Micronization of ketoprofen by the rapid expansion of supercritical solution process

The particle size of the pharmaceutical substances is important for their bioavailability (the percentage of the drug absorbed compared to its initial dosage). The absorption rate can be increased by reducing particle size of the drug particles. This study was conducted to investigate the effects of the extraction pressure (140–220 bar), extraction temperature (308–338 K), nozzle length (2–15 mm), effective nozzle diameter (450–1700 μm), and collection distance (1–10 cm) on the size and morphology of the precipitated ketoprofen particles. The characterization (size and morphology) of the particles was investigated using scanning electron microscopy (SEM). The average particle size of the original material was 115.42 μm, while the average particle size of the micronized particles is between 0.35 and 7.03 μm near to quisi-spherical, needle and irregular shape depending upon the experimental conditions.     

Polymethylmethacrylate (PMMA) sub-microparticles produced by Supercritical Assisted Injection in a Liquid Antisolvent

A recently developed supercritical assisted process, called Supercritical Assisted Injection in a Liquid Antisolvent (SAILA) is proposed to produce polymer micro and nanoparticles in water stabilized suspensions. Polymethylmethacrylate (PMMA) has been selected as the model polymer for a systematic study of the influence of the SAILA operating parameters on particle morphology and diameter. The effect of expanded liquid injection pressure on particle size and distribution was studied and different expanded liquid temperatures and compositions were also explored. Successful precipitation of the polymer in a water stabilized suspension was obtained and narrow particle size distributions were obtained using 70 and 90 bar injection pressures. PMMA particles controlled diameter were produced ranging between 0.2 ± 0.04 μm and 0.9 ± 0.2 μm. Particles are formed from the expanded liquid solution as a consequence of very fast supersaturation produced by spraying it the liquid antisolvent.     

Production of fermentable sugars from enzymatic hydrolysis of pretreated municipal solid waste after autoclave process

A ligno-cellulosic concentrate from municipal solid waste (MSW) obtained after an autoclave separation process was investigated for its potential as a feedstock to produce fermentable sugars for ethanol production. A maximum enzymatic hydrolysis conversion of 53% of the cellulose and hemi-cellulose was found using a particle size range of 150–300 μm hydrolyzed in a 100 ml buffer solution containing 6 wt% lingo-cellulosic MSW concentrate with 90 mg cellulase at pH 4.8 held at 40 °C for 12 h. The hydrolysis rate leveled off at longer hydrolysis time and with increased substrate concentration and was related to enzymatic access to substrate. Lower hydrolysis rate at smaller particle size indicates that the grinding process may change the surface chemistry or morphology of the fibers making them less available for enzyme access. A drop in the hydrolysis rate was observed for the particles above 300 μm associate with the longer diffusion time for the enzyme into the fiber particles. The findings indicate that 152 L of ethanol could be obtained from a ton of lingo-cellulosic concentrate from MSW.     

Preparation of porous silver particles using ammonium formate and its formation mechanism

Here we report the preparation of two different types of macroporous silver particles (round and coral) by simple chemical reduction using ammonium formate. We also discuss the chemical mechanism of silver particle and macroporous silver particle formation. The synthesized round type and coral-type porous silver particles were 20–50 μm and 30–150 μm in size and their pores were 100–200 nm and 1–2 μm across, respectively. They were characterized by particle distribution analysis, X-ray diffraction, and scanning electron microscopy.     

Micronization of salicylic acid and taxol (paclitaxel) by rapid expansion of supercritical fluids (RESS)

The particle sizes of the pharmaceutical substances are important for their bioavailability. The bioavailability can be improved by reducing the particle size of the drug. In this study, salicylic acid and taxol were micronized by the rapid expansion of supercritical fluids (RESS). Supercritical CO₂ and CO₂ + ethanol mixture were used as solvent. Experiments were carried out to investigate the effect of extraction temperature (318–333 K) and pressure (15–25 MPa), pre-expansion temperature (353–413 K), expansion chamber temperature (273–293 K), spray distance (6–13 cm), co-solvent concentration (ethanol, 1, 2, 3, v/v, %) and nozzle configuration (capillary and orifice nozzle) on the size and morphology of the precipitated salicylic acid particles. For taxol, the effects of extraction pressure (25, 30, 35 MPa) and co-solvent concentration (ethanol, 2, 5, 7, v/v, %) were investigated. The characterization of the particles was determined by scanning electron microscopy (SEM), optical microscopy, and LC–MS analysis.The particle size of the original salicylic acid particles was L/D: 171/29–34/14 μm/μm. Depending upon the different experimental conditions, smaller particles (L/D: 15.73/4.06 μm/μm) were obtained. The particle size of taxol like white crystal powders was reduced from 0.6–17 μm to 0.3–1.7 μm The results showed that the size of the precipitated salicylic acid and taxol particles were smaller than that of original particles and RESS parameters affect the particle size.     

How to increase the hydration degree of CA — The influence of CA particle fineness

It is shown that the hydration degree of CA is directly dependent on the fineness of CA-particles. Finer particles lead to an increased degree of hydration and also an increased hydration rate.The reaction of a sample with mainly coarse particles of CA (d₅₀ = 50 μm) is characterized by a low hydration rate and only 34 rel.-% of CA dissolved after 22 h. Whereas in a very fine CA-sample (d₅₀ = 4 μm) hydration starts delayed but then shows the highest hydration rate and a dissolution of 62 rel.-% CA. The behaviour is explained by the coverage of CA-particles with a dense hydrate layer of C₂AH_x and AH_x. This reacted CA-rim is supposed to have the same thickness for different sized CA-particles. Optimization of Gauss distribution curves, which were applied to simulate a more realistic particle size distribution, leads to a reacted rim thickness of 1.3 μm until reaction is stopped.     

Working mechanism of methyl hydroxyethyl cellulose (MHEC) as water retention agent

The working mechanism of methyl hydroxyethyl cellulose, MHEC (M_w = 2.5 · 10⁵ g/mol, DS_methyl = 1.81, MS_hydroxyethyl = 0.15) as water retention agent in cement was investigated. First, the hydrocolloid was characterized and its performance as non-ionic water retention agent was determined employing the filter paper test. Also, water sorption and swelling of individual MHEC fibers under conditions of different humidities were monitored by ESEM imaging. Second, its working mechanism was established. It was found that at low dosages, MHEC achieves water retention by intramolecular sorption of water and concomitant swelling while at higher dosages, MHEC molecules agglomerate into large hydrocolloidal microgel particles (d > 1 μm) which effectively plug the pores in the mortar matrix. MHEC association was evidenced by an exponential increase in solution viscosity as concentration rises, a strong increase in the hydrodynamic diameter of solved MHEC molecules, and a noticeable reduction of surface tension.     

Improved γ-alumina support based pseudo-boehmite shaped by micro-extrusion process for oxygen carrier support application

γ-Alumina extrudates for chemical-looping combustion in fluidized bed reactors were shaped by varying acetic acid concentrations between 0.07 and 3.76 M. Influence of pseudo-boehmite peptization on structural properties, microstructure, chemical phases and attrition resistance was determined. With addition of acetic acid, the d₉₀ of boehmite agglomerates after 1 h kneading decreased from 134 to 40 μm at pH 4. Due to this, the extrusion diameter was reduced from 1500 to 200 μm, as well as median pore radii (from 30.1 to 5.3 nm). Porosity was about 70%. Addition of more than 1.87 M acid lead to a slight increase in mesopore sizes caused by some pore blocking caused by the formation of aluminium acetate salts. A small micropore surface was determined with t-layer model from Harkins and Jura. Higher attrition resistance was observed for samples peptized with lower acid concentration because of the closer contact between particles after decomposition.     

Influence of solvent characteristics in triaxial electrospun fiber formation

Triaxial electrospinning is a novel method for fabrication of multilayered nano and microsize fibers with desirable features for particular applications. Since the effect of solvent volatilities in each layer and relative polymer molecular weights on uniform encapsulation of the core polymer process is not well understood, we evaluated (i) the role of solvent volatilities, and (ii) molecular weights using cellulose acetate (CA, 30 kDa), polycaprolactone (PCL, 45 kDa and 80 kDa), mineral oil, and polyvinyl alcohol (PVA, 30 kDa and 100 kDa). Different solvent mixtures were evaluated based on the boiling points determined using a simulator. Inner mineral oil was selectively removed to form Hollow fibers. Analysis of chemical compositions using FT-IR and DSC revealed the presence of each component. 24-h viability of human umbilical vein endothelial cells indicated the formed fibers were not toxic. Scanning electron micrographs indicated the formation of triaxial structured fiber of outer hydrophobic PCL/CA/Hollow, PCL/PVA/Hollow and outer hydrophilic CA/PCL/Hollow fibers. Tensile tests (both wet and dry) revealed that PCL/CA/Hollow fibers had increased stiffness and load carrying capacity than CA/PCL/Hollow fibers. Successful fiber formation was dependent on ensuring that the outer shell formed first i.e., the relative solvent volatility of encapsulating core polymer to lower than that of the shell polymer.     

Morphology and properties of compatibilized polylactide/thermoplastic starch blends

This paper investigates the properties and interfacial modification of blends of polylactide (PLA) and glycerol-plasticized thermoplastic starch (TPS). A twin-screw extrusion process was used to gelatinize the starch, devolatilize the water to obtain a water-free TPS and then to blend into the PLA matrix. The investigated TPS concentration ranged from 27 to 60 wt%. In the absence of interfacial modification, the TPS/PLA blend morphology observed through scanning electron microscopy was very coarse with TPS particles sizes between 5 and 30 μm. Interfacial modification was achieved by free-radical grafting of maleic anhydride (MA) unto the PLA and then by reacting the modified PLA with the starch macromolecules. Blends comprising MA-grafted PLA showed much finer dispersed phase size, in the 1–3 μm range and exhibited a dramatic improvement in ductility. The paper discusses the effects of two interfacial modification strategies on the blend morphology and tensile properties and investigates the compatibilization efficiency for glycerol plasticizer contents between 30 and 39 wt% and for starches from three different sources: wheat, pea and rice.     

Ultrasonochemical coating and characterization of TiO2-coated zirconia fine particles

Zirconia fine particles were prepared by ultrasonic spray pyrolysis (USP) and employed as a substrate for titanium/titania coating by ultrasonochemistry. The effects of several process factors on the characteristics of the prepared particles were investigated and the particles were then characterized by various techniques. This substrate was coated with various titanium concentrations (0.025–0.1 M) for two ultrasonication time periods (30 min, 2 h) by sonochemistry, and finally calcined at 1100 °C. Raman spectroscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), particle size analysis (PSA), Fourier transformation infrared spectroscopy (FT-IR) and inductively coupled plasma-atomic emission spectroscopy (ICP-AES) comprised the techniques used to characterize them. The particles were prepared in a monodispersed spherical form with no interior cavity; their average size was shown to be 0.62 μm before calcination and 2.57 μm after calcination. The titania surface coating acted to partially stabilize the particles to a tetragonal phase. Based on the analytical results, the optimum conditions for preparing the particles were shown to be 7.5 wt% of titania as an initial solution concentration and 0.5 h of coating time.     

New bio-aerosol collector using a micromachined virtual impactor

For collection and concentration of bioaerosols, we designed and evaluated a single stage virtual impactor, which was fabricated by micro-electro-mechanical systems (MEMS) process. The cut-off diameter of 1 μm was selected, since 1 μm is the lowest size as used in the US Government Joint Biological Point Detection System [Haglund, J. S., & McFarland, A. R. (2004). A circumferential slot virtual impactor. Aerosol Science and Technology, 38, 664–674; Moshier, T., & Buonaugurio, T. (2000). Joint Biological Point Detection System (JBPDS) requirements and design interplay. Proceedings of the First Joint Conference on Point Detection for Chemical and Biological Defense, October 23–27, 2000, Williamsburg, VA.] The design value of a 1 μm cut-off diameter required a nozzle width and thickness of 880 and 200 μm, respectively. The virtual impactor was evaluated for physical and biological collection efficiencies. For the performance evaluation of physical collection efficiency and wall loss, polystyrene latex (PSL) particles were generated from an atomizer and their size distribution was measured using an aerodynamic particle sizer (APS, TSI model 3321) and a scanning mobility particle sizer (SMPS, TSI model 3936). The measured cut-off diameter was 0.95 μm, which agreed with the calculated results (=0.94 μm) determined with a commercial computational fluid dynamics (CFD) package, FLUENT, and the measured wall loss was below 33.5%. For the performance evaluation of biological collection efficiency, Staphylococcus epidermidis bioaerosols were dispersed into air by a nebulizer. The bioaerosols were measured using APS and sampled with a bioaerosol sampler. The overall physical collection efficiency based on the number concentration was 73.8±3%, which was similar to the one based on the number of colonies (=76.7±7%). We found that most of the bioaerosols collected and concentrated by our virtual impactor were viable.     

Supercritical anti-solvent micronization of chromatography purified marigold lutein using hexane and ethyl acetate solvent mixture

This work aims to study supercritical anti-solvent micronization of marigold derived purified lutein that was dissolved in the mixture of hexane and ethyl acetate (70:30 v/v), the solvent used as the mobile phase for chromatographic purification. The results show significant effect of pressure on the morphology of micronized lutein particles. The increase in lutein initial concentration from 1.5 mg/ml to 3.2 mg/ml and the increase in SC-CO₂ flow rate from 15 ml/min to 25 ml/min show no significant effects on the morphology of lutein particles. However, the reduction of mean particle size from about 2 μm to 0.8 μm was observed by increasing SC-CO₂ flow rate. The X-ray diffraction patterns of the micronized lutein particles show apparent amorphous nature, while the Fourier transform infrared spectroscopy results show that no chemical structural changes occurred. Moreover, the solubility of the micronized lutein particles in aqueous solution was found to increase significantly from being almost insoluble to having approximately 20% solubility     

Nanoparticle collection efficiency of capillary pore membrane filters

The surface and overall collection efficiencies of capillary pore membrane filters were measured for sub-micrometer particles. Collection efficiencies were derived from the surface loadings of particles on filters measured by scanning electron microscopy and from airborne particle concentrations measured with a scanning mobility particle sizer. Tests used filters with nominal pore diameters of 0.4 and 0.8 μm and face velocities of 3.7 and 18.4 cm/s. Surface collection efficiencies were below 100% for particles smaller than 316 nm and below 55% for particles smaller than 100 nm. Overall collection efficiencies reached as low as 45% for 70 nm particles. For nanoparticles, collection efficiencies overall were substantially higher than those to the filter surface, indicating that deposition occurs to a large extent inside the filter pores. These results underscore the need to account for surface collection efficiency when deriving airborne concentrations from microscopic analysis of nanoparticles on capillary pore membrane filters.     

Coal–oil–water multiphase fuel: Rheological behavior and prediction of optimum particle size

As the coal–oil–water slurry is gaining importance in place of fuel oil, a better understanding of handling characteristics is in demand. Therefore, experimental investigations have been carried out to investigate the rheological properties of coal–oil–water suspension containing coal particles of different sizes. Different coal stocks with average particle sizes of 108 μm, 75.7 μm and 62.9 μm have been used. The concentration of solid for the experiment varies from 10% to 50% by weight. All experiments have been carried out in a cup and bob type coaxial cylindrical viscometer. Newtonian, shear thinning and shear thickening behavior of suspension has been observed depending on component content and operating conditions. Study with different particle sizes shows that it is possible to achieve an optimum particle size for better handling of such suspension. A generalized correlation has been developed to predict the apparent viscosity of coal–oil–water suspension incorporating the coal concentration, oil concentration, torque and particle diameter. The experimental data are in well agreement with proposed correlation.     

Effect of homogenization parameters on selected physical properties of lemon aroma powder

The aim of this study was to examine the relationship between homogenization parameters of lemon aroma emulsion and selected physical properties of obtained powders. Emulsion was prepared in a high shear homogenizer (10 min, 24,000 rpm) or a two-stage pressure homogenizer (30_10 or 60_20 MPa). A 30% emulsion of maltodextrin and Arabic gum in the ratio 7:1 by mass in water and aroma was prepared. The addition of lemon aroma was 2, 6 and 10% (w/w). It was found that in emulsions an increase of aroma addition caused an increase in diameter from 2.4 to 4 μm for Ultra Turrax high shear homogenization and did not change the diameter size for pressure homogenization. For pressure homogenization similar viscosity values were observed. A different effect was observed for high shear homogenization (31–40 mPa s). Increase in aroma addition caused an increase in viscosity. Moreover, a similar diameter of the aroma phase after reconstitution of emulsion from powder (0.7–1.3 μm) was observed. In powders with an increasing amount of aroma, regardless of homogenization method, an increase in porosity, spread of particle size and total colour differences and also a decrease in loose bulk density, solubility and lightness were observed. The lowest apparent density of powders was found for an emulsion containing 6% aroma. The shape of powder particles did not differ from themselves.     

Sinter forging of rapidly quenched eutectic Al2O3–ZrO2(Y2O3)-glass powders

Spray dried agglomerates of Al₂O₃–ZrO₂ (1% Y₂O₃) with 4 wt.% borosilicate glass were arc plasma sprayed and rapidly quenched into water. Because of the rapid quenching the particles <25 μm were mostly amorphous. After annealing 1 h at 1200 °C the scale of the microstructure of the particles was on the order 30 nm. Hot forging of this powder yielded dense specimens with the width of the ZrO₂ phase still less than 100 nm. Since the particle size ranged from 5 to 25 μm and the scale of the particle microstructure was <100 nm, densification was controlled by creep of the particles rather than by the typical hot pressing mechanism of diffusion along the neck between particles to fill the pores. Thus, the scale of the microstructure controls densification rather than the particle size. These powders offer an alternate source for manufacturing nanostructured parts and should be more suitable for hot pressing or forging than nanoparticulate powders.     

Computational fluid dynamics simulations of submicrometer and micrometer particle deposition in the nasal passages of a Sprague-Dawley rat

Computational fluid dynamics (CFD) simulations were conducted in a model of the complete nasal passages of an adult male Sprague-Dawley rat to predict regional deposition patterns of inhaled particles in the size range of 1 nm to 10 μm. Steady-state inspiratory airflow rates of 185, 369, and 738 ml/min (equal to 50%, 100%, and 200% of the estimated minute volume during resting breathing) were simulated using Fluent?. The Lagrangian particle tracking method was used to calculate trajectories of individual particles that were passively released from the nostrils. Computational predictions of total nasal deposition compared well with experimental data from the literature when deposition fractions were plotted against the Stokes and Peclet numbers for micro- and nanoparticles, respectively. Regional deposition was assessed by computing deposition efficiency curves for major nasal epithelial cell types. For micrometer particles, maximum olfactory deposition was 27% and occurred at the lowest flow rate with a particle diameter of 7 μm. Maximum deposition on mucus-coated non-olfactory epithelium was 27% for 3.25 μm particles at the highest flow rate. For submicrometer particles, olfactory deposition reached a maximum of 20% with a particle size of 5 nm at the highest flow rate, whereas deposition on mucus-coated non-olfactory epithelium reached a peak of approximately 60% for 1–4 nm particles at all flow rates. These simulations show that regional particle deposition patterns are highly dependent on particle size and flow rate, indicating the importance of accurate quantification of deposition in the rat for extrapolation of results to humans.     

Synthesis and characterization of fluorinated polyimide oligomers terminated with a phenylethynyl group

Novel all-aromatic phenylethynyl-terminated imide oligomers were prepared by the reaction of 4,4-oxydiphthalic anhydride (ODPA) or 4,4-(hexafluoroisopropylidene)diphthalic anhydride (6FDA) with 1,4-(4-amino-2-trifluoromethyl-phenoxy)-2-(3′-trifluoro-methylphenyl) benzene and 4-(1-phenylethynyl)1,8-naphthalic anhydride (PENA). The resulting polymers were thermally crosslinked at 370 °C. The cured polymers exhibited good solvent resistance and high thermal stability up to 540 °C under nitrogen. They also exhibited small light absorption at 1.31 and 1.55 μm. The refractive index of the polymers was in the range of 1.5515–1.5976 at 1550 nm. The surface relief depth of the phenylethyl terminated imide (PETI) oligomer films before and after curing was less than 1 nm over a range of 1 μm × 1 μm.     

A novel interconnected fluidised bed for the combined flash pyrolysis of biomass and combustion of char

A novel system of two adjacent fluidised beds operating in different gas atmospheres and exchanging solids was developed for the combined flash pyrolysis of biomass and combustion of the produced char. Fluidised sand particles (200 μm < d_p < 400 μm) are transported from the pyrolysis reactor to the combustor through an orifice and recycled by a standpipe, riser and cyclone. Advantages of the new design are its compactness and the high level of heat integration. The solids circulation rate and holdup distribution between the two compartments could be controlled adequately in experiments at room temperature and atmospheric pressure. A model, developed to predict the solids and gas exchange between the two reactor compartments, was validated with experiments in which the three relevant gas flows, the orifice diameter and the particle diameter were varied.