Solution Feed Rate Research Articles

Parameters influencing electrospun nanofiber diameter of polylactide incorporated with cellulose nanofibrils and nanocrystals

The main purpose of this study was to investigate effects of various electrospinning parameters on the morphology and diameter of cellulose nanofibril (CNF) filled polylactide (PLA) nanofibers. For this purpose, first of all effects of three important electrospinning parameters; polymer solution concentration, solution feeding rate and collector distance to feeding tip were studied. Then, effects of using higher amount of CNF, effects of using cellulose nanocrystal (CNC) particles, and effects of adding potassium chloride salt were also investigated. It was observed that when optimum electrospinning parameters were determined, then it was possible to obtain almost “bead-free” morphology and “finest” average diameter of 232 nm for PLA/CNF electrospun fibers. Increasing values of feeding rate and collector distance parameters resulted in bead formation and thicker diameters. On the other hand, increasing CNF amount, using CNC particles and adding KCl salt, all resulted in further decreases in the diameter down to 152 nm; mainly due to increased charge density of the polymer solution. Moreover, in vitro degradation analysis of all types of electrospun nanofiber mats in a simulated body fluid revealed that increasing the immersion period increased their degradation rate in terms of “% weight loss”. It was also observed that, mats with fine diameter fibers had higher degradation rate.

Silver nanoparticle coatings with adjustable extinction spectra produced with liquid flame spray, and their role in photocatalytic enhancement of TiO2

Silver nanoparticles deposits were produced with liquid flame spray (LFS) on glass and TiO2 substrates to study their optical response and photocatalytic enhancement. The correlation between extinction spectrum of the nanoparticle coating and the LFS process parameters was studied. The spectra consisted of two partly overlapping peaks: one centered in the UV region and the other in the visible light region. The visible light peak redshifted as either the silver mass concentration in the precursor solution or the precursor solution feed rate was increased, which also correlated with growing primary particle size. However, simultaneous correlation with photocatalytic activity of the decorated TiO2 surfaces was not observed, which was attributed to particle sintering on the surface. Instead, the photocatalytic activity was seen to change as the surface coverage of silver nanoparticles was varied. When the surface coverage was raised from ∼10 % to roughly 30 %, the activity, and then decreased as the loading was further raised. The increase was assumed to originate from plasmonic activation, and the decrease was attributed to the excessive amount of silver either blocking reactive area of the TiO2 or absorbing/scattering too much of the incoming light, which hindered the photocatalytic activity.

Fabrication and Optimization of Electrospun Shellac Fibers Loaded with Senna alata Leaf Extract.

Single-fluid electrospinning creates nanofibers from molten polymer solutions with active ingredients. This study utilized a combination of a fractional factorial design and a Box-Behnken design to examine crucial factors among a multitude of parameters and to optimize the electrospinning conditions that impact fiber mats' morphology and the entrapment efficiency of Senna alata leaf extract. The findings indicated that the shellac content had the greatest impact on both fiber diameter and bead formation. The optimum electrospinning conditions were identified as a voltage of 24 kV, a solution feed rate of 0.8 mL/h, and a shellac-extract ratio of 38.5:3.8. These conditions produced nanosized fibers with a diameter of 306 nm, a low bead-to-fiber ratio of 0.29, and an extract entrapment efficiency of 96% within the fibers. The biphasic profile of the optimized nanofibers was confirmed with an in vitro release study. This profile consisted of an initial burst release of 88% within the first hour, which was succeeded by a sustained release pattern surpassing 90% for the next 12 h, as predicted with zero-order release kinetics. The optimized nanofibers demonstrated antimicrobial efficacy against diverse pathogens, suggesting promising applications in wound dressings and protective textiles.

A determination of rational parameters for drying plant extracts of wild and cultivated plants with antioxidant properties

The article focuses on the drying of callus extracts of Ocimum basilicum and Eleutherococcus senticosus by pseudo-boiling bed method. During the study, rational conditions for the drying process were determined: temperature 90 ℃, aspiration 100 ± 0.8 m3/h and solution feed rate of 8 ± 0.3ml/min. It was possible to increase the antioxidant activity of the extract under the given conditions. The study of fluidized bed drying of the extract of callus cultures of basil (Ocimum basilicum) and Eleutherococcus senticosus (Eleutherococcus senticosus) allows to obtain extracts with higher concentration of biologically active substances. The results of the article can be useful for agro-, bio- and food industries.

TECHNOLOGY OF OBTAINING THE SUM OF IRIDOIDS FROM THE WASTE PROCESSING THE AERIAL PART OF AJUGA TURKESTANICA

The processes studied of sedimentation and purification of the number of iridoids from the processing waste of the aerial part of Ajuga turkestanica Regel. Brig. (Turkestan tenacious). Based on the results of the research, it was found that for the effective precipitation of iridoids, the ethanol extract from the aerial part of the Turkestan tenacious is concentrated, diluted with water, treated successively with extraction gasoline and ethyl acetate, from the purified solution iridoids and ecdysteroids, are extracted with n-butanol, then the n-butanol extract is concentrated to 1/10 of the initial volume, after which the iridoids are precipitated, by pouring acetone in a volume ratio of n-butanol-acetone 1 : 5, the precipitate is separated and dried. To clean accompanying substances, the dried amount of iridoids is dissolved in ethyl alcohol and re-precipitated by pouring ethyl acetate in a volume ratio of ethyl alcohol-ethyl acetate 1 : 5. Experiments were carried out on the selection of the type of drying apparatus and the establishment of optimal drying conditions. It was revealed that drying the sum of iridoids from the aerial part of the Turkestan tenacious in the "ZPG 150" spray dryer is more optimal than drying in a drying cupboard (vacuum and without vacuum) and an infrared drying cupboard. At the same time, for drying in the "ZPG 150" spray dryer, the dried aqueous solution of iridoids must be prepared as follows: after the second precipitation, the sum of iridoids is dissolved with water until about 7% of the dry residue in the solution is formed and, with the aim of removing residual organic solvents, the aqueous solution of iridoids is concentrated to the content of not more than 15% and not less than 10% of the dry residue. It has been established that to obtain a finished product that is stable in yield and quality, drying an aqueous solution of iridoids in a spray dryer "ZPG 150" must be carried out implemented at a temperature coolant at the inlet 170 °С, at an outlet of 80 °C and a solution feed rate of 80 l/h, spray head rotation speed 8000 rpm and coolant speed 2200 kg/h. Technology has been developed for the production of the substance of iridoids from the waste products of the production of ekdisten from the aerial part of Turkestan tenacious, which allows the rational use of plant raw materials. Approbation of the developed technology showed that the yield of the target product is 1.5% by weight of the raw material.

Preparation and Characterization of a One-Step Electrospun Poly(Lactic Acid)/Wormwood Oil Antibacterial Nanofiber Membrane.

With the continuous improvement of the standard of living, people are increasingly inclined towards natural, green, and environmentally friendly products. Plant-based products that are safe, natural, non-toxic, and beneficial to human health are often more favored. Poly(lactic acid) (PLA) is a polymer obtained through lactate polymerization using renewable plant resources such as corn and has excellent biocompatibility and biodegradability. It is widely used in the field of food packaging. Wormwood oil (WO) is an oil extracted from the stems and leaves of Artemisia plants, and it has broad-spectrum antibacterial properties. In this article, through electrospinning technology, wormwood oil was directly incorporated into PLA, giving the PLA nanofiber membrane antioxidant and antibacterial functions. Various parameters such as voltage (11 KV, 13 KV, 15 KV), spinning solution concentration (8%, 10%, 12%), distance (15 cm, 17 cm, 19 cm), and feeding rate (0.4 mL/h, 0.5 mL/h, 0.6 mL/h) were explored, and the resulting spun fibers were characterized. Through SEM characterization, it was found that when the spinning voltage was 13 KV, the spinning solution concentration was 10%, the distance was 17 cm, and the feeding rate was 0.5 mL/h, the nanofiber membrane had a smooth morphology without bead formation, with an average diameter of 260 nm. The nanofiber membrane was characterized using FTIR, TG, and SEM, confirming the successful incorporation of artemisia essential oil into PLA. The prepared antimicrobial nanofilm was subjected to antimicrobial testing, and the results showed that as the concentration of the essential oil increased, the inhibition zones also increased. When wormwood oil concentration was 4%, the diameter of the inhibition zone for Staphylococcus aureus increased from 1.0 mm to 3.5 mm, while the diameter of the inhibition zone for Escherichia coli increased from 2.0 mm to 4.5 mm.

Hierarchical Structure of Glucosamine Hydrochloride Crystals in Antisolvent Crystallization

The crystal morphology of glucosamine hydrochloride (GAH) during antisolvent crystallization was investigated in this work. Particles of different shapes, such as plate-like crystals, leaflike clusters, fan-like dendrites, flower-like aggregates, and spherulites, were produced by tuning the type of antisolvents and crystallization operating conditions. The hierarchical structures of GAH crystals tended to be formed in a water + isopropanol mixture. The effects of operation parameters on the polycrystalline morphology were studied, including crystallization temperature, solute concentration, feeding rate of GAH aqueous solution, solvent-to-antisolvent mass ratio, and stirring rate. The evolution process of GAH spherulites was monitored using SEM, indicating a crystallographic branching mode. The crystal habit was predicted to identify the dominant faces. Molecular dynamics simulations were performed and the interaction energy of solute or solvent molecules on crystal surfaces was calculated. The experimental and simulation studies help to understand the branching mechanism and design a desired particle morphology.

Design and operation performance of the plate-heat transfer type hydrogen production reactor for bio-methanol reforming

In this paper, the plate-heat transfer type bio-methanol steam reforming reactor for hydrogen fuel cell vehicles and its operation performance was studied. The structure of the plate-heat transfer type for bio-methanol reforming has been designed and optimized with the application parameters of hydrogen production capacity, hydrogen production rate, bio-methanol conversion rate, volume limitation. Results showed the catalyst particle size has little influence when it less than 0.85 mm; However, when the catalyst loading was 20 g and the feed rate of bio-methanol solution was 1.5 mL/min, the effect of reforming bio-methanol was the best. At this time, the specific hydrogen production was 64.062 mL/gcat.min, the hydrogen production rate was 21.354 mL/s, the bio-methanol conversion rate was 82.25%. This paper can provide scientific reference for further research and development of high-efficiency and low-cost bio-methanol reforming hydrogen production equipment.

OPTIMAL CONDITIONS FOR CLEANING AND DRYING FUROSTANOL SAPONINS FROM TRIBULUS TERRESTRIS

Furostanol saponins from Tribulus terrestris may be separated from ballast substances by liquid-liquid extraction with changing polarity of the extractant, depending on the dynamics of the process. Treatment with chloroform removed the maximum number of lipid-like compounds and showed minimal losses of furostanol saponins, and subsequent treatment with ethyl acetate retrieved low-polarity substances. Fourfold extraction with butanol was used to extract furostanol saponins from an aqueous solution. Optimal conditions were developed for spray drying of furostanol saponins. The greatest yield of “Dry extract Tribulus” was obtained with a solution feed rate of 80 l/h, a spray head rotation speed of 8000 rpm, and a heat carrier velocity of 2000 kg/h. Technology was developed for obtaining “Dry extract Tribulus” from Tribulus terrestris that contained at least 45% furostanol saponins. The reproducibility of the developed technology was shown with the obtaining of 5 series of substances that meet the requirements of regulatory and technical documentation on the lines of the Scientific and Technological Center for GMP Requirements the Institute of Chemistry of Plant Substances.

Development of multilevel amplified methanol steam reforming microreactor with high hydrogen production rate

Methanol steam reforming using microreactors has been regarded as a promising approach for in-situ hydrogen production, while the generally low hydrogen production rate limits its real application. This study proposed a multilevel series scaled-up methanol steam reforming microreactor with the aim to improve the hydrogen production rate, five methanol combustion chambers are parallel arranged and interspersed into the steam reforming chambers to improve the temperature heating rate and temperature distribution uniformity. A numerical model of methanol steam reforming chamber was established to investigate the flow velocity distribution inside the chamber. The flow velocity in the copper foam region are uniformly distributed, the variations of average flow velocity in cross sections of the copper foams are below 20 %. Experimental results showed that the temperature differences between different layers was lower than 6.7 °C and the variation is smaller than 7.3 °C. A stepwise methanol solution feeding rate test was performed and found the developed microreactor has a quite rapid response speed, the maximum reformate flowrate of 20683 ml/min can be achieved with methanol conversion of 88.3 %. The developed microreactor can significantly improve the hydrogen production rate and temperature distribution uniformity, indicating a potential application in high hydrogen consumption equipment.

2 Low-Cost Pm Sensor Performance Testing

Abstract Low-cost particulate matters sensors (LCPMS) are widely used in indoor and outdoor air quality monitoring. Previous studies have explored the accuracy and precision of sensors, showing that LCPMS were most accurate for PM with diameters below 1 μm, and they poorly measured PM in the 2.5–5 μm range. The study aimed to investigate the aspiration and transmission efficiency of LCPMS, to set up a standard aerosol mass concentration generation system, to further comprehend the performance characteristics of LCPMS, and to examine the effect of aerosol loading. Three models of Plantower sensors were tested in this work. An ultrasonic atomizing nozzle was used to generate micrometer-sized NaCl aerosol particles. A TSI aerodynamic particle sizer was used to measure the aerosol concentrations and size distributions upstream and downstream of the LCPMS, to determine the aspiration and transmission efficiency. The mass concentration, from 20 µg/m3 to 200 mg/m3, could be varied by controlling the solution feeding rate and the solution concentration. The high mass concentration was mainly designed for aerosol loading study. The results showed that the aspiration efficiencies of the tested LCPMS were all almost 100% for particle smaller than 5 µm. The transmission efficiency of these sensors was function of particle size and strongly dependent on sampling flow. All sensors tested showed significant performance degrading when challenged with high mass concentration. The orientation of the sensor also played a role affecting the aerosol loading. These sensors performed better when mass concentration is below 100 µg/m3.

Preparation of flexible hollow TiO2 fibrous membranes for thermal-insulation applications by coaxial electrospinning

With the increasingly serious issues of energy conservation and emission reduction, hollow fibers have attracted wide attention as materials that have structural advantages in terms of thermal insulation. Herein, we report the preparation of flexible hollow TiO2 fibrous membranes via coaxial electrospinning. To optimize the thermal-insulation performance of the fibers, hollow fibers with different diameters and pore sizes were prepared by adjusting the feeding rate of the core spinning solution. Optimum conditions were achieved at a feeding rate of 2 mL/h for the shell solution and 0.4 mL/h for the core solution. The hollow fibers had a compact tube wall structure and good mechanical properties, and the tensile strength of the fibrous membranes reached 0.652 ± 0.119 MPa. In addition, the hollow fibrous membranes have excellent thermal insulation properties with an average reflectance of more than 89% and a room temperature thermal conductivity of less than 0.0294 ± 0.00015 W m−1K−1. In practical experiments, the temperature can be reduced from 1174.6 to below 273.6 °C using 15-mm-thick fibrous membranes, which confirms its excellent thermal insulation. Flexible hollow TiO2 fibrous membranes have a wide range of insulation applications.

Dynamic Modeling and Sensitivity Analysis for an MEA-Based CO2 Capture Absorber

The absorber is the key unit in the post-combustion monoethanolamine (MEA)-based carbon dioxide (CO₂) capture process. A rate-based dynamic model for the absorber is developed and validated using steady-state experimental data reported in open literature. Sensitivity analysis is performed with respect to important model parameters associated with the reaction, mass transport and physical property relationships. Then, a singular value decomposition (SVD)-based subspace parameter estimation method is proposed to improve the model accuracy. Finally, dynamic simulations are carried out to investigate the effects of the feed rate of lean MEA solution and the flue inlet conditions. Simulation results indicate that the established dynamic model can reasonably reflect the physical behavior of the absorber. Some new insights are gained from the simulation results.

Fabrication, Optimization, and Characterization of Antibacterial Electrospun Shellac Fibers Loaded with Kaempferia parviflora Extract.

This study aimed to develop a Kaempferia parviflora (KP) extract based on electrospun shellac fibers capable of transporting methoxyflavones. This study used a Box-Behnken design to determine the optimal production parameters that influence the fiber diameter and bead-to-fiber ratio responses. The optimization step produced fibers with a small diameter (574 nm) and a lower bead-to-fiber ratio (0.48 beads per fiber) by combining 37.25% w/w shellac and 1.50% w/w KP extract with a solution feed rate of 0.8 mL/h and an electrical voltage of 18 kV. The KP extract was found to be dispersed throughout the electrospun shellac fibers during the characterization study. The results were highly correlated with the theoretical values, indicating that the regression models used to predict the response variables were adequate. A study of in vitro dissolution confirmed that KP extract-loaded electrospun shellac fibers could produce a sustained-release profile within 10 h. Additionally, KP-infused shellac fibers demonstrated antibacterial activity against Staphylococcus aureus. This KP loading method combined with shellac properties provided a new delivery system and could be used to explore novel biomedical materials.

The Effect of Electrospinning Parameters on Piezoelectric PVDF-TrFE Nanofibers: Experimental and Simulation Study

Polyvinylidene fluoride and its copolymers can be used as active materials for energy harvesting and environmental sensing. Energy harvesting is one of the most recent research techniques for producing stable electrical energy from mechanical sources. Polyvinylidene fluoride–trifluoroethylene (PVDF-TrFE) is applicable for sensors and self-powered devices such as medical implants and wearable electronic devices. The preparation of electrospun P(VDF-TrFE) nanofibers is of great interest for the fabrication of sensors and self-powered devices, nanogenerators, and sensors. In this regard, it is necessary to investigate the effects of various parameters on the morphology and piezoelectric output voltage of such nanofibers. In this study, we have examined the effect of concentration and feed rate on the nanofiber diameter. It has been found that by increasing the concentration and feed rate of the polymer solution, the diameter of the nanofibers increases. The experimental results and the finite element method (FEM) simulation have also shown consistency; when the nanofiber diameter increases, the output voltage of the nanofibers decreases. This behavior can be related to the strain reduction in the deformed nanofibers.

Electrospinning of PVP Nanofibers and Optimization with Taguchi Experimental Design

The aim of this study is the determination of optimum process parameters which will provide the finest and the most uniform electrospun Polyvinylpyrrolidone (PVP) based nanofibers with Taguchi experimental design. For the designed experimental setup, parameters (solvent type, polymer concentration, voltage, distance between the electrodes, solution feed rate and humidity) were used which effect the electospinning process significantly. For this purpose, the appropriate orthogonal array was selected to determine the factors and levels at Taguchi experimental design application. The experimental design aimed which provides to be reduced the number of experiments and minimised the effect of uncontrollable factors with less experiments to obtain target value by using Taguchi orthogonal arrays. In the experimental studies of paper, firstly PVP polymer solutions such as conductivity, surface tension and viscosity were determined with various PVP concentrations (10, 12, 14 wt %) and solvents (ethanol, dimethylformamide, dimethylacetamide, chloroform, acetic acid and distilled water). Scanning Electron Microscope (SEM) images of electrospun PVP based nanofibrous surfaces were obtained, average fiber diameter and fiber diameter coefficient values were calculated by ImageJ image analyses software and fiber diameter distribution histogram curves were obtained by SPSS program. Experimental results were analyzed and commented by Taguchi method in MINITAB program with variance analysis. According to the results; solvent type has the highest effect on the electrospinning of PVP nanofibers. In this study, it is predicted to save in terms of time and cost with decreasing the number of experiments by Taguchi experiment design.

Fabrication of betamethasone micro- and nanoparticles using supercritical antisolvent technology: In vitro drug release study and Caco-2 cell cytotoxicity evaluation

Poor solubility limits the pharmacological activities of betamethasone (BM), including its anti-inflammatory and anti-allergic effects. To improve the aqueous solubility and dissolution rate of BM, supercritical antisolvent (SAS) technology was used to prepare BM microparticles and BM–polyvinylpyrrolidone (PVP) solid dispersion nanoparticles. The effects of temperature, pressure, solution feeding rate, and drug concentration on particle formation were investigated using both single-factor and orthogonal experimental methods, and the optimal preparation process was screened. The physicochemical properties of the BM particles were characterized by scanning electron microscopy, differential scanning calorimetry, Fourier transform infrared spectroscopy, and X-ray diffraction. After the SAS process, the particle size was reduced significantly and the crystalline shape was altered, which considerably increased the solubility and dissolution rate of BM. Furthermore, the toxicity of BM to live cells was reduced because of the BM–PVP solid dispersions.

Taylor cone height as a tool to understand properties of electrospun PVDF nanofibers

Formation of a stable Taylor cone is an important phenomenon during electrospinning of nanofibers for controlling nanofiber properties. Optimizing electrospinning process parameters such as solution feed rate, applied electric voltage and tip to mandrel distance, a stable Taylor cone can be achieved and by maneuvering the parameters within a certain range, the height of the cone can be controlled. Here, we study the influence of the process parameters on the height of the Taylor cone and the corresponding nanofibers produced for polyvinylidene fluoride (PVDF) using dimethylformamide (DMF) as solvent. Characterization of the produced fibers and image analysis confirmed the optimal values as 1 mL/h, 10.8 kV and 10 cm for feed rate, applied voltage and spinning distance, respectively. Observations from the study reveal that contrary to proportional variation of Taylor cone height with nanofiber diameter in case of changing feed rate and applied voltage, the relationship gets inversely proportional when tip to mandrel distance is varied.

Electrospinning of Poly (Acrylamide), Poly (Acrylic Acid) and Poly (Vinyl Alcohol) Nanofibers: Characterization and Optimization Study on the Effect of Different Parameters on Mean Diameter Using Taguchi Design of Experiment Method.

In this study, nanofibers of poly (acrylic acid) (PAAc), polyacrylamide (PAAm) and poly (vinyl alcohol) (PVOH) were prepared using the electrospinning technique. Based on the Taguchi DOE (design of experiment) method, the effects of electrospinning parameters, i.e., needle tip to collector distance, polymer solution concentration, applied voltage, polymer solution feed rate and polymer type, on the diameter and morphology of polymer nanofibers were evaluated. Analyses of the experiments for the diameters of the polymer nanofibers showed that the type of polymer was the most significant factor. The optimal combination to obtain the smallest diameters with minimum deviations for electrospun polymer nanofibers was also determined. For this purpose, the appropriate factor levels were determined as follows: polymer PAAm, applied voltage 10 kV, delivery rate 0.1 mL/h, needle tip to collector distance 10 cm, and polymer solution concentration 8%, to obtain the thinnest nanofibers. This combination was further validated by conducting a confirmation experiment, and the average diameter of the polymer nanofibers was found to be close to the optimal conditions estimated by the Taguchi DOE method.

A green miniaturized QuEChERS based on an electrospun nanofibrous polymeric deep eutectic solvent coupled to gas chromatography-mass spectrometry for analysis of multiclass pesticide residues in cereal flour samples

A new polymeric deep eutectic solvent (DES) composed of poly (2-hydroxyethyl methacrylate):1-tetradecanol ([PHEMA]:[TD]) was prepared through thermally-induced free-radical polymerization using azobisisobutyronitrile (AIBN) as initiator. The [PHEMA]:[TD] DES was mixed with polyamide 6 (PA6) and electrospun into a composite fibrous scaffold for the first time. The PA6/[HEMA]:[TD] nanofibers were characterized by ATR-FTIR, SEM, BET, and BJH techniques and applied as a sorbent in the micro-solid phase extraction (µSPE) step of pesticide residues from cereal flour samples. The analyses were carried out with the GC–MS technique. The effect of sorbent mass, desorption solvent (kind and volume), pH, and ionic strength was investigated to establish the optimal conditions. Besides, the factors influencing the performance of the electrospinning process, such as electrospinning voltage, polymer solution feed rate, syringe needle tip-to-collector distance, and electrospinning duration, were also optimized. Matrix-matched calibration curves showed good linearity (r2 = 0.9803–0.9984) in the concentration range of 0.016–250 μg kg−1. The obtained limits of quantification (0.016–1.805 μg kg−1) were lower than the maximum residue levels (MRLs) established by the European Union and the Food and Agriculture Organization (0.01–0.05 mg kg−1) for the pesticide residues in cereal samples. The intra-day and inter-day precision based on relative standard deviation (RSD) were obtained as 1.1–5.8% and 2.4–8.5%, respectively. The method was applied to the detection of multiclass pesticide residues in maize, rice, wheat, and pastry flour samples, and the obtained relative recoveries were in the range of 71–118% (RSD%<7.5). Finally, the procedure greenness was evaluated based on Complex Green Analytical Procedure Index (Complex GAPI) and the Analytical Eco-Scale (AEC) approaches. This paper also suggests the first application of green hydrophobic PA6/[PHEMA]:[TD] electrospun nanofibers as sorbent for analyzing pesticides in different cereal samples.