ABSTRACT
Membrane separation is a process of separation through semi permeable membrane involving 2
liquid phases or 2 gas phases or liquid and gas phase. In this experiment, the model used was
TR14 model membrane test unit. This experiment was carried out to study the characteristics of
4 type of membrane and the capability of each membrane in separation process. The permeate
mass reflux of membrane 4 was 14.649 g/ min and it is among the highest. However, other membranes
also show the ability in separation process and the objectives was successfully fullfil.
INTRODUCTION
Separations by the use of membranes are becoming increasingly important in industries
nowadays. In this relatively new separation process, the membrane acts as a semi-permeable
barrier and separation occurs by the membrane controlling the rate of movement of various
molecule between 2 liquid, gas phases or liquid and gas phase. 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.
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 pressure membranes, and also
consists of 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 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.
This experiment was carried out to study the characteristic on 4 different types of membranes. The
membrane unit consist of 4 membranes, which are:
I
I. Membrane 1: AFC 99 (Polyamide Film)
II
II. Membrane 2: AFC 40 (Polyamide Film)
III
III. Membrane 3: CA 202 (Cellulose Acetate)
IV
IV. Membrane 4: FP 100 (Polyvinylidene Fluoride)
THEORY
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, reverse osmosis, electrolysis, electro dialysis, gas
separation, vapor permeation, pervaporation, membrane distillation, and membrane contactors. 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 (antibiotic production, 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.
OBJECTIVES
The aims of this experiment are: -
1) To study the characteristic of 4 different types of membrane silicon in terms of separation
process.
2) To plot the graph of permeate weight versus time.
APPARATUS
1. The Membrane Test Unit (TR14)
2. Sodium chloride solution
PROCEDURE
General start-up procedures
1. All valves were ensured to be initially closed.
2. A sodium chloride solution was prepared by adding 100 grams of sodium chloride into 20 litre of
water.
3. The tank was filled up with the salt solution prepared in step 2. The feed should always be
maintained at room temperature.
4. The power for the control panel was turned on. All the sensors and indicators were checked to be
functioning properly.
5. The thermostat was switched on and the thermo oil was made sure to be above the coil
thermostat. The thermostat connections were checked to be properly fitted.
6. The unit was ready for experiments.
General shut-down procedures
1. The plunger pump (P2) was switched off.
2. Valve V2 was closed.
3. All liquid in the feed tank and product tank were drained by opening valves V3 and V4.
4. All the piping was flushed with clean water. V3 and V4 were closed, the clean water was filled to
feed tank until 90% full.
5. The system was run with the clean water until the feed tank is nearly empty.
Procedures
1. The general start-up was performed.
2. Valves V2, V5, V7, V11 and V15 were opened.
3. The plunger pump (P1) was switched on and valve V5 was slowly closed to set the maximum
working pressure at 20 bars. The pressure value at pressure gauge was observed and the pressure
regulator was adjusted to 18 bar.
4. Valve V5 was opened. Membrane maximum inlet pressure was set to 18 bars for membrane 1 by
adjusting the retentate control valve (V15).
5. The system was allowed to run for 5 minutes. The sample was collected from permeate sampling
port and the sample was weighed using digital weighing balance. The weight of permeates was
recorded every 1 minutes for 10 minutes.
6. Step 1 to 5 for membrane 2, 3 and 4 were repeated. The respective valves were open and close
and membrane maximum inlet pressure was adjusted for every membrane.
Membrane
1
2
3
4
RESULTS
Open valves (step 2)
Sampling valves
V2, V5, V7, V11, and
Open V19 and
V15
closed V11
V2, V5, V8, V12 and
Open V20 and
V16
closed V12
V2, V5, V9, V13 and
Open V21 and
V17
closed V13
V2, V5, V10, V14 and
Open V22 and
V18
closed V14
Retentate
Membrane maximum
control valve
inlet pressure(bar)
V15
18
V16
18
V17
18
V18
18
Time (min)
Permeate Mass
Flux (g/min)
Weight of permeates (g)
Membrane 1
Membrane 2
Membrane 3
Membrane 4
1
16.09
37.93
43.27
207.96
2
29.78
87.87
70.54
335.40
3
43.69
149.40
98.86
456.90
4
58.20
199.77
129.12
587.05
5
72.51
249.56
154.72
718.44
6
85.95
300.12
182.20
852.81
7
101.95
347.15
206.49
998.66
8
115.09
394.56
237.65
1141.29
9
130.76
440.80
271.74
1293.51
10
146.49
490.10
299.51
1438.20
Membrane 1
Membrane 2
Membrane 3
Membrane 4
14.649
49.010
29.951
143.820
1600
Weight of permeate (g)
1400
1200
1000
800
600
400
200
0
0
2
4
6
8
10
Time (min)
Weight of permeates (g) Membrane 1
Weight of permeates (g) Membrane 2
Weight of permeates (g) Membrane 3
Weight of permeates (g) Membrane 4
CALCULATIONS
Sample Calculation for Permeate Mass Flux
Final Permeate Weight (T=10min)
Permeate Mass Flux, Pm =
Pm =
146.49 𝑔
10 𝑚𝑖𝑛
Pm = 14.649 g/min
Time (T=10min)
12
DISCUSSION
The purpose of this study to investigate the characteristic of 4 different types of membranes.
These membranes are used as a separation purposes to separate 100 L of sodium chloride with
concentration of 5 g/L. As graph weight permeate vs time for respective membrane AFC 99
Polyamide Film (Membrane 1), AFC 40 Polyamide Film (Membrane 2), CA 202 Cellulose Acetate
(Membrane 3) and FP 100 Polyvinylidene Fluoride (PVDF) (Membrane 4); shown above, we can
conclude that all types of membranes has capability of separating sodium chloride from its
solution. However, the separation occurred at different rate which make membrane 4 at
highest followed by membrane 2, membrane 1 and membrane 3.
These membranes are used as reverse osmosis (membrane 1),
ultrafiltration (membrane 2) and nanofiltration (membrane 3) and microfiltration (membrane
4) and these membrane separations is highly dependent with pressure of the system operated.
Higher pressure increases the separation rates of the membrane but in this experiment, the
variable (pressure) was set as constant at 18 bar. Therefore, the separation rate only
dependent to type and nature of membrane used.
Membrane 4 showed the fastest rate of separation in compare to the others of
membrane with mass reflux of 143.820 gram per minute. This could be due to the high permeability
of sodium chloride through membrane 4 at 18 barcompared to other types of membranes.
Microfiltration process thus allowing molecules that has smaller than 0.1𝜇m to pass through shows the
membrane capability to separate a purer permeate. Other than that, the nature of Polyvinylidene
Fluoride is hydrophilic. Since, the permeate mainly consist water molecule, it easily passes through
the membrane making the mass of the permeate passing through the highest compared to other
membranes.
Membrane 1 shows the lowest separation rate which resulting in mass flux
only at 29.951 gram per minute time. The sodium chloride solution undergoes nanofiltration
process which has the ability to separate nanosized molecules from the solution which is lower than
0.002𝜇m up to 0.001𝜇m. Blockage at the pore of the membrane could be the reason why the
solution is unable to flow pass through the membrane since the porosity of the membrane is very
small. This shows the positive site of the membrane since it allows a purer permeate to be
produced as even small particle is trap at the pore of the membrane. However, cellulose acetate is
naturally hydrophobic as permeate is mainly water based, this could also be the reason why the
mass of permeate for the membrane is the smallest.
Membrane 2 shows slightly higher separation rate compared to membrane 3. Reverse osmosis
allows large molecules to pass through the membrane. Thus, the separation should be highest
among the others. Besides, the nature of the Polyamide Film is hydrophilic allowing water
molecules to easily passes through the membrane. However, this process requires high pressure to
overcome the osmotic pressure.
CONCLUSION
In a conclusion, this experiment was conducted to identify the characteristics of 4 types of
membrane separations by calculating the mass transfer reflux of each of membrane. The
membrane 4 is the highest followed by membrane 2, membrane 3 and membrane 1
respectively, therefore usage of these membranes, membrane 1 for nanofiltration, membrane
2 for ultrafiltration, membrane 3 for reverse osmosis and membrane 4 for microfiltration. The
membrane separation is highly dependent to pressure and the size of molecules used in this
separation and this experiment fulfill the objectives.
RECOMMENDATIONS
In order to obtain best result, there are a few recommendations that can be made for improvement
through the experiment. The students must make sure the weighing balance must be tare to zero
(0) every time changing the sample collection. Then, students should be alert and focus when taking
the reading on the weighing scale because the sample is continuously flow out and the weigh will
change through time. Other than that, students should be alert with the significance figures for the
weighing balance in order to get accurate data. In order to get precise results, students should take
the reading at least three time to get the average value for every trial. The students also need to
conduct the experiment with proper personal protective equipment (PPE), in order to minimize the
risk throughout the experiment. Lastly, students should study and understand the experiment
process from the lab manual to ensure the experiment run smoothly.