Search

[Display omitted] • Microfluidic extraction of U from aqueous phase by using TiAP dissolved in an ionic liquid as the solvent. • Mass transfer coefficient determined treating the microchannel as a differential contactor. • Effect of flow velocity, O/A ratio, contact time, microchannel diameter on mass transfer. • High-speed imaging to observe liquid-liquid two-phase flow patterns. • Effect of coiling the microchannel on mass transfer performance. A microfluidic platform to extract uranium from HNO 3 (nitric acid) medium using tri-isoamyl phosphate (TiAP) dissolved (30% v/v) in ionic liquid ([BMIM]PF 6) is reported. PTFE microbore tubes serve as the microchannels. The quality of dispersion inside the translucent tubes was observed using a camera. The images obtained are used to understand the observed experimental trends. Overall volumetric mass transfer coefficient was determined considering the microchannel as a differential contactor with co-currently flowing phases. The effects of contact time, flow velocity, organic to aqueous (O/A) ratio and microchannel diameter on mass transfer performance are studied. Effect of different coiling configurations on mass transfer performance was compared. Under optimum conditions, 95.3% of uranium present in the feed (corresponding stage efficiency being 99.2%) could be extracted within a contact time of about 200 s in a single contact. Corresponding (K L a) was 0.024 s−1. Coiling was found to have a significant effect on values of K L a especially at low residence times. [ABSTRACT FROM AUTHOR]

A continuous process to obtain ammonium diurate directly from uranium-loaded organic phase in a microbore tube is presented. The proposed process combines two different steps: multistage stripping and precipitation in a microbore tube. The effects of different operating conditions (residence time, O/A ratio, and flow velocity) on percent uranium removal, production rate, and space–time–yield (STY) have been studied. Percent uranium removal as high as 99.5% is attained within a residence time of 3 min for O/A ratio of 4. Corresponding value of STY is 3000 kg/day-m3 while ensuring a uranium concentration below 50 ppm in lean organic phase. Numerical simulations are carried out to understand the two-phase flow pattern inside the microbore tube. The results of the simulations are used to substantiate and explain the observed experimental trends. [ABSTRACT FROM AUTHOR]

The study focuses on single-stage solvent extraction of HNO 3 from 3 M HNO 3 using 30% TBP in dodecane in microbore tubes. The objective of the study is to identify a configuration that ensures high stage efficiency (⩾90%), quick settling and low pressure drop (⩽2 bar) and to demonstrate this configuration at a total throughput of 1 LPH using parallel paths. To find out the right configuration, experiments with single microbore tubes are conducted to observe the effects of flow rate, diameter and length of microbore tube on stage efficiency, pressure drop and settling behavior. The experiments show that the configuration consisting of a Y-junction of 750 μm diameter having a single microbore tube of 800 μm diameter and 300 cm length on its downstream side is capable of handling total flow rate of 0.5 LPH with high stage efficiency, quick settling and low pressure drop. Two such configurations are used in parallel to achieve total flow rate of 1 LPH. Specific extraction rate achieved in the contactor based on microbore tubes is compared with the specific extraction rate estimated for a mixer-settler. The comparison shows that the use of microbore tube contactor leads to process intensification. [ABSTRACT FROM AUTHOR]

• Solvent-free, continuous flow synthesis of [OMIM]Br in a microreactor is reported. • A production rate of 5284 g/day is attained at a space-time-yield of 119.5 g/min-L for a specific energy consumption of 10.46 W/kg. • Kinetic parameters of the alkylation reaction are determined. • Overall reaction is shown to be kinetically controlled. Solvent-free, continuous flow synthesis of [OMIM]Br in a microfluidic platform is reported for the first time. The microreactor comprises of a 862 µm diameter microbore tube attached to a 750 µm diameter opposed T-junction. Systematic experiments are conducted to study the effects of residence time, reaction temperature and flow velocity on product yield, space-time-yield, production rate and specific power consumption. An increase in residence time and reaction temperature is seen to increase product yield and production rate. At constant residence time, an increase in flow velocity is found to slightly increase product yield suggesting presence of mass transfer resistances at low velocities. Kinetic parameters of the alkylation reaction are determined. A pseudo first order kinetics is found to fit the experimental data better than second order kinetics. Frequency factor and activation energy for the pseudo first order reaction are found to be 3361.83 L/mol-s and 47964.76 J/mol, respectively. [OMIM]Br yield of 58.75 % can be achieved within 4.74 min residence time at 90°C. Under these conditions, the overall reaction is kinetically controlled (Ha being 0.004). Corresponding values of space-time-yield, production rate and specific power consumption are 119.15 g/min-L, 5284 g/day and 10.46 W/kg, respectively. [Display omitted] [ABSTRACT FROM AUTHOR]

A novel microfluidic header is proposed for scaling-up microbore tube-based applications of chemical microprocessing. A scale-up factor of up to 24 is demonstrated. The performance of the header is rigorously evaluated for uniform flow distribution and mixing of two incoming reactant streams. The effects of flow velocity and flow rate ratio on coefficient of variance of flow (COV flow) and mixing (COV mixing) are studied. An increase in flow velocity is seen to reduce values of COV mixing as well as COV flow. Experiments are conducted for two different scale-up factors (16X and 24X). COV mixing as low as 8.57% and 5.96% could be attained for the two levels of scale-up studied (i.e. 16X and 24 X case respectively). This indicates the efficient flow distribution and mixing achieved by the header. Euler Lagrangian CFD simulations are carried out to substantiate the experimental trends. The results of numerical simulations are in line with the experimental observations. In addition to predicting values of COV mixing the model also provides information on the quality of mixing at the integrated microfluidic T junctions. [Display omitted] • A scalable microfluidic header for flow distribution in up to 24 microbore tubes. • Coefficient of variance in mixing (COV mixing) of reactants as low as 5.96% achieved. • COV mixing reduced with increase in flow rate, especially so in the lateral channels. • CFD simulations carried out to substantiate and validate the experimental trends. [ABSTRACT FROM AUTHOR]

• Large-scale solvent-free continuous synthesis of ionic liquid [BMIM]Br is carried out in a microbore tube (862 μm). • Effect of temperature, residence time and velocity on space-time-yield, production rate and energy consumption are studied. • A production rate of 7.1 kg/day (100% yield and space-time-yield of 213.1 g/min-L) was achieved with in 4.93 min at 90 °C. • At the optimum condition the reaction was kinetically controlled and specific energy consumption was 27.67 W/kg. • A simple plug flow reactor (PFR) model was found to reproduce experimental data. Large-scale continuous synthesis of ionic liquid [BMIM]Br in solvent-free mode is carried out in a 862 μm diameter microbore tube. A 750 μm diameter T-junction is used to mix the two reactant streams. The effects of reaction temperature, residence time and flow velocity on product yield, space-time-yield (STY), production rate (PR) and specific power consumption are studied. Product yield is observed to increase with an increase in residence time and reaction temperature. The conditions which maximize STY and PR while ensuring that the overall reaction is kinetically controlled and yield is close to 100% are obtained. Maximum STY of 213.1 g/min-L could be attained at reaction temperature of 90 °C and a residence time of 4.93 min. At the same conditions maximum PR of 7.1 kg/day could be attained with 100% yield, the specific power consumption being 27.67 W/kg. Plug flow reactor (PFR) model is found to reproduce experimental data better compared to a laminar flow reactor (LFR) model. Performance of a simple T-junction micromixer is compared with commercially available micromixers and is found to be at par with them. [ABSTRACT FROM AUTHOR]

A liquid-liquid two-phase flow based segmented microfluidics system comprising of a simple microfluidic junction and a PTFE microbore tube to synthesize BaSO 4 nanoparticles is reported. The system is shown to be robust enough for continuous operation without any chocking. The effects of different operating parameters such as A/O ratio, initial concentration of precursors, precursor molar ratio and flow velocity on particle size and polydispersity index are studied. The above-mentioned parameters are important in synthesizing nanoparticles of precise and controlled size. Three different microfluidic junctions are evaluated for their influence on particle size and polydispersity index. Under optimum conditions, small and monodispersed BaSO 4 nanoparticles (particle size and polydispersity index being 65 nm and 0.10, respectively) could be synthesized continuously using a cross microfluidic junction and microbore tube. [ABSTRACT FROM AUTHOR]

A microbore tube is used to synthesize an imidazolium-based ionic liquid 1-butyl-3-methylimidazolium bromide ([BMIM]Br) in continuous and solvent-free mode to achieve high space-time-yield and production rate while ensuring operation in kinetically controlled regime. Within the range of the experiments, product yield is found to increase with an increase in reaction temperature and residence time. Maximum values of space-time-yield and production rate achieved are 216 gm/min-L and 1172 gm/day, respectively. The effects of different parameters (design of the microfluidic junction, flow velocity, and the extent of coiling of the microbore tube) on the product yield and production rate are studied. Opposed T-junction is found to be better than cross T-junction. Product yield increases when flow velocity is increased keeping the residence time unchanged. Product yield is found to increase with reduction in coiling diameter. Though the use of a microbore tube ensures kinetically controlled regime, a few experiments are deliberately carried out in mass transfer controlled regime to understand the issues that become important in mass transfer controlled regime. [ABSTRACT FROM AUTHOR]

• Selective separation of Cu from large excess of Zn by solvent extraction in microchannel. • Stripping of Cu from loaded organic phase in microchannel. • Effects of O/A ratio and flow velocity on percentage extraction and stage efficiency. • Effects of O/A ratio and flow velocity on selectivity and overall volumetric mass transfer coefficient. A microfluidic platform, comprising a 800 μm diameter microbore tube connected to a 750 μm diameter opposed T-junction, to selectively extract copper from a large excess of zinc is reported. The effects of flow velocity (0.033 – 0.167 m/s) and ratio of the organic phase flow rate to the aqueous phase flow rate (O/A ratio, 1−2.5) on percent Cu extraction, Cu selectivity, stage efficiency, and overall volumetric mass transfer coefficient are studied. At O/A ratio of unity, maximum stage efficiency (98.90%) and maximum value of overall volumetric mass transfer (0.039 s−1) are obtained at flow velocity of 0.167 m/s. At these operating conditions, the values of % Cu extraction and Cu selectivity are 79.10% and 54.25%, respectively. Back extraction/stripping studies are also carried out to recover Cu in pure form in the strippant phase. Cu purity as high as 99% is obtained for O/A ratio of 1 and flow velocity of 0.167 m/s. High speed imaging studies are carried out to investigate the liquid-liquid two-phase flow pattern in the microchannels both during extraction as well as stripping. [ABSTRACT FROM AUTHOR]

• Intensification of process of recovery of uranium from lean aqueous streams. • Microfluidic extraction of uranium from aqueous phase by using 30%TBP-dodecane. • Microfluidic direct precipitation of uranium from loaded organic by using NH 4 (OH). • Effects of residence time, O/A ratio and velocity on direct precipitation step. • Confirmation of reusability of organic phase. A continuous, compact process based on microfluidic extraction and microfluidic direct precipitation is presented for recovery of uranium from lean streams. The process involves extraction of uranium from an aqueous phase by using 30% (v/v) tributylphosphate (TBP) in dodecane as solvent followed by precipitation of uranium from loaded solvent using ammonium hydroxide. The effect of the ratio of volumetric flow rates of the organic phase and aqueous phase (O/A ratio) on the extraction step and the effects of O/A ratio, flow velocity and concentration of ammonium hydroxide on the direct precipitation step are studied. At optimum conditions, lean aqueous stream is contacted with the organic phase in a microchannel at a total throughput of 10 mL/min (O/A = 2) to extract 90% of uranium present in the aqueous phase. Loaded organic phase is subsequently contacted with ammonium hydroxide in a microchannel (O/A = 6) for about 92% recovery of extracted uranium in the form of ammonium diuranate (ADU). Space-time-recovery attained in the extraction and precipitation steps are 1,141,373 and 1,047,163 gm U/day/m3, respectively. Continuous operation without chocking despite solid precipitation and reusability of the organic phase are demonstrated. [ABSTRACT FROM AUTHOR]