATION OF POLYVINYL ALCOHOL COMPLEX METAL CHELATE FILMS

A novel method for preparing metalllzed film has been studied.The reduction process and properties of the poly(vinyl alcohol)(PVA)were probed by several analytic means.According to the etudies,a mechanism for the polymer surface reduction metallization was proposed and proved.

硼砂交联PVA降失水剂的合成及滤失性能研究

以聚乙烯醇(PVA1788)为水泥浆降失水剂基础原料,考察了交联剂种类和用量、反应温度、溶液pH值等对PVA胶液粘度和水泥浆滤失性能的影响规律,发现硼砂水解后对PVA的交联效果最显著,而且随着硼砂与PVA配比、反应温度和pH值升高,PVA胶液粘度及水泥浆滤失性能呈现显著增高趋势,所形成的滤饼更加致密,保水能力更好。但一旦超过最佳配比时,水泥颗粒表面降滤失剂膜层变厚,滤饼致密性变差,反而不利于水泥浆保水,滤失性能下降。

各向异性PVA木基水凝胶的制备及其铜离子吸附性能

针对传统水凝胶生成的聚合物网络通常为各向同性,存在机械强度差、刚度低等问题。本研究以巴沙木为原料,通过冰模板法和淬火法,在定向排列的脱木素纤维素骨架中构筑具有纤维取向的聚乙烯醇(PVA)微纳网络,构建用于高效吸附水中铜离子的高强度各向异性PVA木基水凝胶(PWH),结合扫描电子显微镜、傅里叶红外光谱、X射线衍射、电子万能力学试验机表征复合水凝胶的形态结构和性能。实验结果表明:脱木质素工艺可以增加木质纤维的结晶度,PVA成功复合后保留了木材各向异性纤维骨架,脱木质素2 h的水凝胶(PWH-2)综合性能最优;PWH-2在5%应变下循环压缩80次后,样品能量损耗仅为0.022 8 MPa/mm,高度保持率高达97.37%,具有优异的抗压强度和弹性;PWH-2定向排列的多孔结构有助于铜离子在其内部迁移,提高吸附性能,在25℃、pH 5、铜离子质量浓度40 mg/L的模拟废液中,对铜离子的吸附率可达77.27%,经4次循环利用对铜离子的吸附率仍可达40.11%。动力学和等温线研究结果表明,PWH-2吸附铜离子过程满足拟一级动力学模型,遵循Langmuir等温线模型。该研究为构建高效可持续吸附重金属离子的高强度各向异性水凝胶提供理论参考,为生物质高值化利用提供新的方向。

Noria-PEI改性PVA载体固定化溶菌酶用于污泥发酵产VFAs研究

生物酶促进污泥厌氧消化具有反应温和、高效环保等优点,然而回收困难和催化稳定性差严重制约其应用,固定化酶是解决上述问题的关键。采用水轮酚(Noria)和聚乙烯亚胺(PEI)共沉积法改性聚乙烯醇(PVA)载体,并研究了Noria-PEI改性PVA载体固定溶菌酶对污泥厌氧发酵产挥发性脂肪酸(VFAs)效能的影响。结果表明,固定化溶菌酶可强化污泥发酵提高SCOD,在36 h内SCOD最高浓度达到2 892.4 mg/L,相比空白组提升3.4倍(第6天),VFAs质量浓度在第4天达到峰值2 130.8 mg/L,乙酸和丙酸占比达到61.8%~80.7%。固定酶系统中污泥的平均粒径为42.957μm,比表面积为0.413 m^(2)/g,固定化溶菌酶强化了颗粒态污泥水解。微生物群落结构分析显示,在固定酶系统中Firmicutes、Proteobacteria和Bacteroides等水解产酸菌门占比较高;在属水平上,以Macellibacteroides、Petrimonas、Lactobacillus和Clostridium_sensu_stricto_1菌属为主,从微观层面上解释了固定酶强化污泥发酵产酸机理。

PVA复合材料的研究进展

PVA(聚乙烯醇)是由聚醋酸乙烯酯水解而成的一种水溶性聚合物,具有强亲水性、优良的成膜性、可纺性好、并具有较好的力学性能,并且还不易受污染及突出的物理和化学稳定性,具有良好的生物降解性和生物相容性。本文综述了PVA在静电纺丝、相变材料和膜污染三方面的应用展开讨论。

PVA在缓释材料中的研究及应用

主要介绍了膜剂、水凝胶载药、包裹膜缓释等体系中,聚乙烯醇(PVA)医用、农用缓释材料的制备及应用原理,综述了各类PVA缓释材料在生物医学工程、农业生产等领域应用的研究进展。PVA材料所具有的亲水性、反应性、环保性、生物相容性等特点将赋予其广泛的医药及农业应用前景。

PVA纤维对水工抗冲磨混凝土性能的影响

为了改善混凝土的抗裂性能和抗冲磨性能,确保泄水建筑物的安全运行,在抗冲磨混凝土中掺入具有高强度和高弹性模量的聚乙烯醇(PVA)纤维.研究了PVA纤维混凝土的力学性能、变形性能、抗裂性能和抗冲磨性能,并与聚丙烯(PP)纤维混凝土的性能进行了对比.试验结果表明:当PVA纤维掺量为0.9kg/m3时,混凝土的28,90和180d抗压强度基本不变;劈拉强度分别增加了4.4%,8.4%和5.7%;极限拉伸值分别增加了10%,11%和4%.PVA纤维对混凝土早期干缩有一定的抑制效果,但后期混凝土的干缩值略有增加;混凝土塑性阶段的抗裂性能提高;混凝土的90和180d抗冲磨强度增加.与PP纤维相比,PVA纤维对抗冲磨混凝土性能的改善效果更好.

硼砂协同纳米SiO2、TiO2交联改性PVA基膜材料及其透湿和抑菌性分析

为提高聚乙烯醇(polyvinyl alcohol,PVA)基涂膜保鲜材料的阻湿性能,以水蒸气透过系数(water vapor permeability,WVP)为响应值,采用响应面法研究硼砂协同纳米SiO2、TiO2交联改性PVA基膜材料对WVP的影响。结果表明:硼砂协同纳米SiO2、纳米TiO2交联改性PVA能显著降低PVA基膜材料的WVP(P<0.05),硼砂与纳米SiO2及TiO2添加量对WVP有显著的交互作用(P<0.05);以膜材料WVP最低为响应值,优化成膜工艺条件为纳米SiO2添加量0.033 g/100 mL、纳米TiO2添加量0.042 g/100 mL、硼砂添加量0.032 g/100 mL,此条件下WVP为(9.729±0.074)mg/(m·d·kPa),比PVA单膜降低了44.68%。优化的PVA基复合膜抑菌性提高,可以使大肠杆菌菌落总数降低1个数量级。