Polyvinyl Alcohol Concentration Research Articles

Engineering and slow‐release properties of lignin‐based double‐layer coated fertilizer

AbstractChemical fertilizer has become a necessary condition for increasing the production and income of agricultural products in modern agriculture. However, excessive fertilization and fertilizer leakage could cause environmental pollution. To improve the utilization rate of agricultural fertilizers and reduce environmental pollution, the degradability of slow‐release fertilizers (SRFs) has become a research hotspot. In this work, a double‐layer coating material of slow‐release fertilizer was fabricated using low‐cost polyvinyl alcohol (PVA) and methylcellulose (MC) as the inner coating materials, and attapulgite was doped into super absorbent polymer poly acrylic acid (PAA) and polyacrylamide (PAM) grafted natural biodegradable lignin as the outer coating materials. We investigated the chemical structures, mechanical properties, hydrophilic properties, and water retention properties of the double‐layer coating material coated on the surface of urea particles, and optimized the synthesis parameters to obtain the best water absorption properties of the outer layer water absorbent. Simultaneously, urea release was evaluated in dissolution experiments. The results show that at the PVA concentration of 5 wt% and the MC addition amount of 2.0 g, the performance indicators of the inner coating liquid were better than other contents. At the same time, more urea molecules (>30 days) were released in the single‐layer and double‐coated fertilizers, and the cumulative release rates of urea molecules were 92.36% and 85.10%, respectively. Therefore, this work provides research ideas for the preparation of double‐coated slow‐release fertilizers, which can improve soil water retention and fertilizer utilization.

Development of bio-based adhesive using tannery shaving dust: Process optimization using statistical and artificial intelligence techniques

The present work was aimed to develop an optimized process for producing a bio-based adhesive material using tannery chrome shaving dust using statistical and artificial intelligence techniques. The collagen was extracted from the waste dust of tannery shavings using alkali hydrolysis and was used to produce the bio-adhesive. To attain a global optimizing solution, the experimental data were subject to ANN analysis for acquiring the maximized peel strength of bio-based adhesive. The optimal conditions were found to be working temperature 65 °C, concentration of polyvinyl alcohol 3.2 % and concentration of glycerol 4.2 %. The experimental peel strength of 12.5 N/mm was obtained at optimal conditions, thus the predicted conditions fitted well-agreement with ANN the model prediction. The produced bio-adhesive was characterized using FTIR and TGA analyses. In addition, the acquired bio-based adhesive was characterized to be well-comparable with commercially available chemical-based adhesives.

Polyvinyl alcohol improves resistance of epoxy-treated bovine pericardium to calcification in vitro

Background. Around half of bioprosthetic heart valves become dysfunctional 15 years postimplantation because of structural valve deterioration notable for the degradation and calcification of the prosthetic tissue. Protection of bioprosthetic heart valves from structural valve deterioration requires innovative materials, science approaches including enveloping of the bioprosthetic heart valves into the polymer sheath.Aim. To develop a polyvinyl alcohol sheath for improving resistance of bioprosthetic heart valves to calcification.Material and methods. Bovine pericardium fixed with ethylene glycol diglycidyl ether was incubated with distinct concentrations of polyvinyl alcohol (5, 10, 12, or 15%) with the following freezing and thawing to perform cryotropic gelation. Surface and structure of unmodified and polyvinyl alcohol-modified bovine pericardium have been investigated by fluorescence microscopy and scanning electron microscopy, whilst tensile testing was carried out by uniaxial tension test. Haemocompatibility was assessed through the measurements of haemolysis and platelet aggregation/adhesion upon the contact of donor blood with the samples. Resistance to calcification was tested by incubation of the samples in calcium and phosphate supersaturated (10 µmol/L) cell culture medium for 3 and 6 weeks with the following tissue lysis and colorimetric measurement of Ca2+ ions.Results. Using cryotropic gelation, we obtained a polyvinyl alcohol-coated and filled bovine pericardium matrix. Out of all polyvinyl alcohol concentrations, 12% polyvinyl alcohol solution sealed pores and hollows within the bovine pericardium (what was not achieved using 5% or 10% polyvinyl alcohol solutions) and demonstrated the best processability as compared to 15% polyvinyl alcohol solution. Cryotropic gelation did not deteriorate durability, elasticity, or haemocompatibility of bovine pericardium. After 3 and 6 weeks of the incubation in calcium-supersaturated solution, polyvinyl alcoholmodified bovine pericardium contained 5- and 3-fold reduced amount of calcium compared to unmodified bovine pericardium.Conclusions. Enveloping of bovine pericardium into polyvinyl alcohol increases its calcification resistance, retains its tensile properties and haemocompatibility, and can be considered as a promising approach for the modification of bovine pericardium during the manufacturing of bioprosthetic heart valves.

Comparison of the performances of different drying enhancers for waterborne polyvinyl alcohol films

AbstractWaterborne polyvinyl alcohol (PVA) films show lower environmental impact but render high residual solvent on account of hydrophilicity of PVA and low volatility of water. Plasticizers have shown high potential to act as drying enhancers in some recent studies. Plasticizers triphenyl phosphate (TPP) and polyethylene glycol (PEG400) with their favorable chemical structures and relatively low molar masses are promising options. Their performances in drying waterborne PVA films are compared with the plasticizers used in earlier works, at different initial wet film thicknesses, polymer contents, enhancer contents, and enhancer molar masses. Films were solvent casted by drying PVA‐water solutions in a substrate. TPP causes maximum lowering of the residual solvent and does this at high drying rate corresponding to low initial wet film thickness and PVA content. The least value of residual solvent is 0.20% at optimum TPP loading. The next best residual solvent results of 0.21% and 0.59% are, respectively, exhibited by PEG400 and PEG6000, but at low drying rate for high wet film thickness, for both the enhancers; however, at high drying rate for low wet film thickness anomalous skinning increased the residual solvent. At 0.51%, Capstone FS‐63 also gives good results and at high drying rate. Their relative performances are correlated to the viscosity of cast solutions, glass transition temperature of films (DSC), and chemical structures of the polymer and enhancers. TPP thus proved to be most effective. SEM showed dense films and disappearance of defects with optimum loading of TPP, and TGA/DTG showed thermally stable coatings. In spite of the higher cost of TPP it can have useful specialized applications that exploit its excellent flame retardance features.

Interaction of Pulsed Electric Modified Elephant Foot Yam (Amorphophallus paeoniifolius) Starch and Polyvinyl Alcohol to Enhance the Mechanical and Barrier Properties of Film

AbstractElephant foot yam starch (EFYS) is modified by the pulsed electric field (PEF, 4–16 kV cm−1) and used for the development of the biodegradable film. The increase in PEF intensity increases the oil (1.66–2.22 g g−1) and water absorption capacity (1.79–2.08 g g−1) and reduces the gelatinization temperature (Tg) and enthalpy (ΔΗ). Storage modulus (G') is found to be higher than loss modulus (G"), indicating strong gel characteristics of EFYS. Electrical intensity affects the degree of crystallinity and disrupts the granule's surface. Film prepared with PEF‐modified EFYS and different concentrations of polyvinyl alcohol (PVA, 25%, 50%, and 90%) shows that the increase in the concentration of PVA results in increased thickness, tensile strength, % elongation, water vapor permeability, water vapor transmission rate, seal strength, and solubility. PEF modification increases the film's mechanical and moisture barrier properties. The study proves that PEF changes the physico‐functional and structural characteristics of EFYS, making it suitable to be used in the biodegradable film.

Effect of polyvinyl alcohol on the CO2 uptake of carbonated steel slag

Recycled by-products that capture CO2 are seen as a potential solution to reduce global greenhouse gas emissions produced by the construction industry. Steel slag has been used as an alternative binder to cement in the last decade and was most recently investigated as a CO2 sequestration material. However, the production of construction materials from steel slag is accompanied by the release of CO2. In order to achieve carbon-negative or -neutral production, it is necessary to increase the carbon capture capacity of steel slag. In this study, experiments were carried out to determine the degree of carbon sequestration by steel slag when treated with an environmentally friendly solution of polyvinyl alcohol (PVA). The modification of steel slag with PVA treatment before and after carbonation was investigated using the mass gain method, X-ray diffraction, thermogravimetric analysis (TG), Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). The mass gain method showed that after carbonation, steel slag with a PVA content of 1.0% showed a 7% increased uptake of CO2 compared to 4% for the untreated steel slag. Analysis of the endothermic peaks and weight loss from TG thermograms demonstrates an increase in CaCO3 content by PVA treatment. According to the calculation of the mass loss from the decomposition of CaCO3, PVA contributes to an increase in CO2 absorption from 2.8 to 5.9% compared to untreated steel slag. The results reveal that carbon dioxide uptake by steel slag in the presence of PVA was mainly due to the increased formation of calcium carbonate, the reaction result between CO2, CaO, and Ca(OH)2. The results found by SEM show that after the carbonation PVA formed a porous structure in the pore space of the steel slag, covered its particles with a thin film, and formed a structure of polymer-bridge bound particles. The use of PVA as an activator of the process of CO2 uptake with the formation of carbonates and a stable microstructure offers prospects for processing steel slag into a green non-structure component.

Study on modified SA-H3BO3 immobilization microorganism method for wastewater treatment in seawater recirculating aquaculture system

The sodium alginate-H3BO3 (SA-H3BO3) is traditionally used as bioremediation method for wastewater treatment in recirculating aquaculture system. Even though this method has many advantages (e.g., high cell loading) for immobilization, the remove of ammonium is not very effective. In this study, a modified method was built by adding polyvinyl alcohol and activated carbon into SA solution, and then crosslinked with saturated H3BO3–CaCl2 solution for creating new beads. Moreover, response surface methodology was utilized for optimizing the immobilization based on Box-Behnken design. The removal rate of ammonium in 96 h was taken as the primary performance criterion to characterize the biological activity of immobilized microorganisms (i.e., Chloyella pyrenoidosa, Spirulina platensis, Nitrifying bacteria, and Photosynthetic bacteria). Based on the results, the optimal parameter of immobilization as follows: the concentration of SA was 1.46%, the concentration of polyvinyl alcohol was 0.23%, the concentration of activated carbon was 0.11%, the crosslinking time was 29.33 h, and the pH was 6.6.

Preparation and Study of Polyvinyl Alcohol Gel Structures with Acrylamide and 2-Acrylamido-2-methyl-1-propanesulfonic Acid for Application in Saline Oil Reservoirs for Profile Modification.

Polymer gels can be effectively applied to plug fractured reservoirs and carbonate cave strata. Herein, polyvinyl alcohol (PVA), acrylamide, and 2-acrylamido-2-methyl-1-propanesulfonic acid (AMPS) were used as raw materials to prepare interpenetrating three-dimensional network polymer gels using formation saltwater in the Tahe oilfield (Tarim Basin, NW China) as a solvent. The effect of AMPS concentration on the gelation properties of PVA in high-temperature formation saltwater was analyzed. Further, the effect of PVA concentration on the strength and viscoelastic properties of polymer gel was studied. The polymer gel could retain stable continuous entanglement at 130 °C and exhibited satisfactory thermal stability. Continuous step oscillation frequency tests showed that it exhibited an excellent self-healing performance. Scanning electron microscopy images of the simulated core by gel plugging showed that the polymer gel could firmly fill the porous media, indicating that the polymer gel exhibits excellent application prospects in oil and gas reservoirs under high-temperature and high-salinity conditions.

Magnesium phosphate cement for powder-based 3D concrete printing: Systematic evaluation and optimization of printability and printing quality

With the advantages of fast hardening, high early strength, excellent bonding strength and room temperature curing, magnesium phosphate cement (MPC) is highly preferable for powder-based 3D concrete printing. In this paper, a systematic approach via comprehending parametric analysis, visualizing techniques (SEM, XRD and X-Ray CT) and mechanical testing is developed to evaluate and optimize printability and printing quality of powder-based 3D MPC printing. The test printing results show that appropriately mapped proportions of ingredients will orient the specific properties towards the target objectives through navigating different combinations of proportions comprehensively. Specifically, 1,2-propylene glycol is able to significantly increase the viscosity of the binder, and Surfynol 465 can substantially reduce the surface tension of the binder. 25 wt% quartz sand can remarkably improve spreadability and surface flatness of the powder bed. In addition, the penetration and diffusion of the binder in the powder bed is effectively controlled by appropriate content of polyvinyl alcohol (PVA) due to the properties of high viscosity and good film-forming, thus remarkably improves printing accuracy. The compactness and hydration degree of the powder-based 3D printed MPC are optimized by 5 wt% PVA (MPC5) with the total porosity reduced by 2.86% compared to that of MPC0 (without PVA). High printing precision of the printed complex geological canyon river model indicates that MPC with appropriate contents of modulators, such as 1,2-propylene glycol and Surfynol 465 for binder and PVA and quartz sand for base powder, is desirable powder-based 3D printable material.

Filtration Capacity and Radiation Cooling of Cellulose Aerogel Derived from Natural Regenerated Cellulose Fibers

ABSTRACT Natural cellulosic materials are attractive biopolymers for their naturally abundant source, mechanical toughness, bioactivity, etc. However, porosity and flexibility remain challenges for the preparation of aerogels from natural cellulose. To maintain the characteristics of cellulose aerogels possessing the toughness of fibers and high porosity of aerogels, cellulose aerogels with three-dimensional void structures and high compressive resilience were prepared by mixing cellulose fiber suspension and polyvinyl alcohol (PVA). The PM 2.5 removal rate and thermal conductivity of cellulose aerogel reached 92.4% and 0.028 W/mK, respectively, when a PVA content of 0.7% was added, and the radiation cooling temperature was about 10.0°C lower than that of PE foam. The three-dimensional void structure and surface morphology of the cellulose aerogels were investigated by scanning electron microscopy (SEM). The cellulose aerogel porosity and pore size distribution were evaluated by a mercury intrusion meter. The crystal structure of cellulose was analyzed by X-ray diffraction (XRD). UV-Vis-NIR spectroscopy was used to investigate the infrared reflectance of cellulose aerogels. Then the air purification efficiency and radiation cooling effect of porous cellulose aerogels were evaluated in a homemade device, respectively.

Kinetics of polyvinyl butyral (PVB) synthesis reaction catalyzed by deep eutectic solvent

AbstractIn this work, the kinetics of the polyvinyl butyral (PVB) synthesis reaction catalyzed by the deep eutectic solvents (DESs) at the low‐temperature stage was studied to control the particle size of PVB resin and optimize its synthesis process. The effects of stirring speed, the concentration of polyvinyl alcohol (PVA), catalyst dosage, and temperature on the synthesis reaction of PVB were investigated. The data obtained from kinetic experiments at 283.15–298.15 K were fitted with the shrinking core models, and the results showed that the model controlled by internal diffusion fitted well with the experimental data. The internal diffusion coefficient, DA, of n‐butanal in the product layer was further calculated by the obtained model parameters, and it was applied to predict the synthesis reaction of PVB at different concentrations of n‐butanal. The results indicated that the shrinking core model controlled by internal diffusion is suitable to describe the kinetics of the PVB synthesis reaction. DES played a dual role in catalysis and dispersion in the synthesis of PVB, and it was a green catalyst with good potential for PVB industrial applications.

PVA 섬유와 아스팔트 혼합물의 혼화성 및 성능에 관한 연구

In this research, the miscibility of polyvinyl alcohol (PVA) fiber and asphalt under high temperature was explored for improving the performances of PVA/asphalt mixture. Our research shows that the PVA fiber can maintain its properties after heating at 130℃, which lays a foundation for the mixing of PVA fiber with asphalt. According to this, PVA fibers have been uniformly dispersed in asphalt by an extrusion mixing method at 130℃. With the addition of PVA fiber, the viscosity, shear strength, complex modulus and rutting factor of the asphalt at high temperature. Besides, the cumulative strain and non-recoverable creep compliance of the PVA/asphalt mixture decreased with the increase of PVA content, which means the PVA/asphalt mixture had a good recovery ability at high temperature. This research provides a basis for the research on miscibility and performance of PVA/asphalt mixture.

Additively-Manufactured High-Concentration Nanocellulose Composites: Structure and Mechanical Properties.

Additive manufacturing technology (AMT) has transformed polymer composites' manufacturing process with its exceptional ability to construct complex products with unique materials, functions, and structures. Besides limiting studies of manufacturing arbitrarily shaped composites using AMT, printed structures with a high concentration of nanocellulose face adhesion issues upon drying, resulting in shape fidelity issues and low mechanical strength. This research demonstrates an economical approach to printing a high-concentration (25.46 wt%) nanocellulose (NC) layer-wise pattern to fabricate structures. Two different composites are fabricated: (1) 3D-printed pure and high-concentration (10, 15, and 20 wt%) polyvinyl-alcohol (PVA)-blended NC structures followed by freeze-drying and impregnation of Epofix resin by varying hardener contents; (2) 3D-printed PVA-blended NC green composites dried at cleanroom conditions (Relative humidity 45%; Temperature 25 °C). Different contents (10, 15, and 20 wt%) of PVA as a crosslinker were blended with NC to assist the printed layers' adhesions. An optimum PVA content of 15 wt% and an Epofix resin with 4 wt% hardener cases showed the highest bending strength of 55.41 ± 3.63 MPa and elastic modulus of 4.25 ± 0.37 GPa. In contrast, the 15 wt% PVA-blended NC cleanroom-dried green composites without resin infusion showed bending strength and elastic modulus of 94.78 ± 3.18 MPa and 9.00 ± 0.27 GPa, reflecting high interface adhesions as confirmed by scanning electron microscope. This study demonstrated that AMT-based nanocellulose composites could be scaled up for commercial use.

Development of Sustainable Hydrophilic Azadirachta indica Loaded PVA Nanomembranes for Cosmetic Facemask Applications

Nanofiber-based facial masks have attracted the attention of modern cosmetic applications due to their controlled drug release, biocompatibility, and better efficiency. In this work, Azadirachta indica extract (AI) incorporated electrospun polyvinyl alcohol (PVA) nanofiber membrane was prepared to obtain a sustainable and hydrophilic facial mask. The electrospun AI incorporated PVA nanofiber membranes were characterized by scanning electron microscope, Ultraviolet-visible spectroscopy (UV-Vis) drug release, water absorption analysis, 2,2-diphenyl-1-picrylhydrazyl (DPPH) scavenging, and antibacterial activity (qualitative and quantitative) at different PVA and AI concentrations. The optimized nanofiber of 376 ± 75 nm diameter was obtained at 8 wt/wt% PVA concentration and 100% AI extract. The AI nanoparticles of size range 50~250 nm in the extract were examined through a zeta sizer. The water absorption rate of ~660% and 17.24° water contact angle shows good hydrophilic nature and water absorbency of the nanofiber membrane. The UV-Vis also analyzed fast drug release of >70% in 5 min. The prepared membrane also exhibits 99.9% antibacterial activity against Staphylococcus aureus and has 79% antioxidant activity. Moreover, the membrane also had good mechanical properties (tensile strength 1.67 N, elongation 48%) and breathability (air permeability 15.24 mm/s). AI-incorporated nanofiber membrane can effectively be used for facial mask application.

Voriconazole Eye Drops: Enhanced Solubility and Stability through Ternary Voriconazole/Sulfobutyl Ether β-Cyclodextrin/Polyvinyl Alcohol Complexes.

Voriconazole (VCZ) is a broad-spectrum antifungal agent used to treat ocular fungal keratitis. However, VCZ has low aqueous solubility and chemical instability in aqueous solutions. This study aimed to develop VCZ eye drop formulations using cyclodextrin (CD) and water-soluble polymers, forming CD complex aggregates to improve the aqueous solubility and chemical stability of VCZ. The VCZ solubility was greatly enhanced using sulfobutyl ether β-cyclodextrin (SBEβCD). The addition of polyvinyl alcohol (PVA) showed a synergistic effect on VCZ/SBEβCD solubilization and a stabilization effect on the VCZ/SBEβCD complex. The formation of binary VCZ/SBEβCD and ternary VCZ/SBEβCD/PVA complexes was confirmed by spectroscopic techniques and in silico studies. The 0.5% w/v VCZ eye drop formulations were developed consisting of 6% w/v SBEβCD and different types and concentrations of PVA. The VCZ/SBEβCD systems containing high-molecular-weight PVA prepared under freeze-thaw conditions (PVA-H hydrogel) provided high mucoadhesion, sustained release, good ex vivo permeability through the porcine cornea and no sign of irritation. Additionally, PVA-H hydrogel was effective against the filamentous fungi tested. The stability study revealed that our VCZ eye drops provide a shelf-life of more than 2.5 years at room temperature, while a shelf-life of only 3.5 months was observed for the extemporaneous Vfend® eye drops.

Flow rheology of light foams generated from aqueous solutions of polyvinyl alcohol

Recent studies have shown that foam-assisted application of additives into a wet web has advantages over the conventional way of adding the chemicals into the pulp suspension before forming, e.g., increased mechanical retention as well as high dosage giving increased wet strength without impairing the sheet uniformity. To engineer processes utilizing this new technology, the complex flow behavior of applied foams must be quantified. At the minimum, the foam viscosity and the slip velocity at the solid surfaces need to be known to build practical models that can be used in analyzing and upscaling unit processes of the foam-assisted application. In this study, the rheological behavior was quantified for foams having polyvinyl alcohol (PVOH), a widely used strength additive chemical, as the surfactant. The foam density was varied between 100 g/L and 300 g/L, and the concentration of the PVOH solution was varied between 0.5% and 6.0% (w/w). The foams were generated with a commercial foam generator, and the rheological properties of the foams were measured by using a horizontal pipe bank. At the outlet from the generator, the volumetric flow rate, the absolute pressure, and the bubble size distribution of the foam were measured. In the measurement pipe section, the viscous pressure gradient and the slip velocity were measured, after which the foam was discharged to ambient air pressure. The viscosity and the dynamic surface tension of the PVOH solutions were quantified with commercial laboratory devices. In the viscosity analysis, the apparent shear rate was calculated from the volumetric flow rate, and the resulting apparent viscosity was translated to real material viscosity data by applying the Weissenberg-Rabinowitsch correction. The results indicated that PVOH foams can be described with high accuracy as shear-thinning power-law fluids where the detailed behavior depends on the foam density and the PVOH concentration. Slip flow, as usual, increased with increasing wall shear stress, but it was also dependent on the PVOH concentration, the air content, and the bubble size. For both the foam viscosity and the slip flow, a correlation was found that described the quantitative behavior of all the studied foams with good accuracy.

Poly(lactic acid)-aspirin microspheres prepared via the traditional and improved solvent evaporation methods and its application performances

Drug-loaded microspheres are significant for the development of modern pharmaceutical products. It is well known that the taken of aspirin for long-term increases the risk of serious gastrointestinal complications, therefore a controllable delivery of aspirin is of importance to lighten those side effects. In this work, poly(lactic acid) (PLA) was chosen as the carrier to prepare PLA-aspirin microspheres by using the traditional and the improved solvent evaporation methods. It was found that no matter which experimental condition was, the encapsulation efficiency of aspirin was higher by using the improved method than that of the traditional method. Specifically, when the concentration of polyvinyl alcohol = 1% (mass), the polymer concentration = 1:20, the oil/water rate = 1:2.5, PLA-aspirin microspheres were obtained via the improved method with a high yield of 82.83% (mass) and an encapsulation efficiency of 44.09%. PLA-aspirin microspheres were then prepared continuously using the improved method, which further enhanced the encapsulation efficiency to 54.56%. Approximate 85% aspirin released from microspheres within 7 days. Obvious degradation which was represented by reduction on hardness was observed by soaking microspheres in PBS for 60 days. This work is of interest because it provides a continuous route to prepare PLA-aspirin microspheres continuously with a high drug encapsulation efficiency.

Sequential combination of NaClO chain breakage/CuxO catalytic oxidation processes for high efficiency treatment of ultra-high concentration PVA wastewater

Polyvinyl alcohol (PVA) is a kind of refractory organic polymer with high COD and low BOD. Efficient treatment of PVA wastewater has always been a challenging subject especially for ultra-high concentration (UHC). In this paper, based on our previous work, a sequential combination process method including NaClO chain breakage followed by CuxO activated carbon catalytic oxidation was developed to efficient treat UHC PVA wastewater. The sequential combination system was optimized by monitoring the treatment performance with different key parameters (such as oxidant dosage, Cu loading and catalyst dosage, two-stage reaction time, pH value, etc.). And the COD of PVA wastewater declined from the initial 206,240.00 mg/L to 557.78 mg/L (removal rate 99.73 %), the PVA concentration decreased from the initial 171,325.00 mg/L to 19.94 mg/L (removal rate 99.99 %) under the optimal conditions. Through the discussion of the combined processes, it was found that both chain breakage and catalytic oxidation were necessary and indispensable to achieve efficient degradation of PVA wastewater. Additionally, the free radical scavenging experiments show that the combined oxidation process was mainly controlled by the catalytic oxidation process, and followed the free radical reaction mechanism with·OH as the main oxidant. Based on this, it is recommended that subsequent researchers focus on the combined process for the treat of refractory organic wastewater.

CENTRAL COMPOSITE FACE-CENTERED DESIGN-BASED OPTIMISATION, DEVELOPMENT AND CHARACTERISATION OF FAVIPIRAVIR-LOADED PLGA NANOPARTICLES

Objective: The objective of this study is to fabricate favipiravir-loaded PLGA nanoparticulate systems that can increase the solubility along with the sustained release of favipiravir. Methods: The favipiravir-loaded Poly (D, L-lactic-co-glycolide) (PLGA) nanoparticulate systems were prepared by the nanoprecipitation method. A 3-factor, 2-level central composite face-centered design was employed to study the effect of formulation variables having a concentration of PLGA, polyvinyl alcohol (PVA) and stirring rate as critical formulation attributes and particle size, drug entrapment efficiency, and percentage cumulative drug release as critical quality attributes on prepared favipiravir nanoparticles. Drug interaction studies were performed by FTIR and DSC. Surface morphology was analysed by scanning electron microscopy (FEI Quanta 250 FEG, USA). Particle size, zeta potential, and polydispersity index were analysed by the nanoparticle analyser SZ-100 (HORIBA Scientific nanopartica, Japan). In vitro drug release studies were performed using a UV-Visible spectrophotometer at λmax 234 nm. In vitro drug release data obtained was fitted into various mathematical kinetic models. Results: The numerical optimization process predicted the level of PLGA concentration as 69.96 mg, PVA concentration as 4.99%, and stirring rate as 799 rpm for the optimised formulation. The low percentage of relative error for the optimised formulation confirms the validation of the model. The optimised formulation had a 77.65% entrapment efficiency with a particle size of 109.7 nm and the percent cumulative drug release showed 86.46% drug release over 720 min. The drug release was found to follow first-order release kinetics with anomalous non-Fickian diffusion kinetics. Conclusion: Hence, such an attempt at fabrication of favipiravir-loaded PLGA nanoparticulate systems may be useful for sustained release of drug over 720 min.

Effect of polyvinyl alcohol on aggregation and flow characteristics of tetra-n-butylammonium bromide and tetra-n-butylphosphonium bromide semi-clathrate hydrate slurries formed under CO2 bubbling

The rheological properties of tetra-n-butylammonium bromide (TBAB) and tetra-n-butylphosphonium bromide (TBPB) semi-clathrate hydrate (SCH) slurries with polyvinyl alcohol (PVA) were measured using a viscometer to evaluate the anti-agglomeration effect of PVA. The TBAB and TBPB hydrate slurries exhibited a stronger dilatant trend with yield stress and more aggregates with increasing solid fraction. Only TBPB had plate-like crystals, and the frictional force between particles and aggregability in TBPB hydrate slurries were higher than those in TBAB hydrate slurries. The appropriate degree of polymerization (DP) of PVA was 1000, and the appropriate PVA (DP of 1000) concentrations were 0.53 wt% for TBAB hydrate and 1.8 wt% for TBPB hydrate among the SCH solid fractions examined. CO2 bubbling weakens the anti-agglomeration effect of PVA by promoting particle aggregation and enhancing the interactions between plate-like particles. However, adding PVA changed the rheological properties of slurries to a Bingham fluid even under CO2 bubbling conditions.