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Kimia dan Teknik Membran
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Overview
Introduction Membrane materials Preparation of membranes Characterisation of membrane Membrane processes Fouling Process design Applications of membrane
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Introduction
Separation processes
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Introduction
Separation processes based on physical/chemical properties
Physical/chemicalproperty Separation process
Size Filtration, microfiltration, ultrafiltration,dialysis, gas separation
Vapour pressure Distillation, membrane distillation
Freezing point Crystallisation
Affinity Extraction, adsorption, reverse osmosis, gasseparation, pervaporation
Charge Ion-exchange, electrodialysis,electrophoresis, diffusion dialysis
Density Centrifugation
Chemical nature Complexation, carrier mediated transport
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Introduction
PermeateFeed
Phase 1Membrane Phase 2
Driving force
C, P, T, E
A two-phase system separated by a membrane
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Introduction
General definition of a membrane:
A selective barrier between twophases, the term selective beinginherent to a membrane or a
membrane process
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Membrane materials
Membrane polymers
Membranes
Inorganic membranes
Biological membranesLiquid membranes
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Membrane materials
Membrane polymers Porous membranes
Polytetrafluoroethylene,
polyvinylidenefluoride,
polypropylene, polycarbonate,
polyamide
Non porousmembranes
Polymer type can range froman elastomer to a glassymaterial
Poly(m-phenylene)-1,3,4-oxadiazole; poly(m-phenylene)-1,2,4-triazole
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Membrane materials
Inorganic membranes Alumina membranes Titania membranes
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Membrane materials
Inorganic membranesZirconia composite membranes
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Membrane materials
Biological membranes Contain a basic lipid bilayer structure
Each lipid molecule possess a hydrophobicand a hydrophilic part
70A
Hydrophilic region
Hydrophilic region
Hydrophobic region
A lipid bilayer
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Membrane materials
Liquid membranes
Carrier
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Preparation of polymermembranes
Preparation for phase inversion membranesPhase inversion is a process whereby a polymer istransformed from a liquid to a solid state.The process of solidification is initiated by the transitionfrom one liquid state into two liquids (liquid-liquiddemixing).
At a certain stage during demixing, one of the liquid phases(the high polymer concentration phase) will solidify so thata solid matrix is formed.By controlling the initial stage of phase transition, themembrane morphology can be controlled
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Preparation of polymermembranes
PolymerSolvent
Polymer solutionThe polymer solution iscast on suitable support
Preparation techniques for phase inversion: Precipitation by solvent evaporationPrecipitation from the vapour phasePrecipitation by controlled evaporationThermal precipitation
Immersion precipitation
Precipitation
Study of gas separation properties of ethylene vinyl acetate(EVA)copolymer membranes prepared via phase inversion method, SeyyedAbbas Mausavi, et al., Separation and purification technology, 62(2008), 642-647
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Preparation of polymermembranes
Precipitation by solvent evaporationPrecipitation is conducted by evaporating the solvent in aninert (nitrogen) atmosphere, in order to exclude watervapour.
Precipitation from the vapour phasePrecipitation is done in a vapour atmosphere where the vapourphase consist of a non-solvent saturated with the samesolvent. The high solvent concentration in the vapour phaseprevent the evaporation of solvent from the cast film.
Membrane formation occurs because of the penetration(diffusion) of non-solvent into the cast film.This lead to a porous membrane without top layer
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Preparation of polymermembranes
Precipitation by controlled evaporationThe polymer is dissolved in a mixture of solvent and non-solvent (the mixture act as a solvent for the polymer). Sincethe solvent is more volatile than the non-solvent, the
composition shift during evaporation to a higher non-solventand polymer content. This lead to the formation of a skinnedmembrane
Thermal precipitation
A solution of polymer in a mixed or single solvent is cooled toenable phase separation to occur. Evaporation of the solventoften allows the formation of a skinned membrane.
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Preparation of polymermembranes
Immersion precipitation
A polymer solution (polymer + solvent) is cast on a suitablesupport and immersed in a coagulation bath containing a
non-solvent. Precipitation occurs because of the exchangeof solvent and non-solvent. The membrane structureobtained results from a combination of mass transfer andphase separation
J1
J2
Polymer
Non solvent, solvent
Non solvent,solvent Coagulation bath
Polymer solution
Support
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Preparation of polymermembranes
Some factors that affect membrane structure:
The choice of solvent and non solvent system
The polymer concentration
The Composition of the coagulation bath The composition of the polymer solution
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Preparation of polymermembranes
Solvent for cellulose and polysulfone
Cellulose acetate Polysulfone
Dimethylformamide (DMF) Dimethylformamide (DMF)
Dimethylacetamide (DMAc) Dimethylacetamide (DMAc)
Acetone Dimethylsulfoxide (DMSO)
Dioxan Formylpiperidine (FP)
Tetrahydrofuran (THF) Morpholine (MP)Acetic acid (HAc_) N-methylpyrrolidone (NMP)
Dimethylsulfoxide (DMSO)
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Preparation of polymermembranes
Classification of solvent/non solvent pairs
Solvent Non solvent Type of membrane
DMSO water porous
DMF water porous
DMAc water porous
NMP water porous
DMAc n-propanol nonporous
DMAc i-propanol nonporous
DMAc n-butanol nonporous
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Preparation of polymermembranes
Choice of polymer and polymer concentration
Polymer:
PolysulfonePoly(ether sulfone)Poly(vinylidene fluoride)PolyacrylonitrileCellulose acetate
PolyimidePoly(ether imide)Polyamide (aromatic)
Polymerconcentration (%)
Flux(l m-2 h-1)
12 200
15 80
17 2035 0
Pure water flux through polysulfonemembranes
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Preparation of polymermembranes
Posttreatment
Phase-inversionmembrane
Support layer
(non-woven)
Polymersolution
Castingknife
Schematic drawing depicting the preparation offlat membranes
Coagulation bath
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Preparation of polymermembranes
Tubular membranes
a. Hollow fiber membranes (diameter < 0.5 mm)
b. Capillary membranes (diameter: 0.5-5 mm)
c. Tubular membranes (diameter: > 5 mm)
The dimension of the tubular membranes are so large that theyhave to be supported, whereas the hollow fibers and capillariesare self supporting. Hollow fibers and capillaries can be prepared
via three different methods: Wet spinning (or dry spinning)
Melt spinning
Dry spinning
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Preparation of polymermembranes
Schematic drawing of a dry-wet spinning process
Coagulationbath
Flushing bath
Air gap
Spinneret
Bore liquidPolymer solution
Gear pump
pumpBoreliquid
f l
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Preparation of polymermembranes
Polymersolution
Castingbob
Poroustube
Polymersolution
Reservoir
Airpressure
Castfilm
(a) (b)
Coagulationbath
(c)
Pressure is applied to a reservoir filled with a polymer solution, so that the solution is forcedthrough a hollow pipe. At the end of the pipe is a casting bob with small holes which thepolymer solution is forced. The porous tube is moving vertically and a film is cast upon itsinner wall. The pipe is then immersed in a coagulation bath where precipitation of the castpolymer solution leads to the formation of a tubular membrane
P f l
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Preparation of polymermembranes
Microporous polypropylene tubularmembranes via thermally induced phaseseparation using a novel solvent-champene,
M.C. Yang and J.S. Perng, Journal ofmembrane science, 187, (2001), 13-22
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Proses pemisahan cair-cair
Berpori Rapat
t = komposisi pada lapisan atas, b = komposisi pada lapisan bawah
t hubungan kesetimbangan pada antarmuka film/non pelarut