scholarly journals INFLUENCE OF CHITOSAN MOLECULAR WEIGHT AND DEGREE OF DEACETYLATION ON MEMBRANE PHYSICOCHEMICAL AND SEPARATION PROPERTIES IN ETHANOL DEHYDRATION BY THE VAPOUR PERMEATION PROCESS

2020 ◽  
Vol XXV ◽  
pp. 79-93
Author(s):  
Małgorzata Gnus
Keyword(s):  
Molecular Weight ◽  
Contact Angle ◽  
Membrane Separation ◽  
Membrane Surface ◽  
Selectivity Coefficient ◽  
Permeate Flux ◽  
Ethanol Dehydration ◽  
Degree Of Deacetylation ◽  
Molecular Weights ◽  
Surface Contact Angle

Membranes were prepared using three chitosans with different molecular weights and degrees of deacetylation. The influence of chitosan features on membrane physicochemical properties, i.e. degree of swelling, contact angle and tensile strength, as well as membrane separation properties in ethanol dehydration by the vapour permeation process are discussed. The conducted experiments showed that an increase in the chitosan molecular weight led to an increase in the membrane surface contact angle concomitant with a decrease in the material selectivity coefficient. On the other hand, an increase in the chitosan degree of deacetylation caused a reduction in ethanol and improved the water permeate flux. There was greater selectivity in the test process for membranes prepared from chitosan with the lowest molecular weight.

A Wall Film Model for Membrane Fouling

2018 ◽  
Author(s):  
Sina Jahangiri Mamouri ◽  
Volodymyr V. Tarabara ◽  
André Bénard
Keyword(s):  
Multiphase Flow ◽  
Membrane Fouling ◽  
Oil And Gas ◽  
Membrane Separation ◽  
Film Formation ◽  
Membrane Surface ◽  
Permeate Flux ◽  
Water Separation ◽  
Wall Film ◽  
Oil Water

Deoiling of produced or impaired waters associated with oil and gas production represents a significant challenge for many companies. Centrifugation, air flotation, and hydrocyclone separation are the current methods of oil removal from produced water [1], however the efficiency of these methods decreases dramatically for droplets smaller than approximately 15–20 μm. More effective separation of oil-water mixtures into water and oil phases has the potential to both decrease the environmental footprint of the oil and gas industry and improve human well-being in regions such as the Gulf of Mexico. New membrane separation processes and design of systems with advanced flow management offer tremendous potential for improving oil-water separation efficacy. However, fouling is a major challenge in membrane separation [2]. In this study, the behavior of oil droplets and their interaction with crossflow filtration (CFF) membranes (including membrane fouling) is studied using computational fluid dynamics (CFD) simulations. A model for film formation on a membrane surface is proposed for the first time to simulate film formation on membrane surfaces. The bulk multiphase flow is modeled using an Eulerian-Eulerian multiphase flow model. A wall film is developed from mass and momentum balances [3] and implemented to model droplet deposition and membrane surface blockage. The model is used to predict film formation and subsequent membrane fouling, and allow to estimate the actual permeate flux. The results are validated using available experimental data.

The Effect of Flow Pulsation on Ultrafiltration System Limiting Flux Behavior

2013 ◽  
Author(s):  
Chyouhwu Brian Huang ◽  
Hung-Shyong Chen
Keyword(s):  
Membrane Filtration ◽  
Concentration Polarization ◽  
Membrane Separation ◽  
Membrane Surface ◽  
Paper Industry ◽  
Surface Concentration ◽  
Permeate Flux ◽  
Filtration Time ◽  
Protection Systems ◽  
Oil Water

Ultrafiltration (UF) is an important industrial operation and is found in the food industry, separation of oil-water emulsions, treatment effluents from the pulp and paper industry, and environmental protection systems. Despite being widely used in these areas, UF systems exhibit a limiting flux behavior caused by concentration polarization on the membrane surface. Concentration polarization can be severe in macromolecular solutions due to low diffusivity on membrane separation and both mechanical and chemical methods have been used to reduce this phenomenon. This study introduces a new mechanical method that improves the performance of membrane separation and decreases concentration polarization. It involves pulsing the feed flow discontinuously and based on our results, feed flow velocity and solution bypass/membrane filtration time ratio are two vital factors when it comes to improving permeate flux. The proposed method is expected to find wide application, particularly in the processing of macromolecular solution.

Synthesis and Properties of a High-Molecular-Weight Polyimide Based on 4, 4'-(hexafluoroisopropylidene) Diphthalic Anhydride

2012 ◽  
Vol 550-553 ◽  
pp. 742-746
Author(s):  
Hui Wen Wu ◽  
Hua Li ◽  
He Zhou Liu
Keyword(s):  
Molecular Weight ◽  
High Molecular Weight ◽  
Organic Solvents ◽  
Membrane Separation ◽  
Amic Acid ◽  
Molecular Weights ◽  
Chemical Structures ◽  
Synthesis Parameters ◽  
Soluble Polyimide

A soluble polyimide with high molecular weight was synthesized from 4, 4'-(hexafluoroiso propylidene) diphthalic anhydride (6FDA) and 2, 2’-bis(3-amino-4-hydroxyphenyl) hexafluoropropane (BAPAF) via two-step polycondesation procedure involving the preparation of poly(amic acid) (PAA) followed by chemical imidization. Effect of synthesis parameters on polyimide molecular weight involving material ratio, imidization temperature and imidization catalyst were studied. Synthesized PI was analyzed with respect to their molecular weights, chemical structures and solubility through GPC, FTIR, XRD and solubility tests respectively. The results showed that a high-molecular-weight PI was successfully synthesized from 4, 4'-(hexafluoroisopropylidene) diphthalic anhydride and 2, 2’-bis (3-amino-4-hydroxyphenyl) hexafluoropropane with imidization at 80°C for 3h, material ratio of n(BAPAF):n(6FDA) equal to 1:1 and catalyst of n(triethylamine):n (pyridine) less than1:3. The obtained PI showed excellent solubility in polar aprotic organic solvents such as NMP, DMAc, DMSO, THF and Acetone. Poly(6FDA-BAPAF) PI, with high molecular weight and excellent solubility, which was synthesized under lower imidization temperature that was equal to 80°C,could be easily obtained and convenient to process, thus it is a potential material for membrane separation.

scholarly journals Fabrication of ultrafiltration membranes by poly (aryl ether nitrile) with poly (ethylene glycol) as additives

2020 ◽  
Vol 82 (12) ◽  
pp. 2847-2856
Author(s):  
Qi Wang ◽  
Fengna Dai ◽  
Shangying Zhang ◽  
Chunhai Chen ◽  
Youhai Yu
Keyword(s):  
Molecular Weight ◽  
Ethylene Glycol ◽  
Aryl Ether ◽  
Permeate Flux ◽  
Poly Ethylene Glycol ◽  
Molecular Weights ◽  
Effect Of Solvents ◽  
Dimethyl Acetamide ◽  
Solution Preparation ◽  
Poly Ethylene

Abstract A new kind of flat sheet ultrafiltration membrane was prepared by a promising membrane material, poly (aryl ether nitrile) (PEN), via non-solvent induced phase separation. The effect of solvents, N-methyl-2-pyrrolidone (NMP) and dimethyl acetamide (DMAc), as well as additive of poly (ethylene glycol) (PEG) with different molecular weights on the structure and permeation performance of synthesized membranes were investigated. Comparing with NMP, DMAc is more suitable for the casting solution preparation due to better solubility. A gradually changing pore from sponge-like to finger-like can be observed when PEG was added with DMAc as solvent, while a finger-like pore structure always appears in the NMP system with or without PEG. In both systems, the formation of macrovoids is effectively promoted by the addition of PEG, and higher porosity membranes can be obtained by PEG with higher molecular weight. With the increase of PEG molecular weight from 400 to 10,000 Da, the permeate flux increases from 74.5 to 114.3 L·m−2·h−1 and from 102.0 to 130.8 L·m−2·h−1 under a 100 kPa pressure-driven when NMP and DMAc were used as solvents, respectively. The membranes prepared by DMAc exhibit outstanding rejection of BSA with rejections all above 96.5%.

Influence of Multiwall Carbon Nanotube on Polyethersulfone/ Polyvinyl Alcohol Blend Membranes

2014 ◽  
Vol 67 (2) ◽  
Author(s):  
Nur Farahah Mohd Khairuddin ◽  
Ani Idris ◽  
Iqbal Ahmed ◽  
Noordin Mohd Yusof
Keyword(s):  
Molecular Weight ◽  
Contact Angle ◽  
Carbon Nanotube ◽  
Polyvinyl Alcohol ◽  
Water Flux ◽  
Multiwall Carbon Nanotube ◽  
Flux Rate ◽  
Molecular Weights ◽  
Blend Membranes ◽  
Multiwall Carbon

This paper investigates the influence of multiwall carbon nanotube (MWCNT) on the morphology and properties of polyethersulfone (PES) and polyvinyl alcohol (PVA) blend membranes. Several membranes were prepared by blending 0.5 wt% MWCNT , 18%wt PES and 1.5wt% PVA of various molecular weights (60, 145 and 200 kDa) in  dimethyl acetate (DMAC) solvent. The membranes were then evaluated in terms of its morphology, contact angle, water flux rate and porosity. The results revealed that MWCNT nanoparticles have decreased the contact angle and increased the flux rate of PES/PVA blend membranes. The presence of MWCNT in the PES/PVA membranes have promoted the formation of fingerlike pores in the membranes structure and thus increased the porosity of the membranes. Besides that, the use of higher molecular weight PVA helped to reduce the contact angle of the membranes reflecting to their hydrophilic nature. However, the use of lower molecular weight PVA was found to enhance the increased of flux rate and porosity of the membrane.

Article

1998 ◽  
Vol 76 (11) ◽  
pp. 1699-1706 ◽  
Author(s):  
Jonathan Z Knaul ◽  
Mohammad R Kasaai ◽  
V Tam Bui ◽  
Katherine AM Creber
Keyword(s):  
Molecular Weight ◽  
Average Molecular Weight ◽  
Gel Permeation Chromatography ◽  
Solvent System ◽  
Similar Degree ◽  
Degree Of Deacetylation ◽  
Molecular Weights ◽  
Good Accord ◽  
Gel Permeation ◽  
Weight Analysis

Starting from a chitosan sample with a degree of deacetylation of 71%, three separate sample sets were generated by successive deacetylation and reacetylation processes. The degree of deacetylation of samples was determined by UV spectrometry supported by thermogravimetric analysis. The molecular weight of chitosan samples was determined in a solvent system of 0.25 M CH3COOH/0.25 M CH3COONa, using viscometry and gel permeation chromatography (GPC) with a TSK-gel column. The first set of samples had a similar degree of deacetylation (DDA) but differing molecular weights. The second set of samples had a similar molecular weight but differing degrees of deacetylation. The Mark-Houwink-Sakurada constants used for the determination of viscosity average molecular weight and the universal calibration of the GPC system were K = 1.40 × 10-4 dL/g and a = 0.83. Results showed that molecular weights determined from both techniques are in good accord only at lower degrees of deacetylation. This may be attributed to the fact that the chemical structure of chitosan samples could have been largely altered with increasing or decreasing degree of deacetylation. Nevertheless, the trend with which the molecular weights vary with the deacetylation time is consistent over a limited DDA range. A literature review of molecular weight analysis of chitosan is included.Key words: chitosan, degree of deacetylation, gel permeation chromatography, molecular weight, viscometry.

scholarly journals Factors Affecting Membrane Distillation Process for Seawater Desalination

2018 ◽  
Vol 22 (1) ◽  
Author(s):  
Ngo Thi Tra My ◽  
Vo Thi Yen Nhi ◽  
Bui Xuan Thanh
Keyword(s):  
Contact Angle ◽  
Membrane Separation ◽  
Membrane Distillation ◽  
Process Efficiency ◽  
Membrane Properties ◽  
Permeate Flux ◽  
Factors Affecting ◽  
Entry Pressure ◽  
Membrane Lifetime ◽  
Membrane Wetting

Membrane distillation (MD), a process based on the thermal principle, is a combination of distillation and membrane separation in the same unit. There are many factors that can affect the MD performance, but the membrane characteristics are the most important in this process. The changes in the membrane properties affect the process efficiency, the permeate flux as well as the membrane lifetime. Some of the membrane properties mentioned in this paper include liquid entry pressure (LEP), contact angle, pore size, porosity, thickness, thermal conductivity, support layer, tortuosity, etc. This review paper aims to evaluate the membrane properties in order to reduce membrane wetting and to improve desalination efficiency. From this review, it can be seen that the LEP and contact angle are the important factors which directly affect the hydrophobicity of the membrane. When LEP and the contact angle increase, the hydrophobicity of the membrane increases. Thus, the membrane is durable and the MD system works efficiently. The remaining factors indirectly affect the operation of the MD system through LEP and contact angle (hydrophobicity).

scholarly journals Permeate Flux in Ultrafiltration Membrane: A Review

2017 ◽  
Vol 14 (1) ◽  
Author(s):  
A. Beicha ◽  
R. Zaamouch ◽  
N. M. Sulaiman
Keyword(s):  
Membrane Filtration ◽  
Membrane Separation ◽  
Size Range ◽  
Membrane Surface ◽  
Separation Performance ◽  
Permeate Flux ◽  
Predictive Capability ◽  
Separation Processes ◽  
Ultrafiltration Pressure ◽  
Rate Limiting

Membrane processes exist for most of the fluid separations encountered in industry. The most widely used is membrane ultrafiltration, pressure driven process which is capable of separating particles in the approximate size range of 0.001 to 0.1 μm. The design of membrane separation processes, like all other processes, requires quantitative expressions relating material properties to separation performance. The factors controlling the performance of ultrafiltration are extensively reviewed. There have been a number of seminal approaches in this field. Most have been based on the rate limiting effects of the concentration polarization of the separated particles at the membrane surface. Various rigorous, empirical and intuitive models exist, which have been critically assessed in terms of their predictive capability and applicability. The decision as to which of the membrane filtration models is the most correct in predicting permeation rates is a matter of difficulty and appears to depend on the nature of the dispersion to separated.

Treatment of agricultural wastewater and reuse

2002 ◽  
Vol 46 (11-12) ◽  
pp. 177-182 ◽  
Author(s):  
W. Reimann
Keyword(s):  
Membrane Separation ◽  
Membrane Surface ◽  
Pilot Scale ◽  
Wash Water ◽  
Coliform Bacteria ◽  
Permeate Flux ◽  
Log Reduction ◽  
Agricultural Wastewater ◽  
Inorganic Substances ◽  
Process Combination

The use of membrane separation technology, such as ultrafiltration (UF) and subsequent reverse osmosis (RO), for purifying different types of low-contaminated wash water of carrots (COD = 1,314 mg/l) and wash water of different kinds of vegetables (COD = 2,280 mg/l) was investigated on a pilot scale to determine its suitability for reuse in the process. In both membrane processes, UF and RO, the permeate flux first decreased with increasing fouling (deposition of organic and inorganic substances on the membrane surface and in its pores). After that the membrane permeability (permeate flux) and selectivity (rejection of COD) remained constant on a stable level in spite of a concentration with a volumetric concentration factor of up to 39. The tests showed that water can be obtained with a quality complying with the German regulations by applying a process combination of UF and RO. It was found that the membranes gave a 5-log reduction for total bacteria, and no coliform bacteria were present in the permeate after RO. Using UF and RO, part of the wastewater can be recovered for reuse in the process if drinking water is used for the last step of vegetable washing.

The emulsifying stability of soy hull polysaccharides with different molecular weight obtained from membrane-separation technology

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Lina Yang ◽  
Xinghui Wu ◽  
Li Zhao ◽  
Ziyi Wang ◽  
Danshi Zhu ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Particle Size ◽  
Membrane Separation ◽  
Ammonium Oxalate ◽  
Monosaccharide Composition ◽  
Separation And Purification ◽  
Stability Properties ◽  
Separation Technology ◽  
Molecular Weights ◽  
Soy Hull

Abstract Polysaccharides are macromolecules used for food development, and their further separation into different molecular weights allows their broader application in the food industry. Here, we performed microwave-assisted ammonium oxalate extraction of soy hull polysaccharide (SHP; MASP), followed by their separation and purification using membrane-separation technology and analyses of the emulsifying stability and MASP mechanism at different molecular weights. Additionally, we compared the composition and structural differences in SHP components and evaluated the separation and grading-emulsification stability properties of the membrane-emulsified components. The results showed improved emulsification stability properties of high molecular weight SHPs that had been separated and purified by membrane separation, with the formed emulsion exhibiting a high degree of viscosity, uniform particle-size distribution, smaller particle size, less interfacial tension, and a high Zeta potential. Moreover, the chemical composition, monosaccharide composition, and molecular weight of SHP were different.

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