Also, thanks for the fun times on air, they will definitely be treasured memories. To the other members of the Kornfield lab: thank you for your patience with me and my quirks.
MEMBRANE DESIGN AND APPLICATION - BACKGROUND
Introduction to membrane technology
Then consider the drawbacks associated with polymeric membranes: First, polymeric membranes used in separation processes often suffer from an accumulation of unwanted material on the membrane surface through a process known as fouling19,21. An important subclass of polymeric membranes known as mixed matrix membranes (MMMs) are identified by the incorporation of functional materials into the structural polymer matrix.
Nonsolvent Induced Phase Separation – Literature review .1 Brief history of synthetic membranes .1 Brief history of synthetic membranes
- Overview of NIPS mechanism
- Effect of nonsolvent
- Effect of additives
In the metastable region, concentration fluctuations lead to the nucleation and growth of the polymer-lean phase via liquid-liquid demixing. The speed of the phase separation favors liquid-liquid demixing, leading to the formation of asymmetric membranes.
Membrane chromatography
- Resin and membrane protein chromatography
- Efforts to increase binding capacity
- Efforts to improve salt tolerance
The leading method to circumvent the limitations outlined above is the use of microporous membranes as the basis of the chromatographic material5,7,38,40. The hybrid showed a BSA binding capacity more than double that of the ceramic support alone.
Size-based separations
- Size based separation membranes
- Size based separations using inertial microfluidics
- Vortices in confined cavities
However, one of the major disadvantages of size separations using membrane technology is fouling, the process by which unwanted material accumulates on the membrane surface23. As shown in Figure 1.9, at very low Re the fluid is in a regime called 'pendant flow', where there is no recirculation in the microcavity.
The purpose of this work
- Influence of in situ generated microparticles and nonsolvent on membrane morphology
- Mixed-matrix membrane chromatography
- Size based isolation of bacteria using dendritic ceramics
A facile route for the preparation of polyvinylidene fluoride membranes with mixed matrix polyethylenimine particles generated in situ. Mixed-matrix PVDF membranes with in-situ synthesized PAMAM dendrimer-like particles: A new class of sorbents for the recovery of Cu(II) from aqueous solutions by ultrafiltration.
INFLUENCE OF NONSOLVENT AND MIXED-MATRIX COMPOSITION ON MEMBRANE MORPHOLOGY
Introduction
In contrast, both the mechanical strength and piezoelectric character depend on the morphology of the membrane. In MMMs, the presence of the functional particles increases the complexity of the phase separation process by adding new interactions with the solvent, non-solvent and structural polymer11,16.
Experimental methods .1 Materials .1 Materials
- Membrane Synthesis
- SEM characterization
- X-ray scattering
- Water flux measurements
In preparation for imaging, the membrane samples were first dried at room temperature for 24 h. All samples were then coated with a Pt/Pd conductive layer on the surface of interest prior to imaging.
Results and discussion
- Morphological characteristics observed in SEM
- Crystalline behavior of PVDF
- Flux measurements
The phase separation of PEI from the rest of the dope begins when the catalytic hydrochloric acid is added to the casting solution. The hydrophobic nature of the PVDF skin layer reduces the rate of diffusion of water into the dope solution. The morphology of the 6 wt% water-cast membrane differs from these observations only in the arrangement of the PEI particles.
As the concentration of the mixed nonsolvent increases in the PEI microgel, NMP moves to the interface between the PEI-rich and TEP/PVDF-rich regions due to its compatibility with both (Fig. 2.3 e and f). The combined influence of the PEI particles and mixed non-solvent produced a distinct and unique mixed matrix-membrane morphology. The subsequent crystallization promotes the formation of the most thermodynamically favored crystal phase - the α phase.
Without PEI particles present in the membrane, this phenomenon is limited to the skin layer of the membrane due to the mass transfer limitations imposed by the formation of said layer.
Conclusions
At low PEI concentrations – such as the 6 wt% PEI composition – the mass percentage of solids in the dope is low enough (Table 1) to allow defects in the surface layer during casting in mixed NMP:H2O. As the PEI loading and mass percentage of solids increase to 38 wt% PEI composition, the surface layer changes such that membranes cast in water exhibit a continuous dense skin layer and those prepared using the mixed non-solvent , has a more homogeneous surface layer with reduced porosity. These changes in the surface layer result in decreased water fluxes for both sets of membranes.
Preparation and Characterization of Mixed Matrix Membranes Based on PVDF and Three Inorganic Fillers (Nonporous Fumed Silica, Zeolite 4A and Mesoporous MCM-41) for Gas Separation. Mixed matrix membranes with tunable free volumes driven by molecular interactions for efficient bio-fuel recovery. A one-pot method for the preparation of mixed-matrix polyvinylidene fluoride membranes with in situ synthesized and PEGylated polyethylenimine particles.
Formation of porous poly(vinylidene fluoride) membranes with symmetric or asymmetric morphology by immersion deposition in the water/TEP/PVDF system.
MIXED-MATRIX MEMBRANE CHROMATOGRAPHY
- Introduction
- Experimental Methods .1 Materials .1 Materials
- Membrane Synthesis
- SEM characterization
- Protein binding experiments
- Results and Discussion .1 Changes in morphology .1 Changes in morphology
- Static binding
- Salt tolerance
- Dynamic binding
- Conclusions
The resulting membranes benefit from the porosity of the support while increasing the available binding surface to improve volumetric binding capacity. Improving the salt tolerance of membrane adsorbers requires reducing the ionic sensitivity of the binding ligand by manipulating the ligand chemistry. While recent work in this area reliably addresses one of the aforementioned drawbacks, there is still a need for a membrane adsorber that provides consistently high volumetric binding capacity over a wide range of salt concentrations.
This is a notable deviation from the tight size distribution of the spherical microgels when ECH has an NCD of 1.0 (Fig. 2.2c). At NCD 0.5, the gel is open enough to maximize the availability of functional sites, while there are sufficient cross-links to maintain gel cohesion and PEI concentration. It was found that volumetric binding capacity has a nonlinear relationship with crosslink density which is a function of crosslink chemistry.
In addition, DBC measurements confirmed the salt tolerance of the membrane under flow with >90% of binding capacity maintained up to 100 mM NaCl added at all flow rates tested.
DESIGN OF POLYMER-CERAMIC COMPOSITES FOR MEMBRANE CHROMATOGRAPHY
- Introduction
- Experimental methods .1 Chemicals and materials .1 Chemicals and materials
- Ceramic fabrication
- Polymer Dope Synthesis
- Surface Functionalization of Ceramic
- Phase Inversion Micromoulding
- Membrane properties characterization .1 SEM
- Results and discussion
- Phase inversion micromoulding feasibility
- Protein binding and the role of the PEI gel layer
- PEI swelling at high NCD
- Dynamic binding measurements
- Conclusions
After the ceramic was dried, it was added to a 2 v% solution of ATMS in isopropanol and incubated for 3 h at 60 ⁰C. The sample was then thoroughly washed in water and isopropanol before being cured at 110 ⁰C for 30 minutes. The sample was then washed with IPA and dried at room temperature for one hour before the addition of the polymer drug solution. A similar process was used to measure the static binding capacity (SBC) of composite membranes.
The composite material presented in Figure 4.5c&d was infiltrated without modifying the surface of the ceramic. The swelling of the interfacial region leads to more reactive sites being available, which further improves the bonding between the gel layer and the PEI microgels in the polymer solution. The lower PEI concentration in the polymer matrix leads to rapid saturation of the available binding sites, resulting in a low binding capacity.
The SEM characterization showed that functionalizing the ceramic surface with a reactive conformal PEI gel layer improved the adhesion of the polymer matrix to the pore wall in the dry state.
SIZE-BASED CAPTURE OF BACTERIA VIA DENDRITIC FREEZE- CAST CERAMIC MEMBRANES
- Introduction
- Experimental Methods .1 Materials .1 Materials
- Fabrication & characterization of dendritic freeze cast ceramics
- Ceramic functionalization
- Flow-through experiments
- Results and discussion
- Separation efficiency of different ceramic structures
- Influence of functionalized ceramics on E. coli capture
- Influence of functionalized ceramic on polystyrene capture
- Conclusions
When the working fluid reached the end of the outlet tube, the flow rate was adjusted to the experimental conditions listed below. The second solution contained 35 mg/ml BSA in 50 mM TRIS buffer, corresponding to the lower end of the range of human plasma albumin concentrations. Then, 20 µL of the sonicated suspension of 0.28 µm fluorescent particles was added to the vial and the resulting suspension was again vortexed for 20 seconds.
The empty sampler reported more than 90% of the added particles in the filtrate for both particle sizes and flow rates. The PEG-terminated ceramic again showed a performance similar to the control with 36% of the E. coli passing through. The difference in bacteria retention between the neat and PEG-terminated ceramics was attributed to the hydrophilicity of the ethylene glycol groups.
Second, the surface functionality of the different ceramics changes how they interact with both the bacteria and the particles.
CONCLUSIONS AND FUTURE WORK
- Mixed-matrix polymeric membranes
- Composite membranes
- Dendritic ceramic membranes
- Chemical compatibility and reaction kinetics Miscibility and Solubility studies Miscibility and Solubility studies
- Swelling of polymer matrix in water
A natural extension of the BSA binding experiments is to investigate the binding abilities of the compound in the presence of salt. The permeability of the composite membrane will be affected by the composition of the polymer matrix. Solution homogeneity was expected based on the solubility of PEI in both DMSO and TEP at 80 ⁰C.
Due to the viscosity of the TEP/PVDF solution, the solutions were not homogeneous with visible gradients even after mixing for 30 seconds. Dropwise addition of the DMSO/BCAH solution prevents the formation of the precipitate shown in Figure A.3 and instead produces a second phase that settles to the bottom of the vial (Figure A.5b). In contrast, after incubation of the membranes in water, the surface area of the polymer matrix increased by 50%.
The increase in area results from the swelling of the PEI microgels in the presence of water.
FLUID CALCULATIONS FOR CHAPTER 5
- Key assumptions
- Ceramic dimensions
- Particles in glycerol solution
- Particles and bacteria in 35 mg/mL BSA solution
In Table B.1, the primary pore volume % is the percentage of the total porous volume attributed to the primary pores. The total porous volume was determined by multiplying the volume of the ceramic by the percentage of porosity. The total active area was calculated by multiplying the area of the ceramic by first the percentage porosity and then the primary pore volume %.
The turnover volume represents the total volume occupied by the primary pores and was obtained by multiplying the total porous volume by the volume percentage of the primary pores. The density and viscosity of the glycerol solution were obtained from an online calculator3 that based the calculation on parameterization in the literature4. The average velocity was calculated by dividing the volumetric flow rate by the total active surface area in Table B.1.
Panel b of Figure B.1 is an image of the sample holder, showing the conical area placed in front of the ceramic in an attempt to allow even distribution of the liquid across the sample.
CULTURE PROTOCOL FOR E. COLI
Making solid media
When the medium has been added to the petri dishes, the flask is quickly rinsed out before the agar solidifies. When the agar has solidified, stack the Petri dishes upside down and place them in a lid. Using a sterile pipette tip, scrape off some of the frozen broth and streak it across the plate without doubling back on areas that have already been streaked.
Place the now striped plate in the incubator upside down and let it grow.
Growing bacteria culture
Set aside in 4C - solid media will be good to use for a month C.2 Making a line plate. Use a sterile pipette tip to pick a single colony from the plate and drop it into the culture tube.
Making liquid media
