Modified Poly Vinyl Alcohol Research Articles

Accelerating anaerobic propionate degradation and studying microbial community using modified polyvinyl alcohol beads during anaerobic digestion

Modified polyvinyl alcohol beads (PVA) are synthesized by adding conductive materials such as activated carbon (AC), magnetite particles (MT), and green tuff (GT) for serving as potential advantages carriers on anaerobic digestion (AD). This study aimed to study the effect of modified PVA beads on AD performance and investigate the probability of DIET occurrence on syntrophic propionate degradation, including microbial syntrophy of syntrophic partners and methanogens. Under anaerobic sequencing batch reactor (ASBR) operation, chemical oxygen demand (COD) degradation was 1.3-fold higher, and propionate degradation increased 1.7-fold more than sludge. Another on the continuous stirred-tank reactor (CSTR), the COD degradation reached a maximum rate of over 80%, and propionate was completely degraded. Moreover, modified PVA beads were significantly promoted by methane production, methane conversion rate, and methane yield. The microbial syntrophy of “Candidatus Methanofastidiosum” and Syntophobacter co-occurred in modified PVA beads, illustrating the potential of syntrophic partner for propionate degradation.

A Sequential Therapeutic Hydrogel With Injectability and Antibacterial Activity for Deep Burn Wounds' Cleaning and Healing.

As a severe clinical challenge, escharotomy and infection are always the core concerns of deep burn injuries. However, a usual dressing without multifunctionality leads to intractable treatment on deep burn wounds. Herein, we fabricated a sequential therapeutic hydrogel to solve this problem. Cross-linked by modified polyvinyl alcohol (PVA-SH/ε-PL) and benzaldehyde-terminated F127 triblock copolymers (PF127-CHO), the hydrogel demonstrated excellent mechanical properties, injectability, tissue adhesiveness, antibacterial activity, biocompatibility, and satisfactory wound cleaning through both in vitro and in vivo assays. Additionally, based on the conception of “sequential therapy,” we proposed for the first time to load bromelain and EGF into the same hydrogel in stages for wound cleaning and healing. This work provides a strategy to fabricate a promising wound dressing for the treatment of deep burn wounds with injectability and improved patients’ compliance as it simplified the process of treatment due to its “three in one” characteristic (antibacterial activity, wound cleaning, and healing effects); therefore, it has great potential in wound dressing development and clinical application.

Spiropyran modified polyvinyl alcohol sponge as a light-responsive adsorbent for the removal of Pb(II) in aqueous solution

• A photochromic sponge for light-induced removal of Pb 2+ from aqueous solution was developed by Steglich esterification. • The adsorption capacity of sponge to Pb 2+ is 5.78 mg g −1 . • The adsorption capacity and stripping efficiency of sponge can maintain over 85% and 94% after ten cycles. • The regeneration of exhausted sponge can be realized by simple rinsing under visible light conditions. Lead (Pb 2+ ) is notorious for its negative effects on humans and the environment. Herein, a photochromic polyvinyl alcohol sponge (PVA-g-SPC) for light-induced removal of Pb 2+ from aqueous solution was developed using 1′-(4′-carboxybutyl) −3′, 3′-dimethyl-6-nitro-spiro [chromene-2, 2′-indoline] (SPC) and polyvinyl alcohol sponge (PVA) by Steglich esterification. Evidence from experiments shows that the maximum adsorption capacity of PVA-g-MCC (formed by PVA-g-SPC under UV irradiation) was calculated to be 5.78 mg g −1 and the PVA-g-MCC has excellent selectivity to Pb 2+ in the simulated lead–zinc mine leachate, ascribed to the complexation of MCC and Pb 2+ . Importantly, Pb 2+ can be repelled from the sponge effectively by simple rinsing with water under visible light conditions to achieve the regeneration of the PVA-g-SPC with significant change of the colour in whole process, providing a facile method to determining the separation endpoints of Pb 2+ by naked eyes and fully avoiding the secondary contamination caused by chemical desorbent. The adsorption capacity of PVA-g-SPC can maintain over 85% after ten cycles, indicating that the novel light-responsive sponge is a valuable material for Pb 2+ removal.

Preparation and characterization of anti-freezing conductive organohydrogel based on carboxyl modified polyvinyl alcohol and polypyrrole

Functional hydrogels have many excellent properties and many potential applications. However, hydrogels are easy to lose certain moisture or solvent in open environment, which makes volume shrinkage and hardness enhancement, even failure to possess use value. In addition, hydrogels usually lose their flexibilities at lower temperature due to water freezing. Therefore, the study of gels with low temperature flexibility and water retention are of great significance. In this paper, a kind of anti-freezing conductive organohydrogel was prepared from carboxyl modified polyvinyl alcohol which was dissolved in water and dimethyl sulfoxide (DMSO) (molar ratio = 3:1), pyrrole was added to the solution and polymerized, then gels were obtained by freeze-thawing method. It was found that the mixed solvent shows excellent low temperature freezing resistance, the carboxyl groups give favorable water retention property, polypyrrole makes the gel conductivity. The gels show good flexibility even at −60 °C. In open environment the mass loss of gels is only 30% after 17 days at room temperature. When the pyrrole content is 10%, the gel conductivity reaches the maximum value of 1 S/m. However, the introduction of pyrrole brought two changes, on one hand, when the pyrrole content increased from 0% to 10%, the mass retention dropped from 83% to 70%. On the other hand, with the content of pyrrole increased, the fracture stress of the organohydrogel first increased and then decreased. When the pyrrole content was 2%, the fracture stress reached the maximum value of 0.50 MPa. The gels can be further crosslinked by Fe3+, which was helpful for improving the mechanical properties. It is of great importance for recording intricate deformational signals in advanced flexible sensors.

Environmental bioremediation for uranium removing from aqueous solution by modified polyvinyl alcohol (PVA) embedded with Aspergillus versicolor

Development of new functional materials for heavy metals removal from environmental system has attracted considerable attention. In this paper, novel functional polymer consists of modified polyvinyl alcohol (PVA) embedded with Aspergillus versicolor biomass, using gamma radiolysis is prepared for uranium ions removal. Twenty two samples, with different physical conditions, were prepared to investigate the capability of the proposed functional polymer for adsorption and removal of uranyl ions from aqueous solution. Furthermore, comprehensive study was conducted to examine effect of A. versicolor particle size, embedded biomass percentage inside the functional polymer, and gamma ray radiation dose on adsorption efficiency of UO2 2+ ions. Obtained results illustrated that modified PVA with acetic acid, embedded with 1% A. versicolor biomass that has 45 µm particle size, and gamma irradiated at 10kGy is considered as the optimum functional polymer with the highest removal efficiency of UO2 2+ ions of 57.20%. The optimum functional polymer, before and after uranium ions adsorption, were characterized using SEM and FTIR techniques. It was found that the adsorbed UO2 2+ ions can be desorbed effectively by 0.1 M EDTA.

Novel porous matrices based on modified polyvinyl alcohol for air filtration

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Effect of modified polyvinyl alcohol on fluidity of cement slurry

Select appropriate amount of dispersant to modify polyvinyl alcohol, and explore the influence of modified polyvinyl alcohol on the rheology of cement slurry by investigating the thickening time, initial consistency, free liquid and density, fluidity index and viscosity coefficient of cement slurry. The results show that the thickening time of cement slurry is the shortest when the dispersant parameter is 1.5%, and the rheology of cement slurry becomes better and better when the dosage of polyvinyl alcohol increases. When 1.5% polyvinyl alcohol is added, the rheology of cement slurry is good and the viscosity is low.

Multiple effects of nano-CaCO3 and modified polyvinyl alcohol fiber on flexure–tension-resistant performance of engineered cementitious composites

Nanomaterial modification and fiber reinforcement are both effective modifications for concrete toughening. In this study, the cement matrix was reinforced by a combination of nanomaterials and surface-modified polyvinyl alcohol (PVA). The modification of PVA involves the treatment of interface weakening, which is based on the enhancement of the slip effect. The workability and static mechanical properties of engineered cementitious composites (ECCs) were studied, and the micromorphology of the fiber and matrix after bending failure was observed through scanning electron microscopy. Different nanomaterial contents and concentrations of PVA were designed in the experiment, the purpose of which is to investigate the mechanism of the effect of multiple superposed on the toughening effect of ECCs. The research demonstrated that the direct addition of traditional PVA fiber and nanomaterials adversely affects the workability of ECCs, but it can be improved by fiber modification and ultrasonic dispersion of nanomaterials. An experimental study on the compressive properties showed that, with the increase in PVA fiber modification concentration, the compressive strength decreased, but the addition of nano-CaCO3 improved the strength of the matrix, thereby compensating for the strength loss. Four-point bending and tensile tests demonstrated that both PVA fiber modification and the addition of nano-CaCO3 affected the flexural properties of ECCs to some extent. PVA fibers modified with 1% and 2% nano-CaCO3 at vinyl acetate ethylene concentrations of 25% and 50% can improve the toughness of ECCs. Nano-CaCO3 can improve the toughness of ECCs by improving the compactness of the matrix structure and fiber interface, while PVA fiber can supplement the defects of the matrix structure by bridging and sliding and have a positive superposition effect on the toughness of the material after proper treatment.

Reactive compatibilization of poly(hydroxybutyrate-co-hydroxyvalerate)/polyvinyl alcohol blends

ABSTRACT In this work, di(tert-butylperoxyisopropyl)benzene (DB) and multifunctional Epoxide compound (ECE) were incorporated into Poly(hydroxybutyrate-co-hydroxyvalerate) (PHBV)Modified polyvinyl alcohol (mPVOH) (70/30, 30/70) in an internal mixer to improve the compatibility of PHBV/PVOH blend. Prior to blending, glycerol and Maleic anhydride (MA) were added to PVOH (mPVOH). FTIR spectra indicated the reaction of MA grafted PVOH. The addition of DB and ECE showed higher torque values and better interfacial adhesion than nonreactive and reactive blends with DB or ECE. Tensile strength and elongation at break were increased for all reactive blends. The matrix dominated the crystallization whereas the minor phase was not crystallized upon cooling.

Spontaneous emulsification induced by a novel surfactant-polymer compound system and its application to enhance oil recovery

The application of spontaneous emulsification method during oil displacement provides a low-cost and environmentally friendly approach to enhance oil recovery for unconventional reservoirs. A surfactant-polymer mixture system composed of hydrophobically modified polyvinyl alcohol (HPVA) and cetyltrimethylammonium bromide (CTAB) with the ability of spontaneous emulsification was constructed. The optimum formulation of HPVA/CTAB compound system was selected based on the spontaneous emulsification capability and emulsion stability. It is found that the system showed best spontaneous emulsification performance with the concentration of 3000 mg/L and the mass ratio of 7:3 (HPVA:CTAB). The dynamic interfacial tension between oil and water reached ultra-low level to promote oil dispersing into water spontaneously, then rose back to low level to keep the emulsion stable. The synergistic effect of compound system enhanced the intermolecular attraction between HPVA molecule and CTAB molecule, which lead to a tighter interfacial film to maintain a better stability of emulsions. For low permeability cores, displacement tests showed an additional oil recovery of 12.4% by the injection of spontaneous emulsification system. These remarkable performances enable this system an ideal candidate for oil recovery enhancement.

Asphaltene behavior at the interface oil-nanofluids: Implications to adsorption

The mechanisms pertaining to the asphaltene adsorption at the interface oil/silica-based nanofluid and oil/wetted sandstone are examined. Asphaltene sample, extracted from a dead heavy oil using n-heptane, was dissolved into toluene to obtain a solution with a concentration of 3.23 mg/g. The solution was allowed to contact crushed Berea sandstone wetted with different silica-based nanofluids in the presence of carbon dioxide (CO2) bubbling. The silica-based nanofluid was prepared by dispersing silica oxide nanoparticle (0.1 wt%) into an aqueous solution of modified polyvinyl alcohol (1 wt%). Both batch and dynamic adsorptions were performed. A Solid-Liquid Equilibrium (SLE) model was employed not only to describe the adsorption mechanisms, but also to obtain the adsorptions parameters including the adsorption affinity and the asphaltene-self aggregation. The batch adsorption results reveal that asphaltenes develop a stronger affinity with the silica nanofluid film, which leads to an adsorption four-fold lower compared to sandstone wetted with the base fluid (polymer). It is also shown that the adsorption decreases with the decrease in the concentration of the polymer. In respect of the intrinsic properties of asphaltenes, it is found that the asphaltene molecules with a large aromatic core diffuse less, thus have a low adsorption. Irrespective of the core size, the affinity at the nanofluid film increases with the ratio in heteroatom-to-total carbon. Furthermore, the chemistry of the base fluid acts upon both the adsorption affinity and asphaltene self-association. Dynamic adsorption results on a nanofluid-wet sandstone were found three-fold larger compared to batch adsorption results. The primary reason is attributed to the alteration of the diffusion-barrier by the water, which promotes owing to the self-association of asphaltenes.

A novel and facile method for constructing micro-nano porous phytic acid pretreatment layer on metal surface

A novel and environmental-friendly pretreatment layer was prepared on a mild steel from an aqueous solution of polyvinyl alcohol (PVA)-grafted phytic acid (PA). This composite pretreatment layer provides greatly improved adhesion to the metal substrate, owing to the strong chelation and coordination interaction between PA and metals. Meanwhile, PVA modification produces highly porous structure in the hybrid layer. This is beneficial to the improvement of adhesion between metal substrates and subsequent polymer coatings. Further, the highly porous structure is good at loading -corrosion inhibitors, and the polymeric coatings painted on PVA-PA pretreatment layer pre-encapsulated with inhibitors exhibit satisfactory anticorrosion performance.

Tuning the structural and functional properties of HAVOH-based composites via ionic liquid tailoring of MWCNTs distribution

The structural and functional properties of polymer composite materials strictly depend on the spatial distribution of fillers, such as multiwalled carbon nanotubes (MWCNTs), inside the matrix. Herein, novel composites have been obtained by embedding MWCNTs into a modified polyvinyl alcohol (HAVOH) matrix, using the ionic liquid (IL) 1-Benzyl-3-methylimidazolium chloride (BenzImCl) as compatibilizer. The composites were prepared by solvent-wrapping carbon nanotubes onto HAVOH powders, followed by the melt-compounding approach to produce pellets for Fused Deposition Modelling technology (FDM). The efficacy of both the process and the IL on tailoring the spatial distribution of the MWCNTs into the HAVOH matrix is thoroughly studied and correlated with the electrical conductivity of the resulting composites. The sample printed by FDM, containing 6 wt % of MWCNTs and 0.6 wt% of IL exhibited a percolating morphology and led to an electrical conductivity (σ) value of 1.2*10−2 S/m. Moreover, after annealing at 220 °C for 2 h the σ value increased up to 7.9*10−1 S/m. The thermal treatment in presence of the MWCNTs also induces the formation of crosslinked HAVOH molecules changing the composites from easily soluble to completely water insoluble materials. This revealed the potential of HAVOH-based composites as raw material for FDM technology to realize post-printing cross-linkable materials.

Analysis on the applicability of modified polyvinyl alcohol (MPA) for temporary controlling the dust from soil in construction site

ABSTRACT Dust from construction field is one of sources for the atmosphere particulate pollution. In this study, a solidifying material, modified polyvinyl alcohol (MPA), is used to control the dust from soil. The controlling efficiency of the MPA is evaluated based on its anti-wind and anti-rain erosion performance under different conditions such as soil types, spraying amount of MPA, slope morphologies (gradients and unevenness), and treated time. Results indicate that the MPA can bind well with the soil particles and it is able to strengthen the integrity of the surface. Soil treated with MPA exhibits good anti-wind effects, and PM10 and PM2.5 in environment do not increase even under a nine-grade wind erosion. Soil treated with MPA can maintain the surface integrity under a rainstorm, and there are no erosion traces and mud after rain erosion. The application of MPA has no limitation in terms of soil type, soil slope, and surface morphology, and thus, it has a wide applied prospect in engineering. Implications: In order to solve the air pollution problems existing on construction sites in densely populated areas, MPA optimizes a kind of environmental agent to treat, which does not affect the later use of soil. The applicability effect was verified from the perspective of anti-wind and anti-rain erosion doubly. Research results not only can provide data support for the construction management, but also help to promote the civilization and ecological benefit of construction.

Polyvinyl alcohol modification with sustainable ketones

Water-degradable polyvinyl ketals with high glass transition temperatures (78–127 °C) were made via ketalization of polyvinyl alcohol (PVA) with sustainable ketones.

Seawater degradation of PLA accelerated by water-soluble PVA

Abstract In order to promote the degradation of PLA in seawater, a series of seawater-degradable polyester blends PVA/PLA were prepared by blending biodegradable polylactic acid (PLA) with water-soluble modified polyvinyl alcohol (PVA) in this paper. ADR 4370S was introduced to bring a certain degree of improvement in compatibility of PVA/PLA blends. The results of degradation test in natural seawater for 180 days show that the weight loss of PVA/PLA blends in seawater is much higher compared with that of pure PLA. PVA can be used as an effective hydrolysis accelerator for PLA matrix, helping to significantly reduce the molecular weight of PLA. The channels caused by dissolution/swelling of PVA facilitate the entry of water and microorganisms into the materials to contact with PLA, thereby promoting the degradation process of PLA matrix itself. Thus, both dissolution/swelling of PVA and degradation of PLA occur in PVA/PLA blends, and the degree of rapid dissolution of PVA in the early stage determines the degree of degradation of PLA.

Enhancing anaerobic syntrophic propionate degradation using modified polyvinyl alcohol gel beads

Modified polyvinyl alcohol (PVA) beads serve as effective anaerobic microbe immobilization carriers. PVA beads were mixed with different conductive materials, activated carbon, magnetite, and green tuff stone powder. In this study, modified PVA beads were used to investigate the effect of using, promote methane production, and enhance direct interspecies electron transfer (DIET) on the anaerobic syntrophic degradation of propionate, which is an essential intermediate process for generating methane in anaerobic digesters. The batch experiment showed that PVA mixed with activated carbon had the highest methane conversion rate of 72%, whereas the rates for control (sludge) was 61%. Moreover, the lag time during the second and third feedings was shorter by 5-fold than for the first feeding when modified PVA beads were added. The syntrophic propionate degrading microorganisms in the modified PVA beads was Syntrophobacter and Methanobacterium, either Methanoculleus or Methanosaeta. The modified PVA beads hold at least 10 times larger syntrophs than normal PVA. Therefore, composite PVA with conductive materials can promote methane production, accelerate propionate consumption, and enhance electron transfer in related microbial species.

Composite reverse osmosis membrane with a selective separation layer of double-layer structure for enhanced desalination, anti-fouling and durability properties

High performance membrane is crucial for energy-efficient desalination of salty water and reclamation of wastewater. Commercially available reverse osmosis membranes manufactured by interfacial polymerization or phase inversion techniques usually face the obstacle of “trade-off” effect between water permeation ability and salt rejection capability. In this work, a novel approach of constructing selective separation layer of double-layer structure was proposed to break through the difficulty of fabrication of reverse osmosis membrane with both high water permeation and salt rejection capabilities. Selective separation layer comprising loose polyamide (PA) sub bulk and dense hydroxypropyl methylcellulose (HPMC)-modified polyvinyl alcohol (PVA) top skin was constructed by the technique of interfacial polymerization followed with surface coating and cross-linking. The double-layer selective separation layer was found to possess an enhanced balance in water and salt permeations and endow the composite membrane with both high water flux and salt rejection. The desired membrane with an optimized selective layer of PA2/PVA + HPMC0.2 achieved 99.4% salt rejection and 37.9 kg/m2 h MPa water permeance to brackish water, which were higher than those of commercial membrane BW30. Furthermore, the desired membrane also exhibited better separation and antifouling performances in reclamation of secondary industry effluent when compared with the state-of-the-art antifouling membrane BW30FR.

Hydroxyl Group Separation Distances in Anti-Freeze Compounds and Their Effects on Ice Nucleation.

Since the discovery of biological antifreeze glycoproteins (AFGPs), which can inhibit ice nucleation, there has been considerable interest in understanding their mechanisms and mimicking them in synthetic polymers. In this study, we used molecular dynamics simulations of modified polyvinyl alcohol (PVA) compounds to show that the hydroxyl (OH) group distance is a key factor in whether certain compounds promote or inhibit ice nucleation. A hydroxyl distance smaller than ~2.8 Å but greater than ~7.1 Å in modified PVA (MPVA) compounds was associated with the promotion of ice nucleation, while a hydroxyl group separation distance of approximately ~5.0 Å was correlated with a delay in ice nucleation, owing to changes in the energy of the system. Thus, these results may help explain some of the mechanisms of current known anti-freeze compounds and may have implications for designing new anti-freeze compounds in the future.

Nano-silica modified polyvinyl alcohol potassium borate hydrogel electrolyte and its application in supercapacitors

Nano-silica modified polyvinyl alcohol potassium borate hydrogel electrolyte and its application in supercapacitors