Effect of temperature on low-strength wastewater treatment by UASB reactor using poly(vinyl alcohol)-gel carrier

The feasibility of treating low-strength wastewater with an up-flow anaerobic sludge blanket (UASB) reactor, using a poly(vinyl alcohol)-gel carrier, at various temperatures and hydraulic retention times (HRTs) was examined. The temperature was decreased from 35°C to 25°C and then to 15°C. The HRT was reduced from 2.0 h to 0.22 h. The COD removal rate reached 28 kg-COD m(-3)d(-1) at 35°C, 16 kg-COD m(-3)d(-1) at 25°C, and 6 kg-COD m(-3)d(-1) at 15°C. The COD removal rate was reduced by half for each temperature reduction of 10°C.     

Use of poly(vinylpyrrolidone) and poly(vinyl alcohol) for cryoultramicrotomy

Summary Specimens infused with or suspended in a mixture of 10–30% poly(vinylpyrrolidone) and 2.07–1.61m sucrose can often be more easily frozen-sectioned than those infused with sucrose alone. The pH of such a mixture can be efficiently adjusted to neutrality by using Na₂CO₃. Use of poly(vinylpyrrolidone) causes little or no increase in the background level of immunolabelling. Adsorption staining of ultrathin frozen sections with a mixture of uranyl acetate and poly(vinyl alcohol), i.e. a simple thin-embedding of the sections in such a mixture, produces positive staining effects that are often enough to delineate structures of many organelles. When OsO₄-treated frozen sections are stained with uranyl acetate and further adsorption-stained with a mixture of lead citrate and poly(vinyl alcohol), the overall staining effects are similar to those observed in double-stained conventional sections.A large portion of the findings was reported as a part of the author's presentation in the 11th International Congress on Electron Microscopy, held in Kyoto, Japan, in 1986.     

The adsorption of poly (vinyl alcohol) on the hydroxylated β-cristobalite

The adsorption of poly (vinyl alcohol) with different chain lengths on a hydroxylated β-cristobalite (100) surface is studied via molecular simulations. The relative dielectric constant is selected to be 1 and 78 to mimic in vacuum and in solution environment, respectively. Different configurations and dynamic properties are found in the two absolutely different environments, showing that the solvent condition plays an important role in the process of chain adsorption and diffusion on a surface. In equilibrium, the chain possesses (partial) ordered configuration in vacuum condition.     

Imaging and thermal studies of wheat gluten/poly(vinyl alcohol) and wheat gluten/thiolated poly(vinyl alcohol) blends

The morphology of wheat protein (WG) blends with polyvinyl alcohol (PVA) and respectively with thiolated polyvinyl alcohol (TPVA) was investigated by atomic force (AFM) and transmission electron microscopy (TEM) as well as by modulated dynamic scanning calorimetry (MDSC). Thiolated additives based on PVA and other substrates were previously presented as effective means of improving the strength and toughness of compression molded native WG bars via disulfide-sulfhydryl exchange reactions. Consistent with our earlier results, AFM and TEM imaging clearly indicate that the addition of just a few mole percent of thiol to PVA was sufficient to dramatically change its compatibility with wheat protein. Thus, TPVA is much more compatible with WG and phase separates into much smaller domains than in the case of PVA, although there are still two phases in the blend: one WG-rich phase and another TPVA-rich phase. The WG/TPVA blend has phase domains ranging in size from 0.01 to 0.1 microm, which are roughly 10 times smaller than those of the WG/PVA blend. MDSC further illustrates the compatibilization of the protein with TPVA via the dependence of the transition temperatures on composition.     

Immobilization of biocatalysts with poly(vinyl alcohol) supports.

Two polymer materials, poly(vinyl alcohol) (PVA) superfine fibers and photocrosslinkable PVA bearing styrylpyridinium groups, have been developed to immobilize biocatalysts. The former has a large surface consisting of relatively large-size pores and the fibers can immobilize a large amount of biocatalyst on their surface by ionic interaction. The latter entraps many kinds of biocatalysts by cyclodimerization caused by visible light irradiation. The biocatalysts on/in these supports maintain high activity and thermal stability. These materials can easily be formed into various shapes suitable for various applications. A new bioreactor system was constructed for evaluating a variety of biocatalysts and supports.     

High-rate partial nitritation using porous poly(vinyl alcohol) sponge

Poly(vinyl alcohol) (PVA) has been utilized as a support material for the immobilization of nitrifying bacteria without the comprehensive survey of partial nitritation. In the present study, the activities of nitrifiers and the maximum nitrogen conversion rate of partial nitritation with PVA sponge-cubes were specified according to different conditions. The selective enrichment of ammonia-oxidizing bacteria (AOB) on PVA sponge-cubes was achieved by the competition between AOB and nitrite-oxidizing bacteria for dissolved oxygen. The efficiency of ammonia oxidation was proportional to the concentration of HCO₃ ^? with the molar ratio of HCO₃ ^?-C/NH₄ ⁺-N = 1.91 and a half of the ratio was applied to the further experiments to ensure stable partial nitritation. The maximum nitrogen conversion rate of partial nitritation was dependent on the volume, not the size of sponge-cubes. The partial nitritation showed the superior rate performance of 3.09 kg N/m³ day with the packing ratio of 32 % of 5 × 5 × 5 mm³ PVA sponge-cubes.     

Hydrolysis of sucrose using sulfonated poly(vinyl alcohol) as catalyst

The hydrolysis of sucrose was carried out over poly(vinyl alcohol) (PVA) with sulfonic acid groups, at 80 °C. The products of sucrose hydrolysis were glucose and fructose. A series of PVA with different crosslinking degree were prepared. It was observed that the catalytic activity of PVA matrix increases with the crosslinking degree, due to the increases of the amount of sulfonic acid groups on PVA.     

The photocycle of bacteriorhodopsin immobilized in poly(vinyl alcohol) film

The kinetics of photoelectric and optical signals were measured on samples containing oriented purple membranes immobilized in a poly(vinyl alcohol) film and on purple membranes introduced into a PVA-H2O mixture. The bacteriorhodopsin photocycle in the PVA-H2O mixture was complete. The only observed changes were the slowing down of the optical and electrical signals in relation to the M412-O640 and O640-bRall-trans steps. In the PVA film the O640 intermediate disappeared and a negative photoelectric signal appeared.     

Swelling and flow properties of tubular poly(vinyl alcohol) gels

Swelling and flow properties of tubular poly(vinyl alcohol) (PVA) hydrogels prepared with the cooling method were investigated using an inflation testing method. When the tubular hydrogel in liquid paraffin was inflated by using liquid paraffin as a pressure transmitting medium, namely in the case that the liquids inside and outside the gel are both liquid paraffin (P/P combination), the gel showed a slight volume change determined by Poisson's ratio of the gel. When the gel in water was inflated by liquid paraffin (P/W combination), the gel swelled to large extent compared with the case of P/P. The hydrogel in W/W combination, namely in the situation that the gel was immersed in water and also inflated by water, showed a very large volume change if the comparison was done at the same pressure. The origin of the volume change in P/P, P/W and W/W combinations is discussed. The volume change in P/P was governed by the Poisson ratio as a material constant (mu 0) of the PVA gels, and the gels swelled by the change in the application of pressure (or deformation) in P/W. The volume change in W/W was closely related to the flow of solvent in the gel.     

Electrospinning of poly(vinyl alcohol)-water-soluble quaternized chitosan derivative blend

Defect free mats containing a cationic polysaccharide, chitosan derivative such as N-[(2-hydroxy-3-trimethylammonium)propyl] chitosan chloride (HTCC), have been prepared using electrospinning of an aqueous solution of poly(vinyl alcohol) (PVA)-HTCC blends. HTCC, a water-soluble derivative of chitosan, was synthesized via the reaction between glycidyl-trimethylammonium chloride and chitosan. Solutions of PVA-HTCC Blends were electrospun. The morphology, diameter and structure of the produced electrospun nanofibres were examined by scanning electron microscopy (SEM). The average fibre diameter was in the range of 200-600 nm. SEM images showed that the morphology and diameter of the nanofibres were mainly affected by weight ratio of the blend and applied voltage. The results revealed that increasing HTCC content in the blends decreases the average fibre diameter. These observations were discussed on the basis of shear viscosities and conductivities of the spinning solutions. Microbiological assessment showed that the PVA-HTCC mats have a good antibacterial activity against Gram-positive bacteria, Staphylococcus aureus, and Gram-negative bacteria, Escherichia coli.     

Poly(vinyl alcohol) functionalized poly(dimethylsiloxane) solid surface for immunoassay

In this communication, we describe a simple and robust method for the covalent bonding of poly(vinyl alcohol) (PVA) on a silanized poly(dimethylsiloxane) (PDMS) surface. Nonspecific adsorption of proteins via hydrophobic-hydrophobic interactions of the PVA-coated surface is greatly reduced, and biomolecules can be rapidly anchored on the PVA-coated surface with high loading and uniformity. On the basis of a sandwich immunoassay with the anti-rabbit IgG and IgG pair as a model, the detection limit for IgG is down to 1 pg/mL with linearity up to 11 microg the levels often encountered in biological, forensic, and environmental samples.     

Amphiphilic poly(vinyl alcohol) derivatives as complexing agents for fenretinide

Poly(vinyl alcohol) (PVA) substituted with oleyl chains and tetraethyleneglycol monoethyl ether chains (TEGMEE) at 1.5% and 1% degrees of substitution respectively (mol of substituent to mol of hydroxyvinyl monomer) has previously been shown to self-assemble in water, providing aggregates selectively cytotoxic toward tumor cells vs normal cells. These polymers have also been shown to increase the long-term survival of nude mice injected with both human and murine neuroblastoma cell lines. In the present work, we changed the substitution degree of the oleyl chains on the poly(vinyl alcohol) backbone and maintained constant at 1% the degree of TEGMEE substitution. We evaluated the main physicochemical characteristics of the final polymers, their cytotoxicity toward tumor cells, and their complexing ability for hydrophobic molecules. The aim was to investigate the possibility of improving intrinsic antitumor efficacy of the polymer by changing the degree of oleyl chain substitution and further increase activity by complexation with antitumor drugs. The polymers were prepared at oleyl chain substitution degrees ranging from 0.5 to 3% (mol of substituent to mol of hydroxyvinyl monomer). The most active was again the 1.5% substituted polymer. It was further characterized by exhibiting the highest complexing ability toward hydrophobic molecules allowing the formation of a complex with fenretinide (HPR). The polymer-HPR complex was stable in aqueous environment and released the free drug prevalently in the presence of fluid hydrophobic phases. It was cytotoxic toward tumor cells with minimal activity toward normal cells. Antitumor activity exceeded that of the separate complex components resulting from the concomitant effect of the polymer and the HPR solubilized by complexation.     

Wheat gluten-thiolated poly(vinyl alcohol) blends with improved mechanical properties

A multifunctional macromolecular thiol (TPVA) obtained by esterification of poly(vinyl alcohol) (PVA) with 3-mercaptopropionic acid was characterized by a combination of NMR, IR, transmission electron microscopy (TEM), and differential scanning calorimetry (DSC), and was used as a wheat gluten (WG) reactive modifier. The effect of TPVA molecular weight (M(w) = 2000, 9500, 50 000, and 205 000) and blend composition (5, 20, and 40% w/w TPVA/WG) on the mechanical properties of compression-molded bars indicates that TPVA/WG blends increase the fracture strength by up to 76%, the elongation by 80%, and the modulus by 25% above WG. In contrast, typical WG additives such as glycerol and sorbitol improve flexibility but decrease modulus and strength. Preliminary investigations of suspension rheology, water uptake, molecular weight distribution and electron microscopy of TPVA/WG and PVA/WG blends illustrate the different protein interactions with PVA and TPVA. Further work is underway to determine whether TPVA and WG form protein conjugates or microphase-separated morphologies.     

Molecular dynamics study of deformation mechanisms of poly(vinyl alcohol) hydrogel

Molecular dynamics (MD) simulations have been performed on the physically crosslinking poly(vinyl alcohol) (PVA) hydrogel to study the deformation mechanisms under uniaxial tensile conditions. The distributions of hydroxyl oxygens and dihedral angle and the number of hydrogen bonds have been analysed to study the structure of the hydrogel. The water content and temperature dependency of mechanical properties have been investigated. The energy contributions from the partially united atom potential have been calculated as a function of strain. It is found that the stress–strain curve comprises toe region, linear region and yield and failure region which is close to most biomaterials. In the toe and yield region, all the contributions to the internal energy change a little. However, in the linear region, the bond stretching and angle bending energy increase rapidly and mainly dominate the region, and the energy increases more rapidly with the increasing water content but the decreasing temperature. The degree of crosslinking decreases with the increasing deformation. The polymer chains occur significant torsional activity in the toe region. Hydrogen bonds are stable in the toe and yield region, but the hydrogen bonds between hydroxyl groups and waters decrease in the linear region.     

Modification of chitosan membrane with poly(vinyl alcohol) and biocompatibility evaluation

This work aimed to overcome chitosan (CS) membrane' drawbacks: mainly stiffness and hydrophobic surface by adding poly(vinyl alcohol) (PVA) and evaluate their biocompatibility. The chemical structure, crystalline and thermal properties were studied by FT-IR, XRD and DSC. The mechanical properties and wettability of CS/PVA membranes were studied by tensile test and static contact angle measurement. In vitro biocompatibility was also evaluated by MTS cytotoxicity assay and SEM examination. The results suggest that adding PVA into CS membrane could greatly improve CS membrane's flexibility and wettability. All the membranes prepared were biocompatible and have potential applications in GTR technology.     

Effect of partial atomic charges on the calculated free energy of solvation of poly(vinyl alcohol) in selected solvents

It is well-known that properties of poly(vinyl alcohol) (PVA) in the pure and solution states depend largely on the hydrogen bonding networks formed. In the context of molecular simulation, such networks are handled through the Coulombic interactions. Therefore, a good set of partial atom charges (PACs) for simulations involving PVA is highly desirable. In this work, we calculated the PACs for PVA using a few commonly used population analysis schemes with a hope to identify an accurate set of PACs for PVA monomers. To evaluate the quality of the calculated parameters, we have benchmarked their predictions for free energy of solvation (FES) in selected solvents by molecular dynamics simulations against the ab initio calculated values. Selected solvents were water, ethanol and benzene as they covered a range of size and polarity. Also, PVA with different tacticities were used to capture their effect on the calculated FESs. Based on our results, neither PACs nor FESs are affected by the chain tacticity. While PACs predicted by the Merz-Singh-Kollman scheme were close to original values in the OPLS-AA force field in way that no significant difference in properties of pure PVA was observed, free energy of solvation calculated using such PACs showed greater agreement with ab initio calculated values than those calculated by OPLS-AA (and all other schemes used in this work) in all three solvents considered.     

Synthesis and properties of carrageenan grafted copolymer with poly(vinyl alcohol)

The aim of this work was to prepare a carrageenan-g-poly(vinyl alcohol) (CG-g-PVA) polymer using potassium persulphate as an initiator. The effect of different ratios of the polymer blends on the parameters of the grafted polymer was investigated. The grafting ratio decreased with an increase of the CG content in the graft copolymer. The resulting CG-g-PVA was characterized by ATR-FTIR, tensile strength, elongation at break, swelling ratio, contact angle and biodegradation in soil. From the ATR-FTIR the 3,6-anhydride-galactose of the CG showed a peak at 927 cm⁻¹ that was absent in the CG-g-PVA and the ether linkage of PVA-g-CG between the hydroxyl group of PVA and the 3,6-anhydride-galactose of CG showed a peak at 1089 cm⁻¹ in the graft copolymer. The tensile strength and elongation at break decreased with an increase of the CG due to its phase separation. The highest tensile strength was observed at 2:8 CG/PVA. In addition, the swelling ratio decreased and the contact angle increased as a function of the increase of the CG in the grafted copolymer. The best ratio of CG-g-PVA was 2:8 CG/PVA. This graft copolymer was easily biodegraded in natural soil.     

Two stage extrusion of plasticized pectin/poly(vinyl alcohol) blends

Blends of pectin with starch (high amylose and normal), poly(vinyl alcohol) (PVOH), and glycerol were extruded in a twin screw extruder, pelletized, and then further processed into blown film and extruded sheet using a single screw extruder. The samples were analyzed using tensile measurements, dynamic mechanical analysis, and scanning electron microscopy. PVOH levels of 24% or greater were necessary to successfully make blown film, while extruded sheet could be made at a level of 16% PVOH. Tensile strength and initial modulus of the extruded sheets were slightly higher in the machine direction than in the cross direction, while the reverse was true for elongation to break. For the blown films tensile strength tended to be higher in the transverse direction than in the machine direction, while the reverse was seen for initial modulus. Increased levels of PVOH led to increases in tensile strength and elongation to break, while initial modulus was decreased. Morphology as determined by SEM visually indicated stretching in the transverse direction of the blown films. The second stage extrusion appeared to promote -helix formation in the high amylose starch.