Polyvinyl Alcohol Beads Research Articles

Polymer-Based Metal-Organic Framework Composite Beads: Optimization for Methyl Orange Adsorption

Metal-Organic Frameworks (MOFs) have gained traction as an adsorbent due to their high surface area and porosity. MIL-101(Fe), a MOF that has been used for removing dyes in water by adsorption, faces the problem of being inseparable from water after use. To get around this difficulty, MIL-101(Fe) was incorporated into composite beads consisting of polymers Chitosan (CS), and Polyvinyl Alcohol (PVA) crosslinked with Glutaraldehyde (GLA) to remove Methyl Orange (MO) from water. The resulting CS/MIL-101(Fe)/PVA beads were optimized based on the right combination of synthesis parameters that gave the highest percent MO removal. It was found that the maximum MO removal can be achieved by beads made of 1500 ppm MIL-101(Fe), 2.0 % PVA, crosslinked in 2.5% GLA. Using FTIR analysis and SEM imaging, the beads exhibited favorable properties for adsorption, as shown by their coarse and porous structure. The beads proved viable for adsorption, exhibiting a percent MO removal of 69.62% upon validation.

Electrochemical reduction of nitrate in the presence of silver-coated polyvinyl alcohol beads as a spatially suspended catalyst

Increasing concentrations of nitrate in water sources are a growing problem, requiring the development of techniques to remove them. In the present study, nitrate removal was investigated in undivided and divided electrolytic cells in the absence and presence of Ag0-coated polyvinyl alcohol (Ag-PVA) beads. In the undivided cell with graphite anode and iron cathode, nitrate removal was limited to 13 and 28 % in the absence and presence of 6.67 mM Ag-PVA, respectively, with negligible Total Nitrogen (TN) removal in both case. In a divided cell, nitrate and TN removal were 70 and 12 %, respectively, in the absence of Ag-PVA, increasing to 85 and 52 %, respectively, in the presence of 6.67 mM Ag-PVA. Nitrate removal in the divided cell in the presence of Ag-PVA using different cathode materials followed an order: Fe > Ti ≈ Cu > SS > Tin-coated Fe (Fe/Sn). The highest conversion to N2 was obtained with a Fe cathode with negligible nitrite formation. Among different concentrations of Ag-PVA, the highest nitrate removal and selectivity for N2 was achieved at 6.67 mM. Increasing the current density to 15 mA/cm2 increased nitrate reduction with improved selectivity for N2. It appears that the intercalation of nascent hydrogen on Ag0 leads to the formation of reductive species that enhance nitrate reduction. Ag-PVA beads could be reused up to 8 times. This study introduces novel, easily recoverable, and highly reusable Ag-PVA beads as a catalyst for the efficient removal of nitrate from water.

Unravelling capability of two-stage thermophilic anaerobic membrane bioreactors for high organic loading wastewater: Effect of support media addition and irreversible fouling

This study investigated the effects of adding polyvinyl alcohol (PVA) beads on the performance of methanogenic reactors and the fouling behavior of a two-stage thermophilic anaerobic membrane bioreactor (ThAnMBR) for treating wastewater at a feed chemical oxygen demand (COD) of 10 g/L. The PVA-added methanogenic reactor exhibited stable operation performance and offered a relatively low volatile fatty acid concentration effluent with a higher COD removal than the system without PVA addition. The predominant microbial communities in both methanogenic reactors were similar and were assigned to the genus Methanosaeta, followed by Clostridia, which was the predominant genus in the hydrolytic reactor. Ultrafiltration in the PVA-added system offered higher effluent quality and lower fouling resistance. The system was able to operate with hydraulically removable fouling, without any chemical cleaning requirements; however, an elevated flux caused the system to suffer from hydraulically irreversible fouling. PVA beads exhibit their structural stability over long-term operation.

Nanobody-based polyvinyl alcohol beads as antifouling adsorbents for selective removal of tumor necrosis factor-α

Highly efficient removal of tumor necrosis factor-α (TNF-α) from plasma by hemoperfusion for autoimmune disease therapy remains a challenge in the clinical field owing to the low adsorption capacity and poor blood compatibility of adsorbents. In this work, a new class of nanobody (Nb)-coupled antifouling polyvinyl alcohol (PVA) beads was constructed as an immunosorbent for the selective removal of TNF-α from plasma. Notably, our immunosorbent exhibited an exceptionally high specific TNF-α adsorption capacity of 416.9 ng/g in human plasma (at a plasma-to-adsorbent ratio of 300). More importantly, the obtained adsorbent beads showed outstanding blood compatibility. In addition, during in vivo experiments, the blood circulation device was constructed to remove TNF-α in rat models, proving that the beads had good removal performance (∼85%/60 min). Furthermore, 95% of the original capacity was retained after 6-month storage, showed strong stability and prolonged storage of PVA-Nb. Above all, the results indicate that the novel PVA-Nb immunosorbent has possible clinical applications for treating autoimmune diseases in the clinic.

Synthesis and performance of bimetallic poly vinyl alcohol beads in electrocatalytic denitrification

Research in the field of nanoscience and nanotechnology has witnessed significant progress in the last few years. The synthesis of nanoparticles and microparticles for the improvement of functionality of several processes has paved ways for innovation into uninvestigated methods of developing these particles. Significance should be given to such mechanisms which enable easy handling and reusability of the formed micro/nanoparticles. In the presented research a unique and novel method for synthesis of such particles immobilized on the surface of poly vinyl alcohol (PVA) beads has been discussed. The use of silver (Ag) and palladium (Pd) as noble metals has been done for coating the PVA beads; to form a bi-metallic catalyst. These beads have been applied in the denitrification process of synthetic nitrate solution, having initial nitrate concentration (NO3 -N) of 20 mg/L, carried out in a divided reactor cell of 120 mL volume, at 35⁰C for 1.5 h. About 75 % removal of nitrate was obtained. Removal of nitrate took place by destruction of nitrate and its subsequent conversion into nitrite, ammonical nitrogen, and nitrogen gas. The usage of Pd-Ag-PVA beads in the work has been unexplored in the past and the current work provides insights to behold application of catalysed electrochemical reactions for denitrification process on a large-scale.

Electrochemical Reduction of Nitrate in the Presence of Silver-Coated Polyvinyl Alcohol Beads as Spatially Suspended Catalyst

Electrochemical Reduction of Nitrate in the Presence of Silver-Coated Polyvinyl Alcohol Beads as Spatially Suspended Catalyst

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.

Novel PVA-Based Microspheres Co-Loaded with Photothermal Transforming Agent and Chemotherapeutic for Colorectal Cancer Treatment.

Background: We previously designed an electrospinning chitosan (CS) nanofiber-based carrier, using polyvinyl alcohol (PVA) as an adjuvant to deliver doxorubicin (DOX) and MoS2 nanosheets for postoperative tumor re-occurrence inhibition. However, owing to that the nanofibrous mat is un-injectable, this composite nanofiber is far from being clinically applicable. Materials and Methods: Via modulating the electrospray parameters, polyvinyl alcohol (PVA) beads string doped with DOX and MoS2 (PVA/MoS2/DOX microspheres) were prepared, which were further crosslinked with glutaraldehyde to obtain the water-stability. Results: Under the 808-nm laser irradiation, MoS2 nanosheets rendered the prepared PVA/MoS2/DOX microspheres an excellent light-to-heat conversion performance with η of 23.2%. Besides, the heat generated by near-infrared laser irradiation can improve the effect of chemotherapy by promoting the release rate of DOX. HT29 cell and tumor-bearing nude mice were used to systematically study the combined tumor treatment efficiency of composite nanospheres. Conclusion: PVA/MoS2/DOX nanospheres have excellent photothermal effect and chemotherapy effect, which can completely suppress the tumor recurrence. Therefore, the PVA/MoS2/DOX nanospheres are anticipated to find potential applications in the treatment of local colorectal cancer.

Reduction of pollution load of tannery effluent by cell immobilization approach using Ochrobactrum intermedium

The purpose of this present study was to reduce the pollution load of the tannery effluent through a cell immobilization approach using chromium tolerant bacteria isolated from tannery sludge. Among various initially isolated bacteria, strain IITR002 exhibited the highest pollution load reduction was characterized as Ochrobactrum intermedium by 16S rDNA sequencing. The bacterium was successfully immobilized with 10 % polyvinyl alcohol (PVA) and 1% sodium alginate (SA) and tannery effluent treatment were carried out using both free and immobilized cells of O. intermedium. Preliminary chemical oxygen demand (COD) reduction studies demonstrated 85 % and 54 % COD reductions by immobilized and free cells, respectively as compared to blank PVA beads (10 % COD). Both free and immobilized cells were able to degrade tannery effluent after 48 h but the reduction of total dissolved solids-TDS (56 %), COD (85 %), biochemical oxygen demand-BOD (68 %), and total chromium-TC (95 %) were higher with immobilized cells. The reduction of pollutants in tannery effluent was established by GC–MS analysis in which degradation of organic pollutants after treating with free and immobilized cells was observed. Phytotoxicity investigation of tannery effluents on Vigna radiata L seed showed that bacterial treatment not only allowed seeds germination but also supported seedling growth. The results from this flask-scale work suggest that immobilized cell methods of bacterial treatment can potentially be applied in tannery effluent treatment to reduce the pollution load as well as phytotoxic effects.

A novel immobilization technique for the development of sustainable anammox gel beads for low nitrogen loadings

This study aimed to develop a sustainable anammox gel beads using sodium alginate (SA) mixed with three different support materials including sodium silicate (SS), polyvinyl alcohol (PVA), and colloidal silica (CS). A detailed characterization and comparison of anammox gel beads were conducted using four lab-scale semi-continuous stirred tank reactors (Semi-CSTRs) and SA–SS beads showed superior durability with better reactor performance. SA–SS (B2) beads showed the minimum reduction effective diameter of 24% in comparison to SA (B1) beads, SA–PVA​ (B3) beads, and SA–CS(B4) beads of 98%, 57%, and 96%, respectively indicating higher integrity of B2 beads. Moreover, R2 reactor containing B2 beads showed the maximum biomass retention after 30 days of operation, relative to the initial mass of 72% compared to R1, R3, and 3%, 44%, and 5%, in R1, R3, and R4, respectively. Total nitrogen removal efficiencies of 8%, 80%, 64%, and 10% were achieved by R1, R2, R3, and R4 reactors, respectively. The diffusion coefficients (De) of ammonium in anammox gel beads was maximum for B2 beads (26.2μm2/s) compared to B1 (18.8μm2/s), B3 (22.4μm2/s), and B4 (13.9μm2/s) beads indicating the enhanced internal mass transfer.

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.

Tillandsia Aeranthos flower‐like magnetic nanostructures confined into polyvinyl alcohol beads

AbstractMagnetic beads composed by polyvinyl alcohol and iron oxides were developed and fully characterized. The materials were not only cross‐linked by a physical treatment but also the magnetic nanoparticles (MNPs) are acting as cross‐linking dots. Interestingly, the analysis of scanning electron micrographs revealed that, in the case of hydrated samples, flower‐like structures (average diameter 6–9 μm) being constituted by MNPs were present, whereas when the beads were dried the MNPs structure changed to porous spheres (average diameter 2–3 μm). Some of the prepared materials were tested to determine their capability to act as water remediation devices, and good removal results were obtained toward both methylene blue (average removal efficiency higher than 80%) and methyl orange (average removal efficiency lower than 30%) adsorption. The experiments performed confirmed that the adsorbent, once the treatment has ended, can be removed off through the simple employment of a permanent magnet.

Quorum Quenching Cell Entrapping Bead by Polyvinyl Alcohol Method for Biofouling Mitigation in Lab-scale MBR

Quorum Quenching (QQ) bacteria such as Rhodococcus sp. BH4 and Pseudomonas putida have excellent anti-biofouling potential as they disrupt Quorum Sensing (QS) system and inhibit biofilm formation on membranes. Cell Entrapping Beads (CEBs) in which the QQ bacteria are immobilized is one of the most effective methods to mitigate membrane biofouling in MBR. The CEBs are very crucial as they mainly protect QQ bacteria from harsh environment of the sludge for better QQ effect and help in physical cleaning of membranes in a submerged MBR. Previously simple sodium alginate (SA) beads were used but it was found that their durability was very low in real wastewater. Polyvinyl Alcohol (PVA) is a better alternative due to its higher durability, chemical stability and low cost. Several brands of PVAs with different polymerization degrees were used here and small amount of SA was added to avoid agglomeration of PVA beads. Concentrations of SA/PVA were varied and different temperature of cross-linking solution also was examined. Then quality of the beads was evaluated on physical and biological aspect. It was found that a PVA of 2,270 polymerization degree with 8% mixed in 1% SA makes the most stable CEBs. A certain brand of SA didn’t prevent agglomeration of CEBs while a specific brand of SA did even at lower concentrations. Temperature of cross-linking solution also was found to have significant effect on internal structure of beads. The quality of CEBs made by the best method found in this research was confirmed through series of tests, i.e. freeze drying, scanning electron microscopy, activity test after immobilization of QQ bacteria in the beads.

PVA entrapped activated sludge beads coated with PAC for bioremediating 4-chlorophenol-bearing wastewater

This study compared the effectiveness of powdered activated carbon (PAC) to adsorb 4-chlorophenol (4-CP) from wastewater via coated onto and homogenised into polyvinyl alcohol (PVA) bead surface. The bioregeneration of spent PAC for repeated uses via entrapment with 4-CP acclimated biomass of activated sludge was also unveiled. Results showed that the maximum capacity of PAC adsorbing 4-CP was 0.2 g 4-CP/g PAC. It was confirmed that the PAC coated onto bead surfaces with biomass entrapment could be used for 8 cycles with removal efficiency ranging from 80-85%. The removal rate of 4-CP was best fitted by the pseudo-first-order reaction kinetic, permitting plausibly projection to upscale for industrial application in treating wastewater containing chlorophenol more effectively.
 Keywords— Activated sludge; adsorption; bioregeneration; PAC coated beads; biomass entrapment; 4-chlorophenol

STUDY ON POLYVINYL ALCOHOL GEL BEADS AS BIOCARRIER APPLIED IN ANAEROBIC SLUDGE IMMOBILIZATION IN THE UASB REACTOR

In this study, the biocarrier was made of 8 % (w/v) polyvinyl alcohol (PVA) solution dropped into saturated solution of boric acid (6 %, w/v), then immersed for 2 hours to form PVA-boric bead. In order to maintain the crosslinked beads, it is subsequently immersed in 1M sodium sulfate solution for 1 hour. PVA gel beads have the diameter of 3.5 - 5.0 mm, a specific gravity of 1.03 - 1.08 g/cm3, high mechanical strength and good elasticity. The surface and internal structure particle were observed under a scanning electron microscope (SEM). The application of PVA beads in microbial immobilization was initially examined in three UASB reactors treating rubber wastewater with sludge and PVA beads ratios of 1/1, 2/1, 3/1 (v/v), respectively. Promising result of bio-immobilization was achieved, at ratio of 1/1, the SMA of PVA beads was 0.133 g COD/gVSS/day, corresponding to 17 % of the suspended sludge’s value in the same reactor and the attached biomass was 0.936 g VSS/g dried PVA bead after 90 days.

Accurate prediction of shape and size of polyvinyl alcohol beads produced by extrusion dripping

Beads are one of the particulate delivery systems used to achieve protection and/or controlled delivery of different active ingredients or microorganisms. Polyvinyl alcohol is a non-toxic and biodegradable polymer and possesses extensive applications as a biomaterial. In the present work, two different strategies were applied for the prediction of shape and size of polyvinyl alcohol beads. These beads were obtained by extrusion dripping of a boric acid–polyvinyl alcohol aqueous solution into a basic aqueous gelling bath. The shapes and sizes of immature, mature and dry beads were determined using optical microscopy. Two different strategies included statistical and fluid dynamical (mechanistic) models to fit the experimental data. The shape of immature and mature beads was found to be dependent on the viscosity of the dripping solution for the former and the maturation time for the latter. The shape of dry beads was found to be mainly dependent on the particle contraction in the drying process. The size of mature and dried beads was correctly predicted from the operating conditions by means of a statistically developed model and from the dripping solution properties by means of a fluid dynamical approach. The optimal conditions for minimal dried bead size were calculated. The obtained mathematical models allow reduction in the amount of resources and time taken in the initial stages of the development of a novel encapsulated formulation. The mechanistic model may be applied to other polymeric systems once the corresponding parameters have been determined during proof-of-concept experiments.

Treatment efficiency and sludge characteristics in conventional and suspended PVA gel beads activated sludge treating phenol containing wastewater

Protozoa play a significant role in activated sludge systems, since they graze on dispersed bacteria, supporting a healthy food web in the activated sludge artificial ecosystem. However, operational parameters and influent properties are the most important factors affecting the composition of activated sludge microfauna. The objective of this study was the assessment of the treatment efficiency and the protozoan populations in activated sludge systems with and without the addition of polyvinyl alcohol (PVA) gel beads while treating wastewater in the presence of phenol. Six activated sludge reactors - 3 of them supplied with PVA gel beads –were used for the treatment of synthetic wastewater influent containing phenol at concentrations up to 10 mg/L. During the treatment of synthetic wastewater, dominance of the sessile species was observed mainly in the reactors supplied with PVA beads. Physicochemical analyses of the effluent indicated good efficiency of reactors supplied with PVA beads in removing nutrients and organic load. Introduction of phenol in the influent at a concentration of 5 mg/L did not affect significantly the operation of the reactors and the composition and abundance of activated sludge microfauna, while a high phenol removal rate was observed. The increase of influent phenol concentration to 10 mg/L resulted to the formation of foam on the surface of the reactors and the presence of Zoogleasp, while an increase was observed in the abundance of crawling species in activated sludge and PVA supplied reactors respectively.

Immobilization of laccase onto porous polyvinyl alcohol/halloysite hybrid beads for dye removal.

Laccase was immobilized in polyvinyl alcohol beads containing halloysite nanotubes (PVA/HNTs) to improve the stability and reusability of enzyme. The porous structure of PVA/HNTs beads facilitates the entrapment of enzyme and prevents the leaching of immobilized laccase as well. Halloysite nanotubes act as bridge to connect the adjacent pores, facilitating the electron transfer and enhancing the mechanical properties. PVA/HNTs beads have high laccase immobilization capacity (237.02 mg/g) and activity recovery yield (79.15%), indicating it can be used as potential support for laccase immobilization. Compared with free laccase, the immobilized laccase on hybrid beads exhibits enhanced pH tolerance (even at pH 8.0), good thermal stability (57.5% of the initial activity can be maintained at 75 °C), and excellent storage stability (81.17% of enzyme activity could be retained after storage at 4 °C for 5 weeks compared with that for free enzyme of 60%). Also, the removal efficiency for reactive blue can reach as high as 93.41% in the presence of redox mediator 2,2-azinobis(3-ethylbenzthiazoline-6-sulfonate), in which adsorption and degradation exist simultaneously. The remarkable pH tolerance, thermal and storage stability, and reuse ability imply potential application of porous PVA/HNTs immobilized enzyme in environmental fields.

Abstract No. 450 - Visibility of gadolinium enhancement adjacent to radiopaque polyvinyl alcohol beads in a liver phantom

Abstract No. 450 - Visibility of gadolinium enhancement adjacent to radiopaque polyvinyl alcohol beads in a liver phantom

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).