Membrane Microfiltration Fermentation of Glucose Oxidase with Cell Recycling

Membrane microfiltration fermentation (MMF) with cell recycling was successfully applied to the production of glucose oxidase (GOD). A plate microfiltration module was found suitable for such purpose. By feeding whole medium in MMF, the productivity of GOD was much higher than that by feeding glucose alone. With increasing dilution rate the enzyme productivity increased and average enzyme activity decreased. The enzyme productivity of MMF under D = 0.12h-1 and 0.20h-1 were 3871 and 3945U·h-1 respectively, which was about 3 times as that of batch fermentation (BF) and the average enzyme activity was still as high as STU·mL-1 under D = 0.12h-1. The relative efficiency of MMF applied to low yield strain was higher than that applied to high yield strain.

Flow-Induced Clogging in Microfiltration Membranes: Numerical Modeling and Parametric Study

Microfiltration membrane technology has been widely used in various industries for solid-liquid separation. However, pore clogging remains a persistent challenge. This study employs (CFD) and discrete element method (DEM) models to enhance our understanding of microfiltration membrane clogging. The models were validated by comparing them to experimental data, demonstrating reasonable consistency. Subsequently, a parametric study was conducted on a cross-flow model, exploring the influence of key parameters on clogging. Findings show that clogging is a complex phenomenon affected by various factors. The mean inlet velocity and transmembrane flux were found to directly impact clogging, while the confinement ratio and cosine of the membrane pore entrance angle had an inverse relationship with it. Two clog types were identified: internal (inside the pore) and external (arching at the pore entrance), with the confinement ratio determining the type. This study introduced a dimensionless number as a quantitative clogging indicator based on transmembrane flux, Reynolds number, filtration time, entrance angle cosine, and confinement ratio. While this hypothesis held true in simulations, future studies should explore variations in clogging indicators, and improved modeling of clogging characteristics. Calibration between numerical and physical times and consideration of particle volume fraction will enhance understanding.

Preparation and Characterization of the Modified Polyvinylidene Fluoride (PVDF) Hollow Fibre Microfiltration Membrane

A novel thermally induced graft polymerization technique was used to modify a polyvinylidene fluoride （PVDF） hollow fibre microfiltration membrane. An artificial neural network （ANN） was applied to optimize the prepared condition of the membrane. The optimized dosing of acrylic acid （AA）, acrylamide （AM）, N, N＇- methylenebisacrylamide （NMBA） and potassium persulphate （KSP） designed by ANN was that AA was 40.63 ml/L; AM acted as 6.25 g/L; NMBA was 1.72 g/L and KSP was 1.5 g/L, respectively. The thermal stability of the PVDF modified hollow fibre membrane （PVDF-PAA） was investigated by thermogravimetric （TG） and differential scanning calorimetry （DSC） analysis. The polycrystallinity of the PVDF-PAA membrane was evaluated by X-ray diffraction （XRD） analysis. The complex formation of the modified membrane was ascertained by Fourier transform infrared spectroscopy （FTIR）. The morphology of the PVDF-PAA membrane was studied by environmental scanning electron microscopy （ESEM）. The surface compositions of the membrane were analyzed by X-ray photoelectron spectroscopy （XPS）. The adsorption capacity of Cu^2＋ ion on the PVDF-PAA hollow fibre membrane was also investigated.

Purifying chylous plasma by precluding triglyceride via carboxylated polyethersulfone microfiltration membrane

Precluding the excessive lipoproteins from plasma rapidly and effectively is highly needed for biomedical detection and reducing plasma product scrap in blood donation stations.The current centrifugation procedure is high-cost and time-consuming.Herein,we fabricated an anionic microfiltration polyethersulfone(PES)membrane modified by interface swelling and implanting of acrylic acid(AA)for screening out large particle lipoprotein chylomicron(CM)and adsorbing cationic very low-density lipoproteins(VLDL).To improve the separation efficiency,a two-stage filtration through carboxylated polyethersulfone microfiltration membranes with the mean pore size of 0.45 and 0.22μm respectively were conducted.Attenuated total reflection Fourier transform infrared technique(ATR-FTIR),water contact angle(WCA),Zeta potential and scanning electron microscope(SEM)were employed to characterize the modified membrane.To test the effectiveness of this membrane,plasma flux and concentration variation of plasma components were examined to study the purification effectiveness.Furthermore,the hemocompatibility of modified membranes was tested to confirm its practicability on bloodcontacting materials.The carboxylated polyethersulfone microfiltration membrane shows its promising potential application to purify chylous plasma.

Fulvic acid degradation using nanoparticle TiO_2 in a submerged membrane photocatalysis reactor

The degradation of fulvic acid（FA） by nanoparticle TiO2 in a submerged membrane photocatalysis（SMPC） reactor was studied. In this reactor, photocatalytic oxidation and membrane separation co-occured. The continuous air supplier provided O2 for the photocatalytical reaction and mixed the solution through an airflow controller. The particle TiO2 could automatically settle due to gravity without particle agglomeration so it could be easily separated by microfiltration（MF） membrane. It was efficient to maintain high flux of membranes. The effects of operational parameters on the photocatalytic oxidation rate of FA were investigated. Results indicated that photocatalyst at 0.5 g/L and airflow at 0.06 m^3/h were the optimum condition for the removal of fulvic acid, the removal efficiency was higher in acid media than that in alkaline media. The effects of different filtration duration on permeate flux rate of MF with P25 powder and with nanoparticle TiO2 were compared. Experimental results indicated that the permeate flux rate of MF was improved and the membrane fouling phenomenon was reduced with the addition of nanoparticle TiO2 catalyst compared with conventional P25 powder. Therefore, this submerged membrane photocatalysis reactor can faciliate potential application of photocatalytic oxidation process in drinking water treatment.

Experimental Study on Revolving Cross-flow Microfiltration of Highly Viscous Liquids

Experimental investigation of the microfiltration （MF） using a revolving cross-flow membrane filter was performed under the condition of constant pressure difference, and different flat membranes made of polyvinylidene fluoride （PVDF, 0.1 μm）, cellulose acetate （CA, 0.22 μm）, sulfonated polyethersulfone （SPES, 0.22 μm） and polyamide （PA, 0.45 μm）, respectively, were used in filtration experiments. The dependence of the filtrate mass of the cross-flow MF on time was measured on-line. The experimental results showed that the effect of the cross-flow on high viscosity medium was more significant than that on the low viscosity one.

Mechanism of Coalescence Demulsification with Microfiltra- tion Membrane

A study on the membrane coalescence demulsification was carried out with four working systems of water/n-butyl alcohol, water/n-octanol, water/30% TBP(in kerosene) and water/kerosene. The membranes made of polytetrafluoroethylene (PTFE) with 1.0μm pore size were used. The results indicated that the excellent demulsification efficiency for emulsions with various oil contents was obtained. A conductivity probe was used to study the demulsification mechanism. An electrode probe was designed and used to determine the oil content near the membrane surface. The obtained data showed that the oil content in the permeated stream was much higher than that in the feed emulsion. A physical mechanism to explain the membrane demulsification was put forward.

Polyaniline-poly(vinylidene fluoride) blend microfiltration membrane and its spontaneous gold recovery application

Structural regular polyaniline was synthesized via a modified-chemical oxidative polymerization reaction. Highly hydrophilic polyaniline(PANi) and polyaniline-poly(vinylidene fluoride) blend(PANi-PVDF) membranes were prepared by solution casting and phase inversion techniques. Both of the mechanical and filtration properties of the membranes depend on the polymer composition and doping level of the blends. The elasticity of the membrane is greatly improved upon introducing poly(vinylidene fluoride) into the blend. The water permeability of the blend membranes is further enhanced when the membranes are doped with hydrochloric acid. The PANi-PVDF blend membranes are capable of recovering metallic gold from the acid/halide leaching streams spontaneous and sustainably, and are promising candidates for wastewater treatments in electronic industries.

Roles of membrane and organic fouling layers on the removal of endocrine disrupting chemicals in microfiltration

To understand the adsorption behavior of endocrine disrupting chemicals（EDCs） is important for enhancing the treatment performance and preventing potential secondary pollution caused by EDCs desorption in a microfiltration system. The dynamic adsorption of four representative EDCs, namely estriol（E3）, 17β-estradiol（E2）, 17α-ethynylestradiol（EE2）, and 4-nonylphenol（4-NP） in a microfiltration system was investigated using the Thomas＇ model.The product of the equilibrium constant and the total adsorption capacity of the membrane,Ka, for E3, E2, EE2, and 4-NP were 4.91, 9.78, 15.6, and 826, respectively, strongly correlating with the compound octanol–water partition coefficient（KOW）. Adsorption appeared to be enhanced when organic fouling formed on the surface of membrane, indicating the role of an additional adsorption column for EDCs acted by a fouling layer in microfiltration. Results of a comparison between the Ka values for clean membrane and fouled membrane illustrated that the significant contribution made by fouling layers may be attributed to the foulant layer＇s hydrophobicity（in the case of calcium humate layer） and thickness（in the case of calcium alginate layer）. This study provided a novel perspective to quantitatively analyze the dynamic adsorption behavior of trace pollutants in membrane process.