Liquid-liquid Contactor Research Articles

Recovery of bio-based volatile fatty acids from anaerobically treated winery wastewater using a closed-loop liquid-liquid hydrophobic membrane contactor system

This research evaluated a closed-loop hydrophobic liquid–liquid membrane contactor (MC) for the recovery of volatile fatty acids (VFAs) from the effluent of an up-flow anaerobic sludge blanket (UASB) bioreactor treating winery wastewater. Sodium bicarbonate was used as a stripping solution for its operational flexibility and compatibility with downstream bioprocesses. An electrochemical acidification cell (EAC) was tested to continuously adjust of pH of the feed solution to avoid the use of inorganic acids. VFA recovery was optimized under different flow rates and feed pH conditions using a synthetic VFA solution and validated with actual UASB effluent. Lower feed pH resulted in higher VFA recovery due to increased protonation of the acids. This effect was more pronounced when using synthetic VFA solutions compared to real UASB effluent. Specifically, the MC system recovered 16 ± 5 % of acetic acid at 0.3 ± 0.1 gCOD/m2h flux and 34 ± 4 % of butyric acid at 0.5 ± 0.1 gCOD/m2h flux at an unadjusted UASB effluent feed pH of 4.9, compared to 22 ± 3 % at 0.5 ± 0.1 gCOD/m2h flux and 46 ± 5 % at 0.7 ± 0.1 gCOD/m2h flux, respectively, at pH 2. The EAC effectively lowered the feed pH of UASB effluent to 3.9, achieving acetic acid recovery of 22 ± 3 % at a mass flux of 0.2 ± 0.1 gCOD/m2h, and butyric acid recovery of 45 ± 1 % at a mass flux of 0.6 ± 0.1 gCOD/m2h. These moderate recovery efficiencies are likely influenced by the lower pH gradient resulting from the use of sodium bicarbonate. However, the compatibility of sodium bicarbonate with bioprocesses offers the advantage that the proposed UASB-MC system can be seamlessly integrated with downstream bioprocesses to produce valuable end products for other markets, such as PHA for plastics and microbial proteins for animal feed.

Liquid-liquid extraction of phenolic wastewater through a surface modified poly(vinylidene fluoride-co-hexafluoropropylene) hollow fiber membrane contactor and process optimization

BackgroundStrict environmental regulations have been recognized for phenolic wastewater treatment due to toxicity of the phenolic compounds. In this study, solvent extraction of a phenolic wastewater was investigated via a liquid-liquid membrane contactor system. MethodsPorous poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) hollow fiber membranes were modified by coating an ultra-thin layer of hydrophobic surface modifying macromolecule (SMM). The membranes were characterized by various tests such as SEM-EDS, nitrogen permeation, overall porosity, contact angle and critical water entry pressure (CEPw). Significant findingsFrom SEM, an open structure with combination of finger-like and sponge-like structure was produced. The membrane exhibited high surface hydrophobicity (water contact angle of 109°) with good wetting resistance, overall porosity of 82% and mean pore size of 18 nm. From response surface methodology (RSM), the maximum phenol extraction flux of 2.02 × 10−3 kg/m2s was estimated by the model at the optimum process variables as phenol concentration of 448 mg/L, feed temperature of 42 °C, aqueous phase flowrate of 196 mL/min and organic phase flowrate of 117 mL/min. The coefficient of determination (R2) of 0.972 showed a close proximity between the model and the experimental data. The membrane showed a reasonable flux that can be a favorable alternative for industrial phenolic wastewater treatment.

Stability of Porous Polymeric Membranes in Amine Solvents for Membrane Contactor Applications.

Membrane gas-liquid contactors have great potential to meet the challenges of amine CO2 capture. In this case, the most effective approach is the use of composite membranes. However, to obtain these, it is necessary to take into account the chemical and morphological resistance of membrane supports to long-term exposure to amine absorbents and their oxidative degradation products. In this work, we studied the chemical and morphological stability of a number of commercial porous polymeric membranes exposed to various types of alkanolamines with the addition of heat-stable salt anions as a model of real industrial CO2 amine solvents. The results of the physicochemical analysis of the chemical and morphological stability of porous polymer membranes after exposure to alkanolamines, their oxidative degradation products, and oxygen scavengers were presented. According to the results of studies by FTIR spectroscopy and AFM, a significant destruction of porous membranes based on polypropylene (PP), polyvinylidenefluoride (PVDF), polyethersulfone (PES) and polyamide (nylon, PA) was revealed. At the same time, the polytetrafluoroethylene (PTFE) membranes had relatively high stability. On the basis of these results, composite membranes with porous supports that are stable in amine solvents can be successfully obtained to create liquid-liquid and gas-liquid membrane contactors for membrane deoxygenation.

Nitrogen recovery from sludge centrate by membrane contactor: Influence of operating parameters and cleaning conditions

In urban wastewater treatment, the sludge generated is treated by anaerobic digestion, to be subsequently dehydrated by centrifuges. Currently, the liquid fraction obtained in this dehydration process is recirculated at the head of the treatment plant. However, its high nitrogen and phosphorus content makes it an effluent with high added value. The recovery of these nutrients could be an excellent alternative for the production of fertilizers or other industrial applications. In this study, the use of a liquid-liquid phase membrane contactor is presented as a favorable solution for the recovery of ammoniacal nitrogen from sludge centrated. The polypropylene hollow fiber membrane was evaluated considering its ammonia removal and recovery capacity. For this, different parameters were evaluated: the influence of the type and concentration of the acid solution, the wastewater pH, the flow rates of feeding and the acid stripping solution, and the contact time. Results showed that with a contact time of 65 min, ammonia removal and recovery percentages of the order of 90% were achieved. The flow rates of the stripping and feed solutions together with the acid concentration did not have a significant influence on the removal but on the recovery. Concerning used acid, sulphuric and phosphoric acid solutions achieved better results than nitric acid solution. The most critical parameter was the pH, obtaining the highest removal and recovery of ammonium at the highest pH. Finally, a stable cleaning protocol was obtained, between preventive and moderate cleanings to avoid severe cleanings, keeping the membrane at its maximum capacity.

Reclaiming of Amine CO2 Solvent Using Extraction of Heat Stable Salts in Liquid-Liquid Membrane Contactor

Amine CO2 solvents undergo oxidative degradation with the formation of heat stable salts (HSS). These HSS reduce the sorption capacity of amines and lead to intense corrosion of the equipment. In our work, we propose a membrane-supported liquid-liquid extraction of the HSS from alkanolamines. For this purpose, a hollow fiber membrane contactor was used for the first time. A lab-scale extraction system on the basis of a hollow-fiber liquid-liquid membrane contactor with hollow fiber ultrafiltration polyvinylidenefluoride and polysulfone membranes has been studied. The extraction of the HSS-ions from a 30 wt.% solution of monoethanolamine was carried out using a 0.25-1 M solution of OH-modified methyltrioctylammonium chloride in 1-octanol as an extractant. It has been shown that >90% of HSS ions can be extracted from the alkanolamine solvent within 8 h after extraction. The results obtained confirm the possibility of using membrane extraction with a liquid-liquid membrane contactor for the reclaiming of amine CO2 solvents to increase the general efficiency of carbon dioxide capture.

Interphase Surface Stability in Liquid-Liquid Membrane Contactors Based on Track-Etched Membranes.

A promising solution for the implementation of extraction processes is liquid–liquid membrane contactors. The transfer of the target component from one immiscible liquid to another is carried out inside membrane pores. For the first time, highly asymmetric track-etched membranes made of polyethylene terephthalate (PET) of the same thickness but with different pore diameters (12.5–19 nm on one side and hundreds of nanometers on the other side) were studied in the liquid–liquid membrane contactor. For analysis of the liquid–liquid interface stability, two systems widely diverging in the interfacial tension value were used: water–pentanol and water–hexadecane. The interface stability was investigated depending on the following process parameters: the porous structure, the location of the asymmetric membrane in the contactor, the velocities of liquids, and the pressure drop between them. It was shown that the stability of the interface increases with decreasing pore size. Furthermore, it is preferable to supply the aqueous phase from the side of the asymmetric membrane with the larger pore size. The asymmetry of the porous structure of the membrane makes it possible to increase the range of pressure drop values between the phases by at least two times (from 5 to 10 kPa), which does not lead to mutual dispersion of the liquids. The liquid–liquid contactor based on the asymmetric track-etched membranes allows for the extraction of impurities from the organic phase into the aqueous phase by using a 1% solution of acetone in hexadecane as an example.

Sulfonated foam catalysts for the continuous dehydration of xylose to furfural in biphasic media

This paper demonstrates the use of sulfonated foam structures, acting both as catalyst and liquid-liquid contactor, during the continuous dehydration of xylose to furfural in biphasic media. First, we develop and optimize a coating procedure comprising a two-step polymerization technique (polypropylene and polystyrene-divinylbenzene), followed by swelling and sulfonation. The method was highly reproducible and led to a stable, well-adhered, 12–50 μm layer of sulfonic resin with an ion exchange capacity of 0.1 meq/cmfoam3. The catalytic foams showed the same activity than H2SO4 in terms of conversion and selectivity versus residence time and temperature. The enhanced mass transfer properties of the foam-based reactor facilitated rapid furfural extraction, thus allowing for higher temperature operations (ca. 20–50 °C higher) and shorter residence times (ca. 10 min vs. 4–5 h) than conventionally reported in the literature, while preserving high furfural selectivity (ca. 70–80%). Finally, the stability of the sulfonated foam catalyst during operation was demonstrated up to 170 °C, although higher temperatures led to a visible decay in activity. We conclude that the sulfonated foams show great potential for this application.

Study of the operational parameters in the hollow fibre liquid-liquid membrane contactors process for ammonia valorisation as liquid fertiliser

The transformation of wastewater treatment plants (WWTPs) to resources recovery plants (nutrients and energy) is forcing the development of specific technologies for selective recovery. Ion-exchange and hollow fibre liquid-liquid membrane contactors (HF-LLMCs) appeared as promising technologies to reduce operation costs, at ambient temperature, on the N-recovery from main-streams of urban WWTPs. A concentrated ammonia stream (4.5 g/L), recovered from treated wastewater using zeolites and NaOH, was used to test different operational parameters on the performance of the HF-LLMC process for ammonia recovery. These tested parameters were HF-LLMC position (horizontal and vertical), HF-LLMC feed and acid streams inputs (shell and lumen), type of acid stripping solution (0.4 M H3PO4 and 0.4 M HNO3), membrane drying, flow rate for each stream (263–770 mL/min), number of steps (1 and 2) and number of membrane contactors (1 and 2 in series). The maximum ammonia recovery (>95%) was achieved by a one-step configuration using two vertical membrane contactors in series; using the shell side for feed stream and the lumen side for the acid stripping solution (HNO3); at 450 mL/min and 770 mL/min flow rates for feed and acid stripping solutions, respectively. The liquid fertiliser composition obtained was around 4.6% N (from NH4+). Additionally, the ammonia treated stream, rich in NaOH, had residual levels of NH3 (about 200 mg/L) that could be reused for the regeneration of the zeolites. This optimized HF-LLMC process allowed to recover ammonia from a tertiary treatment solution of an urban WWTP and at the same time to produce ammonium salts that could be used as liquid fertilisers in irrigation applications. Therefore, this technology promotes the circular economy concept for nutrient recovery in urban WWTPs.

Entropy and exergy analysis of a liquid-liquid air-gap hollow fiber membrane contactor

A liquid-liquid air-gap hollow fiber membrane contactor consisting of a number of hollow fiber membrane tubes forms a hollow fiber membrane absorption heat pump where the refrigerant (water) and the absorbent (LiCl solution) flow inside the tubes in a cross-flow arrangement. There are defined air-gaps between neighboring tube rows. A lumped parameter model which describes the heat and mass transfer is established by transforming the membrane contactor into a parallel-plate one. The governing equations are solved by the finite difference approach. The model is validated experimentally. The influences of various structural parameters, operation conditions, and membrane parameters on the contactor performances are analyzed. An entropy generation model and an exergy destruction model are established to solve and disclose the thermodynamic properties of the heat and mass transfer process inside the membrane contactor, which is an irreversible process. It has been found that the contactor performance can be improved by using the hollow fiber membranes with larger diffusivity or a smaller diameter of about 1.5 mm. Furthermore, the packing fraction of about 0.349 is optimal for the performance. The maximum mass transfer entropy generation rate usually corresponds to the best performance. The entropy generation minimization method is not suitable for the optimization of this membrane contactor. The optimized regions of the structural parameters, operation conditions, and membrane transport parameters with better performances and smaller entropy generation can be obtained to reduce irreversible loss in future.

Integrating crystallisation into transmembrane chemical absorption: Process intensification for ammonia separation from anaerobic digestate

In this study, reactive crystallisation is introduced into a liquid-liquid membrane contactor for the selective separation, purification and recovery of ammonia from concentrated waste. Whilst liquid-liquid membrane contactor technology has been previously demonstrated for ammonia absorption, further process intensification can be achieved by incorporating crystallisation into transmembrane chemisorption to recover the ammonia as crystalline ammonium sulphate. Reactive crystallisation occurred in the draw solution (sulphuric acid) which was supplied to the lumen-side of the polypropylene hollow-fibre. The ammonium sulphate concentration in the draw solution increased through ammonia mass transfer to supersaturation, at which time induction (the onset of nucleation) commenced. Ammonia mass transfer at draw concentrations above the solubility limit was not limited provided sufficient ‘free’ sulphate was available. This resulted in nucleation which occurred at a low level of supersaturation (C/C*, 1.03) to produce small crystals of around 2.5 μm, which indicated that nucleation was favoured. The nucleation rate was found to be proportional to the ammonia flux in the draw solution. As the solution became more saturated, crystal number increased but crystal growth was comparatively small; this is symptomatic of reactive crystallisation, where the rate of reaction exceeds the rate of mass transfer. Due to the large difference in the ratio between the lumen internal diameter and the mean crystal diameter (dfibre/dmean,CSD, ~180), no fibre clogging was observed despite facilitating crystallisation on the lumen-side of the membrane. Transmembrane chemisorption crystallisation presents a feasible process intensification for the selective separation of ammonia from environmental applications. For its integration into environmental applications, solutions to wetting and fouling remain due to associative interactions with the complex organic matrix that are practically achievable through engineering intervention. Subsequent transformation of ammonia into a crystalline phase of ammonium sulphate presents a new product which is of commercial interest.

Integration of liquid-liquid membrane contactors and electrodialysis for ammonium recovery and concentration as a liquid fertilizer.

The accumulation of ammonia in water bodies can cause eutrophication and reduce water quality. Furthermore, 80% of the ammonia in the world is consumed as fertilizer, which makes it a resource that can be recovered under the circular economy concept. Then, ammonia from wastewater can be valorised for agricultural applications. Liquid-liquid membrane contactors (LLMCs) have been postulated as a novel and eco-friendly technology for ammonia recovery, because they can convert dissolved ammonia into ammonium salts by an acid stripping solution. The concentration of the ammonium salt produced is limited by the co-transport of water in LLMC. Further concentration by electrodialysis (ED) is presented as a solution to overcome this problem. In this work, ammonia streams with different initial ammonia concentrations (1.7-4.0g/L) were treated by LLMCs to produce liquid ammonium salt fertilizers (as NH4NO3 and NH4H2PO4). Then, these ammonium solutions were concentrated by ED in order to achieve the nitrogen content required for direct application in agriculture for fertigation. After the LLMC process, the fertilizer obtained was composed of approximately 5.1% or 10.1% (w/w) nitrogen, depending on the initial ammonia concentration. After that, it was possible to concentrate these ammonium salts by a factor of 1.6±0.3 using ED with an optimal energy consumption of 0.21±0.08kWh/kg ammonium salt and 93.1±4.2% of faradaic yield. This gave a liquid fertilizer composed of 15.6% (w/w) nitrogen as NH4NO3. Overall, it was possible to integrate two innovative membrane technologies for the valorisation and concentration of nutrients from ammonia wastewater streams.

Intensified Liquid-Liquid Extraction Technologies in Small Channels: A Review

Solvent extraction is a key separation process in several industries. Mixer-settlers and agitated or pulsed columns are mainly used as liquid-liquid contactors. However, these units require large solvent inventories and long residence times, while flow fields are often not uniform and mixing is poor. These drawbacks can be overcome with process intensification approaches where small channel extractors are used instead. The reduced volumes of small units in association with the increased efficiencies facilitate the use of novel, often expensive, but more efficient and environmentally friendly solvents, such as ionic liquids. The small throughputs of intensified contactors, however, can limit their full usage in industrial applications, thus robust scale-up strategies need to be developed. This paper reviews promising intensified technologies for liquid-liquid extractions based on small channels. In particular, extractions in single channels and in confined impinging jets are considered. The increase in throughput via scale-out approaches with appropriate manifolds is discussed, based on the use of many channels in parallel. The combination of small channels and centrifugal forces is exploited in counter-current chromatography (CCC) systems where many mixing and settling steps are combined within the contactors. Scale up is possible via centrifugal partition chromatography (CPC) configurations.

Microfluidic solvent extraction of calcium: Modeling and optimization of the process variables

In this study, a new systematic method was proposed for the highly efficient separation of species with very low separation factor. Here, solvent extraction and microfluidic technology were integrated for the extraction and separation of Ca2+ion. A cyclic compound (DC18C6) was used as the selective extractant. Full separation of organic and aqueous phases at the end of the microchannel was achieved by exploiting a flow regime map. N-butyl acetate was chosen as organic solvent among from other potential candidates with different characteristics. The Box-Behnken experimental design was used to provide data for modeling, while the variables of the model were DC18C6 concentration, flow rate and pH of the aqueous phase. The results showed that Ca2+ extraction efficiency was 62.28% under the optimum conditions: DC18C6 concentration was 0.014 M, the aqueous phaseflow rate was 20 µl/min and pH of the aqueous phase was 5.1. Multi-stage microfluidic solvent extraction in series was performed and the possibility of numbering-up with maintaining full phase separation was demonstrated. The overall volumetric mass transfer coefficients were determined quantitatively in a single microchannel, and their values were in the ranges of 0.19–0.41 s−1, which are two orders of magnitude higher than those of conventional liquid-liquid contactors.

Liquid fertilizer production by ammonia recovery from treated ammonia-rich regenerated streams using liquid-liquid membrane contactors

The nitrogen load on urban wastewater should be considered as a secondary resource for nitrogen-based fertilizers. From this point of view, ammonia-rich streams obtained from a regeneration step with zeolites using 70–80 g NaOH/L could contain up to 3.5–4.5 g NH3/L as well as other ionic species (Na+, K+, Ca2+, Mg2+) and dissolved organic matter (DOM). Thus, they could be treated to obtain a valuable product composed by ammonia for fertilizing applications. A sorption pre-treatment process was carried out to remove the residual amount of DOM and to reduce membrane fouling before processing with hollow fibres liquid-liquid membrane contactors (HF-LLMC). Polypropylene HF-LLMC was used to selectively extract ammonia in single or two-step configurations using different acid stripping solutions (H3PO4, HNO3 or a mixture of HNO3/H3PO4). For ammonia recovery, the ammonia mass transfer coefficient (Km(NH3)) and water transport by HF-LLMC were determined. H3PO4 was found to be the best acid stripping solution by one-step HF-LLMC; the ammonia removal was 76% with a Km(NH3) of 8.8 × 10−7 m/s. Additionally, the ammonia was concentrated 26 times, and it was recovered as multi-nutrient liquid fertilizer (NP) composed of 7.8% N and 21.6% P2O5. Furthermore, ammonia recovery was increased, reaching values up to 94%, through two-step HF-LLMC, and again H3PO4 was used as stripping solution. Finally, water transport from the feed to the stripping phase was estimated to be 0.022 L/m2·h for one-step HF-LLMC with H3PO4. Finally, the use of UV–Vis and 2D-Fluorescence was shown to be a successful approach for monitoring pore wetting events.

Membrane contactor aided catalyst recycle and organic acid recovery from aqueous solutions using porous hydrophobic polyvinylidene fluoride barriers

The present study investigates the performance of indigenous hydrophobic polyvinylidene fluoride (PVDF) based porous membranes for separation of valuable organics such as acetamide catalyst and tartaric acid from aqueous media. Dehydration of acetamide was carried using ultraporous hydrophobic PVDF membrane by vacuum membrane distillation (VMD) technique. Effect of feed concentration on membrane performance was studied. Membrane exhibited a high total flux of 0.32 kg/m2h with <1.2% acetamide losses in permeate during concentration of acetamide catalyst from 30% to 70% (w/v). The separation of tartaric acid from synthetic mixture was carried out using indigenous ultraporous PVDF/Polyurethane (PU) blend membrane by liquid-liquid membrane contactor (LLMC) system. Influence of various additives such as LiCl2, ZnCl2, glycerol and polyvinylpyrrolidone (PVP) on membrane performance was studied. PVDF/PU/glycerol membrane exhibited extraction efficiency of nearly 12% for initial acid and extractant concentration of 100 mol/m3 and 30%, respectively, within a processing time of 2 h. All the indigenously synthesized membranes were characterized using analytical tools to study the physico-chemical properties of polymer films. A mathematical model for VMD system has also been developed to validate the experimental results. The study inferred that the processes employed could be considered as alternative techniques over conventional methods for recovery of both solid catalyst and organic acids which are widely used in industry.

Experimental And Mathematical Modeling Studies Of Liquid-Liquid Membrane Contactor

Experimental and modeling studies of the effect of tempetarature on liquid-liquid membrane contactor (LLMC) have been done. The experiments were conducted by varying temperature of 25 up to 80 0C, cross flow velocity from 0.02 to 0.05 m/s and feed concentration of 0, 5000 and 30,000 mg/l. In these experiments microporous hydrophobic hollow fiber polypropylene membrane with 0.2 μm was used as a contacting device. The modeling has been done by compiling mathematic equation of mass and heat transfers in liquid-liquid membrane contactor. Both the experimental and modeling result show, the increase in feed temperature increase the flux of pure water exponentially, whereas the flux decrease with increasing the permeate temperature. The feed temperature increase at higher temperature result in hogher flux increase. The concentration of pure water result in the range of 1.8 to 5.6 mg/l depending on feed concentration.Keywords : membrane contactor, modeling

Recovery of ammonia from domestic wastewater effluents as liquid fertilizers by integration of natural zeolites and hollow fibre membrane contactors.

The integration of up-concentration processes to increase the efficiency of primary sedimentation, as a solution to achieve energy neutral wastewater treatment plants, requires further post-treatment due to the missing ammonium removal stage. This study evaluated the use of zeolites as a post-treatment step, an alternative to the biological removal process. A natural granular clinoptilolite zeolite was evaluated as a sorbent media to remove low levels (up to 100mg-N/L) of ammonium from treated wastewater using batch and fixed bed columns. After being activated to the Na-form (Z-Na), the granular zeolite shown an ammonium exchange capacity of 29±0.8mgN-NH4+/g in single ammonium solutions and 23±0.8mgN-NH4+/g in treated wastewater simulating up-concentration effluent at pH=8. The equilibrium removal data were well described by the Langmuir isotherm. The ammonium adsorption into zeolites is a very fast process when compared with polymeric materials (zeolite particle diffusion coefficient around 3×10-12m2/s). Column experiments with solutions containing 100mgN-NH4+/L provide effective sorption and elution rates with concentration factors between 20 and 30 in consecutive operation cycles. The loaded zeolite was regenerated using 2g NaOH/L solution and the rich ammonium/ammonia concentrates 2-3g/L in NaOH were used in a liquid-liquid membrane contactor system in a closed-loop configuration with nitric and phosphoric acid as stripping solutions. The ammonia recovery ratio exceeded 98%. Ammonia nitrate and di-ammonium phosphate concentrated solutions reached up to 2-5% wt. of N.

Design, Development and Testing of Miniature Liquid-liquid Extraction Contactors for R&D Studies in Nuclear Environment

Testing liquid-liquid extraction flowsheets on radioactive solutions at laboratory scale requires specific contactors, that must be as small as possible (to minimize the quantities of reagents) and suitable for use in glove boxes or hot cells. As such contactors are not commercially available, CEA designs dedicated apparatus for its experiments. Two examples of such contactors are highlighted: a stage-wise one (a miniature mixer-settler) and a differential one (the Taylor-Couette column). Both combine similarities with larger contactors that make possible flowsheet extrapolation to industrial scale, and specific features, mainly because of the major role of materials wettability when volumes are reduced.

Counter-current arrangement of microfluidic liquid-liquid droplet flow contactors

The objective of microfluidic droplet flow is the control and manipulation of fluids on the sub-mm scale. This article describes the microfluidic droplet flow in a liquid-liquid contacting unit utilizing microchannels and millichannels and their counter-current arrangement. A contacting module consists of a droplet generator, a channel to enable an intensified mass transfer between two fluids and a liquid-liquid separation device. Experiments were performed with deionized water as a continuous phase and various organic solvents as a dispersed phase. The organic droplets are generated by direct coflowing injection through a needle located in the center of the microchannel. Droplet generation and flow patterns were optically investigated in straight and winding channels. The adjacent separation unit continuously splits the organic, dispersed phase. The combined effects of gravity, wetting characteristics of the wall material and capillary forces nearly completely separate the two fluids over a wide range of flow rates. Based on the mixer-settler system, a microfluidic extraction unit is proposed that enables a multistage counter-current arrangement.

Modular micro reaction engineering for carboligation catalyzed by benzoylformate decarboxylase

The downscale of different unit operations for the biocatalytic carboligation of benzaldehyde and acetaldehyde catalyzed by benzoylformate decarboxylase from Pseudomonas putida was investigated. The reactor volume was reduced to 115 μl thus enabling a substrate and enzyme saving by a factor of 52 in comparison to standard laboratory techniques. Additionally, the successful downscale of membrane based liquid-liquid contactors was shown, which allows, for example, the screening of solvents for extraction as well as the feed of a substrate. Here, comparable volumes as well as residence times were realized, enabling the integration of all three unit operations.