Membrane Absorption Research Articles

Subconjunctival trypsin injection for anterior chamber fibrin exudates in eyes with globe rupture following vitrectomy.

To compare the safety and clinical outcomes of subconjunctival trypsin and dexamethasone (DEX) injections in the treatment of anterior chamber fibrin exudates in eyes with globe rupture following primary wound repair and vitrectomy. A retrospective analysis included 42 males and 10 females (mean age 46.0±6.0y, range 34 to 58y) who underwent primary wound sutures and vitrectomy for globe rupture. Patients with pupil-covered fibrinous exudate or/and membrane in the anterior chamber were treated. On the first postoperative day, subconjunctival injections of either 5000 units (0.4 mL) of trypsin solution (n=25) or 0.5 mL (1 mg) DEX (n=27) were administered to accelerate exudate absorption. Efficacy was assessed by observing break time and partial absorption of the fibrin exudate membrane. Safety and comfort were evaluated by monitoring intraocular pressure (IOP), allergy, pain, and foreign body sensation. Both groups achieved 1/3 absorption of the anterior chamber fibrin exudate membrane, but the trypsin group exhibited shorter break time and partial absorption time compared to the DEX group (P<0.05). Trypsin treatment was also less irritating to patients. No adverse reactions were reported, and IOP remained stable. Visual acuity improved in both groups without statistical difference. Compared to DEX, trypsin demonstrates a shorter absorption time for the fibrin exudate membrane with a more comfortable process in treating pupil-covered fibrinous exudate or/and membrane after vitrectomy for globe rupture.

CO2/N2 separation using a ceramic membrane contactor and ZIF-8 in [TEPA][MIm]

Capturing CO2 from the flue gas in the power plant is an important measure to realize the low-carbon combustion of the fossil energy. This paper presents a novel technique which combines traditional methods of the chemical absorption, the physical adsorption and the membrane absorption. The ionic liquid ([TEPA][MIm]) is utilized to improve the CO2 absorption performance and reduce the energy consumption. While the porous skeleton (ZIF-8) is added to the ionic liquid to reduce the viscosity while introducing the physical adsorption. Moreover, the hydrophobic ceramic membrane is utilized as the separation interface between the gas phase and the liquid phase, which can avoid the entrainment and overflow of the liquid phase while increasing the specific surface area. In terms of the material preparation and the characterization, the addition of ZIF-8 does not destroy the original chemical composition of [TEPA][MIm]. The average contact angle of the hydrophobic ceramic membrane is 140.55°, and the failure temperature is greater than 400 K, which conforms to the application situation of the power plant. In terms of the CO2 capture and the desorption performance, the maximum CO2 capture amount reaches 2.03 mol/mol. The temperature of complete desorption is 70 °C. Furthermore, the capture performance after five cycles can reach 80 % of the initial performance. The performance is better than that of the CO2 capture technology utilizing the traditional monoethanolamine solution.

Clarify the process of overshoot voltage generation of proton exchange membrane electrolyzer under intermittent operation

Overshoot voltage phenomenon often occurs when the proton exchange membrane (PEM) electrolyzer is in the intermittent operation, which makes H2 production energy consumption increase significantly and its lifetime reduce rapidly, especially to the high-power electrolyzers in the industrial applications. Up to now, the phenomenon has been rarely understood and its process is elusive. Therefore, in this work, firstly, we find that the polarization curve of PEM electrolyzers happening S distortion synchronize with the appearance of overshoot voltage phenomenon. Secondly, through in-situ Raman characterization, we find that involvement and disappearance of H2O in the hydrogen evolution reaction (HER) is the key factor causing and resolving this phenomenon. Finally, we used EPMA to exclude metal cations affection. Also, by micro-CT, EIS test, visualization PEM electrolyzer inside model and COMSOL electromagnetic simulation, we find that anode catalyst layer porosity reduction directly affects water absorption of membrane as well as current variation leads to eddy currents generation which is deepen unequal current distribution. These are two important reasons for the involvement of H2O in HER. In summary, these findings elucidate the mechanism of overshoot voltage phenomenon for the first time, which contributes to design novel electrical protection schemes and advanced membrane electrodes for PEM electrolyzers, thus they can help to achieve cost reduction and efficiency improvement in the green hydrogen industry.

Investigation on sulfonated PVC/polymethyl methacrylate (PMMA)/polystyrene sulfonate (PSS) polymer blends as proton-conducting membrane

The design and development of cost-effective and increased methanol permeable and proton-conductive membranes are critical concerns in the fabrication of polymeric electrolyte membranes (PEM). A solution-casting process was used to create a low-cost PEM based on sulfonated polyvinyl chloride (SPVC)-Polymethyl methacrylate (PMMA) blended with varying concentrations of Poly(sodium 4-styrenesulfonate) (PSS). The contact angle, oxidative stability, swelling ratio, water uptake, and methanol uptake of SPVC/PMMA/PSS membranes were investigated as a function of PSS molar ratio. FT-IR examination, 1H NMR spectra, Raman spectroscopy, X-ray diffraction, thermogravimetric analysis (TGA), and scanning electron microscope micrographs were additionally utilized for confirming the chemical structure, morphology, and thermal stability of SPVC/PMMA/PSS membranes. Furthermore, the ion exchange capacity (IEC), proton conductivity, and methanol permeability of SPVC/PMMA/PSS membranes were investigated depending on the PSS concentration. The results showed a significant increase in proton conductivity from 1.80 × 10–2 for SPVC/PMMA/1%PSS to 4.7 × 10–2 S/cm for SPVC/PMMA/5%PSS at ambient temperature. On the other hand, the methanol permeability (P = 8.53 × 10–8 cm2/s) was noticeably lower than that of Nafion 117 (3.39 × 10–6 cm2/s). Additionally, the IEC of the manufactured membrane was 1.38 ± 0.7 meq g−1 for SPVC/PMMA/5%PSS compared to 0.91 meq g−1 for Nafion 117 membranes. The maximum water uptake of the synthesized membranes was 48.37 ± 2.27%, whereas Nafion 117 membrane absorption was 65.44%. According to conductivity studies and the membrane efficiency factor, the ideal PSS content in a polymer matrix is 4 wt.%. Finally, the developed SPVC/PMMA/PSS polyelectrolytic membranes show improvements in essential properties such as methanol permeability, proton conductivity, and IEC when combined with low-cost materials, making them an attractive contender as PEM for DMFCs.Graphical abstract

Improving the activity of CO2 capturing from flue gas by membrane gas – solvent absorption process

This work is focused on increasing the capturing efficiency of carbon dioxide (CO2) through flue gas purification systems. To maximize the CO2 capture process, many process variables such as temperature, flow rates, absorbent concentrations, and nanoparticles were investigated. This study describes the use of a polypropylene hollow fiber membrane contactor to separate CO2 from nitrogen using different solvents, including Potassium carbonate (K2CO3), N-methyl diethanolamine (MDEA), and monoethanolamine (MEA). Also, the presence of silica nanoparticles and piperazine (PZ) enhances the process performance. On the other hand, the amine and mixed amino absorbents MDEA-PZ and MDEA-MEA were prepared and compared based on the absorption capacity. The optimal order of amine absorbent performance when applied to CO2 membrane absorption is MDEA-MEA followed by MDEA-PZ. At a solute concentration of 9%, MDEA-MEA exhibits the highest CO2 removal efficiency, which is 74.12%. However, at a concentration of 11%, MEA, MDEA-PZ, and MDEA have the highest CO2 removal efficiencies of 80.15%, 75.13%, and 63.12%, respectively.

Omentomyelopexy for the Treatment of a Persistent Lumbar Pseudomeningocele: A Case Report With Technical Note.

Pseudomeningoceles are extradural accumulations of cerebrospinal fluid. In most cases, they appear as a complication of spinal operations. Omentomyelopexy is a surgery in which an autologous omentum flap is implanted over the dural opening. We describe a case of persistent pseudomeningocele treated with omentomyelopexy. A 37-year-old man sustained a T12-L1 AO B3 fracture during a motorcycle accident. He underwent posterolateral fusion and then neurological rehabilitation. Two years later, however, his condition worsened, and he experienced progressive weakness-he was diagnosed with an intramedullary cyst, which was treated with laminectomy, arachnolysis and cystotomy. A pseudomeningocele developed afterward, and the patient underwent multiple reoperations in the following years, none of which were effective. Omentomyelopexy, a complex procedure aimed to facilitate cerebrospinal fluid absorption and subsequent formation of a permanent membrane, was offered to the patient as a "last resort." After undergoing omentomyelopexy, his pseudomeningocele resolved. Although it should be reserved for exceptionally pertinent cases, omentomyelopexy is a viable option for managing persistent pseudomeningocele. However, further research is needed to better understand the effects and benefits of omentomyelopexy in this context.

Anchoring of Fe-MIL-101-NH2 to the Polymer Membrane Matrix through the Hinsberg Reaction to Promote Conductivity of SPEEK Membranes.

SCPEEK@MOF proton exchange membranes, where SCPEEK is sulfinyl chloride polyether ether ketone and MOF is a metal-organic framework, were prepared by doping Fe-MIL-101-NH2 into polymers. The amino group in the MOF and the -SOCl2 group in thionyl chloride polyether ether ketone cross-link to form a covalent bond through the Hinsberg reaction, and the prepared composite membrane has stronger stability than other electrostatic interactions and simple physical doping composite membranes. The formation of covalent bonds improves the water absorption of the composite membrane, which makes it easy for water molecules to form hydrogen bonds. Moreover, SPEEK as a proton conductive polymer and the synergy of MOFs improve the proton conductivity of composite membranes. The composite membranes were characterized by Fourier transform infrared spectroscopy, powder X-ray diffraction, scanning electron microscopy, and atomic force microscopy. The swelling rate, water absorption, mechanical stability, ion exchange capacity, and proton conductivity of the pure sulfonated polyether ether ketone (SPEEK) membrane were compared with those of the mechanically doped SPEEK/MOF membrane and the composite membrane SCPEEK@MOF doped with different ratios of Fe-MIL-101-NH2, and all of the SCPEEK@MOF showed superior performance. When the Fe-MIL-101-NH2 loading rate of the composite membrane is 2%, the proton conductivity of the composite membrane can reach 0.202 S cm-1 at 363 K and a 98% relative humidity, which is much higher than that of the SPEEK/MOF membrane obtained by simple physical doping under the same conditions.

Synthesis and Structural Characterization of Four Different Concentrations of Ant Nest (Myrmecodia pendens) Collagen Membranes with Potential for Medical Applications.

The purpose of this study was to synthesize and structurally characterize four ant nest membranes in four different concentrations and determine the best concentration that could potentially be used as an alternative material for the production of new collagen barrier membranes. Membranes were created by mixing ant nest extracts at various concentrations of 0.5%, 1%, 1.5%, and 2%, as well as collagen, chitosan, and Polyvinyl Alcohol (PVA) using a film casting. A Universal Testing Machine (UTM) was used to evaluate mechanical properties including elastic modulus, tensile strength, maximum elongation, elongation at break, and maximum force. Water absorption was performed, FTIR was used for functional group identification, and morphology was examined using SEM. Additionally, EDS was used to identify the composition and distribution of elements in membranes. Statistical analysis was conducted using ANOVA (analysis of variance) and post hoc testing with a significance level of p <0.01 for quantitative data. The results showed that the mechanical properties produced the following mean (standard deviation): elastic modulus 0.87 Mpa (0.11), tensile strength 16.32 N/mm2 (2.46), maximum elongation 4.96% (1.72), elongation at break 5.23% (1.87), and maximum force 22.50 N (5.06). The average water absorption capacity of all four membranes had a p-value <0.01. FTIR spectrum showed various peaks corresponding to functional groups, while SEM results indicated a homogeneous mixture. EDS analysis confirmed that the addition of ant plant extract at 0.5%, 1%, and 1.5% resulted in the presence of elements C, O, and Ca. Meanwhile, membranes prepared with 2% concentration had a different composition, namely C, O, Ca, and Na. Increasing the concentration of ant nest affects the values of the membrane's mechanical properties parameters, including the elastic modulus (0.87 Mpa), tensile strength (16.32 N/mm2), maximum elongation (4.96%), elongation at break (5.23%), and maximum force (22.50 N). The average membrane absorption of water (p value <0.01) was also affected. SEM images showed homogeneous mixing, and membrane EDS results consisted of C, O, and Ca composition. However, there was no effect on FTIR functional groups. The anthill membrane with a 1% concentration has the potential to serve as an alternative membrane in guided tissue regeneration.

Investigation of CO2 Absorption Rate in Gas/Liquid Membrane Contactors with Inserting 3D Printing Mini-Channel Turbulence Promoters.

The CO2 absorption by Monoethanolamine (MEA) solutions as chemical absorption was conducted in the membrane gas absorption module with inserting 3D mini-channel turbulence promoters of the present work. A mathematical modeling of CO2 absorption flux was analyzed by using the chemical absorption theory based on mass-transfer resistances in series. The membrane absorption module with embedding 3D mini-channel turbulence promoters in the current study indicated that the CO2 absorption rate improvement is achieved due to the diminishing concentration polarization effect nearby the membrane surfaces. A simplified regression equation of the average Sherwood number was correlated to express the enhanced mass-transfer coefficient of the CO2 absorption. The experimental results and theoretical predictions showed that the absorption flux improvement was significantly improved with implementing 3D mini-channel turbulence promoters. The experimental results of CO2 absorption fluxes were performed in good agreement with the theoretical predictions in aqueous MEA solutions. A further absorption flux enhancement up to 30.56% was accomplished as compared to the results in the previous work, which the module was inserted the promoter without mini channels. The influences of the MEA absorbent flow rates and inlet CO2 concentrations on the absorption flux and absorption flux improvement are also illustrated under both concurrent- and countercurrent-flow operations.

Numerical Simulation of Membrane Separation Characteristics of Supercritical Carbon Dioxide and Water.

To solve the problem of water carryover in the supercritical CO2 separation and mining process in the CO2 plume geothermal system, a three-dimensional shell-tube hollow fiber membrane absorption separator is designed in this study. A coupled species transport model, a porous medium model, and an absorption mathematical model are established, and the flow field and separation characteristics in the circular and flat tubes are analyzed using numerical simulation. The results show that the membrane separation efficiency increases with an increase in the flatness and membrane tube length. When the inlet velocity of the mixture is 0.1 m/s, the separation efficiency can reach 75.92%. Selecting a smaller flow Reynolds number and a more significant membrane tube flatness will reduce the water mass fraction at the outlet. When adding baffles of different shapes to the membrane tube, the mixture fluid in the membrane tube meanders forward and flows in the shape of "Z" under the blocking effect of the arcuate baffles. With an increase in the number of arcuate baffles in the membrane tube, the membrane separation efficiency of the separator increases continuously. The mixture fluid flows in the membrane tube with the built-in torsional baffles in a spiral manner, and the separation efficiency of the membrane separator increases with a torsion ratio reduction in the membrane tube.

Performance evaluation and optimization of hollow fiber membrane contactors for carbon dioxide absorption: A comparative study of ammonia, ethanolamine, and diethanolamine solvents

Membrane absorption is an emerging technology that amalgamates the merits of chemical absorption and membrane separation. However, the pivotal choice of solvent profoundly influences the overall performance of the membrane contactor. In this paper, a robust two-dimensional (2D) steady-state non-wetting mathematical and physical model of a hollow fiber membrane contactor (HFMC) was established. COMSOL software was used to solve the model equation of the membrane contactor. The impacts of ammonia, ethanolamine (MEA) and diethanolamine (DEA) on carbon dioxide absorption under different operating conditions and membrane geometry properties were simulated and compared. Results showed that the utilization of NH3 as the solvent in HFMC showcases performance akin to that of MEA, a substantial advantage over DEA. Notably, the performance disparity between ammonia and MEA might alter significantly in response to varying operating parameters. For instance, the CO2 removal performance of HFMC using aqueous ammonia surpasses that of MEA when the CO2 volume fraction exceeds 19 %. Moreover, hollow fibers featuring larger inner diameters and lengths endow a heightened effective mass-transfer area, thereby facilitating superior carbon dioxide removal performance.

CO2 capture performance of ceramic membrane with superhydrophobic modification based on deposited SiO2 particles

Membrane absorption is a promising CO2 capture technology, which is limited by the high cost of membrane materials. Coal fly ash (CFA)-based ceramic membrane as an alternative material for membrane modules can effectively reduce the preparation cost. In this study, CFA-based ceramic membrane with superhydrophobic properties is prepared by depositing SiO2 nanoparticles and grafting 1H, 1H, 2H, 2H-perfluorooctyltriethoxysilane (POTS). Characters including pore size distribution, porosity and N2 flux of superhydrophobic membrane are performed. The superhydrophobic modified ceramic membrane is applied to CO2 capture experiments using ethanolamine (MEA) solution as the absorbent. The result shows that the contact angle of the modified ceramic membrane reaches 155.0°, which significantly improves the anti-wetting properties of the membrane surface. The CO2 capture experiment demonstrates a maximum capture efficiency of 97.45% and a mass transfer rate of 21.17 mol/(m2·h). In addition, the superhydrophobic modified ceramic membrane exhibits excellent thermal and chemical stability, sustaining high performance even after 8 h of continuous operation. This study provides the theoretical and empirical foundation for the application of CFA-based superhydrophobic ceramic membranes in CO2 capture.

Enhancing protein trapping efficiency of graphene oxide-polybutylene succinate nanofiber membrane via molecular imprinting

Filtration of biological liquids has been widely employed in biological, medical, and environmental investigations due to its convenience; many could be performed without energy and on-site, particularly protein separation. However, most available membranes are universal protein absorption or sub-fractionation due to molecule sizes or properties. SPMA, or syringe-push membrane absorption, is a quick and easy way to prepare biofluids for protein evaluation. The idea of initiating SPMA was to filter proteins from human urine for subsequent proteomic analysis. In our previous study, we developed nanofiber membranes made from polybutylene succinate (PBS) composed of graphene oxide (GO) for SPMA. In this study, we combined molecular imprinting with our developed PBS fiber membranes mixed with graphene oxide to improve protein capture selectivity in a lock-and-key fashion and thereby increase the efficacy of protein capture. As a model, we selected albumin from human serum (ABH), a clinically significant urine biomarker, for proteomic application. The nanofibrous membrane was generated utilizing the electrospinning technique with PBS/GO composite. The PBS/GO solution mixed with ABH was injected from a syringe and transformed into nanofibers by an electric voltage, which led the fibers to a rotating collector spinning for fiber collection. The imprinting process was carried out by removing the albumin protein template from the membrane through immersion of the membrane in a 60% acetonitrile solution for 4 h to generate a molecular imprint on the membrane. Protein trapping ability, high surface area, the potential for producing affinity with proteins, and molecular-level memory were all evaluated using the fabricated membrane morphology, protein binding capacity, and quantitative protein measurement. This study revealed that GO is a controlling factor, increasing electrical conductivity and reducing fiber sizes and membrane pore areas in PBS-GO-composites. On the other hand, the molecular imprinting did not influence membrane shape, nanofiber size, or density. Human albumin imprinted membrane could increase the PBS-GO membrane’s ABH binding capacity from 50 to 83%. It can be indicated that applying the imprinting technique in combination with the graphene oxide composite technique resulted in enhanced ABH binding capabilities than using either technique individually in membrane fabrication. The suitable protein elution solution is at 60% acetonitrile with an immersion time of 4 h. Our approach has resulted in the possibility of improving filter membranes for protein enrichment and storage in a variety of biological fluids.

Effect of capillary pressure on the CO2 flux in the pores of membrane contactor: Theory and simulation results

A simulation model was made to evaluate the effect of the capillary pressure on the CO2 capture by membrane absorption. More specifically, the model calculated the changes in the interfacial pressure and CO2 flux as the interface of gas and liquid moves through the pore opening to its exit. Two cases were considered; hydrophilic or hydrophobic membrane materials with a respective contact angle of less or more than 90°. It was revealed that CO2 flux is about 70% higher for the hydrophilic membrane of 10−6 m radius and 50 × 10−6 m length than the hydrophobic membrane of equal pore radius and pore length, when nearly equal to 1.72 × 105 Pa is applied either on the feed side (hydrophilic membrane) or on the permeate side (hydrophobic membrane) to keep the membrane pore dry without gas bubble formation. It should be noted that CO2 flux is higher when a hydrophilic membrane is used, which is against the common belief that a hydrophobic membrane is preferable for membrane absorption. Also, the duration for the interface to get to the pore exit was determined. The effect of capillary pressure increases as the membrane pores become smaller, which turns into an increase in CO2 flux when the porosity and the pore length are maintained constant. It was also revealed that the CO2 flux can be significantly increased when water absorbent is replaced by 1 M monoethanolamine solution due to increased CO2 solubility. Thus, this work is the first attempt to study the effect of capillary pressure on the flux of membrane contactors. It is recommended to collect more data on membrane contactors by the hydrophilic membrane. Electronic structure calculations were also performed to investigate the reaction mechanism between CO2 and MEA, with a focus on non-conventional interactions such as hydrogen bonding and van der Waals interactions. This is to know the details of the reaction occurring between CO2 and MEA.

CO2 capture using superhydrophobic ceramic membrane: Preparation and performance analysis

The application of membrane absorption for CO2 capture has been limited by membrane wetting. In this paper, tubular Al2O3 ceramic membranes (marked as M1 and M2) are hydrophobically modified by sol-gel and dip-coating method and then used for CO2 capture. The surface morphology, surface composition, wettability and flux are characterized in detail. The mass transfer performance of M1 and M2 is studied at different gas and liquid Reynolds numbers. After modification, the surface contact angle can reach as high as 170.7°. The carbon capture performance of the modified M1 and M2 is significantly improved. Under laminar flow condition, CO2 mass transfer coefficient increased from the initial 1.03 × 10−4 m/s to 14.59 × 10−4 m/s, and the CO2 capture efficiency increased from the initial 28.55%–98.55%. The mass transfer resistance of ceramic membrane contactor is also analyzed. The resistance of liquid phase plays a leading role in the mass transfer performance in laminar flow state. For non-wetting membrane, membrane thickness has little effect on the mass transfer performance. In addition, it is shown that the superhydrophobic M1 and M2 exhibit excellent corrosion resistance. The research in this paper shows that superhydrophobic ceramic membrane is more suitable for CO2 capture in industrial production.

Enhancing performance of ceramic membrane in CO2 membrane absorption: Single-to multi-channel

Membrane absorption technology has received high attention for CO2 capture, but the brittleness of ceramic membranes limits its miniaturization. Here, founding that ceramic membrane with multi-channel geometry can not only have high specific surface area but also maintain high mechanical strength with small size. In this work, a four-channel ceramic membrane was used to test and compare performance with several single-channel membranes. This four-channel membrane had highest CO2 absorption flux of 4.83 mol m−3 s−1 and KOG of 1.26 mm s−1 among them. Then membrane phase resistance and its contribution to overall mass transfer resistance were analyzed to evaluate the impact of the membrane thickness or geometry. Owing to the undetermined thickness of multi-channel membrane, the absorption performance equivalent thickness was obtained through the simulation to be 0.23 mm using 2 M MEA. Moreover, a preliminary geometric design was attempted and CO2 absorption performances of different multi-channel membranes were compared based on above model.

Facile fabrication of FAS-PDMS/PEEK composite hollow fiber membrane with honeycomb-like structure for CO2 capture from flue gas by membrane absorption

In this study, as an efficient technology membrane absorption was applied with newly developed polyetheretherketone (PEEK) hollow fiber membrane (HFM) to remove CO2 from flue gas. To alleviate membrane wetting issue, 1H,1H,2H,2H-perfluorodecyltrimethoxysilane (FAS) was integrated into polydimethylsiloxane (PDMS) and then crosslinked FAS-PDMS was coated on porous PEEK membranes to prepare composite membranes. Surface characterization verified that PDMS layer containing fluoroalkylsilane had been successfully formed on membrane surface. As mass ratio of FAS to PDMS in coating solution raised, an interesting honeycomb-like structure was observed dispersing on composite membrane surface. Meanwhile, water contact angle was improved from 90.0° to 133.5° indicating enhanced membrane hydrophobicity. The effects of gas and liquid flow velocities on CO2 absorption performance of FAS-PDMS/PEEK HFM were systematically studied. The highest CO2 removal efficiency of 99.6% was achieved when gas and liquid velocity were 0.027 and 0.019 m s−1. When gas velocity raised to 0.110 m s−1, the maximum absorption flux of 1.22 × 10-4 mol m−2 s−1 and overall mass-transfer coefficient of 2.69 × 10−5 m s−1 could be obtained. Compared with the original membrane, the CO2 absorption flux of FAS-PDMS-0.6 HFM was increased by 50.9%, and the performance had no degradation in 36 h test. This study provides a novel strategy to alleviate the membrane wetting problem during CO2 membrane absorption process.

Characterization of Molecularly Imprinted Polymers (MIPs) as Cholesterol-Absorbing Materials

Molecularly Imprinted Polymer (MIP) membranes as cholesterol absorbers have been successfully synthesized. MIP membranes can absorb cholesterol molecules because they have cavite (pores) and active groups that are selective and sensitive to cholesterol molecules. MIP membranes are synthesized from butyl acrylate monomers, cross-linkers, ethylene glycol dimethacrilate (EGDMA), initiators of 2- 2-dimethoxy-2-phenylacetophenone (DMPP, sodium dodecyl sulfate (SDS) as surfactants, and cholesterol as templates. MIP membranes are synthesized using photopolymerization irradiated with UV light. The results obtained in the form of powder solids can be characterized using UV-Vis spectrophotometry. The results obtained by UV-Vis spectrophotometry showed that the MIP membrane prepared a standard curve with a linear regression equation y = 0.0054x-0.007 with a value of R2 = 0.9982. This suggests that MIP membranes are selective and sensitive to analytes. At optimum absorption of the MIP-cholesterol membrane can absorb cholesterol molecules in the amount of 0.020 grams of cholesterol composition within 20 minutes

Revealing release patterns and availability of phenolics in Tartary buckwheat under simulated digestion

The release patterns of phenolics in digestive tract was elucidated using a simulated digestion protocol, in which the delivery route of rutin was revealed, and the availability of released phenolics was also evaluated using a dialysis membrane absorption model. The results showed that phenolic compounds such as rutin, quercetin, 3,4-dihydroxybenzoic acid (DA), 2,3,4-trihydroxybenzoic acid (TA) and chlorogenic acid (CA) were released from Tartary buckwheat under simulated digestion. The contents of released phenolic compounds in oral-gastrointestinal digestion were significantly higher (p < 0.05) than that in oral and oral-stomach digestion phases. Besides, in oral-gastrointestinal digestion, the proportion of available contents of rutin, DA, TA and CA to corresponding released contents were 71.8%, 73.7%, 68.6% and 100%, and the great majority of rutin was sufficiently degraded into quercetin. The contribution of antioxidant activity of available compounds to corresponding total activity were between 62.2% and 68.9%. These results indicated that phenolics in Tartary buckwheat can be adequately released in oral-gastrointestinal digestion, and a great majority of these phenolics are available. This study illustrates the potential bioavailability of phenolic compounds in Tartary buckwheat during gastrointestinal digestion.

MODIFICATION OF PROTON PUMP MEMBRANE USING POLYVINYLPYRROLIDONE (PVP) FOR POTENTIAL TOTAL ALKALINITY SENSING

Total alkalinity is one of the important parameter in the regulation of seawater carbonate chemistry system to determine the capacity of water to neutralize acid. In this paper, a new proton pump membrane was successfully modified using polyvinylpyrrolidone (PVP) as a supporting material due to its excellent chemical properties. The surface morphology of the membrane was thoroughly studied using Scanning Electron Microscope (SEM), which showed the presence of pore structure, ascribed to the presence of low molecular weight of PVP. The absorption of membrane was studied using Ultraviolet-Visible (UV-Vis) spectrophotometer, where the peak appeared at 539 nm-1. The functional group of the modified membrane was analyzed using Fourier Transform Infrared Spectroscopy (FTIR), and the spectra showed almost similar between modified membrane with PVP and without PVP. The electrochemical behaviour of the membrane was evaluated by cyclic voltammetry (CV) using gold (Au) electrode and the resulting voltammogram showed that the modified membrane with PVP has higher current reading compared to the membrane without PVP, indicating that there is redox reaction occured during the immobilization. The condition and perfomance of modified proton pump membrane with PVP was compared and analyzed.