PVA Beads Research Articles

Meso/macropore emerging from MOF granulation for enhancing performance in the Xe/Kr separation

The eco-friendly water/PVA system (PVA = polyvinyl alcohol) was employed to granulate SBMOF-1 powder to form SBMOF-1@20%PVA beads. The granulated beads maintained the high crystallinity of SBMOF-1 with the emergence of meso/macropores at 3.8, 50, and 76 nm. Owing to its benefit for mass diffusion, the presence of meso/macro porosity led to ∼128% enhancement of the Xe uptake capacity (based on SBMOF-1) of SBMOF-1@20%PVA beads over SBMOF-1 powder at 20% Xe broke through. This further enabled Xe/Kr separation from the simulated used nuclear fuel (UNF) reprocessing off-gas. Moreover, an easier and faster regeneration of SBMOF-1@20%PVA over SBMOF-1 powder through helium purge was obtained at room temperature. These findings demonstrate an enhanced working efficiency of the granulated SBMOF-1 beads over the powder samples by improving uptake capacity, saving energy for regeneration at high temperatures and cooling time after the heating-up regeneration, thereby highlighting the benefit of our engineering protocol in enhancing separation performance via MOF granulation.

Interfacial flame retardance of Poly(vinyl alcohol) bead foams through surface plasticizing and microwave selective sintering

Due to the presence of massive air and porous structure, the high flammability of polymeric foams severely limits their wider application in household, automobile, and aerospace fields. Herein, an interfacial flame-retardant mode based on surface plasticizing and microwave selective sintering was proposed to simultaneously realize the significantly reduced flammability and the enhanced mechanical properties of poly (vinyl alcohol) (PVA)/potassium silicate (KSi) bead foams. First, the foamed PVA beads with unique cell structure were prepared by supercritical carbon dioxide extrusion foaming and pelletizing. Then the KSi aqueous solution was coated on the surfaces of as-prepared PVA beads through surface plasticizing and acted as the excellent microwave absorber. Upon exposure to microwave irradiation, the interfacial heating caused by KSi coating layer induced the surface melting and cohesion of the neighboring PVA beads. The intense molecular diffusion occurred between PVA and KSi in the interfacial regions, improving the mechanical properties of foam parts. Meanwhile, KSi enriched at the bead interface and quickly decomposed into silicon-containing compounds once ignition, which constituted a dense physical Si and C barrier preventing the propagation of combustible substance and oxygen. Thus, the PVA/KSi bead foam reached the UL-94 level of V-0 and LOI value as high as 33.7%.

Adsorptive seawater desalination using MOF-incorporated Cu-alginate/PVA beads: Ion removal efficiency and durability

With the worsening water scarcity problem, seawater desalination has been receiving gradually increasing attention. Ion adsorptive desalination was introduced as one of the seawater desalination techniques. In our previous study, metal–organic framework (MOF)-incorporated single-network alginate (MOF-Alg(Cu)) beads were used to adsorb ions in seawater. In the present study, MOF-incorporated Cu-based alginate/PVA hydrogel (MOF-Alg(Cu)/PVA) beads were fabricated to enhance the ion adsorption desalination technique. Cu-based MOFs were successfully synthesized in situ on an interpenetrating polymer network (IPN). Given that the IPN hydrogel beads have high stability, the amount of MOF particles extracted during the adsorption of ions is reduced. The fabricated MOF-Alg(Cu)/PVA beads exhibit efficient removal of dissolved ions in artificial seawater and NaCl solution with varied concentrations. The ion adsorption characteristics were evaluated on the basis of adsorption kinetics, adsorption isotherms, and dosage of adsorbent. The repeat cycle tests show that more than half of the ion removal efficiency was maintained after 10 cycle tests. The concentration of artificial seawater was reduced to 1500 ppm by employing MOF-Alg(Cu)/PVA beads through a multistage experiment. Compared with other seawater desalination techniques, the proposed adsorptive desalination technique using MOF-Alg(Cu)/PVA beads will pave the way for developing a new ecofriendly and energy-saving approach.

An ultrafast and clean method to manufacture poly(vinyl alcohol) bead foam products

Poly (vinyl alcohol) (PVA) foam is a promising environment‐friendly packaging material due to the good biodegradability and excellent mechanical properties. Besides, PVA can be produced on a large scale viathe non‐petroleum routes. However, the preparation of complex‐shaped PVA foam products has not been realized, because PVA is a water‐soluble and semi‐crystalline polymer with a high melting temperature (226°C), which cannot be welded through the conventional bead foaming technology. In this article, a clean and efficient strategy based on microwave foaming and sintering was innovatively developed to manufacture the PVA bead foam products. First, the expandable PVA beads were prepared through polar solvent‐plasticization, followed by supercritical carbon dioxide (scCO2)‐impregnation in solid‐state. The impregnated beads were then surface plasticized with polar solvent by simple coating. Thus, the incorporated polar solvent in the internal and superficial regions of PVA beads was rapidly heated upon exposure to the microwave irradiation, which simultaneously induced the CO2 foaming and interfacial melting, respectively. In this way, the expansion and welding of PVA beads were completed in a one‐step procedure. Meanwhile, the complex‐shaped PVA bead foam products with excellent elasticity and intra‐bead adhesive strength were prepared within a short period of 30 seconds. Therefore, the microwave heating can be considered as an efficient strategy for preparing the high‐performance polymer bead foam products, especially for these high‐melting temperature or glass‐transition temperature polymers.

Deposition of Au nanoparticles on PDA-functionalized PVA beads as a recyclable catalyst for degradation of organic pollutants with NaBH4 in aqueous solution

A highly active and recyclable catalyst for the deposition of Au nanoparticles on the surface of polydopamine-functionalized poly(vinyl alcohol) macroporous beads was fabricated through the oxidative polymerization of dopamine and in-situ reduction route. The morphology and structure of PVA-PDA@Au beads were characterized using scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, energy dispersive X-ray spectroscopy, Fourier transform infrared spectroscopy, X-ray power diffraction and N2 adsorption–desorption measurement. The as-prepared PVA-PDA@Au beads combined the advantages of PVA-PDA beads and Au NPs. PVA-PDA@Au beads exhibited enhanced catalytic activity towards the degradation of Rhodamine B (RhB) in the presence of NaBH4 with removal efficiency up to 99.5% in 5 min at an initial RhB concentration of 100 mg/L and a catalyst amount of 0.5 g/L. PVA-PDA@Au beads could be easily separated and recycled from the reaction system by simple filtration, and reused for the degradation of RhB in six consecutive cycles with a conversion of >99%. Moreover, the mechanism for the degradation of RhB by PVA-PDA@Au beads was proposed. In addition, the catalytic ability of PVA-PDA@Au beads was further studied to remove Tetrabromobisphenol A (TBBPA), in which approximately 100% TBBPA (initial concentration of 25 mg/L) was removed within 90 min. In practical application, RhB as a pollutant in river water was degraded rapidly by PVA-PDA@Au beads with removal efficiency higher than 94%. Thus, PVA-PDA@Au beads possessed high catalytic activity, fast reduction rate and good reusability as well as easy separation and simple preparation, endowing this catalyst with potential application prospect in the treatment of wastewater containing organic pollutants.

Synthesis and characterization of simple and binary drug delivery systems for sustainable release of ciprofloxacin

Biopolymers are widely used for design sustained drug delivery systems (SDDS) and biomaterials for tissue engineering. Reducing wound infections still constitutes one of the major challenges facing the wound care. The aim of this study was to synthetize, characterize and evaluate a single (polymeric spheres) and a binary polymeric biomaterial (polymeric spheres imbedded in a poly(vinyl alcohol) (PVA) scaffold) as a SDDS. Polymeric spheres were prepared by complex coacervation and the binary system of the chitosan (CH) -PVA beads embedded in a PVA scaffold prepared by Ice Segregation Induced Self-Assembly (ISISA) process. Both systems were physicochemically characterized using Fourier Transform Infrared spectroscopy (FTIR), X-Ray Diffraction (XRD) and Scanning Electron Microscopy (SEM). In vitro ciprofloxacin (CFX) release kinetics were evaluated simulating physiological conditions under sink conditions. Physicochemical characterization showed interactions between all components forming beads; in contrast, beads-scaffold interactions were not detected making evident the presence of two different phases in the binary system. The CFX release kinetics revealed that both systems were SDDS, simple system release 97.0 ± 6.9% in 7 days, while the binary was 68.56 ± 6.6% during 14 days of evaluation. Binary system emerges as a potential tool for evaluate the long-lasting infection control in the treatment of skin wounds.

Structure and properties of porous poly(vinyl alcohol) hydrogel beads prepared through a physical–chemical crosslinking method

ABSTRACTPorous poly(vinyl alcohol) (PVA) hydrogel beads (PC beads) are potential microorganism carriers applied in wastewater treatment industries. However, improving the mechanical strength and stability of traditional PVA hydrogel beads in water is still a challenge. In this research, a new kind of PC bead was successfully prepared by a combination of physical and chemical crosslinking methods. The structures and properties of the PC beads and conventional PVA beads obtained by individual chemical (boric acid) or physical (cyclic freezing and thawing) processes were investigated by Fourier transform infrared spectroscopy, differential scanning calorimetry, scanning electron microscopy, and tensile and hydraulic stability testing. Compared with the conventional products, the PC beads displayed a more homogeneous and porous structure, bigger surface area, higher hydraulic stability, and better mechanical properties and showed better applicability for the water treatment field. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 46402.

ATNT-05INTRAOPERATIVE INTRAPARENCHYMAL INJECTION OF IRINOTECAN DRUG LOADED BEADS IN PATIENTS WITH RECURRENT GLIOBLASTOMA (GBM): A SAFE NEW DEPOT APPROACH FOR LOCO-REGIONAL THERAPY (NCT02433392)

BACKGROUND: Chemotherapy for brain tumours has been limited because of difficulty in achieving exposure to the tumour without systemic toxicity. Parenteral Irinotecan despite activity against glioma has an uncertain entry into the brain that has questioned its actual efficacy against glioma and a poor profile of enhanced systemic toxicity. In this study we have injected irinotecan sulphonated to PVA beads (1-1000 ) into the brain around tumour following resection of recurrent GBM to assess vehicle and drug safety from disease and procedure related problems. METHODS:10 patients who have failed available therapy for proven recurrent GBM with single focal recurrences as determined by gadolinium enhanced MRI with good performance and ages from 34 -76 were consented for this Phase I study. At operation tumour was removed and the cavity wall injected up to 5mm depth with up to 60 injections of beads suspended in alginate solution delivered using a 24 gauge flexible catheter to a total volume of 3mls and a drug dose of 100mg. Clinical assessments and blood samples were assessed for CTC criteria over 5/7 and imaging and clinical a assessment performed post operation at two and four and eight weekly to 6 months post surgery. RESULTS: To date one (6/15) patient has died at 4/12post treatment of progressive disease and there have been no CTC >2 or procedure related falls in performance despite these patients previous treatment and condition. We have no evidence from this study to suggest any local chemical meningitis or untoward swelling from the injection process. Follow-up is ongoing for survival comparison with other depot therapies. CONCLUSIONS: This novel form of depot therapy offers a stable safe drug loading platform and an accessible generic approach to ensuring local delivery of new agents or those with an uncertain access profile.

Production of xanthan gum by free and immobilized cells of Xanthomonas campestris and Xanthomonas pelargonii

Production of xanthan gum using immobilized cells of Xanthomonas campestris and Xanthomonas pelargonii grown on glucose or hydrolyzed starch as carbon sources was investigated. Calcium alginate (CA) and calcium alginate–polyvinyl alcohol-boric acid (CA–PVA) beads were used for the immobilization of cells. Xanthan titers of 8.2 and 9.2g/L were obtained for X. campestris cells immobilized in CA–PVA beads using glucose and hydrolyzed starch, respectively, whereas those for X. pelargonii were 8 and 7.9g/L, respectively. Immobilized cells in CA–PVA beads were successfully employed in three consecutive cycles for xanthan production without any noticeable degradation of the beads whereas the CA beads were broken after the first cycle. The results of this study suggested that immobilized cells are advantageous over the free cells for xanthan production. Also it was shown that the cells immobilized in CA–PVA beads are more efficient than cells immobilized in CA beads for xanthan production.

Efficiency of barium removal from radioactive waste water using the combination of maghemite and titania nanoparticles in PVA and alginate beads

In this paper, both maghemite (γ-Fe2O3) and titanium oxide (TiO2) nanoparticles were synthesized and mixed in various ratios and embedded in PVA and alginate beads. Batch sorption experiments were applied for removal of barium ions from aqueous solution under sunlight using the beads. The process has been investigated as a function of pH, contact time, temperature, initial barium ion concentration and TiO2:γ-Fe2O3 ratios (1:10, 1:60 and 1). The recycling attributes of these beads were also considered. Furthermore, the results revealed that 99% of the Ba(II) was eliminated in 150min at pH 8 under sunlight. Also, the maghemite and titania PVA–alginate beads can be readily isolated from the aqueous solution after the process and reused for at least 7 times without significant losses of their initial properties. The reduction of Ba(II) with maghemite and titania PVA–alginate beads fitted the pseudo first order and second order Langmuir–Hinshelwood (L–H) kinetic model.

A comparison of sodium sulfate, sodium phosphate, and boric acid for preparation of immobilized Pseudomonas putida F1 in poly(vinyl alcohol) beads

Poly(vinyl alcohol) (PVA) gel beads crosslinked with sodium phosphate or boric acid have been widely utilized for microorganism immobilization. We previously utilized sodium sulfate to induce crosslinking of PVA for preparing immobilized yeast cells in PVA beads. In this study, we compared the toxicities of sodium sulfate and conventional crosslinkers (sodium phosphate and boric acid) toward Pseudomonas putida F1 (PpF1) and the performance of the corresponding immobilized PpF1 in PVA beads. The toxicity of sodium sulfate to PpF1 was lower than those of the conventional crosslinkers. PVA–sodium sulfate beads showed a higher gel fraction of PVA and a lower swelling ratio in water than PVA–sodium phosphate beads, which indicates that the former had higher stability. PpF1 immobilized in the PVA–sodium sulfate beads completely degraded the pollutant trichloroethylene (TCE) with an initial concentration (0.42 mg/l) within the most common range of TCE concentration found in contaminated field sites.

Reject water treatment by improvement of whole cell anammox entrapment using polyvinyl alcohol/alginate gel

Reject water treatment performance was investigated by whole cell anammox sludge entrapped polyvinyl alcohol/sodium alginate gel in the stirred tank reactor (STR). The whole experiment was conducted through Phase 1 and Phase 2 in which synthetic wastewater and modified reject water were used as feeding medium, respectively. The anammox reactor demonstrated quick start-up after 22days as well as stable and relatively high nitrogen removal rate of more than 8.0kg-Nm(-3)day(-1) during the two both phases even under moderately low temperature of 25±0.5°C during the last 2months of Phase 2. The matured brownish red PVA beads had good characteristics with buoyant density of 1.10gcm(-3), settling velocity of 141mh(-1) and diameter of 4mm. The bacterial community was identified by 16S rDNA analysis revealing the concurrent existence of KSU-1 and new kind anammox bacterium Kumadai-I after changing influent from synthetic wastewater to reject water. It was speculated that Kumadai-I might play a role as "promotion" factor together with KSU-1 on high nitrogen removal rate. These results demonstrate the potential application of whole cell anammox entrapment by PVA/alginate gel for achieving stable and high-rate nitrogen removal from high ammonium with low C/N ratio contained wastewaters, such as reject water, digester liquor or landfill leachate.

Optimization of Entrapping Conditions of Nitrifying Bacteria and Selection of Entrapping Agent

Sodium alginate and polyvinyl alcohol were selected as entrapping agents to immobilize nitrifying microbia. Through orthogonal tests, optimal conditions of entrapping nitrifying bacteria by the two agents were determined by ammonia nitrogen removal efficiency. The properties of the two immobilized microbial beads produced under their optimum embedding conditions were compared. Results indicate that the optimum embedding conditions of calcium alginate beads (briefly CA beads) were 10ml of nitrifying bacteria, 4% of sodium alginate content, 3mm in bead diameter and 24-hr crosslinking time. The optimum embedding conditions of polyvinyl alcohol beads (briefly PVA beads) were 10ml of nitrifying bacteria, 10% of PVA content, 3mm in bead diameter and 24-hr crosslinking time. Comprehensive comparisons on mechanical strength, stability, mass transfer property and ammonia nitrogen removal efficiency of the two immobilized microbial beads indicate that polyvinyl alcohol is a better embedding agent for nitrifying bacteria in wastewater treatment compared with sodium alginate.

Fluorescent bracelet-like Cu@cross-linked poly(vinyl alcohol) (PVA) microrings by a hydrothermal process

Novel bracelet-like Cu@cross-linked poly(vinyl alcohol) (PVA) microrings have been prepared through a PVA-assisted hydrothermal process. Bracelet-like microrings are composed of inner copper nanorings and outer cross-linked PVA beads. The formation of bracelet-like microrings consists of two steps, i.e. the growth and self-coiling of PVA-wrapped copper nanowires and corresponding adhering of cross-linked PVA to form bracelet-like structures. Copper nanowires are formed by reduction from a mixed copper source consisting of CuCl2 and CuBr in the presence of NaBr by PVA. When an appropriate amount of NaBr was added, a product with a high yield of microrings can be obtained. A further investigation on ultra-thin section TEM images indicates that addition of the appropriate amount of NaBr leads to thinner copper nanowires within the crosss-linked PVA coatings. We proposed that thinner copper nanowires have less elastic resistance during bending processes, so PVA wrapped copper nanowires are more easily bent arbitrarily during vigorous Brownian motion at 210 °C. When two ends of one single nanowire join, the formation of van der Waals bonds and diminishing of the interfacial area through overlapping compensate the elastic resistance to get stable ring-like structures.

Selective removal for Pb 2+ in aqueous environment by using novel macroreticular PVA beads

Batch sorption experiments were conducted using macroreticular poly(vinyl alcohol) (MR-PVA) beads as a adsorbent to adsorb Pb(II) from both single component system and multi-metal solution in which experimental parameters were studied including solution pH, contact time, adsorbent dose, initial concentration of metal ions and ionic strength. The equilibrium isotherms were determined at pH 6 under constant ionic strength and at different temperatures. The results showed that the maximum adsorption capacity of Pb(II) (213.98 mg g −1) with 1 g L −1 of adsorbent was observed at 300 mg L −1 at an initial pH value of 6.0 under temperature of 288 K. Removals of about 60% occurred in 30 min, and equilibrium was attained at around 150 min. The equilibrium data for the adsorption of Pb(II) on MR-PVA beads was tested with various adsorption isotherm models among which three models were found to be suitable for the Pb(II) adsorption. In addition, the kinetic adsorption fitted well to the pseudo-second-order model and the corresponding rate constants were obtained. Thermodynamic aspects of the adsorption process were also investigated.

Preparation, Characterization, and Application of Poly(vinyl alcohol)-graft-Poly(ethylene glycol) Resins: Novel Polymer Matrices for Solid-Phase Synthesis

Spherical crosslinked poly(vinyl alcohol) (PVA) beads with good mechanical stability were prepared by reverse-suspension polymerization, using dimethyl sulfoxide (DMSO) as a cosolvent in an aqueous phase. Poly(ethylene glycol)s with varying chain lengths were grafted onto the PVA beads by anionic polymerization of ethylene oxide. The thermal behavior, morphology, and swelling were evaluated for each of the new polymer matrices. High loading and good swelling in water and organic solvents were characteristic of the PEG-grafted PVA beads. The polymer beads also exhibited good mechanical and chemical stability and were unaffected by treatment with 6 N HCl and with 6 N NaOH. The hydroxyl groups of the PVA-PEG beads were converted into aldehyde, carboxylic acid, and isocyanate functions to provide scavenger resins and were extended by way of a benzyl alcohol in a Wang linker. The transglutaminase substrates dipeptides (Z-Gln-Gly) and heptapeptides (Pro-Asn-Pro-Gln-Leu-Pro-Phe) were synthesized on PVA-PEG_5, PVA-PEG_20, and the Wang linker-derivatized PVA-PEG resins. The cleavage of the peptides from the resins using MeOH/NH3 mixture at different temperatures (0 degrees C and room temp) and 50% TFA/DCM provided, respectively, peptide methyl esters, amides, and acids in good yields and purity as assessed by LC-MS analysis.

Biosorption of copper by immobilized marine algal biomass

Abstract The characteristics of poly(vinyl alcohol) (PVA) cryogel as an immobilization matrix were examined for the uptake of copper by a brown marine algal biomass, and compared with freely suspended biomass. Biomass-embedded PVA cryogel beads were robust and showed stability under a wide range of pH (1–13). SEM analysis revealed the rugged surface of the beads and changes in its surface compositions before and after metal binding. The surface area and pore size of the beads were highly dependent on the concentration of the biomass immobilized within the PVA beads. The immobilized beads showed lower copper uptake capacity than the freely suspended Sargassum . A positive correlation was also found between copper uptake capacity and the concentration of the immobilized biomass (5–30 g/L). The metal uptake capacity of the beads was also dependent on the solution pH. It was shown that immobilization matrix exerted mass transfer resistance for copper uptake by the PVA- Sargassum beads. The metal sorption rates were enhanced at higher biomass loading within the beads, or with an increase in the initial copper concentration, or with hydration of the beads before use. The kinetics of copper biosorption by the immobilized PVA cryogel bead could be well modeled by a pseudo first-order equation.

Controlled‐release polymers for delivery of dipyridyls and tetraalkyl ammonium hydroxide

AbstractA method to incorporate 2,2′‐(or 4,4′‐)dipyridyl and tetra‐n‐butylammonium hydroxide into poly(vinyl alcohol) (PVA) monoliths and the controlled‐release properties of these polymer monoliths for delivery of the reagents are reported. The monoliths were prepared by heating PVA beads until they formed a viscous liquid and then loading the molten polymers with the desired reagents. Several freeze‐thaw cycles were then carried out to provide the mechanically stable, reagent‐loaded monoliths. The release of the reagents from the PVA monoliths was monitored by UV–vis spectroscopy, and the release was found to proceed in a controlled manner, yielding consistent results among different reagent‐loaded PVA monoliths. In addition, the reagents underwent no chemical changes upon their release from the monoliths. Limitations of the use of the controlled‐released chemicals as replenished reagents in Fujiwara reactions for the continuous monitoring of halocarbons are discussed. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 1043–1048, 2007

Poly(vinyl alcohol)-graft-poly(ethylene glycol) resins and their use in solid-phase synthesis and supported TEMPO catalysis

New poly(vinyl alcohol)-graft-poly(ethylene glycol) (PVA-g-PEG) resins with various PEG chain lengths, which have high loadings and good swelling both in water and organic solvents, have been prepared via an anionic polymerization of ethylene oxide onto PVA beads and applied in solid-phase synthesis, supported TEMPO catalysis and in HR-MAS 1H NMR spectral analysis.

Preparation and characterization of monodisperse superparamagnetic poly(vinyl alcohol) beads by reverse spray suspension crosslinking

A novel protocol for preparing magnetic poly(vinyl alcohol) (PVA) beads by reverse spray suspension crosslinking was reported. The hydrophilic Fe3O4 nanoparticles were mixed with PVA, glutaraldehyde, and water to form aqueous phase. Then the aqueous phase was sprayed into vegetable oil by a pressure of nitrogen gas to form water in oil (W/O) suspension. The magnetic PVA beads were obtained in the presence of hydrochloric acid catalyst. It was found that the magnetic PVA beads obtained good properties when the PVA concentration was 10%, and the oil phase temperature was controlled at 40 °C. The mechanical stirring has little impact on the size of magnetic PVA beads in the process of reverse spray suspension crosslinking. The Cibacron Blue (CB) was coupled on the surface of magnetic PVA beads by surface chemical reaction. The morphology, size, and magnetic properties of the magnetic PVA beads were examined by scanning electron microscopy, laser diffraction, and vibrating sample magnetometer, respectively. Compared with the stirring method, it was found that the size of magnetic PVA beads was monodisperse and their saturation magnetization was much higher. Fourier transform infrared and X-ray photoelectron spectroscopy experimental results proved that CB molecules were covalently immobilized onto the surface of the magnetic PVA beads. Meanwhile, the protein affinity separation experiments demonstrated that the magnetic PVA beads can potentially be used as a carrier for large-scale protein separation. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 203–210, 2008