Kimia Dan Teknik Membrane

8/2/2019 Kimia Dan Teknik Membrane

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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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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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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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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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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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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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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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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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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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Posttreatment

Phase-inversionmembrane

Support layer

(non-woven)

Polymersolution

Castingknife

Schematic drawing depicting the preparation offlat membranes

Coagulation bath


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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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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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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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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

Kimia Dan Teknik Membrane

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