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ABSTRACT 2

INTRODUCTION 3

AIMS 4

THEORY 5

APPARATUS 9

PROCEDURE 9

RESULTS 11

DISCUSSION 12

CONCLUSION 14

RECOMMENDATIONS 16

REFERENCES 17

APPENDICES 18

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ABSTRACT

This experiment is conducted to study the characteristics on 4 different types of membranes

which are AFC 99 (polyamide film), AFC 40 (polyamide film), CA 202 (cellulose acetate)

and FP 100 (PVDF) by using membrane test unit (TR14). Membrane separation is a

technology which fractionates materials through pores and minutes of gaps in the molecular

arrangement of a continuous structure. Membrane separation can be classified by pore size

and by the separation driving force for example Microfiltration (MF), Ultrafiltration (UF),

Nanofiltration (NF), Ion-Exchange (IE) and Reverse Osmosis (RO). We need to operate the

plunger pump, control the valves, and collect the samples as well as weighing the samples.

After weighing the sample, graph of permeates weight versus time is plotted. Based on the

graph, membrane 1 and membrane 3 used in membrane process that operates at higher

pressure while membrane 2 and membrane 4 used in membrane that operates at lower

pressure. Membrane 1 used in reverse osmosis process and membrane 3 is in nanofiltration

which both of the tubes in these membranes are fitted with polyamide. The tubes fitted in

membrane 2 is polyethersulphone which for ultrafiltration while for membrane 4 is PVDF

which for microfiltration. This experiment is conducted successfully.

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INTRODUCTION

This Membrane Test Unit (Model: TR 14) has been designed to demonstrate the technique of

membrane separations which has become highly popular as they provide effective separation

without the use of heating energy as in distillation processes. This type of membrane is

widely used biotechnology and process industry. Heat sensitive materials, such as fruit juices,

can be separated or concentrated by virtue of their molecular weights. The unit consists of a

test module supplied with four different membranes, namely the reverse osmosis (RO),

nanofiltration (NF), ultrafiltration (UF) and microfiltration (MF) membranes, thus allowing

students or researchers to carry out membrane separation processes that are most widely used

in the food, dairy, pharmaceutical and chemical industries. This self-contained unit on a

mobile epoxy coated steel framework, requires only connection to a suitable electricity

supply and a normal cold water supply to be fully operational. It consists of a feed tank, a

product tank, a feed pump, a pressure regulator, a water bath, and a membrane test module.

All parts in contact with the process fluid are stainless steel, PTFE, silicone rubber or nitrile

rubber. The unit comes with a high pressure feed pump for delivering the feed to the

membrane unit at the desired flow rate and pressure. The retentate line can be either returned

to the feed tank or straight to the drain. Appropriate sensors for flow, pressure and

temperature are installed at strategic locations for process monitoring and data acquisitions.

In this experiment we need to study the characteristic on 4 different types of membranes. The

TR 14 unit is supplied with 4 membranes which are:

Membrane 1: AFC 99 (polyamide film)

Membrane 2: AFC 40 (polyamide film)

Membrane 3: CA 202 (cellulose acetate)

Membrane 4: FP 100 (PVDF)

The AFC 99 is rated with 99% NaCl rejection at maximum pressure and temperature which is

64 bar and 80 whereas the AFC 40 has 60% CaCl2 rejection at 60 bar and 60 Both of

these membranes use in operation of reverse osmosis. Meanwhile, the CA 202 is rated with

apparent retentation of 2000 MWCO and the FP 100 is 100000 MWCO. Both of these two

membranes use in ultrafiltration process which CA 202 operates at 25 bars and 30 while

the FP 100 is at 10 bar and 80

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The advantages of cross-flow membrane separations are the concentrate remains in a mobile

from suitable for further processing, possible to fractionate solutes of different sizes, can

prevent solid buildup on membrane surface so that higher overall liquid removal rate is

achieved and solute content of the concentrate ma be varied over a wide range.

AIMS

To study the characteristics of membrane by performing a characteristic study on 4

different types of membranes.

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THEORY

Membrane separation is a technology which fractionates materials through pores and minutes

of gaps in the molecular arrangement of a continuous structure. Membrane separation can be

classified by pore size and by the separation driving force for example Microfiltration (MF),

Ultrafiltration (UF), Nanofiltration (NF), Ion-Exchange (IE) and Reverse Osmosis (RO).

This figure is examples of different substance that correspondence to the pore size of the

membrane separation method.

Reverse osmosis separates aqueous ionic solutions of different concentration. There is an

osmotic pressure when the solvent moves from an area of high water potential to low water

potential so that equal ionic concentrations on each side of membranes. When a hydraulic

pressure is applied to the concentrated solution which is greater and in reverse to the osmotic

pressure, water molecules will pass to dilute solution side through the membrane. This

process can separate water from ions and low-molecular weight organic constituents.

Ultrafiltration enables precise separation, concentration and purification of dissolved and

suspended constituents based on the relative molecular size of substance. Microfiltration

membranes enable efficient and precise separation as well as concentration of suspended and

colloidal particles.

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REVERSE OSMOSIS ULTRAFILTRATION

MICROFILTRATION

The membrane separation techniques utilized in the dairy industry serve different purposes:

RO -used for dehydration of whey, UF permeate and condensate.

NF -used when partial desalination of whey, UF permeates or retentate is required.

UF -typically used for concentration of milk proteins in milk and whey and for

protein standardization of milk intended for cheese, yoghurt and some other products.

MF -basically used for reduction of bacteria in skim milk, whey and brine, but also

for defatting whey intended for whey protein concentrate (WPC) and for protein

fractionation.

Many theoretical models and the identification of new factors controlling flux, J or mass

transfer through membranes have been proposed. The build-up of deposited materials on the

surface has introduced the terms of hydrodynamic resistance which are the best outlined basic

operating patterns.

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The flux J will be given by:

J =

=

=

(1)

For most biological materials, is a variable depending on the applied pressure and time (the

compressible deposit), so that the expression requires a numerical solution.

A useful method for the effects of cross-flow removal of depositing materials is to write:

J =

(2)

Removal of solute by cross-flow is sometime assumed constant, and equal to the convective

particle transport at steady state which can be obtained experimentally or from an

appropriate model. In many situation however, steady state of filtration is seldom achieve. In

such case, it is possible to describe the time dependence of filtration by introducing an

efficiency factor, , representing the fraction of filtered material remaining deposit rather

than being swept along by the bulk flow. This gives:

RC =

, where o < < 1 (3)

Although deposition also occurs during ultrafiltration, an equally important factor controlling

flux is concentration polarization.

a) Applied pressure b) ln CA c) ln (cross-flow velocity)

Figure: typical dependence of membrane flux

a) applied pressure difference

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b) Solute concentration

c) cross-flow velocity

Solution containing molecular gel-forming solute will form a gel on the surface of the

membrane. The gel formation will contribute to formation of dynamic membranes. The

mechanism is as follows;

Due to convective flux through the membrane a concentration of the solution at the surface

CW increase and eventually reaches a gel formation concentration Cg (figure b) the flux, J

through the membrane depends on a concentration according to the relation;

J = k ln

(4)

Combining equation (1) and (4)

ln

=

(5)

As long as concentration Cw is less than Cg, Cw will increase with pressure, but the moment

Cw equals to Cg, an increase in bring about an increase of the layer resistance Rp, and the

flux will no longer vary with pressure.

Assuming no fouling effect, the membrane resistance Rm can be calculate from the flux

equation below:

J =

(6)

The slope obtain from the plot of flux J vs is equals to

the retention of any solute can

be express by the rejection coefficient, R

R =

(7)

Where Cf is final macrosolute concentration in the retentate

C0 is initial macrosolute concentration

V0 is initial volume

Vf is final retentate volume

This expression assumed complete mixing of retentate seldom accomplishes due to

concentration polarization. The apparent rejection coefficient depends on factors affecting

polarization including UF rate and mixing. For material entirely rejected, the rejection

coefficient is 1 (100% rejection); for freely permeable material it is zero.

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Rejection is a function of molecular size and shape. Nominal cut-off levels, defined with

model solute, are convenient indicators.

Fractional rejection membrane with low MW cut-off spans a narrower range of molecular

size than by more open membranes. For maximum retention of a solute, select a membrane

with nominal cut-off well below the MW of the species.

Many biological macromolecules tend to aggregate so that effective size may be much larger

that the native molecule, causing increase rejection. Degree of hydration, counter ions and

steric effect can cause molecule with similar molecular weights to exhibit very different

retention behaviour.

APPARATUS

The membrane test unit (TR14)

Sodium chloride solution

PROCEDURE

General start-up procedures

1. Ensure all valves are initially closed.

2. Prepare a sodium chloride solution by adding 100 gram of sodium chloride into 20

litre of water.

3. Fill up the tank with the salt solution prepared in step 2. The feed shall always be

maintained at room temperature.

4. Turn on the power for the control panel. Check that all sensors and indicators are

functioning properly.

5. Switch on the thermostat and make sure that the thermo oil is above the coil inside

thermostat. Check that the thermostat connections are properly fitted.

6. The unit is now ready for experiments.

General shut-down procedures

1. Switch off the plunger pump (P2).

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2. Close valve V2.

3. Drain all liquid in the feed tank and product tank by opening valves V3 and V4.

4. Flush all the piping with clean water. Close V3 and V4, fill the clean water to feed

tank until 90% full.

5. Run the system with the clean water until the feed tank is nearly empty.

Procedures

1. The general start-up is performed.

2. Valves V2, V5, V7, V11 and V15 are opened.

3. The plunger pump (P1) is switched on and valve V5 is slowly closed to set the

maximum working pressure at 20 bars. The pressure value at pressure gauge is

observed and the pressure regulator is adjusted to 20 bars.

4. Valve V5 is opened. Membrane maximum inlet pressure is set to 18 bars for

membrane 1 by adjusting the retentate control valve (V15).

5. The system is allowed to run for 5 minutes. The sample is collected from permeate

sampling port and the sample is weighed using digital weighing balance. The weight

of permeates every 1 minutes for 10 minutes.

6. Step 1 to 5 for membrane 2, 3 and 4 are repeated. The respective valves are open and

close and membrane maximum inlet pressure is adjusted for every membrane.

Membrane Open valves (step

2)

Sampling valves Retentate

control valve

Membrane

maximum inlet

pressure(bar)

1 V2, V5, V7, V11,

and V15

Open V19 and

closed V11

V15 18

2 V2, V5, V8, V12

and V16

Open V20 and

closed V12

V16 12

3 V2, V5, V9, V13

and V17

Open V21 and

closed V13

V17 10

4 V2, V5, V10, V14

and V18

Open V22 and

closed V14

V18 8.5

7. The graph of permeate versus time is plotted.

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RESULTS

Time (min) Weight of permeates (g)

Membrane 1 Membrane 2 Membrane 3 Membrane 4

1 49.21 236.63 265.43 536.17

2 83.43 394.11 297.60 768.43

3 117.27 465.75 327.29 1001.07

4 151.59 536.07 357.81 1233.24

5 185.40 605.49 386.91 1465.07

6 221.04 676.01 418.09 1696.85

7 255.55 746.12 448.69 1924.43

8 290.83 817.00 479.79 2153.87

9 327.34 889.99 512.76 2393.55

10 367.77 959.10 539.92 2608.04

0

500

1000

1500

2000

2500

3000

1 2 3 4 5 6 7 8 9 10

we

igh

t o

f p

erm

eat

es(

g)

Membrane 1

Membrane 2

Membrane 3

Membrane 4

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DISCUSSION

Membrane separation is based on separation mechanisms and size of the separated particles.

The membrane processes that have been widely used are microfiltration, ultrafiltration,

nanofiltration, reverse osmosis, electrolysis, dialysis, electrodialysis, gas separation, vapour

permeation, pervaporation, membrane distillation and membrane contactors. Pervaporation is

the only process that involves phase change. All processes except electrodialysis are pressure

driven.

We conduct this experiment to study the characteristics on 4 different types of membranes

which are AFC 99 (polyamide film), AFC 40 (polyamide film), CA 202 (cellulose acetate)

and FP 100 (PVDF). From the graph that has been plotted, the slope of the membrane 4 is the

steepest compared to other membranes. This followed by membrane 2, membrane 3 and

membrane 1 respectively.

Based on the graph, membrane 1 is used for reverse osmosis process. This is because the

weight of permeates for membrane 1 have the lightest weight. Reverse osmosis operates at

very high pressure which is more than 20 bras. Reverse osmosis require the greatest operating

pressure as it has the smallest pore-size range and has the ability to remove solids as small as

salts. Only small amounts of very low molecular weight solute can pass through the

membranes. Membrane 1 is nonporous, asymmetric, and composite with homogeneous layer

which has dense pore size. Reverse osmosis is mainly applied in production of pure water.

Apart from that, nanofiltration is a type of membrane process that uses membrane 3. This is

also same as reverse osmosis that operates at high pressure but not as higher as pressure used

in reverse osmosis. The driving force used in nanofiltration is between 4 to 20 bars.

Nanofiltration is used for organic, color and contaminant removal as well as for softening.

Membrane 3 is also asymmetric, microporous which has pore size between 1 to 5 nm. Main

application of nanofiltration is to separate small organic compounds and multivalent ions.

Membrane 2 operates in ultrafiltration. Ultrfiltration designates a membrane separation

process, driven by a pressure gradient, in which the membrane fractionates components of a

liquid as a function of their solvated size and structure. The membrane configuration is

usually cross-flow. The feed water flows across the membrane surface by limiting the extent

of particle deposition and formation on the membrane surface. The membrane pore size is

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larger allowing some components to pass through the pores with the water. Ultrafiltration

operates at lower pressure compared to nanofiltration and reverse osmosis. A type of

membrane 3 is asymmetric microporous and the size of pore is 5-100nm. The driving force

for this membrane is between 1-9 bars. Nanofiltration is applied in separation of

macromolecular solutions.

The membrane process for membrane 4 is microfiltration. In microfiltration, the membrane

separation process is similar to ultrafiltration but it has larger membrane pore size. Thus, this

will allow particles in the range of 0.1 to 10 micrometers to pass through. The pressure used

is basically lower than that of ultrafiltration process which is 0.5 to 2 bars. The membrane

configuration is usually cross-flow. This membrane is symmetric and asymmetric porous.

Microfiltration used in the clarification and sterile filtration.

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Reverse osmosis have been used to remove nitrate from contaminated groundwater as well as

remove high concentrations of naturally occurring fluoride from deep groundwater. It is also

effective in removing specific synthetic organic contaminates from contaminated

groundwaters. Nanofiltration is used as an alternative treatment method to lime softening in

order to reduce the level of calcium and magnesium in hard waters. NF also can remove

naturally occurring color and dissolved organic species which is responsible for the formation

of THMs and DBPs regulated by US EPA.

Microfiltration and ultrafiltration can be used for particulate removal to comply with surface

water treatment rule. Both of MF and UF can precede by pretreatment systems to precipitate

or co-precipitate dissolved inorganic and dissolved organic compound. MF used in separation

of bacteria and cells from solution whereas UF used in separation of protein and virus,

concentration of oil-in-water emulsions.

CONCLUSION

From this experiment, it can be concluded that membrane 1 is operate in reverse osmosis

process while membrane 3 is in nanofiltration process. Both of this membrane process

operate at very high pressures and are typically deployed for the removal of dissolved

inorganic and organic constituents. Low pressure membrane processes which are

microfiltration and ultrafiltration are applied for the removal of particulate and microbial

contaminants and can be operated under negative or positive pressure. Membrane 2 and

membrane 4 has been used in ultrafitration and microfiltration respectively.

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RECOMMENDATIONS

In this experiment, there are some recommendations that can be done in order to get the best

results which are:

During taking the weight of permeates by using digital weighing balance, the reading

should be taking in more significant figures so that the reading of the actual weight of

permeates are more accurate and the value of true error could be minimized.

The average weight of permeates should be calculated by taking the weight of

permeates in three times in order to get more accurate value of weight of permeates.

When collecting the sample from permeates sampling port, make sure that we used a

big container to support the volume of the sample and to avoid the sample from spill

out in order to get more accurate weight of permeates.

The system should be run in more than 5 minutes so that the system and membrane

maximum inlet pressure is more stabilized in order to get the accurate value of weight

of permeates.

To collect the sample, the sampling valves should be open and close simultaneously

so that there is no interruption during collecting the sample from permeates sampling

port.

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REFERENCES

1. (1986). Dairy Processing Handbook. In Dairy Processing Handbook (p. 125). sweeden:

Tetra Pak Processing Systems AB.

2. Eliane Rodrigues dos Santos Goes,Elisabete Scolin. Mendes, Nehemias Curvelo

Pereivela, Sueli Teresa Davantel de Barros. (2005). influence at different condition on the

concentration by reverse osmosis. Retrieved 9 april, 2012, from Alim.Nutr.Araquara:

http://serv-bib.fcfar.unesp.br/seer/index.php/alimentos/article/viewFile/489/452

3. http://www.solution.com.my/pdf/TR14(A4).pdf. (n.d.). membrane test unit. Retrieved 9

april, 2012, from solteq: http://www.solution.com.my/pdf/TR14(A4).pdf

4. membrane separation technology primer. (n.d.). Retrieved 8 april, 2012, from asahi kasei

chemicals: http://www.asahi-kasei.co.jp/membrane/microza/en/kiso/index.html

5. nakagawa, o. (2012, february 12). membrane separation. Retrieved april 8, 2012, from

wikipedia:

http://en.wikipedia.org/wiki/Membrane_technology#Membrane_separation_processes

6. Ripperger S., Schulz G. (1986). Microporous membranes in biotechnical applications. In

Bioprocess Engineering (pp. 43-49).

7. Zeman, Leos J., Zydney, Andrew L. (Inc,1996). Microfiltration and Ultrafitration,

Principles and Applications. In M. Dekker, Microfiltration and Ultrafitration, Principles

and Applications. New York.

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APPENDICES

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