-
8/10/2019 Modification of Existing Membranes and Properties Enhancements
1/21
Modification of Existing
Membranes and Proper
EnhancementHafiz Imran Akhter Muhammad Nade
2013-MS-PE-1 2013-MS-PE-15
-
8/10/2019 Modification of Existing Membranes and Properties Enhancements
2/21
Introduction
Membrane TechnologyMembrane technology has become an emerging separation tethe past few decades.
Use
We use the membranes in industrial applications for many advaphase changes or chemical additives needed. A modular is simoperation and it is easy to scale up, and relatively low energy co
-
8/10/2019 Modification of Existing Membranes and Properties Enhancements
3/21
Cont..
Material of Construction
Primary material used forinorganic membranes are:
aluminum oxide, zirconium oxide,
Organic materials are:
polysulfone, poly(ether sulfone), polyacrylonitrile, polyamide, popoly(vinylidenefluoride) and polytetrafluoroethylene.
-
8/10/2019 Modification of Existing Membranes and Properties Enhancements
4/21
Driving force
The driving force is pressure difference, concentration gradient, variation and electrical force across the membrane for the permmolecules through a membrane barrier.
-
8/10/2019 Modification of Existing Membranes and Properties Enhancements
5/21
Membrane surface
Surface characteristics are important in membrane separatiomolecules from the feed stream will first contact with the memsurface.
Two common surface features of membrane are
1. hydrophobicity
2. hydrophilicity.
The hydrophobic property is water repellent and prohibiting twettability. Hydrophobic surface resist to spread water and recontact with the surface
-
8/10/2019 Modification of Existing Membranes and Properties Enhancements
6/21
Membranes Modification
Fouling and wetting will reduce the membrane efficiency and dperformance, consequently increasing the operation cost and efailure
Modification of membranes with hydroxyl and ethylene-glycogroups can reduce membrane fouling.
-
8/10/2019 Modification of Existing Membranes and Properties Enhancements
7/21
Cont..
Fouling can be effected by
Increased hydraulic resistance
Changes in colloid surface properties due to organic adsorpt
Membrane fouling depends upon:
i. pH,
ii. ionic composition,
iii. ionic strength and type and
iv. concentration of foulants in the feed water.
-
8/10/2019 Modification of Existing Membranes and Properties Enhancements
8/21
Feed water pretreatment
Pretreatment can reduce fouling potential, increase membramaintain performance level by altering the physical, chemicbiological properties of the feed water
Most frequently processes are used for feed water pretreatm
Coagulation
The role of coagulants is to effectively neutralize same charges asuspended solids to group together in flocs
-
8/10/2019 Modification of Existing Membranes and Properties Enhancements
9/21
Cont..
Activated carbon adsorption
Adsorption is an important way to remove soluble non-polar orgin water, natural organic matter as well as emerging pollutants sendocrine disrupting compounds.
Activated carbon adsorption, either in granular or powder form,
considered as a feasible mean for reducing membrane fouling, in combination with other pretreatment processes.
Filtration
-
8/10/2019 Modification of Existing Membranes and Properties Enhancements
10/21
Cont..
Chemical agent addition
Acid addition
Antiscalant addition
Disinfectant addition
Disinfection is a necessary and effective way to kill bacterial celachieved through addition of a strong oxidant, such as chlorine hypochlorite (NaClO), monochloramie (NH2Cl), chlorine dioxide (O3), or UV irradiation
-
8/10/2019 Modification of Existing Membranes and Properties Enhancements
11/21
Membranes Modification Techn
Generally membranes modification techniques
1. surface coating
2. surface grafting
3. incorporation with hydrophilic monomers
4. Incorporation with inorganic particles
5. zwitterionic modification
6. low temperature plazma
-
8/10/2019 Modification of Existing Membranes and Properties Enhancements
12/21
Surface Coating
The modified membrane revealed more hydrophilic, smootheanti-bacterial property than unmodified one.
It can be seen that the materials used for surface coating arehydrophilic polymers containing hydroxyl, carboxyl, amino grenzyme. The presence of coating layer could significantly enhydrophilicity and reduce surface charge and roughness of mrendering a better anti-fouling property
Surface coatings are relatively simple to apply and selective of the membrane is not likely to be affected by the adsorbedHowever, coating layer tended to offer an additional resistanpermeation and render flux decline.
-
8/10/2019 Modification of Existing Membranes and Properties Enhancements
13/21
Cont..
One of the major concerns is that anti-fouling property of themay be gradually deteriorated, because the coating layer aattached to the membrane surface by van der Waals attrachydrogen bond, or/and electrostatic interaction, which may washing away of the coating layer in the chemical cleaning long term operation process.
Commercial TFC aromatic polyamide RO membrane is modi
coating a layer of natural polymer sericin that contains hydroamino, and amide groups to improve anti-fouling property. Bmodification membrane show improved surface hydrophilicitsurface negative charge, and smooth surface morphology apure water permeability.
-
8/10/2019 Modification of Existing Membranes and Properties Enhancements
14/21
Surface grafting
Surface grafting has been widely used because of its simpliciand breadth field of applications.
Free radical-, photochemical-, radiation-, redox-, plasma-indand chemical crosslinking are currently used to covalently athydrophilic monomers onto the surface of NF/RO membrane
Short wavelength (254 nm) possessing high energy may dammembrane support resulting in polymer degradation due to t
scission of polymer backbone and poor chemical selectivity imodification reactions. In generally, UV-system with 350 nm wwas used to prevent damaging TFC RO membrane. Thereforechallenge to modify the TFC polyamide membranes for bothfouling resistance and enhanced separation performance, i.epermeation flux and salt rejection
-
8/10/2019 Modification of Existing Membranes and Properties Enhancements
15/21
Cont..
The activation of carboxylic acid groups by coupling reagenethy-3-(3-dimethyl amidopropyl) carbodiimide (EDC) has beechemical grafting to enhance anti-fouling ability of NF/RO m
The modified membranes were more resistant to fouling in prcationic surfactant feed water compared to unmodified me
Nanoparticles can also be grafted to the surface of polyamidmembrane to reduce biofouling through covalent bonding.
Membrane surface modification by grafting hydrophilic or aningredients on membrane top layer has been reported to haeffect on anti-fouling, but it has uncontrollable grafting densioperation step, and may damage the membrane pore struca decline performance
-
8/10/2019 Modification of Existing Membranes and Properties Enhancements
16/21
Incorporation with hydrophilic mono
Incorporation of hydrophilic monomers into membrane selecconsidered to be a convenience and effective strategy to emembrane anti-fouling capacity.
Incorporation with hydrophilic monomers could improve the ability of the NF/RO membranes, the thermal stability,mechanicalproperties, dimensional stability, anti-swelling perthe ductility of these membranes.
-
8/10/2019 Modification of Existing Membranes and Properties Enhancements
17/21
Incorporation with inorganic par
For inorganic nanoparticles, which have a higher specific arenegatively charged hydroxyl groups existing on the surface, inew good properties such as thermostability, anti-fouling, andproperties for the composite materials.
Several types of inorganic materials have been used as addipolymers in NF/RO membrane preparation process, which incdioxide (TiO2), silicon dioxide (SiO2), zeolite, carbon nanotube
nanosilver (nAg).
-
8/10/2019 Modification of Existing Membranes and Properties Enhancements
18/21
Modification with zwitterionic ma
Zwitterionic materials possess both negative and positive chacan create stronger and more stable electrostatic bonds withhydrophilic materials, resulting in excellent biocompatibility aproperty.
zwitterionic polyelectrolytes can improve the anti-fouling of tmembranes to a great extent with changing other membranperformances slightly. However, the synthesis process of the z
polyelectrolyte is complicated and the consumption of chemabundant.
-
8/10/2019 Modification of Existing Membranes and Properties Enhancements
19/21
Low temperature plazma
Low-temperature plasma is a potential technique becausesurface hydrophilicity of polymer membrane without alteriproperties and unfavorable thermal effects; i.e., the favorattributes can be maintained .
-
8/10/2019 Modification of Existing Membranes and Properties Enhancements
20/21
Advantages and DisadvantageModification Methods
M/Modification Methods Advantages Disadvantages
Surface coating Process simplicityNo damage to selective layerstructure
Permeability dPoor Stability
Surface grafting More stable than surface coating Uncontrollable Cost for extra oMay damage mstructureMay cause per
Incorporation with hydrophilicmonomers
Without permeability decline May cause themechanical prstability, anti-swdecline
Incorporation with inorganic particles Without permeability decline Nanoparticle leBiotoxicity
Modification with zwitterionicmaterials
With performance altering slightly Process compleConsumption aagents
-
8/10/2019 Modification of Existing Membranes and Properties Enhancements
21/21
Thank you
For your great patience and valuable time