The Effect of Amorphous Rice Husk Silica to the Polysulfone Membrane Separation Process

Zawati Harun1,2,a, Mohd Riduan Jamalludin3,b, Muhamad Zaini Yunos4,c , Muhamad Fikri Shohur4,d and Ahmad Fauzi Ismail5,e

1,3,4 Department of Materials and Design Engineering, Faculty of Mechanical and Manufacturing Engineering, Universiti Tun Hussein Onn Malaysia, 86400 Parit Raja, Johor, Malaysia

2Advanced Materials and Manufacturing Centre (AMMC), Faculty of Mechanical and Manufacturing Engineering, Universiti Tun Hussein Onn Malaysia, 86400 Parit Raja, Batu Pahat, Johor Darul

Takzim, Malaysia.

5Advanced Membrane Technology Research Centre (AMTEC), Universiti Teknologi Malaysia, Skudai, 81310 Johor Bahru, Johor, Malaysia

a zawati@uthm.edu.my, b ridowan88@gmail.com , c mzaini@uthm.edu.my, d fiqer88@yahoo.com, e afauzi@utm.my

Keywords: Polysulfone (Psf), Polyethelene glycol (PEG), Rice husk silica

Abstract. This study investigates the effect of additive rice husk silica and Polyethylene glycol

(PEG) on the performance of polysulfone (PSf) membrane. The membrane was prepared by phase

inversion method using PSf, N-methyl-2-pyrrolidone (NMP) and rice husk silica was added as an

additive. The performance of the membrane was analyzed by using distilled water for permeation test

and humic acid for the rejection test. The result showed that the hydrophilic of PSf/PEG membrane

has significantly improved the permeation and rejection performance with addition of rice husk silica.

The results showed that with addition of 3% rice husk silica give the highest rejection flux at 196.63

L/m²hr with the rejection value 98%.

Introduction

Polysulfone (PSf) has a good mechanical, thermal and chemical stability and widely used in

fabrication of ultrafiltration membrane. However due it hydrophobic nature, PSf membranes is

susceptible to cause membrane fouling by the adsorption of proteins and other biomolecules in the

feed stream [1]. The fouling mechanism caused the flux decline through concentration polarization

where a membrane undergoes plugging or coating by some element in the stream being treated, in

such a way that its output or flux is reduced. Overall, when fouling occurs in separation process, it

may affect the performance of membrane such flux permeation, water permeability, and rejection [2].

In the previous studies, [3, 4] it showed that additive function and raw formulation can be a crucial

stage and play an important role in preventing the fouling problem. The incorporation of different

material or additive has contributes to a significant increase of membrane performance by reducing

fouling and increasing rejection. The addition of additives in membrane formation may add-value to

the membrane properties by forming more porous structure [3], larger pore sizes, increase

hydrophilicity or hydrophobicity, increase antibacterial properties [5, 7] and enhance the membrane

performances. Furthermore, the incorporation of most organic fillers such as polyvinylpyrrolidone

(PVP) to dope solutions tends to produce membrane with higher porosity and well-interconnected

[8]. These changeable properties of membrane such as pore size, pore distribution, physical

properties and mechanical characteristic will improve the performance of membrane i.e increase

antifouling and rejection mechanism.

In this work, the incorporation of potential organic fibers from natural sources (non-hazardous

element) i.e. rice husk was considered as contain high silica compound. Besides that it also has

biodegradable properties and offers green technology. As documented in many papers [9, 10, 11, 12],

additive of silica able to suppress the formation of amphiphilic component, macrovoids, enhance pore

formation and improve pore interconnectivity and hydrophilicity for the membrane.

Advanced Materials Research Vol. 701 (2013) pp 319-322Online available since 2013/May/27 at www.scientific.net© (2013) Trans Tech Publications, Switzerlanddoi:10.4028/www.scientific.net/AMR.701.319

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Membrane preparation

Polysulfone (PSf) membranes were prepared by using the phase inversion process via casting

method. Casting solution were prepared by dissolving Polysulfone (PSf) in N-methyl-2-pyrrolidone

(NMP) and stirred for 4 h. Then, PEG and rice husk silica additive at differences concentration (0%,

0.5%, 1.0%, 1.5%, and 2%) was subsequently added with continuous stirring and heating at 60°C

until the solution was completely dissolved and homogeneous. Meanwhile, rice husk silica additive

was prepared by burning the rice husk in the furnace at temperature range up to 600˚C and maintain

for 1 h. Subsequently, the casting solution is poured into bottle and ultrasonicated for 1 h to release

the bubbles. After the bubbles completely released, the solution were cast by using flat sheet

membrane casting system, and then immersed in a coagulation bath of distilled water. Finally, the flat

sheet membranes were dried for 24 h.

Membrane performance

The filtration experiment was conducted by using the water permeability testing unit [13]. This

experiment were measured the volume of water flow rate that can penetrate the membrane layer at the

time period specified. Tested membranes were prepared with diameter size 5.5cm. The permeation

test was carried out by using distilled water and for rejection was carried out by using humic acid.

Each membrane samples were fixed with pressure up to 2 bars.

Pure water flux calculation

The permeation fluxes of the membrane were measured by an Ultrafiltration cross flow filtration

experimental setup feed with distilled water at a transmembrane pressure of 2 bars. The membrane

performance of permeation water flux (PWF) for the PSf/PEG/silica membrane was calculated from

the equation (Eq. 1) below [12]:

��� =�

�×∆ (1)

Where PWF is the pure water flux ( )-1-2hLm , Q is the permeate volume (L), A is the membrane

area (m2), and ∆t is the time (h). The feed and permeate solution will be tested using UV rejection test.

The equation solute separation of the membrane is following below (Eq. 2):

. %100C

C-1

f

p×

(2)

Where Cp is solute concentration in permeate stream and. Cf is solute concentration in feed.

Results and Discussion

Water Permeability Test. Figure 1 shows the performance and capability of membrane to resist

their permeability by water permeation flux testing unit. As shown in graph below, the flux has

significantly improved by addition of rice husk silica with weight percentage in range of 1% until 5%.

From the plot 1, the flux of pure water is increased up to 303.03 L/m2h. This condition might be due to

addition of rice husk silica can enhance the hydrophilic properties of the membrane surface [9] and

tends to create larger pore formation at drain out layer system [14]. Thus, this will assist the

permeation mechanism especially in the fouling stage.

320 Key Engineering Materials III

Figure 1: The pure water flux permeation rice husk silica

Humic acid rejection. Figure 2 shows the rejection graph of humic acid concentration. From the

plot, the rejection is increased with addition the rice husk silica from 1% until 3% and slightly

reduced when approach to 4% rice husk silica. Based on the rejection plot, it is noticed that the

addition of 3% rice husk silica give the highest rejection with 98%. Thus, 3% membrane can be

considered as an optimum membrane. As reported by others researcher that the addition of silica can

reduce the pore size formation at the separation layer and this caused the better rejection mechanism

[14].

Figure 2: Rejection of rice husk silica

Flux rate rejection. Figure 3 shows that the flux rate rejection of humic acid for the results five

different concentrations of silica percentage. Based on the flux rate rejection plot, it was observed that

the flux increased with addition of the rice husk silica from 1% until 3%. However, the plot slightly

decreased with the addition of 4% rice husk silica and above. According to the plot, the highest flux

rates rejection is achieved at the addition of 3% rice husk silica with permeation value at 196.63

L/m²hr. It was noticed that, the addition of silica with hydrophilic propertise also can prevent fouling

mechanism in membrane filtration and this was agree with the previous study [3].

Figure 3: Flux rate rejection of rice husk silica

0

50

100

150

200

250

300

350

0% 1% 2% 3% 4% 5% 6%

Pu

re W

ate

r F

lux

(l.

m¯²

.h¯¹

)

Rice husk silica (%)

84

86

88

90

92

94

96

98

100

102

104

0% 2% 4% 6%

Re

ject

ion

(%

)

Rice husk percentage silica (%)

708090

100110120130140150160170180190200210

0% 2% 4% 6%

Flu

x r

ate

(J)(

L/m

². h

)

Rice husk silica (%)

Advanced Materials Research Vol. 701 321

Conclusion

In this work, flat sheet membrane was prepared from casting solutions containing 18% of PSf and

82% of N-methyl-2-pyrrolidone (NMP), by using diffusion induced phase separation process with

addition of different additives. The addition of different weight percentage (0%, 1%, 2 %, 3%, and

4%, 5%) of rice husk silica in casting solution improved the performance of membrane in term of

pure water permeation rate and rejection. The results of experiment demonstrated that with addition

of 1% to 3% increased the flow rate and rejection but slightly reduced as rice husk increased from 4%

to 5%. As a conclusion, the experimental results showed that the addition of amorphous rice husk

increased the permeation and rejection (with the highest was given at 3%) of PSf membrane by

increasing the hydrophilic properties.

References

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322 Key Engineering Materials III

Key Engineering Materials III 10.4028/www.scientific.net/AMR.701 The Effect of Amorphous Rice Husk Silica to the Polysulfone Membrane Separation Process 10.4028/www.scientific.net/AMR.701.319

DOI References

[1] Haijun Yua, b, Yiming Caoa, Guodong Kanga, Jianhui Liua, Meng Li a, Quan Yuana. Journal of

Membrane Science 342 (2009) 6–13.

http://dx.doi.org/10.1016/j.memsci.2009.05.041