MEMBRANE EMULSIFICATION SYSTEMS

Microcapsules (or microspheres) with small size and narrow size distribution have potential applications as carriers of proteins and polypeptides. However the conventional preparation methods severely limit their real applications. Membrane emulsification technology may become a new preparation method of microcapsules with monodisperse droplets, mild conditions, good stability, low energy consumption and easy to realize mass production. In this paper, studies on membrane emulsification systems and the possible existing problems are summarized, and primary attempts on preparing alginate/chitosan microcapsules are conducted.

Preparation of HNS microspheres by rapid membrane emulsification

In order to improve the dispersibility and loading efficiency of 2,2',4,4',6,6'-hexanitrostilbene(HNS),HNS microspheres were prepared by rapid membrane emulsification method with nitrocellulose(NC)as binder.The effects of NC solution concentration,stirring speed and polyvinyl alcohol(PVA)solution concentration on microspheres were investigated.It was characterized by scanning electron microscope(SEM),X-ray diffractometer(XRD),differential thermal analysis(DTA)and angle of repose analyzer.The results show that the HNS microspheres prepared with 5 wt%NC solution concentration,stirring speed of 100 rpm and 2 wt%PVA solution concentration have better regular morphology,higher sphericity,unchanged crystalline shape,increased activation energy and significantly improved dispersibility compared with the refined HNS.Rapid membrane emulsification has a series of advantages such as green,low cost and easy scale up,which provides a better way to prepare microspheres of energy materials.

Fabricating biopolymer-inorganic hybrid microspheres for enzyme immobilization:Connect membrane emulsification with biomimetic mineralization

The organic-inorganic hybrid composites displayed great potential for biotechnological and biomedical application.In this research,a gelatin/alginate/silica hybrid microsphere was developed by a synergy of membrane emulsification process and biomimetic mineralization method.The gelatin was mixed and complexed with alginate solutions(water phase).The water phase was extruded through a Shirasu Porous Glass(SPG)membrane,and then was crosslinked,which formed gelatin/alginate microspheres.The biomimetic mineralization was occurred in situ by immersing gelatin/alginate complex in a Na_(2)SiO_(3) solution,while silica was formed around the organic microspheres,resulting in the final gelatin/alginate/silica hybrid microspheres.These microspheres were characterized by SEM,TEM,EDS,TGA/DTA,and DSC.The hybrid microcapsules present a more than 40%mass fraction of the inorganic component,and displayed superior swelling resistance to biopolymer complex microspheres.Glycerol dehydrogenase(GlyDH)was immobilized in the obtained novel gelatin/alginate-silica hybrid microspheres as the model enzyme.Due to the protective effect of carriers,the pH tolerance stability,storage and recycling stability of the immobilized GlyDH were all improved in comparison with free GlyDH.

Performance of slotted pores in particle manufacture using rotating membrane emulsification

This paper addresses the use of different slotted pores in rotating membrane emulsification technology. Pores of square and rectangular shapes were studied to understand the effect of aspect ratio （1-3.5） and their orientation on oil droplet formation. Increasing the membrane rotation speed decreased the droplet size, and the oil droplets produced were more uniform using slotted pores as compared to circular geometry. At a given rotation speed, the droplet size was mainly determined by the pore size and the fluid velocity of oil through the pore （pore fluid velocity）. The ratio of droplet diameter to the equivalent diameter of the slotted pore increased with the pore fluid velocity. At a given pore fluid velocity and rotation speed, pore orientation significantly influences the droplet formation rate： horizontally disposed pores （with their longer side perpendicular to the membrane axis） generate droplets at double the rate of vertically disposed pores. This work indicates practical benefits in the use of slotted membranes over conventional methods.

Temperature-induced hydrophobicity transition of MXene membrane for directly preparing W/O emulsions

Although hydrophilic membranes are desired for reducing resistance to water permeation, hydrophilic surfaces are not used in the water-in-oil(W/O) membrane emulsification process because water spreads on the hydrophilic surface without forming droplets. Here, we report that a hydrophilic ceramic membrane can form a hydrophobic interface in diesel at a higher temperature;interestingly, the experiments show that the contact angle increases when the temperature rises. The hydrophilic membrane surface evolves into a hydrophobic interface, particularly near the boiling point of water, resulting in a water contact angle of 147.5° ± 1.2°. This work established a method for preparing W/O monodispersed emulsions by direct emulsification of hydrophilic ceramic membranes at a temperature close to the boiling point of water.Additionally, it made high flux of membrane emulsification of monodispersed W/O emulsions possible,which satisfied the industrial requirements of fluidized catalytic cracking in the petrochemical industry.

Large scale manufacture of magnetic polymer particles using membranes and microfluidic devices

Magnetic polymer particles have found applications in diverse areas such as biomedical treatments, diagnosis and separation technology. These applications require the particles to have controlled sizes and narrow size distributions to gain better control and reproducibility in use. This paper reviews recent developments in the preparation of magnetic polymer particles at nano- and micro-scales by encapsulating magnetic components with dissolved or in situ formed polymers. Particle manufacture using emulsification and embedment methods produces magnetic polymer particles at micro-scale dimensions. However, the production of particles in this range using conventional emulsification methods affords very limited control over particle sizes and polydispersity. We report on alternative routes using membrane and microfluidics emulsification techniques, which have a capability to produce monodisperse emulsions and polymer microspheres （with coefficients of variation of less than 10%） in the range from submicrometer to a few 100 μm. The performance of these manufacturing methods is assessed with a view to future applications.

Facile one-pot emulsion/sol-gel method for preparing wrinkled silica microspheres

The present manuscript describes a facile and versatile method for preparing uniform wrinkled silica microspheres with diameters of tens of microns.The method comprises a one-pot emulsion/sol-gel method using silica precursors of organosilane and tetraethoxysilane.By controlling the sol-to-gel transition of the silica precursors,a series of silica microspheres based on uniform emulsion droplets was synthesized by membrane emulsification.The silica microspheres had a variety of surface morphologies ranging from smooth,maze-like wrinkles to polygon-like ravines.It was possible to alter the surface morphologies of the microspheres by controlling the amount of organosilane in the dispersed phase and the amount of ammonia catalyst in the continuous phase of the emulsion.The grooves on the wrinkled microspheres were able to trap polymer nanoparticles of matching size,thereby demonstrating the potential usefulness of the microspheres in separation science and drug delivery.

Recent advances in the production of controllable multiple emulsions using microfabricated devices

This review focuses on recent developments in the fabrication of multiple emulsions in micro-scale systems such as membranes, microchannel array, and microfluidic emulsification devices. Membrane and microchannel emulsification offer great potential to manufacture multiple emulsions with uniform drop sizes and high encapsulation efficiency of encapsulated active materials. Meanwhile, microfluidic devices enable an unprecedented level of control over the number, size, and type of internal droplets at each hierarchical level but suffer from low production scale. Microfluidic methods can be used to generate high-order multiple emulsions （triple, quadruple, and quintuple）, non-spherical （discoidal and rod-like） drops, and asymmetric drops such as Janus and ternary drops with two or three distinct surface regions. Multiple emulsion droplets generated in microfabricated devices can be used as templates for vesicles like polymersomes, liposomes, and colloidosomes with multiple inner compartments for simultaneous encaosulation and release of incomoatible active materials or reactants.

An effective process for the separation of U(Ⅵ),Th(Ⅳ)from rare earth elements by using ionic liquid Cyphos IL 104

Separation and recovery of U(Ⅵ)and Th(Ⅳ)from rare earth minerals is a very challenging work in rare earth industrial production.In the present study,a homemade membrane emulsification circulation(MEC)extractor was used to separate U(Ⅵ)and Th(Ⅳ)from rare earth elements by using Cyphos IL 104 as an extractant.Batch experiments were carried out using a constant temperature oscillator to investigate the extraction parameters of the single element and the results indicated that Cyphos IL 104could reach the extraction equilibrium within 30 min for all the three elements,i.e.,U(Ⅵ),Th(Ⅳ),and Eu(Ⅲ).Besides,the MEC extractor possessed a strong phase separation ability.The extraction efficiencies of U(Ⅵ),Th(Ⅳ),La(Ⅲ),Eu(Ⅲ)and Yb(Ⅲ)increased with the increase of pH.La(Ⅲ),Eu(Ⅲ)and Yb(Ⅲ)were hardly extracted when pH≤1.50,which was beneficial for effectively separating U(Ⅵ)and Th(Ⅳ)from La(Ⅲ),Eu(Ⅲ)and Yb(Ⅲ).In the multi-stages stripping experiments,when the stripping stage number was 3,the effective separation could be achieved by using HCl and H_(2)SO_(4),since the stripping efficiency reached 80.0%and 100.0%for Th(Ⅳ)and U(Ⅵ),respectively.Slope method and FT-IR spectra showed that Cyphos IL 104 reacted with U(Ⅵ)and Th(Ⅳ)by chelation mechanism.The extraction of multi-elements indicated that U(Ⅵ)and Th(Ⅳ)could be well separated from the solution which contains all rare earth elements,and the extraction efficiencies of U(Ⅵ)and Th(Ⅳ)both were close to 100.0%.Based on the above experimental results,a flowchart for efficient separation of U(Ⅵ)and Th(Ⅳ)from rare earth elements was proposed.