TKK 435 Pemisahan 2.1 (Materia)

Membrane Materials3.1: Polymer Membranes

Selection criteria

1. The material must be available.1. The material must be available.

2. The material must be chemically stable in a range of conditi2. The material must be chemically stable in a range of conditionsons

3. The material must be formable.3. The material must be formable.

4. The material may need to be approved for food or water contr4. The material may need to be approved for food or water contract foract for

certain markets.certain markets.

3.1.1: Cellulose Acetate

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This group of materials was one of this first to be used for memThis group of materials was one of this first to be used for membranesbranes

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For reverse osmosis the degree of salt retention can be varied bFor reverse osmosis the degree of salt retention can be varied by curing y curing the membranes with heat.the membranes with heat.

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The advantage of cellulose acetate (CA) is that it is relativelyThe advantage of cellulose acetate (CA) is that it is relatively

inexpensive and that it is hydrophilicinexpensive and that it is hydrophilic.

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Good resistance to fouling in some circumstances, particularly wGood resistance to fouling in some circumstances, particularly where here fats and protein are at present.fats and protein are at present.

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It also shows some limited resistance to the use of chlorine as It also shows some limited resistance to the use of chlorine as sodium sodium hypochloratehypochlorate

solution, which can be used for solution, which can be used for sanitisationsanitisation

and cleaning.and cleaning.

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One example of the use of this membrane is in the concentration One example of the use of this membrane is in the concentration of of potato fruit water, an effluent stream that arises from the manupotato fruit water, an effluent stream that arises from the manufacture of facture of starch from potatoes.starch from potatoes.

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The disadvantage is a tendency to hydrolysis outside a narrow pHThe disadvantage is a tendency to hydrolysis outside a narrow pH

and temperature range and temperature range

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rapid hydrolysis occurs at pH values below 3, or above 7, or ifrapid hydrolysis occurs at pH values below 3, or above 7, or if

the the temperature exceeds 30 temperature exceeds 30 --

3535°°C. C.

3.1.2: Polyimide thin film composites

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These membranes are used for reverse osmosis and These membranes are used for reverse osmosis and nanofiltrationnanofiltration.

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The thin film is a dense layer of polyamide approximately 0.1 mmThe thin film is a dense layer of polyamide approximately 0.1 mm

thick thick that is formed at the top surface of an that is formed at the top surface of an ultrafiltrationultrafiltration

membrane by membrane by polymerisingpolymerising

two or more monomers in situ.two or more monomers in situ.

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The thin film has a relatively low resistance to flow, which resThe thin film has a relatively low resistance to flow, which results in ults in higher water fluxes than cellulose acetate membranes, and the chhigher water fluxes than cellulose acetate membranes, and the chemical emical stability of the resulting composite in considerably better thanstability of the resulting composite in considerably better than

comparable comparable cellulosiccellulosic

membranes.membranes.

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Typically a pH range of 2 to 12 can be exploited for cleaning, Typically a pH range of 2 to 12 can be exploited for cleaning, and and process temperatures of up to 70process temperatures of up to 70°°C are possible.C are possible.

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The general weakness of this membrane is its very low tolerance The general weakness of this membrane is its very low tolerance to free to free chlorinechlorine.

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In some cases, particularly where caustic cleaning regimes are iIn some cases, particularly where caustic cleaning regimes are in use n use the effective maximum concentration tolerable is zero. This memthe effective maximum concentration tolerable is zero. This membrane brane can also be easily fouled.can also be easily fouled.

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For example an effluent from coffee manufacture that was successFor example an effluent from coffee manufacture that was successfully fully concentrated with cellulose acetate membranes reduced the flux oconcentrated with cellulose acetate membranes reduced the flux of a f a polyamide thin film composite membrane to zero in less than 12hrpolyamide thin film composite membrane to zero in less than 12hrs of s of operation.operation.

3.1.3: Polysulfone

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This is an engineering polymer that can be used for This is an engineering polymer that can be used for ultrafiltrationultrafiltration, ,

microfiltrationmicrofiltration

and gas separation membranesand gas separation membranes.

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It has good chemical and temperature stability allowing operatioIt has good chemical and temperature stability allowing operation up to n up to

8080°°C, and will tolerate a pH from 1.5 to 12 for cleaning.C, and will tolerate a pH from 1.5 to 12 for cleaning.

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The limits for sustained operation on process are slightly more The limits for sustained operation on process are slightly more restrained.restrained.

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Prolonged exposure, or contact with high concentrations can causProlonged exposure, or contact with high concentrations can cause e

cracking of the membrane filmcracking of the membrane film.

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This is usually manifests itself as a rapid loss of process fluxThis is usually manifests itself as a rapid loss of process flux

after each after each

clean, whilst exhibiting unusually high clean water fluxes at thclean, whilst exhibiting unusually high clean water fluxes at the end of e end of

the cleans.the cleans.

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The material finds wide use, with applications covering cheese wThe material finds wide use, with applications covering cheese whey hey

protein recovery, protein recovery, lignosulphonatelignosulphonate

fractionation and fractionation and clarifactionclarifaction

of of

pharmaceutical broths.pharmaceutical broths.

3.1.4: Sulphonated polysufone

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This is a patented variation of polysulfone.This is a patented variation of polysulfone.

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It is available as a It is available as a nanofiltrationnanofiltration

membrane for water treatment.membrane for water treatment.

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This membrane is claimed to have a high tolerance to chlorine whThis membrane is claimed to have a high tolerance to chlorine which ich

eliminates the need for eliminates the need for dechlorinationdechlorination

of feed water in certain water of feed water in certain water

treatment applications.treatment applications.

3.1.5: Polyethersulfone

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This material has similar chemical and thermal limits to polysulThis material has similar chemical and thermal limits to polysulfone and it fone and it

is also available with similar molecular weight cutis also available with similar molecular weight cut--off.off.

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However, its performance when in contact with process fluids canHowever, its performance when in contact with process fluids can

be be

markedly different.markedly different.

3.1.6: Polyvinylidenedifluoride (PVDF)

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The material is a popular choice for The material is a popular choice for ultrafiltrationultrafiltration

and and microfiltrationmicrofiltration

membranes.membranes.

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Similar pH and temperature limits as Similar pH and temperature limits as polysulphonepolysulphone, but has a higher , but has a higher tolerance to tolerance to oxidisingoxidising

agents such as chlorine.agents such as chlorine.

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This type of membrane is in the This type of membrane is in the clarifationclarifation

of fruit juicesof fruit juices

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PVDF shows a clear advantage in performance over polysulfone PVDF shows a clear advantage in performance over polysulfone membranes, with fluxes of up to double those of similar membranemembranes, with fluxes of up to double those of similar membranes.s.

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In addition PVDF can resist exposure to limonene, which is presIn addition PVDF can resist exposure to limonene, which is present in ent in citrus fruitscitrus fruits.

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PVDF membranes are, therefore, extensively used for the clarifiPVDF membranes are, therefore, extensively used for the clarification of cation of lime juice.lime juice.

3.1.7: Polyacrylonitrile

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Membranes made from this material, either alone or as a copolymeMembranes made from this material, either alone or as a copolymer, are r, are

often claimed to be hydrophilic and to exhibit a wider toleranceoften claimed to be hydrophilic and to exhibit a wider tolerance

to to

solvents than some of the other membranessolvents than some of the other membranes.

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It is produced using the phase inversion technique and is availIt is produced using the phase inversion technique and is available for able for

separations in the separations in the ultrafiltrationultrafiltration

range.range.

3.1.8: Polytetrafluoroethylene (PTFE)

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Not in widespread use in crossNot in widespread use in cross--flow systems, but some flow systems, but some microfiltrationmicrofiltration

membranes are available in a spiral format.membranes are available in a spiral format.

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Sheets of the material are stretched, producing randomly spaced Sheets of the material are stretched, producing randomly spaced PTFE PTFE

fibresfibres

radiating from a series of nodes.radiating from a series of nodes.

3.2: Ceramic Membranes

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As with the polymeric membranes, a number of different materialsAs with the polymeric membranes, a number of different materials

are are used.used.

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The French company The French company TecSepTecSep

manufacture a membrane with a porous manufacture a membrane with a porous carbon support and a membrane layer of zirconium oxidecarbon support and a membrane layer of zirconium oxide.

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MembraloxMembralox

range, also produced in France, use a monolith of range, also produced in France, use a monolith of αα--alumina alumina with a selective layer made of with a selective layer made of γγ--alumina.alumina.

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The American company, The American company, CeramemCeramem

Separations uses Separations uses CordiuriteCordiurite, a , a material used for catalytic converters, as the material for theimaterial used for catalytic converters, as the material for their monolith.r monolith.

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Currently these membranes are available in Currently these membranes are available in microfiltrationmicrofiltration

and and ultrafiltrationultrafiltration

format.format.

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In most cases, ceramic membranes enjoy a greater tolerance to acIn most cases, ceramic membranes enjoy a greater tolerance to acid and id and alkali than alkali than polymericspolymerics..

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pH range of 1 to 14 are quoted.pH range of 1 to 14 are quoted.

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This has led to these membranes being looked at for recovery of This has led to these membranes being looked at for recovery of spent spent caustic wash solution in the food industry and for the regeneratcaustic wash solution in the food industry and for the regeneration of ion of caustic degreasing baths.caustic degreasing baths.

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They also compete with polymeric membranes in various fields whThey also compete with polymeric membranes in various fields where ere the economics of long membrane life, or perceived robustness of the economics of long membrane life, or perceived robustness of the the ceramics, are seen to favour the ceramic system.ceramics, are seen to favour the ceramic system.

3.3: Other Materials

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Both glass and steel are used for membranes.Both glass and steel are used for membranes.

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The glass membranes are in the form of hollow The glass membranes are in the form of hollow fibresfibres, and are available , and are available with pore sizes ranging from 10 with pore sizes ranging from 10 ––

90 nm.90 nm.

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Their use is in the Biotech industries where the resistance to aTheir use is in the Biotech industries where the resistance to adsorption dsorption exhibited by these membranes results in significant reductions iexhibited by these membranes results in significant reductions in product n product loss.loss.

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Steel membranes are made from sintered stainless steel and are Steel membranes are made from sintered stainless steel and are available in tubular formats.available in tubular formats.

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The membranes are very robust, making them suitable for aggressThe membranes are very robust, making them suitable for aggressive ive environments, but the pore size is currently limited to the largenvironments, but the pore size is currently limited to the larger pore size er pore size end of end of microfiltrationmicrofiltration..

3.4: Non-membrane materials

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Most membranes are supported by a nonMost membranes are supported by a non--woven sheet which is woven sheet which is commonly made of polyester, polypropylene or polyethylene commonly made of polyester, polypropylene or polyethylene fibresfibres..

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Seals are produced from commonly used Seals are produced from commonly used elastomerselastomers

such as such as nitrilenitrile

rubber, EDPM or rubber, EDPM or VitonViton..

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Glues are widely used for module and element construction.Glues are widely used for module and element construction.

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Many of these are two part epoxy resinMany of these are two part epoxy resin--types or polyurethane. types or polyurethane. Frequently these have USFDA (United States Food and Drug Frequently these have USFDA (United States Food and Drug Administration) approval for contact with foods.Administration) approval for contact with foods.

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Finally a wide variety of plastics, which range from Finally a wide variety of plastics, which range from polysulphonepolysulphone

to PVCto PVC

Struktur dan morfologi Simetrik Membran

Active skin layer semua

permukaan

sama

Active skin layer

Porous membrane sublayer

Surface layer

Struktur dan morfologi Tak Simetrik Membran

Active Skin layer Porous substructure

Zeolite particle

Struktur dan morfologi composite Membran