• Fibers and Polymers
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• v.3 no.2
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• pp.73-79
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• 2002

Nanoscaled PVA fibers were prepared by electrospinning. This paper described the electrospinning process, the processing conditions fiber morphology, and some potential applications of the PVA nato-fibers. PVA fibers with various diameters (50-250 nm) were obtained by changing solution concentration, voltage and tip to collector distance (TCD). The major factor was the concentration of PVA solution which affected the fiber diameter evidently. Increasing the concentration, the fiber diameter was increased, and the amount of beads was reduced even to 0%. The fibers were found be efficiently crosslinked by glyoxal during the curing process. Phosphoric acid was used as a catalyst activator to reduce strength losses during crosslinking. Scanning electron micrograph (SEM) and differential scanning calorimetric (DSC) techniques were employed to characterize the morphology and crosslinking of PVA fibers. It was fecund that the primary factor which affected the crosslinking density was the content of chemical crosslinking agent.

• Polymer(Korea)
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• v.27 no.2
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• pp.159-166
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• 2003

For the purpose of obtaining surface-anionized poly(vinyl alcohol) (PVA) hydrogel beads, vinyl acetate(VAc) and methacrylic acid(MMA) were copolymerized by the suspension polymerization technique and followed by the saponification. It was confirmed by $^1$H-NMR that the copolymerized microspheres contained carboxylic acid groups in their surface. poly(VAc-co-MAA) microspheres were completely saponified in the heterogeneous system. The saponification reaction was laster than that of PVAc microspheres. We observed the swelling property of saponified PVA microspheres treated in the acidic solution and in the alkaline solution successively. Saponified microspheres shrank in acidic solution and swelled in alkaline solution respectively, which was reversible. from the result, saponified microspheres were highly water-absorbing hydrogel beads and were certified -COOH group at their surface by $^1$H-NMR and FT-IR.

• Journal of the Korean Society of Clothing and Textiles
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• v.42 no.2
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• pp.269-277
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• 2018

This study extracted Artemisia capillaris Thunberg with distilled water and ethanol to investigate its antioxidant effect. We then investigated the possibility of producing nanofibers by an electrospinning process by adding the extracts to polyvinyl alcohol (PVA). The electrospinning method used a PVA concentration of 12wt.%, an applied voltage of 10kV, and a tip-to-collector distance of 15cm. Total polyphenol and total flavonoid contents were measured to verify the antioxidant activity of Artemisia capillaris Thunberg extracts (ACEs). The total polyphenol content of the distilled water extract and the ethanol extract were measured as 218.47 and 271.26mg/g, respectively, and the total flavonoid content of the distilled water extract and the ethanol extract were measured as 141.68 and 34.98mg/g, respectively. As the content of the ACEs in the PVA nanofibers increased, the Diameters of the nanofibers and the uniformity of the diameters decreased. The electrospinning process was fabricated in a relatively uniform form without beads, and the diameters of the nanofibers that were produced ranged from 340 to 390nm. The results of FT-IR, XRD and DSC analyses confirmed that the ACEs were well mixed with the PVA molecules and were electrospun.

• Journal of Environmental Science International
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• v.10 no.3
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• pp.233-237
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• 2001

Immobilized nitrifier bead in airlift bioreactor were used to remove high levels of ammonia nitrogen from synthetic wastewater. Polyvinylalcohol(PVA) bead for immmobilization of nitrifier consortium were prepared by PVA-boric acid method by varying concentration of PVA and nitrifier consortium. By determining viscosity, sphercity and tailing, the characteristics of prepared beads were investigated and the continous immobilization process was developed. Synthetic wastewater containg 25g/$\textrm{m}^3$ of ammonia nitrogen could be treated within 0.5 hour and the highest removal rate of ammonia nitrogen was 934.2g/$\textrm{m}^3{\cdot}$ day.

• Journal of Industrial and Engineering Chemistry
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• v.67
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• pp.326-332
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• 2018

In this study,the result shows that polyvinyl alcohol-sodium alginate (PVA-SA) gel bead crosslinked with sodium sulfate are better among the different methods by comparing the relative mechanical strength, mechanical strength swelling and expansion coefficient of beads in water. Subsequently, anammox biomass entrapment by PVA-SA gel was introduced into continuous stirred tank reactor (CSTR). After 24 operation days, the nitrogen removal efficiency achieved 60%, while the nitrogen loading rate (NLR) was $0.14kgN/m^3/d$ and the experiment data indicated that PVA-SA gel bead crosslinked with sodium sulfate can be used to initiate anammox process. Furthermore, it is an alternative for culturing anammox in a long-term operation.

• Journal of Marine Bioscience and Biotechnology
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• v.1 no.2
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• pp.91-97
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• 2006

For efficient removal of nitrogenous compounds produced in recirculating aquaculture system, the N removal characteristics of immobilized mixed microorganisms were investigated at various mixing ratios of photosynthetic bacteria (PSB) immobilized in PVA beads or CTA cubes and ammonium utilizing bacteria (AUB) immobilized in PVA beads. On the optimal medium of AUB, the maxium gas production rate was obtained at the mixing ratio of 10:40 (PSB:AUB), and the gas production rate increased as the portion of AUB beads in the mixed beads increased. When the mixing ratios of PSB:AUB beads were 50:0, 40:10, 25:25 and 10:40, the final pHs were measured to be 6.29, 6.01, 5.69 and 5.13, respectively. On the optimal medium of PSB, however, the volume and the rate of gas production decreased remarkably as the portion of AUB beads in the mixed beads increased. The final pH was measured to be approximately 6.5, regardless of the mixing ratio. In the reactions by the mixed culture of PSB cubes and AUB beads, all results showed the same tendency of those by the mixed culture of PSB and AUB beads, but the volume and the rate of gas production decreased remarkably, even with 0.2ml of gas production in control. From all the results, the use of mixed PSB and AUB beads at the ratio of 10:40 seems to be efficient to remove nitrogenous compounds in wastewater from recirculating aquaculture system.

• Journal of the Korean Wood Science and Technology
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• v.42 no.2
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• pp.119-129
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• 2014

This work undertook to prepare nanofibers of cellulose nanofibrils (CNF)/polyvinyl alcohol (PVA) composite by electrospinning, and characterize the electrospun composite nanofibers. Different contents of CNFs isolated from hardwood bleached kraft pulp (HW-BKP) by 2,2,6,6-tetramethylpiperidine-1-oxy radical (TEMPO)-mediated oxidation were suspended in aqueous polyvinyl alcohol (PVA) solution, and then electrospun into CNF/PVA composite nanofibers. The morphology and dimension of CNFs were characterized by transmission electron microscopy (TEM), which revealed that CNFs were fibrillated form with the diameter of about $7.07{\pm}0.99$ nm. Morphology of the electrospun nanofiber observed by field-emission scanning electron microscopy (FE-SEM) showed that uniform CNF/PVA composite nanofibers were manufactured at 1~3% CNF contents while many beads were observed at 5% CNF level. Both the viscosity of CNF/PVA solution and diameter of the electrospun nanofiber decreased with an increase in CNF content. The diameter and its distribution of the electrospun nanofibers helped explain the differences observed in their morphology. These results show that the electrospinning method was successful in preparing uniform CNF/PVA nanofibers, indicating a great potential for manufacturing consistent and reliable cellulose-based nanofibrils for scaffolds in future applications.

• 한국생물공학회:학술대회논문집
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• 2000.11a
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• pp.329-331
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• 2000

A marine bacterium, Pseudomonas aeruginosa BYK-2 KCTC 18012P was immobilized in modified polyvinyl alcohol for the continuous production of rhamnolipids. The stability of rhamnolipids production, the mechanical strength of beads and the scanning electron microscope of immobilized cell were determined in a repeated batch culture. The rhamnolipids production was maintained $80{\sim}90%$ stability of initial production, and the mechanical strength also was stable during the repeated batch culture more than 14 cycles. In the case of SEM studies, the internal distribution pattern of the cell entrapped in modified PVA beads was observed. On the basis of optimal conditions, the continuous culture was investigated in 1.8L air lift bioreactor. The result suggested 0.1g/h rhamnolipids was obtained from 1%(v/v) fish oil continuously in conditions of 1.2L working volume, 0.5vvm and 20ml/h flow rate.

• Environmental Engineering Research
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• v.24 no.3
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• pp.376-381
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• 2019

In this study, a poly(vinyl) alcohol/sodium alginate (PVA/SA) mixture was used to fabricate core-shell structured gel beads for autotrophic single-stage nitrogen removal (ASNR) using aerobic and anaerobic ammonia-oxidizing bacteria (AAOB and AnAOB, respectively). For stable ASNR process, the mechanical strength and oxygen penetration depth of the shell layer entrapping the AAOB are critical properties. The shell layer was constructed by an interfacial gelling reaction yielding thickness in the range of 2.01-3.63 mm, and a high PVA concentration of 12.5% resulted in the best mechanical strength of the shell layer. It was found that oxygen penetrated the shell layer at different depths depending on the PVA concentration, oxygen concentration in the bulk phase, and free ammonia concentration. The oxygen penetration depth was around $1,000{\mu}m$ when 8.0 mg/L dissolved oxygen was supplied from the bulk phase. This study reveals that the shell layer effectively protects the AnAOB from oxygen inhibition under the aerobic conditions because of the respiratory activity of the AAOB.

• KSBB Journal
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• v.10 no.3
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• pp.241-248
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• 1995

For the treatment of poorly biodegradable polyvinyl alcohol(PVA) in dye-processing wastewater, immobilized microbial beads were prepared by uslng agar-acrylamide method. PVA removal efficiency for the synthetic wastewater was 85% at the PVA volume loading rate of $3.1g/\ell$.day. In case of real desizing wastewater, PVA removal efficiency was 81.3% at the PVA volume loading rate of $3.25g/\ell$.day. In observation of cross section of immobilized bead passed 5 months with diameter of 2.4mm, the growth of cell was limited by the resistance of substrate and oxygen transfer for the inners region of more than 48% of bead radius from the surface. It was estimated that 70% of total removed PVA was degraded by the immobilized cells in the continuous immobilized reactor. Substrate utilization rate in the suspended reactor was decreased with increasing dilution rates above 0.083 hr-1, but that in the immobilized reactor was increased with increasing dilution rates up to 0.125hr-1. The substrate removal efficiency of immobilized reactor was much superior to that of suspended reactor with increasing dilution rates. Saturation constant of substrate utilization rate equation, Ks was $6.6 g PVA/\ell$, and maximum specific substrate utilization. k was 0.175g PVA/g cell.hr