Phase Flow Rate Ratio Research Articles

Flow pattern and pressure drop analysis of two-phase segmented flow driven by a thermomagnetic pump

The two-phase segmented flow is a flow pattern in which two immiscible fluids alternate in a flow channel with distinct segments. In this study, a thermomagnetic pump operated by heat and an external magnetic field was used to drive the flow and the temperature-sensitive magnetic fluid (TSMF) was chosen as the continuous-phase fluid to generate a two-phase segmented flow. The dispersed-phase fluid was selected as air or deionized water driven by a syringe pump. The two-phase segmented flow experiments were conducted to investigate the relation between segment length and the dispersed-continuous phase flow rate ratio at the air flow rate from 0.90 ml/h to 4.49 ml/h for air-TSMF experiment and water flow rate from 0.36 ml/h to 0.72 ml/h for water-TSMF experiment. The ratio was proportional to the bubble/droplet length and inversely proportional to the slug length. The air/water length per channel width can be up to 3.28 and 1.79, respectively, at the highest air/water flow rate in the current experiment. Moreover, the pressure drop was measured to increase with the dispersed-continuous phase flow rate ratio. The maximum pressure drop was observed as 428.2 Pa in the water-TSMF experiment with the highest water flow rate and the maximum pressure drop was 314.7 Pa for the air-TSMF experiment. These findings provide valuable insights for controlling the segment length in the two-phase segmented flow driven by a thermomagnetic pump and it could be used as precise control of liquid/gas fuel delivery in a micro-propulsion system in small satellites.

Fabrication of PEG-PLGA Microparticles with Tunable Sizes for Controlled Drug Release Application.

Polymeric microparticles of polyethyleneglycol-polylactic acid-co-glycolic acid (PEG-PLGA) are widely used as drug carriers for a variety of applications due to their unique characteristics. Although existing techniques for producing polymeric drug carriers offer the possibility of achieving greater production yield across a wide range of sizes, these methods are improbable to precisely tune particle size while upholding uniformity of particle size and morphology, ensuring consistent production yield, maintaining batch-to-batch reproducibility, and improving drug loading capacity. Herein, we developed a novel scalable method for the synthesis of tunable-sized microparticles with improved monodispersity and batch-to-batch reproducibility via the coaxial flow-phase separation technique. The study evaluated the effect of various process parameters on microparticle size and polydispersity, including polymer concentration, stirring rate, surfactant concentration, and the organic/aqueous phase flow rate and volume ratio. The results demonstrated that stirring rate and polymer concentration had the most significant impact on the mean particle size and distribution, whereas surfactant concentration had the most substantial impact on the morphology of particles. In addition to synthesizing microparticles of spherical morphology yielding particle sizes in the range of 5-50 µm across different formulations, we were able to also synthesize several microparticles exhibiting different morphologies and particle concentrations as a demonstration of the tunability and scalability of this method. Notably, by adjusting key determining process parameters, it was possible to achieve microparticle sizes in a comparable range (5-7 µm) for different formulations despite varying the concentration of polymer and volume of polymer solution in the organic phase by an order of magnitude. Finally, by the incorporation of fluorescent dyes as model hydrophilic and hydrophobic drugs, we further demonstrated how polymer amount influences drug loading capacity, encapsulation efficiency, and release kinetics of these microparticles of comparable sizes. Our study provides a framework for fabricating both hydrophobic and hydrophilic drug-loaded microparticles and elucidates the interplay between fabrication parameters and the physicochemical properties of microparticles, thereby offering an itinerary for expanding the applicability of this method for producing polymeric microparticles with desirable characteristics for specific drug delivery applications.

Chromium hydroxide microsphere synthesis using droplet microfluidics

In this work, a capillary microfluidic platform based on microbore tubes is demonstrated to continuously synthesize chromium hydroxide microspheres with a narrow particle size distribution using sol-gel process. Chromium hydroxide microspheres are later calcined to obtain chromium oxide microspheres. An in-situ mixing technique is utilized to mix the chromium precursor with the gelling agent. The effects of different design (microfluidic junction configuration, size of the microbore tube) and operating variables (continuous to dispersed phase flow rate ratio, flow velocity, residence time) on the average diameter and polydispersity index of microspheres are studied systematically. Microspheres of an average size of 574 μm with polydispersity index of 6.6% could be prepared using a double T-junction at an organic to aqueous (O/A) flow rate ratio of 60 in an 800 µm diameter microbore tube. The detailed analysis of the flow conditions reveals that the regime of drop (of aqueous phase) formation varies between transition and dripping. Finally, a correlation is proposed to predict average diameter of the microspheres based on values of capillary number (Ca) and organic to aqueous (O/A) flow rate ratio.

Enhancement of immiscible fluid mixing using passive micromixers to increase the performance of liquid–liquid extraction

This paper aims to simulate an immiscible two-phase flow in two-dimensional T-shaped, modified T-shaped, cross-shaped, and modified cross-shaped micromixers numerically. The effects of various parameters, including Capillary number, phase flow rate ratio, and channel width ratio, on the generation of droplets were studied. Also, modification of T-shaped and cross-shaped micromixers was proposed. The results reveal that equidistant tiny droplets are generated in the modified micromixers compared to ordinary geometry under the same conditions. Three types of squeezing regime, laminar regime, and jetting regime were observed in different values of the capillary number. It was also observed that the droplet size decreases with the increase in capillary number. Moreover, this study demonstrates that the multiphase flows in micro-devices are very sensitive to even small changes in the channel geometry.

Scalable and high-throughput production of an injectable platelet-rich plasma (PRP)/cell-laden microcarrier/hydrogel composite system for hair follicle tissue engineering

BackgroundTissue engineering of hair follicles (HFs) has enormous potential for hair loss treatment. However, certain challenges remain, including weakening of the dermal papilla cell (DPC) viability, proliferation, and HF inducibility, as well as the associated inefficient and tedious preparation process required to generate extracellular matrix (ECM)-mimicking substrates for biomolecules or cells. Herein, we utilized gelatin methacryloyl (GelMA) and chitosan hydrogels to prepare scalable, monodispersed, and diameter-controllable interpenetrating network GelMA/chitosan-microcarriers (IGMs) loaded with platelet-rich plasma (PRP) and seeded with DPCs, on a high-throughput microfluidic chip.ResultsThe ECM-mimicking hydrogels used for IGMs exhibited surface nano-topography and high porosity. Mass production of IGMs with distinct and precise diameters was achieved by adjusting the oil and aqueous phase flow rate ratio. Moreover, IGMs exhibited appropriate swelling and sustained growth factor release to facilitate a relatively long hair growth phase. DPCs seeded on PRP-loaded IGMs exhibited good viability (> 90%), adhesion, spreading, and proliferative properties (1.2-fold greater than control group). Importantly, PRP-loaded IGMs presented a higher hair inducibility of DPCs in vitro compared to the control and IGMs group (p < 0.05). Furthermore, DPC/PRP-laden IGMs were effectively mixed with epidermal cell (EPC)-laden GelMA to form a PRP-loaded DPC/EPC co-cultured hydrogel system (DECHS), which was subcutaneously injected into the hypodermis of nude mice. The PRP-loaded DECHS generated significantly more HFs (~ 35 per site) and novel vessels (~ 12 per site) than the other groups (p < 0.05 for each).ConclusionTaken together, these results illustrate that, based on high-throughput microfluidics, we obtained scalable and controllable production of ECM-mimicking IGMs and DECHS, which simulate an effective micro- and macro-environment to promote DPC bioactivity and hair regeneration, thus representing a potential new strategy for HF tissue engineering.

Scaled-up droplet generation in parallelised 3D flow focusing junctions

Monodispersed organic phase droplets with an average diameter from 20 to 200 µm were produced at the rate of up to 20,000 droplets per second in a glass microfluidic chip composed of 7 parallel 3D flow focusing junctions with 100 µm-deep channels. The continuous phase was 2 wt% polyvinyl alcohol solution, while the dispersed phase was dichloromethane, n-dodecane, and polydimethylsiloxane 10 cSt fluid corresponding to the dispersed-to-continuous-phase viscosity ratio of 0.2, 0.8 and 6.1, respectively. Four different droplet generation regimes were observed, dripping, squeezing, jetting, and threading. The regions where each of these regimes was stable were mapped using Weber number of the dispersed phase and capillary number of the continuous phase. The transitions between the droplet formation regimes were governed by the Weber number of the dispersed phase, indicating that inertial forces in the dispersed phase were more relevant than viscous forces in controlling the transition. Stable droplet generation in dripping regime in each junction was maintained for at least 6 h. The coefficient of variation of droplet sizes from individual junctions and all junctions combined was < 3% under optimal conditions. The droplet size variations between different junctions were greater than those within each junction. Liquid plugs were produced in the squeezing regime at the dispersed-to-continuous phase flow rate ratio greater than one. This study is the first investigation of droplet generation in multiple 3D flow-focusing junctions with potential applications for the production of drug microcarriers using emulsification solvent evaporation, especially for the encapsulation and controlled delivery of lipophilic drugs.

Experimental and CFD scale-up studies for intensified actinide/lanthanide separations

In this paper, systematic studies are performed to identify the parameters that influence the selective separation of actinides from a mixture with lanthanides in small channels. In particular, the separation of dioxouranium metal ions (UO2+2) from a binary U(VI)/Er(III) mixture in a nitric acid solution by an organic TBP/kerosene (Exxsol D80) phase, relevant to spent nuclear fuel reprocessing is investigated. The effects of parameters such as TBP concentration, organic-to-aqueous phase flow rate ratio, channel size, and residence time on mass transfer are evaluated, whilst the mass transfer performance in the extraction channels is further analysed using two important hydrodynamic features, i.e. plug formation time and interfacial area to volume ratio. Circular channels with diameters from 1 to 3 mm are used to investigate the effect of scale on the mass transfer characteristics. The importance of the mixing zone on mass transfer is also evaluated. A CFD model is proposed to simulate the mass transfer during plug flow. Using only one experimental point, once the plug has been formed, the model is able to predict extraction percentage with less than 4% difference compared to the experiments.

Continuous Synthesis of Monodisperse Yolk–Shell Titania Microspheres

A microfluidic strategy is developed for continuous synthesis of monodisperse yolk–shell titania microspheres. The continuous flow synthesis of titania microparticles is achieved by decoupling the microdroplet formation and interfacial hydrolysis reaction steps by utilizing a polar aprotic solvent as the continuous phase in the microreactor. The decoupling of the precursor microdroplet formation and the hydrolysis reaction allows titania synthesis throughputs an order of magnitude higher than those previously reported in a single-channel flow reactor (∼0.1 g/h calcined microparticles), without affecting the microreactor lifetime due to clogging. Flow synthesis and dynamics across a broad range of precursor flow rates are examined, while effects of flow synthesis parameters, including the precursor to continuous phase flow rate ratio, precursor composition, and calcination temperature on the surface morphology, size, and composition of the resulting titania microparticles, are explored in detail. Titania m...

Mass transfer characteristics of rotating spiral gas-liquid contacting

The first substantial experimental measurements of mass transfer in a rotating spiral channel are reported for counter-current physical desorption of a range of organic solutes from water into air. General relations in terms of bulk properties are developed that allow analysis and comparison across different solute properties, operating conditions and contacting equipment. The phase flow rate ratio and cleaned-phase throughput per passage volume emerge as parameters of principal importance, the former measuring sufficiency of solvent phase flow and the later mass transfer effectiveness and, consequently, required device size. The analytical solution for an infinitely wide channel is used to probe the finite-width experimental results and an apparently universal pattern of differences involving a peak in mass transfer coefficient emerges. As liquid flow rate decreases, the thickness of the liquid layer decreases and the mass transfer coefficient rises. But with further decrease in liquid flow rate and liquid layer thickness, an increasing fraction of the liquid flows in the corner regions under the end-wall menisci and the poor contact in these regions leads to a falling mass transfer coefficient. The peak is found to occur at a similar liquid layer thickness regardless of gas flow rate or solute equilibrium characteristics. Comparison is made with packed columns and rotating packed beds using available data in the literature. The rotating spiral performance suggests device sizes will be many times smaller than those for the two packed devices considered. Dependence of rotating spiral device volume on the square of channel size is demonstrated, showing that further reduction in device volume is possible.

Liquid-liquid dispersions in intensified impinging-jets cells

The formation of dispersions of two immiscible liquids in a confined impinging-jets cell was studied experimentally. The jets of the liquids formed at two opposing channels and collided in a main channel, which was perpendicular to the previous two. Jet channels with diameters either 0.25 or 0.5mm and main channels with diameters either 2 or 3mm were used. The jet velocities varied from 0.17 to 6.2m/s and the dispersed to continuous phase ratios varied from 0.05 to 0.28. Deionised water and kerosene (Exxsol D80: ρ=795kg/m3 and μ=1.73mPas) were used as test fluids. Drop sizes were measured with high-speed imaging. It was found that the total velocity of the two jets was the main parameter that affected both the average drop size and the interfacial area, whilst the dispersed to continuous phase flow rate ratio was less significant. Both phases could become continuous depending on the phase flowrate ratio; drops were, however, larger in the organic continuous dispersions. The interfacial area produced with the impinging-jets cell was almost 3 times larger than in capillary contactors at similar conditions (umix=0.024–0.19m/s). The size of the main channel affected the drop size and smaller drops formed in the large channel compared to the small one. With increasing energy dissipation rate, ε, in the impingement zone, the Sauter mean diameter decreased following a relation of the form ∼ε−b. Apart from the lower velocities, the drop sizes did not change significantly at distances equal to 15 channel diameters downstream the impingement area.

A microreactor-based continuous process for controlled synthesis of poly-methyl-methacrylate-methacrylic acid (PMMA) nanoparticles.

We have developed a microreactor-based continuous process for synthesizing PMMA nanoparticles (NPs), based on the principle of nanoprecipitation. Our objective was to identify the critical parameters governing the size of nanoparticles, produced in microreactors, to enable reproducible synthesis of mono-disperse particles. Experiments were carried out in a microreactor, where parameters like flow rates of aqueous and organic phases, residence time and polymer concentrations were varied to examine their influence on particle size and homogeneity. The results from Dynamic Light Scattering confirmed that the particle size decreased with decreasing residence time, whereas when the aqueous to organic phase flow rate ratio was changed sequentially from 9 : 1, 4 : 1, 7 : 3, 3 : 2, to 1 : 1 (v/v), the particle size increased. Particles fabricated using a microreactor demonstrated a narrow and homogenous distribution, thus confirming their monodispersity. TEM, SEM and XRD were also performed for morphology analysis and phase identification of the particles. Further, paclitaxel encapsulated PMMA nanoparticles were prepared using the microreactor, demonstrating an increase in mean size of around 30 nm and a slightly higher polydispersity index compared to the blank nanoparticles. The drug encapsulation efficiency and drug release kinetics of these nanoparticles were comparable to those prepared in batch-experiments, thus establishing the suitability of the technology for preparing drug-loaded nanoparticles. Also, it was observed that at all the residence times (10 min to 10 s), about 80% of the polymer got transformed into nanoparticulate form, thus confirming the efficiency of the microreactor. In recent times, much work has been conducted to synthesize polymeric nanoparticles using different types of microreactors, but they lack detailed investigation of the effect of various parameters on the physiochemical properties of the resulting particles. Our investigation synthesizes PMMA NPs, using microreactor technology, for the very first time, to the best of our knowledge. Furthermore, we have performed a detailed analysis of the influence of various process parameters on the size and uniformity of the resulting nanoparticles. These critical parameters can serve as a useful tool to synthesize a myriad of nanoparticles of alternative polymers, using microreactor technology.

Microfluidic Fabrication of Hydrocortisone Nanocrystals Coated with Polymeric Stabilisers.

Hydrocortisone (HC) nanocrystals intended for parenteral administration of HC were produced by anti-solvent crystallisation within coaxial assemblies of pulled borosilicate glass capillaries using either co-current flow of aqueous and organic phases or counter-current flow focusing. The organic phase was composed of 7 mg/mL of HC in a 60:40 (v/v) mixture of ethanol and water and the anti-solvent was milli-Q water. The microfluidic mixers were fabricated with an orifice diameter of the inner capillary ranging from 50 µm to 400 µm and operated at the aqueous to organic phase flow rate ratio ranging from 5 to 25. The size of the nanocrystals decreased with increasing aqueous to organic flow rate ratio. The counter-current flow microfluidic mixers provided smaller nanocrystals than the co-current flow devices under the same conditions and for the same geometry, due to smaller diameter of the organic phase stream in the mixing zone. The Z-average particle size of the drug nanocrystals increased from 210–280 nm to 320–400 nm after coating the nanocrystals with 0.2 wt % aqueous solution of hydroxypropyl methylcellulose (HPMC) in a stirred vial. The differential scanning calorimetry (DSC) and X-ray powder diffraction (XRPD) analyses carried out on the dried nanocrystals stabilized with HPMC, polyvinyl pyrrolidone (PVP), and sodium lauryl sulfate (SLS) were investigated and reported. The degree of crystallinity for the processed sample was lowest for the sample stabilised with HPMC and the highest for the raw HC powder.

Intensified Eu(III) extraction using ionic liquids in small channels

The extraction of Eu(III) from nitric acid solutions was studied in intensified small scale separation units using an ionic liquid solution (0.2M n-octyl(phenyl)-N,N-diisobutylcarbamoylmethyphosphine oxide (CMPO)–1.2M Tributylphosphate) (TBP)/1-butyl-3-methylimidazolium bis[(trifluoromethyl)sulfonyl]amide; ([C4min][NTf2])as the extraction phase. The investigations were carried out in channels with 0.2mm and 0.5mm diameter for phase flowrates that result in plug flow with the aqueous solution as the dispersed phase. The interfacial area in plug flow and the velocity profiles within the plugs were studied with high speed imaging and bright field micro Particle Image Velocimetry. Distribution and mass transfer coefficients were found to have maximum values at nitric acid concentration of 1M. Mass transfer coefficients were higher in the small channel, where recirculation within the plugs and interfacial area are large, compared to the large channel for the same mixture velocities and phase flow rate ratio. Within the same channel, mass transfer coefficients decreased with increasing residence time indicating that significant mass transfer takes place at the channel inlet where the two phases come into contact. The experimental results were compared with previous correlations on mass transfer coefficients in plug flows.

Studies of plug formation in microchannel liquid–liquid flows using advanced particle image velocimetry techniques

Two complementary micro Particle Image Velocimetry (μPIV) techniques have been developed in this work to study plug formation at a microchannel inlet during the flow of two immiscible liquids. Experiments were conducted for different fluid flow rate combinations in a T-junction, where all branches had internal diameters equal to 200μm. The dispersed phase was a water/glycerol solution and was injected from the side branch of the junction, while the continuous phase was silicon oil and was injected along the main channel axis. In the two-colour μPIV technique two laser wavelengths are used to illuminate two different tracer particles, one in each fluid, and phase averaged velocity profiles can be obtained in both phases simultaneously. In the high speed bright field μPIV technique, a backlight illuminates the test section, where the dispersed phase plug is seeded with tracer particles. This approach allows velocity profiles of the forming dispersed plugs to be followed in time.Non-dimensional plug lengths were found to vary linearly with the aqueous to organic phase flow rate ratio, in agreement with a well-known scaling correlation. The flowrate ratio also affected the velocity profiles within the forming plugs. In particular, for a ratio equal to one, a vortex appears at the tip of the plug in the early stages of plug formation. The interface curvature at the rear of the forming plug changes sign at the later stages of plug formation and accelerates the thinning of the meniscus leading to plug breakage. The spatially resolved velocity fields obtained in both phases with the two-colour PIV show that the continuous phase resists the flow of the dispersed phase into the main channel at the rear of the plug meniscus and causes the change in the interface curvature. This change of interface curvature was accompanied by an increase in vorticity inside the dispersed phase during plug formation.

Preparation of biodegradable polymeric nanoparticles for pharmaceutical applications using glass capillary microfluidics

The aim of this study was to develop a new microfluidic approach for the preparation of nanoparticles with tuneable sizes based on micromixing/direct nanoprecipitation in a coaxial assembly of tapered-end glass capillaries. The organic phase was 1wt% poly(ε-caprolactone) (PCL) or poly(dl-lactic acid) (PLA) in tetrahydrofuran and the antisolvent was Milli-Q water. The size of nanoparticles was precisely controlled over a range of 190–650nm by controlling phase flow rates, orifice size and flow configuration (two-phase co-flow or counter-current flow focusing). Smaller particles were produced in a flow focusing device, because the organic phase stream was significantly narrower than the orifice and remained narrow for a longer distance downstream of the orifice. The mean size of PCL particles produced in a flow focusing device with an orifice size of 200μm, an organic phase flow rate of 1.7mLh−1 and an aqueous-to-organic flow rate ratio of 10 was below 200nm. The size of nanoparticles decreased with decreasing the orifice size and increasing the aqueous-to-organic phase flow rate ratio. Due to higher affinity for water and amorphous structure, PLA nanoparticles were smaller and exhibited a smoother surface and more rounded shape than PCL particles.

Liquid–liquid mixing enhancement rules by microbubbles in three typical micro-mixers

Micro-mixers are good platforms to realize liquid–liquid mixing, but they still need intensification when treating extreme flow conditions, such as relatively higher fluid viscosity than water (μ>3mPas) or high flow rate ratio (R>10). In this work, the quantitative mixing enhancement rules with inert gas phase as enhancing medium in three typical micro-mixers, T-junction microchannel, cross-junction microchannel as well as co-flowing microchannel, are experimentally studied using “Villermaux–Dushman” parallel competitive reaction. The results show that the gas makes Xs reduced by 2–5 times in the working systems with various viscosities (0.86mPas≤μ≤11.46mPas) and operated in a wide range of flow rate ratio (1≤R≤25). The mixing enhancement mechanism is the two-phase segmented flow and we find only 0.05–0.1 gas–liquid phase flow rate ratio (Rgas) is enough for the gas phase to develop its enhancing effect. Based on the characteristics of segmented liquid flow, a mathematical model is established to predict the variation of Xs in three micro-mixers.

Microfluidic conceived pH sensitive core–shell particles for dual drug delivery

In current study, we report on the synthesis of core–shell microparticles for dual drug delivery by means of a two co-axial microfluidic device and online UV assisted free radical polymerization. Before developing pH-sensitive particles, ketoprofen loaded poly(methyl acrylate) core–ranitidine HCl loaded poly(acrylamide) shell particles were produced. Influence of inner and outer phases flow rates on particle size, shape, core diameter, shell thickness, and drug release properties was studied. All the particles were monodispersed with coefficient of variation below 5%. Furthermore, their diameter ranged from 100 to 151μm by increasing continuous (Qc) to middle (Qm) phase flow rate ratio (Qc/Qm). Core diameter varied from 58 to 115μm by decreasing middle (Qm) to inner (Qi) phase flow rate ratio (Qm/Qi) at constant continuous phase flow rate as confirmed by SEM images. It was observed that an optimum concentration of acrylamide (30wt%) and an appropriate combination of surfactants were necessary to get core–shell particles otherwise Janus structure was obtained. FTIR confirmed the complete polymerization of core and shell phases. MTT assay showed variation in viability of cells under non-contact and contact conditions with less cytotoxicity for the former. Under non-contact conditions LD50 was 3.1mg/mL. Release studies in USP phosphate buffer solution showed simultaneously release of ketoprofen and ranitidine HCl for non pH-sensitive particles. However, release rates of ranitidine HCl and ketoprofen were higher at low and high pH respectively. To develop pH-sensitive particles for colon targeting, the previous shell phase was admixed with few weight percentage of pH sensitive carboxyethyl acrylate monomer. Core and shell contained the same hydrophobic and hydrophilic model drugs as in previous case. The pH-sensitive shell prevented the release of the two entrapped molecules at low pH while increasing significantly their release rate at higher pH with a maximum discharge at colonic pH of 7.4.

Preparation of Ultrafine Carbon Spheres by Controlled Polymerization of Furfuryl Alcohol in Microdroplets

Carbon microspheres with mean particle sizes of 0.7–1.2 μm were prepared by polymerization of furfuryl alcohol (FA) in H2SO4 solution droplets without any surfactant, followed by pyrolysis. FA was introduced by diffusion from FA-containing oil phase into the droplets formed in an interdigital micromixer. The oil to aqueous phase flow rate ratio and the FA and H2SO4 concentrations should be kept at medium values. A decrease in the total flow rate ratio, oil to aqueous phase flow rate ratio, or FA concentration results in small-sized carbon microspheres, and a decrease in the FA or H2SO4 concentration leads to formation of the carbon microspheres exhibiting rough surface. The carbon microspheres show good dispersity in ethanol and microporosity. Their particle sizes could be further reduced to 150 nm by using polyvinyl pyrrolidone, and their mesoporosity can easily be endowed by adding silica nanoparticles in the droplets.

Dioxouranium(VI) extraction in microchannels using ionic liquids

The extraction of uranium(VI) from aqueous nitric acid solutions by tributylphosphate {TBP; 30%(v/v)} dissolved in the ionic liquid 1-butyl-3-methylimidazolium bis{(trifluoromethyl)sulfonyl}amide was investigated. The experiments were performed in a Teflon microchannel of 0.5mm internal diameter, while the dioxouranium(VI) concentrations in the aqueous and the ionic liquid phases were determined by UV–Vis spectroscopy. The effects of initial nitric acid concentration (0.01–3M), residence time, and phase flow rate ratio were studied. It was found that, with increasing nitric acid concentration, the percentage of dioxouranium(VI) extracted decreased and then increased again, while the extraction efficiency followed a slightly different trend. Overall mass transfer coefficients varied between 0.049s−1 and 0.312s−1.

Generation of micromonodispersed droplets and bubbles in the capillary embedded T‐junction microfluidic devices

AbstractThis work focuses on the dispersion of micromonodispersed droplets and bubbles in the capillary embedded T‐junction microfluidic devices. The effects of the microchannel structure, operating conditions, and physical properties on the dispersion rules were carefully investigated. It was found that the extended capillary could greatly affect the dispersion rules, which was favorable for reducing the dispersed size. The dispersed size was mainly dominated by the Ca number, and the effects of dispersed phase flow rate and viscosity ratio of the two phases were also very important. The dispersion mechanism and size rules in the capillary embedded microfluidic devices were discussed seriously by comparing the similarities and differences of the liquid/liquid and gas/liquid dispersion processes. © 2010 American Institute of Chemical Engineers AIChE J, 2011