Hollow Fiber Membrane Device Research Articles

Membrane fouling diagnosis of membrane components based on multi-feature information fusion

CBAM-MUL-CNN (convolutional block attention module - multiple - convolutional neural networks) model based on attention mechanism is proposed to solve the problem that the membrane fouling feature extraction capability of membrane bioreactor membrane component is insufficient, which resulted in the complex structure of the membrane fouling data, so that the efficient localization and classification of membrane fouling in membrane bioreactor could not be achieved. First, the time domain and frequency domain information about the fault data is used as the input of CNN (convolutional neural networks), and the features are extracted by convolution layer. Then, the input classifier is classified by splicing the time domain and frequency domain features using the full connection layer. BN (batch normalization) layer in the model can effectively prevent the disappearance of gradients, ReLU (rectified linear uint) layer can improve the non-linear model expression ability, CBAM (convolutional block attention module) can simplify the model complexity, improve the network features expression ability, and pooling layer can improve the model fault tolerance. The comparison results show that the model has excellent comprehensive performance in the membrane fouling diagnosis experiments of series tubular membrane devices and parallel hollow fiber membrane devices, and can effectively classify and locate all membrane fouling, making the treatment of water by membrane process improve the quality of effluent while reducing energy consumption, which provides a theoretical basis for actual production.

Porous Hollow Fiber Membrane-Based Continuous Technique of Polymer Coating on Submicron and Nanoparticles via Antisolvent Crystallization

This paper introduces a facile antisolvent crystallization technique to continuously coat submicron and nanosized particles with a thin polymer layer using a porous hollow fiber membrane device. Submicron (550 nm) and nanosized (12 nm) silica particles were the host particles; Eudragit RL 100 and poly(lactide-co-glycolide) were the coating polymers. A suspension of the particles in an acetone solution of the polymer was continuously pumped through the shell-side of a hollow fiber membrane module. The antisolvent (water) flowing in the hollow fiber lumen was forced through the membrane pores into the shell-side liquid, generating intense mixing with the flowing suspension and rapid precipitation of the polymer, coating the particles. Coated silica particles collected in a vacuum filtration device were analyzed after vacuum drying using scanning electron microscopy, scanning transmission electron microscopy, energy dispersive spectrometry, laser diffraction spectroscopy, and thermogravimetric analysis. Thes...

Precipitation of barium sulphate in a hollow fiber membrane contactor: Part II The influence of process parameters

In this second of two papers, we investigated the influence of process parameters on BaSO 4 particle precipitation in a hollow fiber membrane device. The solution of barium chloride was passed tangentially over the membrane surface and reacted with a solution of K 2SO 4 introduced through the membrane pores. The resulting supersaturation induced nucleation and particle growth on the lumen side of the hollow fibers. A specific technique was developed to measure crystal size directly at the outlet of the hollow fiber device by using EDTA as a neutralizing agent of crystal nucleation and growth. Concentrations of barium chloride and potassium sulphate were shown to influence mainly the CSD, the effect of inlet flow rates on the lumen and shell sides being less pronounced. The chemical conversions measured were between 3.7% and 20.5%. We propose improvements in the design of hollow fiber devices in order to give higher chemical conversions.

Precipitation of barium sulphate in a hollow fiber membrane contactor, Part I: Investigation of particulate fouling

Particle formation by precipitation is an important unit operation for the production of fine solids such as catalysts, pigments, and pharmaceuticals. It is the decisive step for determining properties such as particle size, shape, and purity, which in turn determine the quality of the end product. In this study, we investigated the precipitation of BaSO 4 particles in a hollow fiber membrane device. A solution of BaCl 2 was passed tangentially over a membrane surface and reacted with a solution of K 2SO 4 introduced through the membrane pores. The resulting supersaturation induced nucleation and particles grew on the lumen side of the hollow fibers. Particulate fouling was observed using X-ray images with BaSO 4 as a radiocontrast agent. It was shown that this fouling was attributed primarily to fiber blockage by newly formed crystals rather than to pore blockage. Moreover, a larger inner diameter of hollow fiber was shown to slow down considerably the fouling of the device. A numerical simulation was developed to calculate the supersaturation inside a hollow fiber, and the results of the simulation were compared with experimental data.

Characterization of mixing in a hollow fiber membrane contactor by the iodide–iodate method: Numerical simulations and experiments

Abstract This paper presents numerical simulations and experimental data on the iodide–iodate reaction in a hollow fiber membrane device. The principle of reactive mixing in a membrane device is the following. Component A flows through the inlet of the lumen side and component B comes from the membrane pores (shell side). Components A and B then mix and react inside the lumen side. Experimental measurements of the segregation index were carried out under various experimental conditions and for two different hollow fiber devices. The numerical and experimental segregation indexes, X S , were found in the range 10 −2 –10 −3 , indicating effective mixing. The numerical simulations showed that I 3 − ions were produced mainly in the first part of the lumen side of the hollow fiber. This confirmed our previous results on precipitation which showed that high supersaturation data and experimental fouling were obtained in this part of the hollow fibers.

Numerical simulation of mass transfer in a liquid–liquid membrane contactor for laminar flow conditions

Liquid–liquid phase membrane contactors are increasingly being used for mixing and reaction. The principle is the following: component A flows through the membrane device inlet to mix/react with component B which comes from the membrane pores. This study presents a numerical simulation using computational fluid dynamics (CFD) of momentum and mass transfer in a tubular membrane contactor for laminar flow conditions. The velocity and concentration profiles of components A–C are obtained by resolution of the Navier-Stokes and convection-diffusion equations. The numerical simulations show that mixing between A and B is obtained by diffusion along the streamlines separating both components. The mixing/reaction zone width is within the region of a few hundred of microns, and depends on the diffusion coefficients of A and B. Hollow fiber membrane devices are found to be of particular interest because their inner diameter is close to the mixing zone width.

Immunoaffinity centrifugal precipitation chromatography

Purification of proteins based on immunoaffinity has been performed using a solid support coated with antibody against the target proteins. The method requires immobilizing the antibody onto the solid support using protein A or G, and has a risk of adsorptive loss of target proteins onto the solid support. Centrifugal precipitation chromatography has been successfully used to purify enzymes, such as ketosteroid isomerase and hyaluronidase without the use of solid support. The purpose of this study is to demonstrate that immunoaffinity centrifugal precipitation chromatography is capable of isolating an antigen by exploiting antigen–antibody binding. The separation was initiated by filling both channels with 40% saturated ammonium sulfate (AS) of pH 4–4.5 followed by loading 20 μl of human plasma (National Institutes of Health blood bank) mixed with 2 mg of rabbit anti-HSA (human serum protein) antibody (Sigma). Then, the sample channel was eluted with water at 0.03 ml/min and AS channel with 40% AS solution of pH 4–4.5 at 1 ml/min until all non-binding components were eluted. Then, the releasing reagent (50% AS solution containing 0.5 M glycine and 10% ammonium hydroxide at pH 10) was introduced through the AS channel to release the target protein (HSA). The retained antibody was recovered by eluting the sample channel with water at 1 ml/min. A hollow fiber membrane device at the outlet (MicroKros, Spectrum, New Brunswick, NJ, USA) was provided on-line dialysis of the eluent before fractions were collected, so that the fractions could be analyzed by SDS-PAGE (sodium dodecyl sulfate – polyacrylamide gel electrophoresis) without further dialysis. The current method does not require immobilizing the antibody onto a matrix, which is used by the conventional immunoaffinity chromatography. This method ensures full recovery of the antigen and antibody, and it may be applied to purification of other proteins.

Antisolvent crystallization in porous hollow fiber devices

This paper examines antisolvent crystallization under a new perspective and in the unique environment offered by porous hollow fiber membrane devices. The latter are compact, extremely efficient on a volumetric basis, easy to scale up and control. Their inherent characteristics promote the creation of homogeneous concentration conditions on a scale considerably smaller than existing industrial crystallizers without the necessity of a large energy input, properties that are desirable but rarely achieved in industrial crystallizers. Mixing studies were performed to examine the maximum achievable supersaturation in porous hollow fiber devices. It was shown that they are able to offer the supersaturation levels necessary to perform antisolvent crystallization. Moreover, supersaturation is created uniformly due to the large number of feed introduction points, the membrane pores. In addition, radial mixing is substantial in contrast with traditional tubular devices and the characteristic time involved in this process is comparable to the device residence time. Porous hollow fiber antisolvent crystallization of aqueous L-asparagine monohydrate systems proved successful. Mean crystal sizes up to two times smaller compared to batch stirred crystallizers were obtained in standalone membrane hollow fiber crystallizers (MHFC) and their combinations with completely stirred tanks. The CSD was confined below 165 μ m for the former and 75 μ m for the latter, levels that are sufficient for most pharmaceutical crystalline products, for which bioavailability and formulation concerns dictate the desired CSD. In addition, porous hollow fiber devices achieved comparable or slightly higher nucleation rates with respect to batch stirred crystallizers and similar values compared to tubular precipitators. Considerable improvements can be obtained by carefully designing membrane hollow fiber crystallizers.

Degradation of hydroxylated compounds using laccase and horseradish peroxidase immobilized on microporous polypropylene hollow fiber membranes

Microporous polypropylene hollow fiber membranes (HF) impregnated with horseradish peroxidase (HRP) and laccase were used to study the degradation of selected hydroxylated aromatic compounds (3,4-dimethylphenols, 4-ethylphenol, 2-hydroxy-1,2,3,4-tetrahydronaphthalene, 2-hydroxy-decahydronaphthalene and 4-hydroxy-biphenyl). It was found that, with the exception of 2-hydroxy-decahydronaphthalene, all substrates were efficiently degraded (50–100% within 48 h). In preliminary investigations, the transport behavior of the analytes through the membranes before and after enzyme immobilization was studied in batch experiments. In addition, a continuous-flow hollow fiber membrane device was used to examine the degradation performance of the immobilized enzymes on the substrates. It was successfully demonstrated that freshly prepared radish juice can be used to replace the commercially available horseradish peroxidase. The method of overall monitoring used was a combination of solid-phase microextraction/gas chromatography/mass spectrometry (SPME–GC–MS).

On-line coupling of high performance gel filtration chromatography with imaged capillary isoelectric focusing using a membrane interface.

A high performance liquid chromatography system, a sample preparation device, and an imaged capillary IEF (CIEF) instrument are integrated and multiplexed on-line. The system is equivalent to two-dimensional polyacrylamide gel electrophoresis (2-D PAGE), by transferring the principle of 2-D separation to the capillary format. High performance liquid chromatography (HPLC) provides protein separation based on size using a gel filtration chromatography (GFC) column. Each eluted protein is sampled and directed to a novel microdialysis hollow fiber membrane device, where simultaneous desalting and carrier ampholyte mixing occurs. The sample is then driven to the separation column in an on-line fashion, where CIEF takes place. The fluidic technology used by our 2-D system leads to natural automation. The coupling of the two techniques is simple. This is attributed to high speed and efficiency of the sample preparation device that acts as an interface between the two systems, as well as the speed and simplicity of our whole column absorption imaged CIEF instrument. To demonstrate the feasibility of this approach, the separation of a mixture of two model proteins is studied. Sample preparation and CIEF were complete in just 4-5 min, for each of the eluted proteins. Total analysis time is about 24 min. Three-dimensional data representations are constructed. Challenges and methods to further improve our instrument are discussed, and the design of an improved horseshoe-shaped sample preparation sample loop membrane interface is presented and characterized.

Regenerative Oil Scrubbing of Volatile Organic Compounds from a Gas Stream in Hollow Fiber Membrane Devices

A regenerative membrane-based absorption process has been extensively studied to remove volatile organic compounds (VOCs) from air/N2 using silicone oil as the absorbent. The absorbent liquid is regenerated by applying a vacuum in a membrane-based stripper. In this process, there are no flooding, loading, and entrainment, which limit the gas/liquid flow rate in the traditional absorption process. In the present study, attention has been focused on the removal of volatile component(s) from binary gas mixtures such as methanol−N2 and toluene−N2 and from a model multicomponent mixture of gasoline vapor constituents and nitrogen. The process performance was tested under three conditions: (i) absorption with fresh absorbent; (ii) absorption and stripping modules at the same (room) temperature; (iii) maintaining different temperatures in the absorption and stripping modules. Henry's law constants and diffusivities of VOCs in silicone oil needed to simulate the process performances have been experimentally measured at different temperatures. The experimental results have been compared with theoretical predictions.

Extraction of lactic acid from fermented broth with microporous hollow fiber membranes

Non-dispersive solvent extraction of lactic acid based on anion-exchange reaction with tri- n-octylmethylammonium chloride dissolved in oleyl alcohol, the optimum extraction reagents selected for extractive fermentation of lactic acid with Lactobacillus rhamnosus, was attempted in a microporous hollow fiber membrane device. A satisfactory recovery of lactic acid from both aqueous solution and actual fermented broth was accomplished, signifying the great potential of integrating the membrane extraction with fermentation process. A theoretical model which took into account the mass transfer resistances across organic and aqueous films and membrane was developed to analyze and predict the extraction behavior. The model prediction was found to be in good agreement with the experimentally observed results.

Enzymatic acylglycerol synthesis in a membrane bioreactor

Lipases can catalyze the esterification reaction in a two‐phase system. TheCandida rugosa lipase‐catalyzed esterification of decanoic acid with glycerol is described in this work for an emulsion system and for a hydrophilic membrane bioreactor. The enzymatic activity is studied in relation to the interface area between the two phases, the enzyme load and the reactor volume. The initial rate per unit interface area, the interfacial activity, is roughly equal for both systems indicating that the cellulose membrane does not hinder the esterification. Because the interfacial activities are equal, the volumetric activity of a membrane system is only specific area related, so a hollow fiber membrane device is preferable. The activity is also a function of the enzyme load. The optimum load in a hydrophilic membrane reactor is one to three times the amount of a monolayer, while in an emulsion system several times this amount. This could indicate that in the emulsion system the adsorption is in a dynamic state while at the membrane surface the adsorption reached its equilibrium state.

A general description of flows and pressures in hollow fiber membrane modules

A coherent description of flow phenomena in hollow fiber membrane devices is given that predicts pressures and flows occuring under various operating modes. The analysis also has relevance to the more general case of laminar or turbulent flow in porous ducts. Flow phenomena in porous ducts have been studied. A general model has been derived that predicts the pressure drop and the magniture and direction of flows in hollow fiber modules for different modes of operation. Only two dimensionless parameters are needed to predict all pressures and flows. One parameter is equal to the ratio of viscous flow resistance in the fibers and the fiber wall permeation resistance whereas the other is related to the entrance flow and its physical properties. The analysis has been carried out for an incompressible pure fluid with laminar or turbulent flow inside the fibers. A constant pressure on the module shell side has been assumed. For the closed-shell mode of operation the laminar-flow model has been extended to include a pressure drop on the shell side. Here a third dimensionless parameter was introduced representing the ratio of viscous flow resistances on the shell and the fiber side.

Membrane technology and biotechnology

The rapidly growing field of biotechnology, which now encompasses sophisticated fermentation processes utilizing normal and genetically altered microorganisms, biochemical conversions employing immobilized enzymes and cells, and the production of biological products from mammalian cell cultures, is demanding increasingly more efficient and economic means of culturing microorganisms, of recovering and isolating costly labile products, and of disposing of objectionable toxic wastes. Membrane and membrane-separation technology is finding increasing attention today as a means for solving these problems. Continuous crossflow filtration with microporous or ultrafiltration membranes is now being used to separate cells from supernatant in whole fermentation broths with high product recovery, and elimination of a major waste-disposal problem. Reverse osmosis and ultrafiltration are receiving increased attention as a means for concentrating fermentation liquors to facilitate final product recovery, or for demineralizing or removing colloidal impurities from product-containing solutions to improve product yield and purity. Hollow-fiber membrane devices have been found to serve as excellent “artificial capillary beds” for the maintenance of mammalian cell cultures; such devices are now being used as artificial organs, and for the production of hormones, viruses, vaccines, and antibodies for diagnostic and therapeutic uses. Recently, hollow-membrane fibers have been shown to be attractive media for the growth and support of microbial (bacteria, yeast, etc.) populations at very high cell densities (10 12/cm 3), and may provide the basis for a new family of high-capacity, continuous-production bioreactors. Immobilized enzyme reactors, which employ membranes as matrices for enzyme containment, are now gaining increasing popularity for the conduct of continuous biochemical transformations. In addition, enzyme-containing membranes are showing considerable promise in the development of novel electrochemical and thermo-chemical sensors for detection and measurement of complex biochemical substances; such sensors are expected to play an important role in the design of control instrumentation for biochemical manufacturing processes.