seminar report on membrance technology

7/27/2019 seminar report on membrance technology

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S.S.G.B.C.O.E.&T. BHUSAWAL Page 1

CHAPTER - 1

INTRODUCTION

Water contains beside of the necessary dissolved matters suspended and dissolved

impurities. The water sources often bear disease causing bacteria, viruses, and parasites and

this water must be treated and purified to meet human needs. Chemical disinfection is in

wide use to treat water but disinfection forms again disinfection by-products (DBP). To avoid

the generation of such DBPs it is necessary to remove natural organic matters efficiently prior

to disinfection. Pesticides and nitrates in ground water is a growing problem in agricultural

areas.

Beside of flocculatio, coagulation and clarification membranes have demonstrated

excellent results in natural organic matter separation and have gained a high potential in

future in the production of drinking water.

The major fields of membrane applications are in the treatment of different sources of

water and are shown in Fig.1. Membrane and membrane processes are generally alternative

ways to conventional techniques and it should be noted to choose the classical way when ever

this is technically and economically possible. Membrane processes are combined with a

relevant demand for electrical energy. The minimization of the energy demand of water

treatment systems is an important task facing our future water resources [4]. Membrane

processes need hydraulic pressure to force water through a semi-permeable membrane which

needs energy and if we are speaking of energy, we have to face the mass of CO2 which is

emitted therefore to get water in defined quality. If we count the quantity of CO2 which we

will emit to produce softwater out of ground water, we have to realize that we are emitting

between 200 to 500 g CO2 per produced 1000 l of product water. Its a relatively wide CO2

emission range which is a result of different process parameters and of the feed water quality.

However membranes are applicable for water sources which cannot be treated

anymore successfully by e.g. convetional techniques combined with disinfection chemicals.

Membranes exhibit the ability to reject most contaminants and have attained for these tasks a

high acceptance in the last 20 to 30 years and many membrane applications in watertreatment have been realized therefore and devepment of economically and ecologically

processes is needed.In the water industry there have been collected parallel to this

development experienced ways of operations in the treatment of different water sources. The

scale of application of membrane plants has grown as well and the sizes of membrane plants

will have further more a rising demand for developments to eneable the purifying water in

areas where water is available but the quality for human consumption is not given. The

challenge to apply membrane processes for the different raw water qualities is to make these

techniques applicable in respect to specific plant and energy costs. Certain plant concepts and

process combinations are inevitable to meet these designated targets and some of them will


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be presented in this paper and practical experiences from field tests discussed. Variations of

this technology include reverse osmosis (RO), nanofilitration or low pressure RO,

ultrafiltration and microfiltration. As membrane plants need energy it is crucial to minimize

the energy consumption for this fast growing demand in water treatment applications also inview of climate change emission reduction.


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CHAPTER- 2

MEMBRANE OPERATIONS

According to driving force of the operation it is possible to distinguish:

2.1Pressure driven operations microfiltration ultrafiltration nanofiltration reverse osmosis2.2Concentration driven operations

dialysis pervaporation forward osmosis artificial lung gas separation

2.3 Operations in electric potential gradient

electrodialysis membrane electrolysis electrodeionization electrofiltration fuel cell2.3Operations in temperature gradient

membrane distillation
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purpose of softening (polyvalent cation removal) and removal of disinfection by-product

precursors such as natural organic matter and synthetic organic matter.[1][2]

Nanofiltration is also becoming more widely used in food processing applications suchas dairy, for simultaneous concentration and partial (monovalent ion) demineralisation.

2.1.4 REVERSE OSMOSIS

Reverse osmosis (RO) is a water purification technology that uses a semipermeable

membrane. This membrane-technology is not properly a filtration method. In RO, an applied

pressure is used to overcome osmotic pressure, a colligative property, that is driven by

chemical potential, a thermodynamic parameter. RO can remove many types

ofmolecules and ions from solutions and is used in both industrial processes and in

producing potable water. The result is that the solute is retained on the pressurized side of the

membrane and the pure solvent is allowed to pass to the other side. To be "selective," this

membrane should not allow large molecules or ions through the pores (holes), but should

allow smaller components of the solution (such as the solvent) to pass freely.

In the normal osmosisprocess, the solvent naturally moves from an area of low solute

concentration (High Water Potential), through a membrane, to an area of high solute

concentration (Low Water Potential). The movement of a pure solvent is driven to reduce the

free energy of the system by equalizing solute concentrations on each side of a membrane,

generating osmotic pressure. Applying an external pressure to reverse the natural flow of pure

solvent, thus, is reverse osmosis. The process is similar to other membrane technology

applications. However, there are key differences between reverse osmosis and filtration. The

predominant removal mechanism in membrane filtration is straining, or size exclusion, so the

process can theoretically achieve perfect exclusion of particles regardless of operational

parameters such as influent pressure and concentration. Moreover, reverse osmosis involves a

diffusive mechanism so that separation efficiency is dependent on solute concentration,

pressure, and water flux rate.[1]Reverse osmosis is most commonly known for its use in

drinking water purification from seawater, removing the salt and othereffluent materials from

the water molecules.
http://en.wikipedia.org/wiki/Valence_(chemistry)http://en.wikipedia.org/wiki/Cationhttp://en.wikipedia.org/wiki/Organic_compoundhttp://en.wikipedia.org/wiki/Nanofiltration#cite_note-WQ-1http://en.wikipedia.org/wiki/Nanofiltration#cite_note-WQ-1http://en.wikipedia.org/wiki/Nanofiltration#cite_note-FilmTec-2http://en.wikipedia.org/wiki/Nanofiltration#cite_note-FilmTec-2http://en.wikipedia.org/wiki/Nanofiltration#cite_note-FilmTec-2http://en.wikipedia.org/wiki/Food_processinghttp://en.wikipedia.org/wiki/Dairyhttp://en.wikipedia.org/wiki/Ionhttp://en.wikipedia.org/wiki/Semipermeable_membranehttp://en.wikipedia.org/wiki/Semipermeable_membranehttp://en.wikipedia.org/wiki/Membrane_technologyhttp://en.wikipedia.org/wiki/Filtrationhttp://en.wikipedia.org/wiki/Osmotic_pressurehttp://en.wikipedia.org/wiki/Colligative_propertyhttp://en.wikipedia.org/wiki/Moleculeshttp://en.wikipedia.org/wiki/Ionshttp://en.wikipedia.org/wiki/Solutionhttp://en.wikipedia.org/wiki/Solventhttp://en.wiktionary.org/wiki/porehttp://en.wikipedia.org/wiki/Osmosishttp://en.wikipedia.org/wiki/Osmotic_pressurehttp://en.wikipedia.org/wiki/Filtrationhttp://en.wikipedia.org/wiki/Reverse_osmosis#cite_note-water-1http://en.wikipedia.org/wiki/Reverse_osmosis#cite_note-water-1http://en.wikipedia.org/wiki/Reverse_osmosis#cite_note-water-1http://en.wikipedia.org/wiki/Water_purificationhttp://en.wikipedia.org/wiki/Seawaterhttp://en.wikipedia.org/wiki/Salthttp://en.wikipedia.org/wiki/Effluenthttp://en.wikipedia.org/wiki/Effluenthttp://en.wikipedia.org/wiki/Salthttp://en.wikipedia.org/wiki/Seawaterhttp://en.wikipedia.org/wiki/Water_purificationhttp://en.wikipedia.org/wiki/Reverse_osmosis#cite_note-water-1http://en.wikipedia.org/wiki/Filtrationhttp://en.wikipedia.org/wiki/Osmotic_pressurehttp://en.wikipedia.org/wiki/Osmosishttp://en.wiktionary.org/wiki/porehttp://en.wikipedia.org/wiki/Solventhttp://en.wikipedia.org/wiki/Solutionhttp://en.wikipedia.org/wiki/Ionshttp://en.wikipedia.org/wiki/Moleculeshttp://en.wikipedia.org/wiki/Colligative_propertyhttp://en.wikipedia.org/wiki/Osmotic_pressurehttp://en.wikipedia.org/wiki/Filtrationhttp://en.wikipedia.org/wiki/Membrane_technologyhttp://en.wikipedia.org/wiki/Semipermeable_membranehttp://en.wikipedia.org/wiki/Semipermeable_membranehttp://en.wikipedia.org/wiki/Ionhttp://en.wikipedia.org/wiki/Dairyhttp://en.wikipedia.org/wiki/Food_processinghttp://en.wikipedia.org/wiki/Nanofiltration#cite_note-FilmTec-2http://en.wikipedia.org/wiki/Nanofiltration#cite_note-WQ-1http://en.wikipedia.org/wiki/Organic_compoundhttp://en.wikipedia.org/wiki/Cationhttp://en.wikipedia.org/wiki/Valence_(chemistry)


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2.2 CONCENTRATION DRIVEN OPERATIONS

2.2.1 DIALYSIS

In medicine dialysis meaning through is a process for removing waste and excess

water from the blood, and is used primarily as an artificial replacement for lost kidney

function in people withrenal failure.[1]Dialysis may be used for those with an acute

disturbance in kidney function (acute kidney injury, previously acute renal failure), or

progressive but chronically worsening kidney functiona state known as chronic kidney

disease stage 5 (previously chronic renal failure or end-stage renal disease). The latter form

may develop over months or years, but in contrast to acute kidney injury is not usually

reversible, and dialysis is regarded as a "holding measure" until a renal transplant can be

performed, or sometimes as the only supportive measure in those for whom a transplant

would be inappropriate.[2]

The kidneys have important roles in maintaining health. When healthy, the kidneys

maintain the body's internal equilibrium of water and minerals (sodium, potassium, chloride,

calcium, phosphorus, magnesium, sulfate). The acidic metabolism end-products that the body

cannot get rid of via respiration are also excreted through the kidneys. The kidneys also

function as a part of the endocrine system, producing erythropoietin and calcitriol.

Erythropoietin is involved in the production of red blood cells and calcitriol plays a role in

bone formation.[3]Dialysis is an imperfect treatment to replace kidney function because it

does not correct the compromised endocrine functions of the kidney. Dialysis treatments

replace some of these functions through diffusion (waste removal) and ultrafiltration (fluid

removal).[4]

2.2.2 MEMBRANE GAS SEPARATION

Membrane technologies are not as well developed as other gas separation techniques

and as a result they are less widely used. Manufacturing challenges mean the units are better

suited for small to mid scale operations.

The use partially permeable membranes which allow "fast" gases to pass through and

be removed, while "slow" gases remain in the airstream and emerge without the original
http://en.wikipedia.org/wiki/Bloodhttp://en.wikipedia.org/wiki/Renal_replacement_therapyhttp://en.wikipedia.org/wiki/Renal_functionhttp://en.wikipedia.org/wiki/Renal_functionhttp://en.wikipedia.org/wiki/Renal_failurehttp://en.wikipedia.org/wiki/Dialysis#cite_note-1http://en.wikipedia.org/wiki/Dialysis#cite_note-1http://en.wikipedia.org/wiki/Dialysis#cite_note-1http://en.wikipedia.org/wiki/Acute_kidney_injuryhttp://en.wikipedia.org/wiki/Chronic_kidney_diseasehttp://en.wikipedia.org/wiki/Chronic_kidney_diseasehttp://en.wikipedia.org/wiki/Renal_transplanthttp://en.wikipedia.org/wiki/Dialysis#cite_note-Pendse-2http://en.wikipedia.org/wiki/Dialysis#cite_note-Pendse-2http://en.wikipedia.org/wiki/Dialysis#cite_note-Pendse-2http://en.wikipedia.org/wiki/Kidneyhttp://en.wikipedia.org/wiki/Metabolismhttp://en.wikipedia.org/wiki/Endocrine_systemhttp://en.wikipedia.org/wiki/Erythropoietinhttp://en.wikipedia.org/wiki/1,25-dihydroxycholecalciferolhttp://en.wikipedia.org/wiki/Dialysis#cite_note-3http://en.wikipedia.org/wiki/Dialysis#cite_note-3http://en.wikipedia.org/wiki/Dialysis#cite_note-3http://en.wikipedia.org/wiki/Diffusionhttp://en.wikipedia.org/wiki/Ultrafiltrationhttp://en.wikipedia.org/wiki/Dialysis#cite_note-4http://en.wikipedia.org/wiki/Dialysis#cite_note-4http://en.wikipedia.org/wiki/Dialysis#cite_note-4http://en.wikipedia.org/wiki/Dialysis#cite_note-4http://en.wikipedia.org/wiki/Ultrafiltrationhttp://en.wikipedia.org/wiki/Diffusionhttp://en.wikipedia.org/wiki/Dialysis#cite_note-3http://en.wikipedia.org/wiki/1,25-dihydroxycholecalciferolhttp://en.wikipedia.org/wiki/Erythropoietinhttp://en.wikipedia.org/wiki/Endocrine_systemhttp://en.wikipedia.org/wiki/Metabolismhttp://en.wikipedia.org/wiki/Kidneyhttp://en.wikipedia.org/wiki/Dialysis#cite_note-Pendse-2http://en.wikipedia.org/wiki/Renal_transplanthttp://en.wikipedia.org/wiki/Chronic_kidney_diseasehttp://en.wikipedia.org/wiki/Chronic_kidney_diseasehttp://en.wikipedia.org/wiki/Acute_kidney_injuryhttp://en.wikipedia.org/wiki/Dialysis#cite_note-1http://en.wikipedia.org/wiki/Renal_failurehttp://en.wikipedia.org/wiki/Renal_functionhttp://en.wikipedia.org/wiki/Renal_functionhttp://en.wikipedia.org/wiki/Renal_replacement_therapyhttp://en.wikipedia.org/wiki/Blood


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contaminants. Membrane technology is most often used for moisture removal, hydrogen

removal and nitrogen enrichment.

2.2.3 FORWARD OSMOSIS

FIG.2.2.3 Osmotic Membrane Processes

Forward osmosis is an osmoticprocess that, like reverse osmosis, uses a semi-

permeable membrane to effect separation ofwaterfrom dissolved solutes. The driving force

for this separation is an osmotic pressure gradient, such that a "draw" solution of

high concentration (relative to that of the feed solution), is used to induce a net flow of waterthrough the membrane into the draw solution, thus effectively separating the feed water from

its solutes. In contrast, the reverse osmosis process uses hydraulic pressure as the driving

force for separation, which serves to counteract the osmotic pressure gradient that would

otherwise favor water flux from the permeate to the feed. The simplest equation describing

the relationship between osmotic and hydraulic pressures and water flux is:

where is waterflux, A is the hydraulic permeability of the membrane, is the

difference in osmotic pressures on the two sides of the membrane, and P is the difference

in hydrostatic pressure (negative values of indicating reverse osmotic flow). The

modeling of these relationships is in practice more complex than this equation indicates, with

flux depending on the membrane, feed, and draw solution characteristics, as well as the fluid

dynamics within the process itself.[1]
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An additional distinction between the reverse osmosis (RO) and forward osmosis

(FO) processes is that the water permeating the RO process is in most cases fresh water ready

for use. In the FO process, this is not the case. The membrane separation of the FO process in

effect results in a "trade" between the solutes of the feed solution and the draw solution.

Depending on the concentration of solutes in the feed (which dictates the necessary

concentration of solutes in the draw) and the intended use of the product of the FO process,

this step may be all that is required.

The forward osmosis process is also known as osmosis or in the case of a number of

companies who have coined their own terminology 'engineered osmosis' and 'manipulated

osmosis'.

2.2.4 PERVAPORATION

Pervaporation (or pervaporative separation) is a processing method for the separation

of mixtures of liquids by partial vaporization through a non-porous or porous membrane.

The term 'pervaporation' is derived from the two steps of the process:

(a) permeation through the membrane by the permeate, then (b) its evaporation into the vapor

phase. This process is used by a number of industries for several different processes,

including purification and analysis, due to its simplicity and in-line nature.

The membrane acts as a selective barrier between the two phases: the liquid-phase

feed and the vapor-phase permeate. It allows the desired component(s) of the liquid feed to

transfer through it by vaporization. Separation of components is based on a difference in

transport rate of individual components through the membrane.

Typically, the upstream side of the membrane is at ambient pressure and the

downstream side is under vacuum to allow the evaporation of the selective component after

permeation through the membrane. Driving force for the separation is the difference in

the partial pressures of the components on the two sides and not the volatility difference of

the components in the feed.

The driving force for transport of different components is provided by a chemical

potential difference between the liquid feed/retentate and vapor permeate at each side of the
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membrane. The retentate is the remainder of the feed leaving the membrane feed chamber,

which is not permeated through the membrane. The chemical potential can be expressed in

terms offugacity, given byRaoult's law for a liquid and by Dalton's law for (an ideal) gas.

During operation, due to removal of the vapor-phase permeate, the actual fugacity of the

vapor is lower than anticipated on basis of the collected (condensed) permeate.

Separation of components (e.g. water and ethanol) is based on a difference in

transport rate of individual components through the membrane. This transport mechanism can

be described using the solution-diffusion model, based on the rate/ degree of dissolution of a

component into the membrane and its velocity of transport (expressed in terms of diffusivity)

through the membrane, which will be different for each component and membrane type

leading to separation.

2.3 OPERATIONS IN ELECTRIC POTENTIAL GRADIENT

2.3.1 ELECTRODIALYSIS

FIG 2.3.1Electrodialysis

Electrodialysis (ED) is used to transport salt ions from one solution through ion-

exchange membranes to another solution under the influence of an applied electric

potential difference. This is done in a configuration called an electrodialysis cell. The cell
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consists of a feed (diluate) compartment and a concentrate (brine) compartment formed by

an anion exchange membrane and a cation exchange membrane placed between

two electrodes. In almost all practical electrodialysis processes, multiple electrodialysis cells

are arranged into a configuration called an electrodialysis stack, with alternating anion and

cation exchange membranes forming the multiple electrodialysis cells. Electrodialysis

processes are different compared to distillation techniques and other membrane based

processes (such as reverse osmosis) in that dissolved species are moved away from the feed

stream rather than the reverse. Because the quantity of dissolved species in the feed stream is

far less than that of the fluid, electrodialysis offers the practical advantage of much higher

feed recovery in many applications.

2.3.2 ELECTROFILTRATION

Electrofiltration is a method that combines membrane filtration and electrophoresis in

a dead-end process.

Electrofiltration is regarded as an appropriate technique for concentration and

fractionation ofbiopolymers. The film formation on the filter membrane which hinders

filtration can be minimized or completely avoided by the application ofelectric field,

improving filtrations performance and increasing selectivity in case of fractionation. This

approach reduces significantly the expenses fordownstream processing in bioprocesses.
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FIG 2.2.4 ELECTROFILTRATION

Electrofiltration is highly innovative state of the art technique for separation,

respectively concentration of colloidal substances - for instance biopolymers. The principle of

electrofiltration is based on overlaying electric field on a standarddead-end filtration. Thus

the created polarity facilitates electrophoretic force which is opposite to the resistance force

of the filtrate flow and directs the charged biopolymers. This provides extreme decrease in

the film formation on the micro- or ultra-filtration membranes and the reduction of filtration

time from several hours by standard filtration to a few minutes by electrofiltration. In

comparison to cross-flow filtration electrofiltration exhibits not only increased permeate flowbut also guarantees reduced shear force stress which qualifies it as particularly mild technique

for separation ofbiopolymersthat are usually unstable.

The promising application in purification of biotechnological products is based on the

fact that biopolymers are difficult for filtration but on the other hand they are usually charged

as a result of the presence of amino and carboxyl groups. The objective of electrofiltration is

to prevent the formation of filter cake and to improve the filtration kinetic of products

difficult to filtrate.
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2.3.3 MEMBRANE DISTILLATION

FIG 2.3.3 REM-image of a PTFE membrane

Membrane distillation is a thermally driven separational process in which separation

is enabled due to phase change. A hydrophobic membrane displays a barrier for the liquid

phase, letting the vapour phase (e.g. water vapour) pass through the membrane's pores. The

driving force of the process is given by a partial vapour pressure difference commonly

triggered by a temperature difference.

Principle of membrane distillation

FIG 2.3.3 Capilary depression of water on a hydophobic membrane
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FIG 2.3.3 MEMBRANE DISTILATION

FIG2.3.3

Schematic image of the membrane distillation process

Temperature and pressure profile through the membrane considering temperature

polarisation

State of the art processes that separate mass flows by a membrane, mostly use a

staticpressure difference as the driving force between the two bounding surfaces (e.g. RO), a

difference in concentration (dialysis) or an electric field (ED). Selectivity of a membrane is

produced by, either its pore size in relation to the size of the substance to be

retained,itsdiffusion coefficient orelectrical polarity. However, the selectivity of membranes

used for membrane distillation (MD) is based on the retention of liquid water with-at the

same time-permeability for free watermolecules and thus, for water vapour. These

membranes are made ofhydrophobic synthetic material (e.g. PTFE, PVDF or PP) and offer

pores with a standard diameter between 0.1 to 0.5 m. As water has

strong dipole characteristics, whilst the membrane fabric is non-polar, the membrane material

is not wetted by the liquid. Even though the pores are considerably larger than the molecules,
http://en.wikipedia.org/wiki/Pressurehttp://en.wikipedia.org/wiki/Dialysishttp://en.wikipedia.org/wiki/Electric_fieldhttp://en.wikipedia.org/wiki/Diffusionhttp://en.wikipedia.org/wiki/Electrical_polarityhttp://en.wikipedia.org/wiki/Permeationhttp://en.wikipedia.org/wiki/Moleculeshttp://en.wikipedia.org/wiki/Hydrophobichttp://en.wikipedia.org/wiki/Dipolehttp://en.wikipedia.org/wiki/File:Dampfdruckprofil_MD.pnghttp://en.wikipedia.org/wiki/File:Schema_Membrandestillations-Prozess.pnghttp://en.wikipedia.org/wiki/File:Dampfdruckprofil_MD.pnghttp://en.wikipedia.org/wiki/File:Schema_Membrandestillations-Prozess.pnghttp://en.wikipedia.org/wiki/Dipolehttp://en.wikipedia.org/wiki/Hydrophobichttp://en.wikipedia.org/wiki/Moleculeshttp://en.wikipedia.org/wiki/Permeationhttp://en.wikipedia.org/wiki/Electrical_polarityhttp://en.wikipedia.org/wiki/Diffusionhttp://en.wikipedia.org/wiki/Electric_fieldhttp://en.wikipedia.org/wiki/Dialysishttp://en.wikipedia.org/wiki/Pressure


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the liquid phase does not enter the pores because of the high watersurface tension. A

convex meniscus develops into the pore. This effect is named capillary action. Amongst other

factors, the depth of impression can depend on the external pressure load on the liquid. A

dimension for the infiltration of the pores by the liquid is the contact angle =180 '. As

long as > 90 and accordingly ' > 0 no wetting of the pores will take place. If the

external pressure rises above the so-called wetting pressure, then = 90resulting in a bypass

of the pore. The driving force which delivers the vapour through the membrane, in order to

collect it on the permeate side as product water, is the partial water vapour pressure

difference between the two bounding surfaces. This partial pressure difference is the result of

a temperature difference between the two bounding surfaces. As can be seen in the image, the

membrane is charged with a hot feed flow on one side and a cooled permeate flow on the

other side. The temperature difference through the membrane, usually between 5 and 20 K,

conveys a partial pressure difference which ensures that the vapour developing at the

membrane surface follows the pressure drop, permeating through the pores and condensing

on the cooler side.[1]
http://en.wikipedia.org/wiki/Surface_tensionhttp://en.wikipedia.org/wiki/Meniscushttp://en.wikipedia.org/wiki/Infiltration_(medical)http://en.wikipedia.org/wiki/Membrane_distillation#cite_note-joako-1http://en.wikipedia.org/wiki/Membrane_distillation#cite_note-joako-1http://en.wikipedia.org/wiki/Membrane_distillation#cite_note-joako-1http://en.wikipedia.org/wiki/Membrane_distillation#cite_note-joako-1http://en.wikipedia.org/wiki/Infiltration_(medical)http://en.wikipedia.org/wiki/Meniscushttp://en.wikipedia.org/wiki/Surface_tension


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CHAPTER - 3

MEMBRANE SHAPES AND FLOW GEOMETRIES

There are two types of geometries.

Dead end geometry Cross flow geometry.

FIG 2.3.4 Dead end geometry

3.1 DEAD-END GEOMETRY:-

In cross-flow filtration the feed flow istangential to the surface of membrane,

retentate is removed from the same side further downstream, whereas the permeate flow is

tracked on the other side. In dead-end filtration the direction of the fluid flow is normal to the

membrane surface. Both flow geometries offer some advantages and disadvantages. The

dead-end membranes are relatively easy to fabricate which reduces the cost of the separation

process. The dead-end membrane separation process is easy to implement and the process is

usually cheaper than cross-flow membrane filtration. The dead-end filtration process is
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usually a batch-type process, where the filtering solution is loaded (or slowly fed) into

membrane device, which then allows passage of some particles subject to the driving force.

The main disadvantage of a dead end filtration is the extensive

membrane fouling and concentration polarization. The fouling is usually induced faster at the

higher driving forces. Membrane fouling and particle retention in a feed solution also builds

up a concentration gradients and particle backflow (concentration polarization.

Flat plates are usually constructed as circular thin flat membrane surfaces to be used

in dead-end geometry modules. Spiral wounds are constructed from similar flat membranes

but in a form of a pocket containing two membrane sheets separated by a highly porous

support plate.[2]

Several such pockets are then wound around a tube to create a tangential flowgeometry and to reduce membrane fouling. Hollow fibermodules consist of an assembly of

self-supporting fibers with a dense skin separation layers, and more open matrix helping to

withstand pressure gradients and maintain structural integrity.[2]The hollow fiber modules

can contain up to 10,000 fibers ranging from 200 to 2500 m in diameter; The main

advantage of hollow fiber modules is very large surface area within an enclosed volume,

increasing the efficiency of the separation process.

FIG 3.1 Spiral wound membrane module.
http://en.wikipedia.org/wiki/Batch_productionhttp://en.wikipedia.org/wiki/Foulinghttp://en.wikipedia.org/w/index.php?title=Concentration_polarization&action=edit&redlink=1http://en.wikipedia.org/wiki/Gradientshttp://en.wikipedia.org/wiki/Membrane_technology#cite_note-O-2http://en.wikipedia.org/wiki/Membrane_technology#cite_note-O-2http://en.wikipedia.org/wiki/Membrane_technology#cite_note-O-2http://en.wikipedia.org/wiki/Fiberhttp://en.wikipedia.org/wiki/Membrane_technology#cite_note-O-2http://en.wikipedia.org/wiki/Membrane_technology#cite_note-O-2http://en.wikipedia.org/wiki/Membrane_technology#cite_note-O-2http://en.wikipedia.org/wiki/File:Spiral_flow_membrane_module-en.svghttp://en.wikipedia.org/wiki/Membrane_technology#cite_note-O-2http://en.wikipedia.org/wiki/Fiberhttp://en.wikipedia.org/wiki/Membrane_technology#cite_note-O-2http://en.wikipedia.org/wiki/Gradientshttp://en.wikipedia.org/w/index.php?title=Concentration_polarization&action=edit&redlink=1http://en.wikipedia.org/wiki/Foulinghttp://en.wikipedia.org/wiki/Batch_production


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3.2 CROSS FLOW GEOMETRY:-

The tangential flow devices are more cost and labor intensive, but they are less

susceptible to fouling due to the sweeping effects and high shear rates of the passing flow.

The most commonly used synthetic membrane devices (modules) are flat plates, spiral

wounds, and hollow fibers.

FIG 3.2 Cross-flow geometry

CHAPTER - 4
http://en.wikipedia.org/wiki/File:Cross-flow.svg


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MASS TRANSFER:

Two basic models can be distinguished for mass transfer through the membrane:

thesolution-diffusion modeland thehydrodynamic model.

In real membranes, these two transport mechanisms certainly occur side by side, especially

during the ultra-filtration.

4.1 SOLUTION-DIFFUSION MODEL

In the solution-diffusion model, transport occurs only by diffusion. The component

that needs to be transported must first be dissolved in the membrane. This principle is more

important fordensemembranes without natural pores such as those used for reverse osmosis

and in fuel cells. During the filtrationprocess a boundary layerforms on the membrane.

This concentration gradient is created by molecules which cannot pass through the

membrane. The effect is referred as concentration polarization and, occurring during the

filtration, leads to a reduced trans-membrane flow (flux). Concentration polarization is, in

principle, reversible by cleaning the membrane which results in the initial flux being almost

totally restored. Using a tangential flow to the membrane (cross-flow filtration) can also

minimize concentration polarization.

4.2 HYDRODYNAMIC MODEL

Transport through pores in the simplest case is done convectively. This requires

the size of the pores to be smaller than the diameter of the to separate components.

Membranes, which function according to this principle are used mainly in micro- and

ultrafiltration. They are used to separate macromolecules from solutions, colloids froma dispersion or remove bacteria. During this process the not passing particles or molecules are

forming on the membrane a more or less a pulpy mass (filter cake). This hampered by the

blockage of the membrane the filtration. By the so-called cross-flow method (cross-flow

filtration) this can be reduced. Here, the liquid to be filtered flows along the front of the

membrane and is separated by the pressure difference between the front and back of the

fractions into retentate (the flowing concentrate) and permeate (filtrate). This creates a shear

stress that cracks the filter cake and lower the formation offouling.
http://en.wikipedia.org/wiki/Diffusionhttp://en.wiktionary.org/wiki/porehttp://en.wikipedia.org/wiki/Filtrationhttp://en.wikipedia.org/wiki/Boundary_layerhttp://en.wikipedia.org/wiki/Concentration_gradienthttp://en.wikipedia.org/wiki/Moleculehttp://en.wikipedia.org/w/index.php?title=Concentration_polarization&action=edit&redlink=1http://en.wikipedia.org/wiki/Fluxhttp://en.wikipedia.org/wiki/Convectionhttp://en.wikipedia.org/wiki/Macromoleculehttp://en.wikipedia.org/wiki/Solution_(chemistry)http://en.wikipedia.org/wiki/Colloidhttp://en.wikipedia.org/wiki/Dispersion_(chemistry)http://en.wikipedia.org/wiki/Filter_cakehttp://en.wikipedia.org/wiki/Cross-flow_filtrationhttp://en.wikipedia.org/wiki/Cross-flow_filtrationhttp://en.wikipedia.org/w/index.php?title=Retentate&action=edit&redlink=1http://en.wikipedia.org/wiki/Permeatehttp://en.wikipedia.org/wiki/Membrane_foulinghttp://en.wikipedia.org/wiki/Membrane_foulinghttp://en.wikipedia.org/wiki/Permeatehttp://en.wikipedia.org/w/index.php?title=Retentate&action=edit&redlink=1http://en.wikipedia.org/wiki/Cross-flow_filtrationhttp://en.wikipedia.org/wiki/Cross-flow_filtrationhttp://en.wikipedia.org/wiki/Filter_cakehttp://en.wikipedia.org/wiki/Dispersion_(chemistry)http://en.wikipedia.org/wiki/Colloidhttp://en.wikipedia.org/wiki/Solution_(chemistry)http://en.wikipedia.org/wiki/Macromoleculehttp://en.wikipedia.org/wiki/Convectionhttp://en.wikipedia.org/wiki/Fluxhttp://en.wikipedia.org/w/index.php?title=Concentration_polarization&action=edit&redlink=1http://en.wikipedia.org/wiki/Moleculehttp://en.wikipedia.org/wiki/Concentration_gradienthttp://en.wikipedia.org/wiki/Boundary_layerhttp://en.wikipedia.org/wiki/Filtrationhttp://en.wiktionary.org/wiki/porehttp://en.wikipedia.org/wiki/Diffusion


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CHAPTER-5

MEMBRANE PERFORMANCE AND GOVERNING EQUATIONS


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The selection of synthetic membranes for a targeted separation process is usually

based on few requirements. Membranes have to provide enough mass transfer area to process

large amounts of feed stream. The selected membrane has to have high selectivity properties

for certain particles; it has to resist fouling and to have high mechanical stability. It also

needs to be reproducible and to have low manufacturing costs. The main modeling equation

for the dead-end filtration at constant pressure drop is represented by Darcys law:[2]

where Vp and Q are the volume of the permeate and its volumetric flow rate respectively

(proportional to same characteristics of the feed flow), is dynamic viscosity of permeating

fluid, A is membrane area, Rm and R are the respective resistances of membrane and growing

deposit of the foulants. Rm can be interpreted as a membrane resistance to the solvent (water)

permeation. This resistance is a membrane intrinsicproperty and expected to be fairly

constant and independent of the driving force, p. R is related to the type of membrane

foulant, its concentration in the filtering solution, and the nature of foulant-membrane

interactions. Darcys law allows to calculate the membrane area for a targeted separation at

given conditions. The solute sieving coefficient is defined by the equation:

[2]

where Cfand Cp are the solute concentrations in feed and permeate respectively. Hydraulic

permeability is defined as the inverse of resistance and is represented by the equation:[2]

where J is the permeate flux which is the volumetric flow rate per unit of membrane area. The

solute sieving coefficient and hydraulic permeability allow the quick assessment of the

synthetic membrane performance.

CHAPTER-6

MEMBRANE SEPARATION PROCESSES
http://en.wikipedia.org/wiki/Binding_selectivityhttp://en.wikipedia.org/wiki/Foulinghttp://en.wikipedia.org/w/index.php?title=Mechanical_stability&action=edit&redlink=1http://en.wikipedia.org/wiki/Pressure_drophttp://en.wikipedia.org/wiki/Membrane_technology#cite_note-O-2http://en.wikipedia.org/wiki/Membrane_technology#cite_note-O-2http://en.wikipedia.org/wiki/Membrane_technology#cite_note-O-2http://en.wikipedia.org/wiki/Flow_ratehttp://en.wikipedia.org/wiki/Dynamic_viscosityhttp://en.wikipedia.org/wiki/Intrinsichttp://en.wikipedia.org/wiki/Solutionhttp://en.wikipedia.org/wiki/Sievinghttp://en.wikipedia.org/wiki/Membrane_technology#cite_note-O-2http://en.wikipedia.org/wiki/Membrane_technology#cite_note-O-2http://en.wikipedia.org/wiki/Membrane_technology#cite_note-O-2http://en.wikipedia.org/wiki/Membrane_technology#cite_note-O-2http://en.wikipedia.org/wiki/Membrane_technology#cite_note-O-2http://en.wikipedia.org/wiki/Membrane_technology#cite_note-O-2http://en.wikipedia.org/wiki/Fluxhttp://en.wikipedia.org/wiki/Fluxhttp://en.wikipedia.org/wiki/Membrane_technology#cite_note-O-2http://en.wikipedia.org/wiki/Membrane_technology#cite_note-O-2http://en.wikipedia.org/wiki/Sievinghttp://en.wikipedia.org/wiki/Solutionhttp://en.wikipedia.org/wiki/Intrinsichttp://en.wikipedia.org/wiki/Dynamic_viscosityhttp://en.wikipedia.org/wiki/Flow_ratehttp://en.wikipedia.org/wiki/Membrane_technology#cite_note-O-2http://en.wikipedia.org/wiki/Pressure_drophttp://en.wikipedia.org/w/index.php?title=Mechanical_stability&action=edit&redlink=1http://en.wikipedia.org/wiki/Foulinghttp://en.wikipedia.org/wiki/Binding_selectivity


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Membrane separation processes have very important role in separation industry.

Nevertheless, they were not considered technically important until mid-1970. Membrane

separation processes differ based on separation mechanisms and size of the separated

particles.The widely used membrane processes

include microfiltration, ultrafiltration, nanofiltration, reverseosmosis, electrolysis,dialysis,

electrodialysis, gas separation, vapor permeation, pervaporation, membrane distillation,

and membrane contactors.[3]All processes except for pervaporation involve no phase

change. All processes except (electro)dialysis are pressure driven. Microfltration and

ultrafiltration is widely used in food and beverage processing (beer microfiltration, apple

juice ultrafiltration), biotechnological applications and pharmaceutical

industry (antibioticproduction, protein purification), water purification and wastewater

treatment, microelectronics industry, and others. Nanofiltration and reverse osmosis

membranes are mainly used for water purification purposes. Dense membranes are

utilized for gas separations (removal of CO2 from natural gas, separating N2from air,

organic vapor removal from air or nitrogen stream) and sometimes in membrane

distillation. The later process helps in separating of azeotropic compositions reducing the

costs of distillation processes.

TABLE OF DIFFERENT LIQUID TECHNIQUE
http://en.wikipedia.org/wiki/Microfiltrationhttp://en.wikipedia.org/wiki/Ultrafiltrationhttp://en.wikipedia.org/wiki/Nanofiltrationhttp://en.wikipedia.org/wiki/Reverse_osmosishttp://en.wikipedia.org/wiki/Electrolysishttp://en.wikipedia.org/wiki/Dialysishttp://en.wikipedia.org/wiki/Electrodialysishttp://en.wikipedia.org/wiki/Gas_separationhttp://en.wikipedia.org/wiki/Pervaporationhttp://en.wikipedia.org/wiki/Distillationhttp://en.wikipedia.org/wiki/Membrane_technology#cite_note-Pi-3http://en.wikipedia.org/wiki/Membrane_technology#cite_note-Pi-3http://en.wikipedia.org/wiki/Membrane_technology#cite_note-Pi-3http://en.wikipedia.org/wiki/Pharmaceutical_industryhttp://en.wikipedia.org/wiki/Pharmaceutical_industryhttp://en.wikipedia.org/wiki/Antibiotichttp://en.wikipedia.org/wiki/Wastewater_treatmenthttp://en.wikipedia.org/wiki/Wastewater_treatmenthttp://en.wikipedia.org/wiki/Wastewater_treatmenthttp://en.wikipedia.org/wiki/Wastewater_treatmenthttp://en.wikipedia.org/wiki/Antibiotichttp://en.wikipedia.org/wiki/Pharmaceutical_industryhttp://en.wikipedia.org/wiki/Pharmaceutical_industryhttp://en.wikipedia.org/wiki/Membrane_technology#cite_note-Pi-3http://en.wikipedia.org/wiki/Distillationhttp://en.wikipedia.org/wiki/Pervaporationhttp://en.wikipedia.org/wiki/Gas_separationhttp://en.wikipedia.org/wiki/Electrodialysishttp://en.wikipedia.org/wiki/Dialysishttp://en.wikipedia.org/wiki/Electrolysishttp://en.wikipedia.org/wiki/Reverse_osmosishttp://en.wikipedia.org/wiki/Nanofiltrationhttp://en.wikipedia.org/wiki/Ultrafiltrationhttp://en.wikipedia.org/wiki/Microfiltration


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Ranges of membrane based separations.
http://en.wikipedia.org/wiki/File:Cut-offs_of_different_liquid_filtration_techniques.png


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CHAPTER -7

PORE SIZE AND SELECTIVITY

The pore sizes of technical membranes are specified differently depending on the

manufacturer. One common form is the nominal pore size. It describes the maximum of the

pore size distribution[4]and gives only a vague statement about the retention capacity of a

membrane. The exclusion limit or "cut-off" of the membrane is usually specified in the form

ofNMWC(nominal molecular weight cut-off, orMWCO, Molecular Weight Cut Off,

Unit:Dalton). It is defined as the minimum molecular weight of a globular molecule which isretained by the membrane to 90%. The cut-off, depending on the method, can by converted in

the so-calledD90, which is then expressed in a metric unit. In practice the MWCO of the

membrane should be at least 20% lower than the molecular weight of the molecule that is to

be separated.

Filter membranes are divided into four classes according to their pore size:

Pore

size

Molecular

massProcess Filtration Removal of

> 10 "Classic" filter

> 0.1 m > 5000 kDa microfiltration < 2 barlarger bacteria, yeast,

particles

100-

2 nm5-5000 kDa ultrafiltration 1-10 bar

bacteria, macromolecules,

proteins, larger viruses

The form and shape of the membrane pores are highly dependent on the

manufacturing process and are often difficult to specify. Therefore, for characterization, test
http://en.wikipedia.org/wiki/Membrane_technology#cite_note-4http://en.wikipedia.org/wiki/Membrane_technology#cite_note-4http://en.wikipedia.org/wiki/Molecular_Weight_Cut_Offhttp://en.wikipedia.org/wiki/Dalton_(unit)http://en.wikipedia.org/wiki/Molecular_weighthttp://en.wikipedia.org/wiki/Filtrationhttp://en.wikipedia.org/wiki/Microfiltrationhttp://en.wikipedia.org/wiki/Microfiltrationhttp://en.wikipedia.org/wiki/Ultrafiltrationhttp://en.wikipedia.org/wiki/Ultrafiltrationhttp://en.wikipedia.org/wiki/Ultrafiltrationhttp://en.wikipedia.org/wiki/Microfiltrationhttp://en.wikipedia.org/wiki/Filtrationhttp://en.wikipedia.org/wiki/Molecular_weighthttp://en.wikipedia.org/wiki/Dalton_(unit)http://en.wikipedia.org/wiki/Molecular_Weight_Cut_Offhttp://en.wikipedia.org/wiki/Membrane_technology#cite_note-4


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filtrations are carried out and the pore diameter refers to the diameter of the smallest particles

which could not pass through the membrane.

The rejection can be determined in various ways and always provide an indirectmeasurement of the pore size. One possibility is the filtration of macromolecules

(often Dextran, polyethylene glycol oralbumin), and the measurement of the cut-off by gel

permeation chromatography. These methods are mainly for the measurement of ultrafiltration

membranes application. Another methods of testing are the filtrations of particles with

defined size and their measurement with a Particle Sizeror by Laser induced breakdown

detection (LIBD). A very vivid characterization is to measure the rejection ofDextranblue or

other colored molecules. Also the retention ofbacteriophage and bacteria, the so-called

"Bacteria Challenge Test", can provide statements of the pore size.

SIZES OF MICROORGANISM

Nominal pore size micro-organism ATCC root number

0.1 m Acholeplasma laidlawii 23206

0.3 m Bacillus subtilisspores 82

0.5 m Pseudomonas diminuta 19146

0.45 m Serratia marcescens 14756

0.65 m Lactobacillus brevis

To determine the pore diameter, physical methods such as porosimetry (mercury,

liquid-liquid porosimetry and Bubble Point Test) are also used, but a certain form of the pores

(such ascylindrically or concatenated spherical holes) is assumed. Such methods are used for

membranes whose pore geometry does not match the ideals, we get "nominal" pore diameter,
http://en.wikipedia.org/wiki/Dextranshttp://en.wikipedia.org/wiki/Polyethylene_glycolhttp://en.wikipedia.org/wiki/Albuminhttp://en.wikipedia.org/wiki/Gel_permeation_chromatographyhttp://en.wikipedia.org/wiki/Gel_permeation_chromatographyhttp://en.wikipedia.org/w/index.php?title=Particle_Sizer&action=edit&redlink=1http://en.wikipedia.org/w/index.php?title=Laser_induced_breakdown_detection&action=edit&redlink=1http://en.wikipedia.org/w/index.php?title=Laser_induced_breakdown_detection&action=edit&redlink=1http://en.wikipedia.org/w/index.php?title=Dextranblue&action=edit&redlink=1http://en.wikipedia.org/wiki/Bacteriophagehttp://en.wikipedia.org/wiki/Bacteriahttp://en.wikipedia.org/wiki/American_Type_Culture_Collectionhttp://en.wikipedia.org/wiki/Acholeplasmahttp://en.wikipedia.org/wiki/Bacillus_subtilishttp://en.wikipedia.org/wiki/Pseudomonashttp://en.wikipedia.org/wiki/Pseudomonashttp://en.wikipedia.org/wiki/Serratia_marcescenshttp://en.wikipedia.org/wiki/Serratia_marcescenshttp://en.wikipedia.org/wiki/Lactobacillus_brevishttp://en.wikipedia.org/wiki/Lactobacillus_brevishttp://en.wikipedia.org/wiki/Physicshttp://en.wikipedia.org/wiki/Porosimetryhttp://en.wikipedia.org/wiki/Cylinder_(geometry)http://en.wikipedia.org/wiki/Spherehttp://en.wikipedia.org/wiki/Spherehttp://en.wikipedia.org/wiki/Cylinder_(geometry)http://en.wikipedia.org/wiki/Porosimetryhttp://en.wikipedia.org/wiki/Physicshttp://en.wikipedia.org/wiki/Lactobacillus_brevishttp://en.wikipedia.org/wiki/Serratia_marcescenshttp://en.wikipedia.org/wiki/Pseudomonashttp://en.wikipedia.org/wiki/Bacillus_subtilishttp://en.wikipedia.org/wiki/Acholeplasmahttp://en.wikipedia.org/wiki/American_Type_Culture_Collectionhttp://en.wikipedia.org/wiki/Bacteriahttp://en.wikipedia.org/wiki/Bacteriophagehttp://en.wikipedia.org/w/index.php?title=Dextranblue&action=edit&redlink=1http://en.wikipedia.org/w/index.php?title=Laser_induced_breakdown_detection&action=edit&redlink=1http://en.wikipedia.org/w/index.php?title=Laser_induced_breakdown_detection&action=edit&redlink=1http://en.wikipedia.org/w/index.php?title=Particle_Sizer&action=edit&redlink=1http://en.wikipedia.org/wiki/Gel_permeation_chromatographyhttp://en.wikipedia.org/wiki/Gel_permeation_chromatographyhttp://en.wikipedia.org/wiki/Albuminhttp://en.wikipedia.org/wiki/Polyethylene_glycolhttp://en.wikipedia.org/wiki/Dextrans


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which characterize the membrane, but does not necessarily reflect their actual filtration

behavior and selectivity.

The selectivity is highly dependent on the separation process, the composition of themembrane and their electrochemical properties in addition to the pore size. By a high

selectivity, isotopes can be enriched (uranium enrichment) in nuclear engineering or

industrial gaseous like nitrogen be recovered (gas separation). Ideally, can be enriched with a

suitable membrane even racemics.

In the selection of the membrane selectivity has priority over a high permeability, as

can low flows easily offset by increasing the filter surface with a modular structure. For the

gas phase is to be noted that, in a filtration process different deposition mechanisms act, so

that particles having sizes below the pore size of the membrane can be retained as well.

FIG 7.1

The pore distribution of a fictitious ultrafiltration membrane with the nominal pore size
http://en.wikipedia.org/wiki/Gaseous_diffusionhttp://en.wikipedia.org/wiki/Gas_separationhttp://en.wikipedia.org/wiki/Racemic_mixturehttp://en.wikipedia.org/wiki/File:Porengr%C3%B6sse_und_Verteilung.pnghttp://en.wikipedia.org/wiki/Racemic_mixturehttp://en.wikipedia.org/wiki/Gas_separationhttp://en.wikipedia.org/wiki/Gaseous_diffusion


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CHAPTER-8

APPLICATIONS

FIG 8.1

Ultrafiltration for a swimming pool

FIG 8.2

Venous-arterial ECMO scheme

The particular advantage of membrane separation processes is that

2 They operate without heating and therefore use less energy than conventional thermalseparation processes (distillation,Sublimation orcrystallization).

3 This separation process is purely physical and because it is a gentle process, bothfractions (permeate and retentate) can be used.
http://in.ask.com/wiki/Distillation?qsrc=3044&lang=enhttp://in.ask.com/wiki/Sublimation_(phase_transition)?qsrc=3044&lang=enhttp://in.ask.com/wiki/Crystallization?qsrc=3044&lang=enhttp://in.ask.com/wiki/Permeation?qsrc=3044&lang=enhttp://in.ask.com/wiki/Retentate?qsrc=3044&lang=enhttp://en.wikipedia.org/wiki/File:Ecmo_schema-1-.jpghttp://en.wikipedia.org/wiki/File:Waldsassen_Ultrafiltration.JPGhttp://en.wikipedia.org/wiki/File:Ecmo_schema-1-.jpghttp://en.wikipedia.org/wiki/File:Waldsassen_Ultrafiltration.JPGhttp://in.ask.com/wiki/Retentate?qsrc=3044&lang=enhttp://in.ask.com/wiki/Permeation?qsrc=3044&lang=enhttp://in.ask.com/wiki/Crystallization?qsrc=3044&lang=enhttp://in.ask.com/wiki/Sublimation_(phase_transition)?qsrc=3044&lang=enhttp://in.ask.com/wiki/Distillation?qsrc=3044&lang=en


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4 Cold separation by means of membrane processes is commonly applied in the foodtechnology, biotechnology andpharmaceutical industries.

5 With the help of membrane separations realizeable that with thermal processes are notpossible. For example, because azeotropics orisomorphicscrystallization making a

separation by distillation orrecrystallization impossible.

6 Depending on the type of membrane, the selective separation of certain individualsubstances or substance mixtures is possible.

7 Important technical applications include drinking water by reverse osmosis (worldwideapproximately 7 million cubic meters annually), filtrations in the food industry, the

recovery of organic vapors such as gasoline vapor recovery and the electrolysis for

chlorine production.

8 Also in wastewater treatment, the membrane technology is becoming increasinglyimportant. With the help of UF and MF (Ultra-/Mikrofiltration) it is possible to remove

particles, colloids and macromolecules, so that wastewater can be disinfected in this way.

This is needed if wastewater is discharged into sensitive outfalls, or in swimming lakes.

About half of the market has applications in medicine. As an artificial kidney to remove

toxic substances by hemodialysis and as artificial lung for bubble-free supply of oxygen in

the blood. Also the importance of membrane technology is growing in the field of

environmental protection (NanoMemPro IPPC Database). Even in modern energy recovery

techniques membranes are increasingly used, for example in the fuel cell or the osmotic

power plant.
http://in.ask.com/wiki/Food_technology?qsrc=3044&lang=enhttp://in.ask.com/wiki/Food_technology?qsrc=3044&lang=enhttp://in.ask.com/wiki/Biotechnology?qsrc=3044&lang=enhttp://in.ask.com/wiki/Pharmaceutical?qsrc=3044&lang=enhttp://in.ask.com/wiki/Azeotrope?qsrc=3044&lang=enhttp://in.ask.com/wiki/Isomorphism_(crystallography)?qsrc=3044&lang=enhttp://in.ask.com/wiki/Recrystallization_(chemistry)?qsrc=3044&lang=enhttp://in.ask.com/wiki/Reverse_osmosis?qsrc=3044&lang=enhttp://in.ask.com/wiki/Food_industry?qsrc=3044&lang=enhttp://in.ask.com/wiki/Chloralkali_process?qsrc=3044&lang=enhttp://in.ask.com/wiki/Dialysis?qsrc=3044&lang=enhttp://in.ask.com/wiki/Extracorporeal_membrane_oxygenation?qsrc=3044&lang=enhttp://in.ask.com/wiki/Blood?qsrc=3044&lang=enhttp://in.ask.com/wiki/NanoMemPro_IPPC_Database?qsrc=3044&lang=enhttp://in.ask.com/wiki/Fuel_cell?qsrc=3044&lang=enhttp://in.ask.com/wiki/Osmotic_power_plant?qsrc=3044&lang=enhttp://in.ask.com/wiki/Osmotic_power_plant?qsrc=3044&lang=enhttp://in.ask.com/wiki/Osmotic_power_plant?qsrc=3044&lang=enhttp://in.ask.com/wiki/Osmotic_power_plant?qsrc=3044&lang=enhttp://in.ask.com/wiki/Fuel_cell?qsrc=3044&lang=enhttp://in.ask.com/wiki/NanoMemPro_IPPC_Database?qsrc=3044&lang=enhttp://in.ask.com/wiki/Blood?qsrc=3044&lang=enhttp://in.ask.com/wiki/Extracorporeal_membrane_oxygenation?qsrc=3044&lang=enhttp://in.ask.com/wiki/Dialysis?qsrc=3044&lang=enhttp://in.ask.com/wiki/Chloralkali_process?qsrc=3044&lang=enhttp://in.ask.com/wiki/Food_industry?qsrc=3044&lang=enhttp://in.ask.com/wiki/Reverse_osmosis?qsrc=3044&lang=enhttp://in.ask.com/wiki/Recrystallization_(chemistry)?qsrc=3044&lang=enhttp://in.ask.com/wiki/Isomorphism_(crystallography)?qsrc=3044&lang=enhttp://in.ask.com/wiki/Azeotrope?qsrc=3044&lang=enhttp://in.ask.com/wiki/Pharmaceutical?qsrc=3044&lang=enhttp://in.ask.com/wiki/Biotechnology?qsrc=3044&lang=enhttp://in.ask.com/wiki/Food_technology?qsrc=3044&lang=enhttp://in.ask.com/wiki/Food_technology?qsrc=3044&lang=en


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CHAPTER-9

ADVANTAGES AND LIMITATIONS OF MEMBRANE PROCESSES

In many applications, e.g. water desalination and purification the membrane

processes compete directly with the more conventional water treatment techniques.

However, compared to these conventional procedures.

Membrane processes are often energy efficient. More simple to operate and yield a higher quality product. The same is true for the separation, concentration, and purification of drugs and food

products or in medical and pharmaceutical applications.

These membrane processes have in addition to high energy efficiency, simpleoperation, easy up and down scaling the advantage of operating at ambient

temperature avoiding any change or degradation of products.

In water desalination reverse osmosis or electrodialysis can be used. Depending on

local conditions, including water quality, energy cost and the required capacity of the

desalination plant, either electrodialysis or reverse osmosis can be the more efficient

process. For very large capacity units and in case a power plant can be coupled with the

desalination unit, distillationis generally considered to be more economical. For surface

water purification and waste-water treatment membrane processes, micro- and ultrafiltration

are competing with flocculation, sand bed filtration, carbon adsorption, ion-exchange and

biological treatment. In these applications the membrane processes are usually more costly

but generally provide a better product water quality. Very often a combination of

conventional water treatment procedureswith membrane processes results in reliable and

cost-effective treatment combined with high product water quality.

ADISADVANTAGE OF MEMBRANE PROCESSES

It is that in many applications, especially in the chemical and petrochemical industry,

their long-term reliability is not yet proven. Furthermore, membrane processes sometimes


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require excessive pretreatment due to their sensitivity to concentration polarization and

membrane fouling due to chemical interaction with water constituents. Furthermore,

membranes are mechanically not very robust and can be destroyed by a malfunction in the

operating procedure. However, significant progress has been made in recent years,

especially in reverse osmosis seawater desalination, in developing membrane.


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CHAPTER-10

COST CONSIDERATIONS AND ENVIRONMENTAL IMPACT

Membrane processes are considered as very energy efficient compared to

many other separation processes. However, the energy requirement of a process is only one

cost determining factor.

CURRENT MARKET AND FORECAST :-

The global demand on membrane modules was estimated at approximately 15.6

billion USD in 2012. Driven by new developments and innovations in material science and

process technologies, global increasing demands, new applications, and others, the market is

expected to grow around 8% annually in the next years. It is forecasted to increase to 21.22billion USD in 2016 and reach 25 billion in 2018.


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CONCLUSION

It begins with the definition of terms and provides a description of membrane structures and

membrane processes that are used today in mass separation, in (bio)chemical reactors, in

energy conversion and storage, and in the controlled release of drugs.The advantages as well

as the limitations of membrane processes are indicated. Major applications of membranes are

described and their technical and commercial relevance pointed out.A short overview over

the historical development of membrane science and technology is given and possible future

developments and research needs are indicated.


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REFERENCES

1 Aptel Ph., Neel J., Pervaporation, in Synthetic Membranes: Science, Engineering

and Applications, edts., Bungay, P.M., Lonsdale, H.K., de Pinho, M.N., pp. 403-436.

2. D. ReidelPubl. Company, Boston 1968.

Baker R. W., Membrane Technology and Applications, J. Wiley& Sons, Chichester, U.K.

2004.3.Bechhold H., Durchlssigkeit von Ultrafilter, Z. Phys. Chem. 64 (1908) 328.

4. Bhattacharyya D., Butterfield D. A., New Insights into Membrane Science and

5.Technology: Polymeric and Biofunctional Membranes, Elsevier, Amsterdam 2003.

Bray T. D., Reverse Osmosis Purification Apparatus, US-Patent 3 417 870 (1968).

6. Cadotte J. E., Petersen R.I., Thin Film Reverse Osmosis Membranes: Origin,

Development, and Recent Advances, in Synthetic Membranes, ACS Symposium

Series Vol. I, Desalination, edts. Turbak, A.F. pp. 305 -325, Washington, D.C.:American Chemical Society 1981.

7.Donnan F. G., Theorie der Membrangleichgewichte und Membranpotentiale bei

Vorhandensein von nicht dialysierenden Elektrolyten, Z. fr Elektrochemie und

angewandte physikalische Chemie 17 (1911) 572.

8. Drioli E., Giorno L., Biocatalytic Membrane Reactors: Application in Biotechnology and

the Pharmaceutical Industry, Taylor & Francis Publisher, London, UK 1999

seminar report on membrance technology

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Transcript of seminar report on membrance technology