Modified Poly Vinyl Alcohol Research Articles

Graphene-oxide modified polyvinyl-alcohol as microbial carrier to improve high salt wastewater treatment

This work discussed the preparation and characterization of graphene oxide (GO) modified polyvinyl alcohol (PVA) for bacteria immobilization to enhance the biodegrdation efficiency of saline organic wastewater. GO–PVA material has lamellar structure with higher surface area to support bacterial growth and high salinity tolerance. It significantly stimulated the bacterial population by 1.4 times from 2.07×103CFU/mL to 5.04×103CFU/mL, and the microbial structure was also improved for salinity tolerance. Acinetobacter, Pseudomonas and Thermophilic hydrogen bacilli were enriched inside GO–PVA materials for glucose biodegradation. Compared to the CODCr removal efficiency with only PVA as the carrier (52.8%), GO–PVA material had better degradation performance (62.8%). It is proved as a good candidate for bioaugmentation to improve biodegradation efficiency in hypersaline organic wastewater.

Improving the biodecolorization of reactive blue 13 by sodium anthraquinone-2-sulfonate immobilized on modified polyvinyl alcohol beads

In order to enhance the biodecolorization rate and avoid the wash-out problems of redox mediators in continuous systems such as a fluidized bed reactor, polyvinyl alcohol (PVA) beads modified with N-containing function groups were investigated and employed as a new sodium anthraquinone-2-sulfonate (AQS) carrier material. Elementary and XPS analyses confirm the existence of AQS on modified PVA bead. The modified PVA beads suit with immobilizing AQS better in adsorption capability and stability. AQS supported on modified PVA beads shows high catalytic activity for biodecolorization of reactive blue 13 in a long process (>10 runs).

Synthesis of polyvinyl alcohol with methacrylate groups and of hydrogels based on it

Polyvinyl alcohol containing unsaturated methacrylate groups was prepared by the reaction of polyvinyl alcohol with glycidyl methacrylate and was characterized by IR and 1H NMR spectroscopy. The influence of temperature, molecular mass of polyvinyl alcohol, and reactant concentration and ratio on the rate and limiting degree of substitution of hydroxy groups by methacrylate groups was examined. The modified polyvinyl alcohol is capable of cross-linking under mild conditions by the radical mechanism with the formation of biocompatible biodegradable hydrogels.

Preparation and Properties of Slag Wool Board using Modified Polyvinyl Alcohol as Binder

Slag wool boards were produced by using slag wool as the main raw material and adding modified polyvinyl alcohol (PVA) as the binder. The microstructure, thermal conductivity, compression strength, hydrophobicity, and other properties of the slag wool board were analyzed by using scanning electron microscopy, thermal conductivity tester, electronic universal testing machine, and other equipments. Also, the influence of different types and amount of binder on the properties of the slag wool board was studied. The results show that the addition of silica sol can improve the high temperature resistance of the slag wool board, and the addition of borax can improve the hydrophobic rate and compression strength of the slag wool board. Also, the concentration of PVA has obvious influence on the usage of silica sol and borax. In this study, we found that the optimal ratio of the binder should be 3 wt% addition of PVA, 20 wt% addition of silica sol, and 0.2 wt% of borax (relative to the amount of PVA), under the condition of satisfying the performance index of slag wool board and the convenience to spray the adhesive.

Removal of Cd(II) and Pb(II) from aqueous solutions by modified polyvinyl alcohol

In this study, modified polyvinyl alcohol (PVA) was prepared and characterized by element analysis, scanning electron microscopy, Fourier transform infrared spectroscopy, and surface area and proximity analysis. The isotherms and thermodynamic parameters of the modified PVA adsorption process were estimated. The data indicate that the adsorption process is exothermic, feasible, spontaneous, and fit to the Langmuir isotherm model. The maximum adsorption capacities for Cd(II) and Pb(II) were calculated to be 1.19 and 1.48 mmol/g, respectively. Sorption was rapid, with the removal percentage higher than 98% after 10 min. Adsorption behavior mechanisms were analyzed using pseudo-first-order and pseudo-second-order models, which were highly fitted to pseudo-second-order model. This suggests the main adsorption mechanism is a chemical adsorption, involving ion exchange and valence forces through sharing or exchange of electrons between metal ions and modified PVA. The modified PVA is a good reusable sorbent, enhancing the economics of practical application for the removal of Cd(II) and Pb(II) from water and wastewater.

Removal of benzene, toluene and xylene (BTX) from wastewater using immobilized modified prepared activated sludge (MPAS)

AbstractBACKGROUNDImprovements in biological oxidation approaches are required due to significant problems associated with this simple and commonly used approach. The work presents use of immobilized modified prepared activated sludge using modified polyvinyl alcohol (PVA)‐alginate beads for removal of BTX and modifications based on the use of Fenton chemistry as pretreatment scheme.RESULTSImproved synthesis processes for immobilized sludge beads have been developed based on understanding the effect of PVA and alginate loadings. Stable beads with high levels of sludge activity were shown to give similar levels of COD removal efficiency compared with free sludge. In the case of Fenton pretreatment, 40 min of treatment was found to increase BOD5:COD value to about 0.31. Maximum COD efficiency of 93.1% was obtained using a biological process on a Fenton‐treated sample which is significantly higher than that obtained with the untreated sample. The immobilized sludge was reused over nine batches without substantial loss in BTX degradation ability. Kinetic studies have also been presented.CONCLUSIONAn improved and promising approach for treatment of BTX containing wastewater with proven efficacy of the bioactivity and mechanical stability of the immobilized sludge, has been presented with better results based on Fenton pretreatment. © 2014 Society of Chemical Industry

Fixed-bed column sorption of borate onto pomegranate seed powder-PVA beads: a response surface methodology approach

Pomegranate seed powder (PS) was functionalized with polyvinyl alcohol (PVA) and utilized for boron removal from the aqueous system. Results of Brunauer--Emmett--Teller (BET) surface area analysis and Boehm titration indicated notable decrease in total surface area and increase in acidic surface functional groups of PS after PVA modification. Enhanced sorption is indicative of complex formation between diol groups of the pomegranate seed powder--polyvinyl alcohol (PS–PVA) and borate ions. Under column test, the saturated sorption capacity of boron was noted to be dependent on flow rate and bed height. The developed central composite design (CCD) was adequate to elucidate the sorption mechanism. Mathematical modeling of the column data was conducted, and a modified-dose-response model was the most suitable to describe the breakthrough curve and observed to be consistent with CCD analysis. This is further supported by extensive error analyses conducted between the model predicted and experimental data.

Pervaporation dehydration of ethyl acetate aqueous solution using the doubly modified polyvinyl alcohol (PVA) composite membrane

Polyvinyl alcohol–tetraethoxysilane–perfluorosulfonic acid (PVA–TEOS–PFSA) hybrid membrane was prepared by sol–gel method through PVA being modified doubly by PFSA and TEOS. With polyacrylonitrile (PAN) ultrafiltration membrane as a substrate membrane, PVA–TEOS–PFSA/PAN composite membrane was fabricated by dip-coating method for pervaporation (PV) dehydration of ethyl acetate (EAc) aqueous solution. The hybrid membrane was characterized by swelling degree, static contact angle, Fourier transform infrared spectra and scanning electron microscope. Effects of PFSA and TEOS contents in coating solution on PV performance of composite membrane were investigated, respectively. With increasing PFSA content, the permeation flux of composite membrane increased, while the separation factor decreased. Just the opposite, the increase of TEOS content resulted in the decrease in permeation flux and the increase in separation factor. In addition, the PV performances of composite membranes were also investigated at different feed temperatures and water concentrations in feed, respectively. The PVA–TEOS–PFSA/PAN composite membrane, which was prepared from coating with PVA/PFSA mass ratio of 80/20 and TEOS content of 20 wt%, exhibited the permeation flux of 347.9 g m−2 h−1 and the separation factor of 2218 for PV dehydration of 2 wt% water of EAc solution at 40 °C.

Enhanced boron adsorption using PVA-modified carbonaceous materials

Activated carbon and carbon nanotubes (CNTs) were modified with polyvinyl alcohol (PVA) and used for boron removal from aqueous solution. Results from the Boehm titration showed significant increase of the total acidic surface functional groups of both activated carbon and CNTs after PVA modification, and demonstrated that PVA was successfully grafted onto adsorbent surfaces. BET surface area of activated carbon decreased significantly after PVA modification, while only limited decrease was found for PVA-modified CNTs. The adsorption kinetics of boron could be described by pseudo-first-order and pseudo-second-order models. Langmuir adsorption isotherm fitted the equilibrium adsorption well. Significant enhancement of boron adsorption onto PVA-modified activated carbon and CNTs was found as evidenced by the remarkable increase in adsorption constant. In general, boron adsorption increased with increasing pH. It was proposed that enhanced boron adsorption onto PVA-modified CNTs was via complex formation between boron and cis-diol groups of the PVA-modified adsorbents, whereas physical force was the driving force for the original ones.

Study on the stability of modified colloidal silica with polymer in aqueous environment

The influence of polyvinyl alcohol (PVA) and polyacrylamide (PAM) on the stability of acidic colloidal silica in aqueous environment was examined. Experiments were carried out on the original colloidal silica (CS), PVA modification and PAM modification. PVA- and PAM-modified CS could remain stable for 20 and 13 days in the oven under 50 °C; however, nonmodified CS is only stable for 9 days. The thermal stability of CS was significantly improved through PVA modification. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) results show that the modified particles reveal better dispersibility. The action mechanism between polymer and CS was studied by particle size distribution, zeta potential, thermogravimetric analysis (TGA), Fourier transform infrared spectroscopy (FT-IR). The results show that the modified silica particles acquire more negative charge and the interactions among silica particles and PVA are stronger than among silica particles and PAM. Such differences appeared to be due to the loss of water molecules between C–OH of PVA and Si–OH bonds, which form a dense monomolecular adsorbed layer on the surface of the silica particles, thus increasing space steric repulsion. However, for the situation of PAM, the interaction was weakened. The results provided important basis to optimize stability of acidic CS in the aqueous environment.

Delta-sleep inducing peptide entrapment and release from polymer hydrogels based on modified polyvinyl alcohol

The aim of the study was to entrap delta-sleep inducing peptide (DSIP) in cross-linked poly(vinyl alcohol)-based hydrogels of different structures and to evaluate peptide release kinetics from these hydrogels using an in vitro model. Isotropic and macroporous hydrogels on the basis of poly(vinyl alcohol) acrylic derivative (Acr-PVA) as well as macroporous hydogels containing epoxy groups which were synthesized by copolymerization of this monomer with glycidyl methacrylate. The isotropic hydrogels were fabricated at positive temperatures while the macroporous hydrogels (cryogels) were prepared at the temperatures below zero. The peptide was entrapped into macroporous modified PVA hydrogels by addition of a peptide solution on previously fabricated matrices, while into PVA-GMA hydrogels containing epoxy groups peptide immobilization was carried out by incubation of hydrogel matrices in the peptide solution. In the case of isotropic hydrogels the peptide was added into the polymer mixture at a hydrogel formation reaction. The peptide release kinetics was studied by incubation of hydrogels in PBS (pH 7.4), in physiological solution (0.9% NaCl) and in water. DSIP concentration in supernatants was determined by phase-reverse HPLC. DSIP release from the macroporous PVA hydrogel after 30 min incubation was 74, 70 and 64% in water, PBS and 0.9% NaCl, relatively, and it was completed in 3 hs. From the isotropic hydrogel the release neither peptide nor products of its degradation was not observed even after 48 hs of incubation. For freshly prepared hydrogel the release kinetics was as follows: 27 and 78% in 30 and 33 hs, relatively. In the case of the lyophilized hydrogel samples the peptide release was 63% in 30 min incubation while drying patterns at room temperature for 3 days resulted in significant peptide loss because its structure damage.

玉米淀粉为原料制备高性能集成材拼板胶的研究

介绍一种不含甲醛的利用玉米淀粉改性聚乙烯醇的方法，分析了玉米淀粉与聚乙烯醇的比例及其他原料加入量对粘接强度的影响，在固化剂加入量为12%~15%时得到了理想的粘接效果，探讨了用玉米淀粉改性聚乙烯醇制作集成材拼板胶的适用条件。 A kind of non formaldehyde method of modified polyvinyl alcohol using corn starch was introduced in our research. The influences of the proportion of corn starch and polyvinyl alcohol, and other raw materials on the bonding intensity of the adhesive were analyzed. We get the ideal bonding effect by adding 12% - 15% curing agent. At the same time, the applicable conditions of making plastic glulam puzzle with corn starch polyvinyl alcohol were discussed.

Immobilization of Rhizopus oryzae in a modified polyvinyl alcohol gel for L(+)-lactic acid production

The production of L(+)-lactic acid (LA) by Rhizopus oryzae immobilized in polyvinyl alcohol (PVA) was investigated. To decrease diffusional resistance, we modified the PVA gel through the addition of sodium alginate and phosphate esterification. The production of L(+)-LA improved notably in the immobilized Rhizopus oryzae. Maximum L(+)-LA production (106.27 g/L), with a yield of 73.1 % and rate of 2.95 g/L·h, was obtained at a temperature of 38 °C, 6 % PVA, and 0.8 % sodium alginate. The immobilized R. oryzae was stable in 14 serial-batch cultures using non-growth medium. The immobilized beads also displayed good tolerance to low temperature and long-term storage at 4 °C with the preservation of biochemical properties.

Entrapment and in vitro release of delta-sleep inducing peptide from polymer hydrogels based on modified polyvinyl alcohol

The aim of this study was to entrap delta-sleep inducing peptide (DSIP) in cross-linked poly(vinyl alcohol)-based hydrogels of different structures and to determine kinetics of the peptide release from these hydrogels using an in vitro model. Isotropic and macroporous hydrogels based on poly(vinyl alcohol) acrylic derivative (Acr-PVA) and also macroporous epoxy groups containing hydrogels synthesized by copolymerization of this macromer and glycidyl methacrylate, have been used in this study. Isotropic hydrogels were prepared at positive temperatures while macroporous ones were obtained by formation in cryo-conditions. The peptide was entrapped into macroporous PVA hydrogels by adding the peptide solution onto preformed matrices, while peptide immobilization on PVA-GMA hydrogels, containing free epoxy groups, was carried out by sorption of peptide from its aqueous solution. In the case of DSIP entrapment into isotropic PVA gel the peptide solution was added into the polymer mixture at hydrogel formation. The kinetics of peptide release from hydrogels was studied by incubating matrices in PBS solution (pH 7.4), in physiological solution (0.9% NaCl) and in water. DSIP concentration in supernatants was determined by reverse-phase HPLC. Incubation of macroporous PVA gels in PBS, 0.9% NaCl, and water for 30 min caused release of 74, 70, and 64% DSIP, respectively, and this processes completed within 3 h. From hydrogel containing epoxy groups the release of neither peptide nor its degradation products was observed even after incubation for 48 h. For freshly prepared isotropic hydrogel the release kinetics was as follows: 27 and 78% DSIP were released within first 30 min and 33 h, relatively. For the lyophilized hydrogel samples the peptide release was 63% after incubation for 30 min, while drying of samples at room temperature for 3 days caused significant peptide loss because of its structure damage.

Modified Polyvinyl Alcohol Layer with Hydrophobic Surface for the Passivation of Pentacene Thin-Film Transistor

We modified the surface of a polyvinyl alcohol (PVA) layer by self assembly monolayer technique using a fluorine substituted silane compound (1H,1H,2H,2H-perfluorooctyl-trichlorosilane: FTS) to protect a pentacene thin-film transistor (TFT) from O2 and H2O. Surface modified PVA showed very low surface energy with water contact angle of 106.2 degrees. Surface treatment of PVA layer on pentacene TFT device was done in toluene solvent and we did not observe any damage to the PVA layer or pentacene TFT devices during surface modification process. Pentacene TFT with surface modified PVA passivation layer exhibited very stable TFT operation with almost no field effect mobility drop or threshold voltage shift up to 400 hrs. The performance of unpassivated OTFTs exponentially degraded and almost failed in 290 hrs. We propose that modified PVA layer can be used as a good passivation layer for oxygen and water in OTFT.

Feasibility of saline soil reinforced with treated wheat straw and lime

Saline soils in inshore areas have characteristics that are problematic to engineering such as salt expansion, dissolution and water absorption; therefore, these soils cannot meet the requirements of strength and anti-deformation in construction. A method of reinforcing saline soil with wheat straw and lime was investigated in this study. Specifically, the feasibility of using wheat straw treated with an SH (modified polyvinyl alcohol) agent as reinforcement and the compaction and strength of saline soil reinforced with wheat straw and lime were investigated. The results indicated that wheat straw treated with SH agent is suitable for use as a reinforced material owing to its higher corrosion resistance, tensile force and elongation. Additionally, reinforcement with wheat straw and lime was found to have a positive effect on the mechanical properties of soil. Reinforcement with wheat straw fiber enhanced the strength of soil during the early curing period and reduced the brittle failure problem associated with lime soil. Reinforcing soil with wheat straw and lime is an effective method for improving soil in the geotechnical field.

Enhanced cellular delivery of idarubicin by surface modification of propyl starch nanoparticles employing pteroic acid conjugated polyvinyl alcohol

Enhanced intracellular internalization of the anti-cancer active idarubicin (IDA) was achieved through appropriate surface modification of IDA loaded propyl starch nanoparticles. This was conducted by synthesizing pteroic acid modified polyvinyl alcohol (ptPVA) and employing this stabilizer for formulating the said nanoparticles. Pteroic acid attached at the nanoparticles improved the surface protein adsorption of the nanoparticle, a condition which the nanoparticles would largely experience in vitro and in vivo and hence improve their cellular internalization. Spherical, homogenous IDA nanoparticles (214 ± 5 nm) with surface modified by ptPVA were formulated using the solvent emulsification–diffusion technique. The encapsulation efficiency and drug loading amounted around 85%. In vitro release studies indicated a controlled release of IDA. Safety and efficacy of the nanoparticles was confirmed by suitable cellular cytotoxicity assays. Protein binding studies indicated a higher adsorption of the model protein on nanoparticles formulated with ptPVA as compared to PVA. Cellular uptake studies by confocal laser scanning microscopy revealed a higher cellular uptake of ptPVA stabilized nanoparticles thus confirming the proposed hypothesis of higher protein adsorption being responsible for higher cellular internalization.

Structure and Magnetic Properties of CoFe<sub>2</sub>O<sub>4</sub> Nanocrystal Thin Films Prepared by Sol-Gel Method

Thin films of CoFe2O4 spinel ferrite were prepared on silicon (100) substrates at low temperature by means of a modified polyvinyl alcohol processing, and the structure and magnetic properties as a function of the only one varied calcination temperature were investigated in detail and optimized. The CoFe2O4 ferrite films had a single phase spinel structure and were well-crystallized at temperature above 600 °C, which is much lower than the required temperature in the traditional ceramic method (about 1000 °C). The films annealed at and above 500 °C for 1h showed the grain sizes between 9 and 40 nm, and exhibited high coercivities and high saturation magnetization. Co-ferrite films prepared by sol-gel method and annealed at 700 °C had excellent potential for important technological applications, such as information storage and magnetooptical devices.

High volume fraction and uniform dispersion of carbon nanotubes in aluminium powders

A slurry-based powder process was developed to disperse a high volume fraction of carbon nanotubes (CNTs) in aluminium (Al) powders. In this process, Al nanoflake powders with a high surface area were used and the powder surface was modified by polyvinyl alcohol (PVA) hydrosol before being mixed with CNTs aqueous dispersion. The PVA modification resulted in the formation of a hydrophilic membrane on the Al surface, which enhanced the water wettability and makes the surface property of the Al powder more compatible with that of the CNTs. Furthermore, the PVA membrane forms relatively strong bonds with the CNTs and prevent them from agglomeration during subsequent processing. Consequently, a high volume fraction and uniform dispersion of up to 10 vol% CNTs was achieved in the Al nanoflake powders.

Macroporous polymeric hydrogels formed from acrylate modified polyvinyl alcohol macromers

Macroporous polymeric hydrogels for the last several years have found broad application in areas connected with medicine, especially in such new disciplines as cell and tissue engineering. In present work a novel combine approach is proposed for preparation of polyvinyl alcohol macroporous hydrogels by cross-linking of polyvinyl alcohol acrylic derivatives in the presence of heterophase of frozen aqueous media. Hydrogels prepared using this method does not need additional structure fixing and are characterized by high thermal stability in swollen state sustaining even heating to more than 100 °С. The influence of different factors and reaction conditions on the cross-linked hydrogel formation process was studied. The high yield of products (80 ÷ 95%) was observed when reaction was conducted at temperature range −12 ÷ −18 °С, concentration of macromer 4–12 weight %, and amount of initiator 0.8 ÷ 1.6 mg/ml. Moreover, the equilibrium swelling of synthesized macroporous hydrogels was investigated and it was shown that synthesized cross-linked hydrogels are characterized by high water absorption which is weakly depended on solution pH and ionic force values.