Dr.rer.nat. Heru Susantomembrane

1. Concentrate 2. Purify a dilute (aqueous or non aqueous)1. Stucture membrane 2. Pore size3. Pore size distributionPORE SIZE

Is the membrane process which most closely resembles conventional coarse filtration. Pore size:Suitable for retaining suspensions and emulsions The Darcys Law :Where the permeability constant A contains structural factors such as the porosity and pore size (pore size distribution)For laminar convective flows through a porous systems :Where r is the pore radius, x is the membrane thickness, is he dynamic viscosity and is the tortuosity factor ehich is unity in the case of cylindrical pores.

May be prepared from organic materials (polymers) and inorganic (ceramics, metals, glasses)Various techniques can be employed :1. Sintering 2. Streching 3. Track - etching4. Phase inversionFrequently, inorganic membranes are used instead of polymeric membranes because of their outstanding chemical and thermal resistances.

ProcessPorosityPore size distributionSinteringLow / mediumNarrow / wideStretchingMedium / high Narrow / wideTrack-etchingLowNarrowPhase inversion HighNarrow / wide

These various techniques allow to prepare microfiltration membranes from virtually all kinds of materials of which polymers and ceramics are the most important. HYDROPHOBIC POLYMERIC MEMBRANESHYDROPHILIC POLYMERIC MEMBRANESPolytetrafluoroethylene (PTFE)Poly(vinylidene fluoride) (PVDF)Polyproylene (PP)Polyethylene (PE)Cellulase estersPolycarbonate (PC)Polysulfone / poly(ether sulfone) (PS/PES)Aliphatic polyamide (PA)Polyetheretherketone (PEEK)CERAMIC MEMBRANESAlumina (Al2O3)Zirconia (ZrO2)Titania (TiO2)Silicium carbide (SiC)

FLUX DECLINENEEDNEED

DEAD END FILTRATIONThe feed flow is perpendicular to the membrane surface, so that the retained particles accumulate and form a type of a cake layer at the membrane surface. The thickness of the cake increases with filtration times and consequently the permeation rate decreases with increasing cake layer thicknessCROSS FLOW FILTRATIONThe feed flow is along the membrane surface, so that part of the retained solutes accumulate

Cold sterilisation of beverages and pharmaceuticalCell harvestingClarification of fruit juice, wine and beerUltrapure water in the semiconductor industryMetal recovery as colloidal oxides or hydroxidesWaste-water treatmentContinuous fermentationSeparation of oil-water emulsionsDehydration of latices

Membranes :(a)Symmetric porousThickness :10 150 umPore sizes :0,05 10 umDriving force :Pressure (< 2 bar)Separation principles :Sieving mechanismMembrane material :Polymeric, and ceramicMain application :Analytical applicationsSterilisation (food, pharmaceutical)Ultrapure water (semiconductor)

Is a membrane process whose nature lies between nanofiltration and microfiltrationPore size:UF is typically used to retain macromolecules and colloids from a solution. UF and MF can oth be consider as porous membrane where rejection is determined by the size and shape of the solutes relatives to the pore size in he membrane and where the transport of solvent is directly proportional to the applied pressure. In fact both UF and MF involve similar membrane processes based on the same separation principle. However, an important difference is that UF membrane have an asymmetric structure with a much denser top layer (small pore size and lower surface porosity) and consequently a much higher hydrodynamic resistance.

Most of UF membrane used commercially these day are prepared from :POLYMERIC MEMBRANESPolytetrafluoroethylene (PTFE)Poly(vinylidene fluoride) (PVDF)PolyacrylonitrilePolyimidePolyetheretherketoneAliphatic polyamidesCellulosics INORGANIC (CERAMIC)Alumina (Al2O3)Zirconia (ZrO2)

FOOD AND DAIRY INDUSTRYPHARMACEUTICAL INDUSTRYTEXTILE INDUSTRYCHEMICAL INDUSTRYMETALLURGYPAPER INDUSTRYLEATHER INDUSTRYRecovery of whey proteinsRecovery of potato starch and proteinsConcentration of egg productClarification of fruit juices and alcoholic beverages

Membranes :Asymmetric porousThickness :150 um (or monolithic for some ceramics)Pore sizes :1 100 nmDriving force :Pressure (1-10 bar)Separation principles :Sieving mechanismMembrane material :Polymeric (PS, Polyacrilonitrile)Ceramic (zirconium oxide, aluminium oxide)Main application :Dairy (milk, whey, cheese making)Food (potato starch and protein)Metallurgy (oil-water emulsion, electropaint recovery)Textile (indigo)Pharmaceutical (enzymes, antibiotics, pyrogens)Automotive (electropaint)Water treatment

Salt solutionPure waterMembrane Complete barrier to dissolved saltRO and NF are used when low molecular weight solutes such as inorganic salts or small organic mocules such as glucose, and sucrose have to be separated from solvent.The membrane is permeable to the solvent (water) but not to the solute (salt). In order to allow water to pass through the membrane, the applied pressure must be higher than the osmotic pressure.

Both process are considered as one process since the basic principles are the same.NF membranes are the same as RO membranes only the network structure is more open.Comparison of retention characteristic between nanofiltration (NF) and reverswe osmosis (RO) are listened :The pressure used in reverse osmosis range from 20 100 bar and ini nanofiltration from about 10 20 bar, which much higher than those used in ultrafitration

SoluteRONFMonovalent ions (Na, K, Cl, NO3)>98%99%>90%Bacteria and virusses>99%100)>90%>50%Microsolutes (Mw < 100)0-99%0-50%

The flux is approximately inversely proportional to the membrane thickness and for this reason most reverse osmosis membranes have an asymmetric structure with a thin dense toplayer (thickness 1um) supported by a porous sublayer (thickness 50 150 um), the resistance towards transport being determined mainly by distinguished: (i) integral asymmetric membranes, and (ii) composite membranes.

Both toplayer and sublayer consists of the same material. These membrane are prepare by phase inversion technique. The polymeric material from which the membrane it to be prepared is soluble in a solvent or a solvent mixture.An important class of asymmetric membranes are :cellulose esters. This materials are very suitable for desalination because of their high permeability towards water in combination with a (very) low solubility towards salt. 12Aromatic pides. These material also show high selectivities towards salts but their water flux is somewhat lower.Polybenzimidazoles, polybenzimidazolones, polyamidedehydrazide, and polyimides3

The second type of structure frequently used in RO while most of the NF membrane are in fact composite membrane.In such membranes the top layer and sublayer are composed of different polymeric materials so that each layer can be optimised separately.The first stage is the are preparation of the porous sublayer. Important criteria forthis sublayer are surface porosity and pore size distribution and asymmetric ultrafiltration membranes are often used. Different methods have been employed for placing a thin dense layer on top of this sublayer :

dip coatingIn-situ polymerisationInterfacial polymerisationPlasma polymerisation

purification water, desalination of brackish and seawater to produce potable waterProduction of ultrapure water for the semiconductor industryConcentration step particularly in the food industry ( concentration of fruit juice)Galvanis industry (concentration of waste stream)Dairy industry (concentration of milk to prior cheese manufacture)ROWhen a high retention is required for NaCl with high feed concentrations reverse osmosis reverse osmosis is the preferred process. In other cases with much lower concentrations, divalent ions and micro solutes with molecular weight nanofiltration is the preferred process. Since the water permeability is (much) higher in nanofiltration the capital cost for a certain application will be lower. NF

Membranes :Composite Thickness :Sublayer : 150 um Toplayer : 1 umPore sizes :< 2 nmDriving force :Pressure (10 25 bar)Separation principles :Solution diffusionMembrane material :Polyamide (interfacial polymerisation)Main application :Desalination of brackish and seawaterRemoval of micropllutentsWater softeningWastewater treatmentRetention of dyes (textile industry)

Membranes :Asymmetric or compositeThickness :Sublayer : 100 umToplayer : 1 umPore sizes :< 2 nmDriving force :Pressure : brackish water (15 25 bar) seawater (40 80 bar)Separation principles :Solution-diffusionMembrane material :Cellulose triacetate, aromatic polyamide, polyamide and poly(ether urea) (interfacial polymerisation)Main application :Desalination of brackish and seawaterProduction of ultrapure water (electronic industry)Concentration of food juice and sugars (food industry) and the concentration of milk dairy industry)

Microfiltration Ultrafiltration Nanofiltration / reverse osmosisSeparation of particlesSeparation of macromolecules (bacteris, yeasts)Separation of low MW solute (salt, glucose, lactose, micropollutent)Osmotic pressure negligibleOsmotic pressure negligibleOsmotic pressure high (1-25 bar)Applied pressure low (< 2bar)Applied pressure low (1-10 bar)Applied pressure high (10-60 bar)Symmetric structureAssymetric structure Asymmetric structureAsymmetric structureThickness of separating layer:Symmetric structure : 10-150 umAssymetric structure :1 umThickness of actual separating layer : 0,1-1,0 umThickness of actual separating layer : 0,1 1 umSeparation based on particle sizeSeparation based on particle sizeSeparation based on differences in solubility and diffusivity