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Dead terminal membrane filtration is a batch procedure that can divide liquid and suspended solids efficaciously. Membrane filtration is widely used in H2O purifications and chemical industries in order to extinguish out the foreign affairs in liquid. Membrane and coat oppositions every bit good as filtration behavior on macromolecular system are investigated through dead terminal filtration. In this experiment, 0.22 micrometer GVWP Millipore PVDF membrane was used. Water was used to find the membrane opposition while the barm cells were used to find the bar opposition and fouling theoretical account. Pressure of 50 kPa was applied from gas cylinder and magnetic scaremonger was set to 300 revolutions per minute. The information was collected and analysed by LabView package. Based on the information from H2O testings, the steady province membrane opposition was 8.55*1010 A±3.38*108 Garand rifle. The steady province flux of H2O testings was 6.5*10-4 m/s. Flux was diminishing over the concentrations of yeast solution. Two types of fouling theoretical account were found in this experiment: pore bottleneck and coat filtration. Deposit of barm cells before get downing experiment besides caused the initial bar oppositions became negative value or negative filter medium. On top of that, filtration force per unit area was increasing proportionately to tallness of bar. Since changeless force per unit area was used, flux was diminishing as tallness of bar was increasing as a map of clip. In order to cut down the operating cost, membrane can be cleaned with backward flower or chemical cleansing every bit long as the membrane construction has non been destroyed by the foreign affairs.

Table of Contentss

Introduction

Presents, H2O deficit becomes more serious and concerned by the universe leaders. Water pollution is a chief cause to H2O deficit. Contaminated H2O may dwell of industrial wastes and toxic substances every bit good as non suited for imbibing H2O. In order to get the better of this job, membrane filtration may be an effectual and economical method. Membrane is a physical barrier and has many micro or nanometers pore diameter. Tiny pore diameter can extinguish the mineral salts and micro-organisms from contaminated H2O. Because of this, colourless and clean H2O is produced. The illustration for this instance is NEWater in Singapore. The production of NEWater consists of four barriers and three phases. The beginning for doing NEWater is from sewerage and sublimating through dual-membrane.

In this experiment, dead terminal membrane filtration was chosen to transport out the experiment. A 0.22 micrometer GVWP Millipore PVDF membrane was used. Feed was forced by a force per unit area to flux through the membrane. If the yeast solution was used, the barm would roll up on the membrane and organize a bar. The dead terminal membrane filtration in this experiment was carried out as batch procedure due to all the suspended atoms would lodge on membrane and turn bar. Size of barm cells was much bigger than the diameter of membrane pore. Therefore, the barm cells could non go through through the membrane while the H2O would be collected as filtrate. Some of yeast cells might choke off the pores on membrane and this could diminish filtration capacity. In fact, the dead terminal membrane filtration is a really good ways to concentrate the compounds.

The purpose of this experiment was to find the membrane and coat oppositions and compare the consequences to porous media theory. This experiment besides could look into the filtration behavior and macromolecular systems. This could be verified by utilizing H2O and different concentrations of yeast solution ( 3, 4 and 6 g/L ) testings. Water was used to find the membrane opposition while yeast solution was used to find the bar opposition as map of clip. The types of membrane and barm were kept changeless.

Theory/ Literature

3.1 Membrane Resistance ( Rm )

The membrane opposition is calculated by utilizing equation below:

( 1 )

3.2 Cake Resistance ( Rc )

Since the same membrane was used on all testings, the membrane opposition was changeless. The bar opposition could be calculated as follow:

( 2 )

3.3 Hagen Poseuille Equation

This equation can cipher the theoretical flux on the membrane by presuming the canals are cylindrical and unvarying. This equation besides assumes the membrane surface has figure of cylindrical pores which on analogue. The equation is shown as below:

( 3 )

3.4 Specific Cake Resistance ( I± )

Specific bar opposition depends on force per unit area and is a parametric quantity in this experiment. Specific bar opposition measures the filterability of the suspension solids and determines the velocity of filtration. The equation is shown as below:

( 4 )

3.5 Fouling theoretical account ( n )

When the changeless force per unit area is used, the fouling theoretical account on membrane can be determined by plotting ln ( d2I„/dV2 ) against ln ( dI„ /dV ) . The equation is shown as below:

( 5 )

where n=0 is cake filtration, n=1 is intermediate obstruction, n=1.5 is pore bottleneck and n=2 is complete pore obstruction.

Premises:

Viscosity of H2O was 8.9*10-4 N.s/m2 at 25oC.

Viscosity of barm was same with viscousness of H2O at 25oC.

Tortuosity ( I„ ) was 1.

Yeast solution was good assorted.

The membrane was cleaned and no contaminated.

TranMembrane Pressure ( TMP ) was same as force per unit area applied from N gas cylinder.

Filtrate collected was H2O merely and denseness was 1000 kg/m3.

Cake mass formed per unit volume of filtrate was 1.

Area of filter was 0.0014 M2.

Incompressible bar formation.

Mistake was chiefly contributed from force per unit area gage. The mistake of force per unit area gage 0.1.

Procedure

At the beginning of experiment, the cell and reservoir were inspected and cleaned. LabView package was turned on and the cringle was set to 5 seconds. Microfiltration membrane ( 0.22 micrometer GVWP Millipore PVDF membrane ) was cut into right sized circle stencilled from the cell. The membrane was soaked with H2O for a few seconds. Then, the membrane was assembled in cell and tightened with twist. The reservoir was filled with H2O and connected to nitrogen gas cylinder through a tubing. The cell was placed on base and the beaker was placed on electronic balance and the balance was set to zero. The experiment set up was shown as Figure 1. After the permeate valves was closed, the force per unit area was increased to 50 kPa based on the largest force per unit area gage graduated table. The LabView package was at the same time get downing to roll up and analyze informations. Each testing was carried out for five proceedingss. When completing the testing, the valve on gas cylinder was turned off and the reservoir force per unit area was reduced be opening the reservoir adjustment. The H2O proving on membrane was repeated for four times.

For yeast proving on membrane, the different concentrations were used. 3 g/L of barm cells was fade outing in Milli-Q H2O. A new membrane was fitted on the cell ; the cell provender and reservoir were filled with yeast mixture. The scaremongers in cell and reservoir were set to 300 revolutions per minute. 50 kPa of nitrogen force per unit area was used and the consequence was recorded as map of clip. The processs for other concentrations of yeast solution were same with 3g/L of barm cells. The membranes for H2O and barm testing were kept on separate evaporating dishes. The types of proving carried out and concentrations of barm used were tabulated in Table 1.

Figure: Experiment Set Up

Testing

Types/ Concentration of barm

Pressure used ( kPa )

1

Water

50

2

Water

3

Water

4

Water

5

Yeast ( 3g )

6

Yeast ( 4 g )

7

Yeast ( 6 g )

Table: Types of proving

Consequence

Harmonizing to Merck Millipore, the pore radius for 0.22 micrometer GVWP Millipore PVDF membrane was 2.2*10-7 m. The thickness of this membrane was 1.25*10-4 m and porousness was 70 % . The membrane was hydrophilic.

Since the TranMembrane Pressure was the same for all testings, the theoretical flux from Equation ( 3 ) was changeless in H2O and yeast solution experiment. The theoretical flux was 0.0019 m/s. The steady province membrane opposition at 50 kPa was calculated as 8.55*1010 A±3.38*108 Garand rifle. The steady province flux on H2O testings was 6.5*10-4 m/s. For H2O testing, the membrane oppositions for each test were plotted as map of clip and shown in Figure 2 under Appendix.

The mean bar oppositions on 3g, 4g and 6g of barm were calculated as 5.18*1011A±2.48*109 Garand rifle, 2.73*1011A±7.23*109 Garand rifle and 3.3*1011A±6.66*108 Garand rifle. The bar oppositions on different concentrations of yeast solution were plotted as map of clip and shown as Figure 3 under Appendix. Flux against clip and coat opposition against flux were shown as Figure 4 and 5. These figures showed that flux was depending on the bar opposition as map of clip.

The specific bar oppositions for 3g, 4g and 6g of barm were 6.92*106 m/kg, 5.55*106 m/kg and 8.76*106 m/kg. These consequences were calculated from gradients in Figure 6.

In this experiment, fouling theoretical account applied. 3g and 4g of barm had pore bottleneck fouling theoretical accounts while 6g of barm had cake filtration fouling theoretical account. These were done with utilizing Figure 7 and 8.

From the experiment, the public presentation of filtration was diminishing over clip. Flow rate of filtrate gradual decreased and could be observed from the reading on electronic balance. The surface of membrane was deposited with a batch of barm cells.

Discussions

6.1 Flux

Flux depended on opposition of membrane and bar. Resistance was reciprocally relative to flow based on Equation ( 1 ) and ( 2 ) . The opposition was chiefly come from choke offing on membrane pores and tallness of bar. When the opposition increased, the liquid permeated through the membrane was diminishing and the flux decreased excessively. For yeast solution, the flux was diminishing when the concentration of yeast solution became more concentrated. As more concentrated yeast solution was used, yeast cells would lodge much rapidly on the membrane. The deposited barm cells would organize bar and increase its tallness. Some of yeast cells might barricade the pores on membrane. Therefore, the opposition of bar occurred and decreased the flux rate.

6.2 Membrane Resistance

Water testing was used to find the membrane opposition due to it did non incorporate any supermolecules. From the consequences on H2O testing, the mean membrane opposition was diminishing over each proving. This might due to the cell was non cleaned plenty and had been contaminated from old users. The Milli-Q Water was extremely purity and did non incorporate any suspended affair. Furthermore, the accretion of H2O in complexness membrane construction besides might do minor consequence on the membrane opposition. The membrane used was hydrophilic which would absorb H2O. The captive H2O might impact the pore diameter on the membrane which might do the membrane to spread out and swollen. After a few H2O testings, the membrane opposition became steady due to the taint had been washed off.

6.3 Cake Resistance

Based on the consequence of each barm solution testing, the initial bar opposition was found negative value or negative filter opposition. Due to the barm cells were rather heavier, they might get down deposit before filtration starting. The bar opposition could non be accurately measured by utilizing above equations one time the deposit occurred. Because of this mistake, the bar opposition was inaccurately measured when utilizing saturated yeast solution.

6.4 Specific Cake Resistance

Harmonizing to Jenny Ni Mhurchu BE ( 2008 ) , specific bar opposition could be determined from the gradient of t/V against V under changeless force per unit area. Specific bar opposition could find the efficiency of filtration. Due to specific bar opposition depended on excessively many variables, it could be simplified and replaced with entire applied force per unit area. This force per unit area was chiefly influence the specific bar opposition if the bar opposition was dominant in whole experiment.

6.5 Fouling Model

Harmonizing to Cristiana Luminita ( 2012 ) , Equation ( 5 ) was used to find the fouling theoretical account. The gradients from Figure 8 were used to cipher the N values which able to happen out the fouling theoretical account. From fouling theoretical account, the pore bottleneck was defined as fouling occurred in membrane internal pores. It was assumed that radius of pore was diminishing by adhesion stuff and straight through pores. The bar filtration was defined as deposit of solid on membrane and created filtration opposition. Based on the consequence, 6g of yeast solution was cake filtration. This might due to the high concentration of barm cells deposited on membrane and inefficient of magnetic scaremonger. This job caused the flux to diminish due to H2O necessitate more force per unit area to pervade through the bar compared to concentrate bottleneck. For 3g and 4g of barm, they had pore bottlenecks. Some of yeast cells might lodge in pore and unable to travel. This phenomenon was known as clogging. This had decreased the porousness of membrane and affected the filtrate flow.

6.6 Membrane Performance

Due to the size of barm cells was much larger than diameter of membrane pore, most the barm cells were left on membrane and choke offing the membrane pores. Filtrate needed more energy to pervade through the membrane when the membrane surface was clogged. Under changeless applied force per unit area, the flow rate of filtrate would diminish due to they did non hold excess energy to pervade through the clotted membrane. In order to recycle the membrane and increase the efficiency, clogged membrane could be cleaned with backward flower or chemical cleansing. Besides that, membrane could be affected by three fouling factors: provender features, membrane belongingss and hydrodynamic environment encountered by the membrane. Harmonizing Herbert H.P. Fang ( 2005 ) , pervasion flux of PVDF membrane was to the full recovered after sonication. Sonication could efficaciously take the bar on PVDF membrane. Based on Natural Organics Removal utilizing Membranes, the pure H2O flux for 0.22 micrometer GVWP Millipore PVDF membrane was 2.21*10-3 A±8.06*10-5 m/s. The H2O flux from this experiment was much smaller than the value from Natural Organics Removal utilizing Membranes. This might due to the different country of membrane was used. The Natural Organics Removal utilizing Membranes used 1.52*10-3 M2 while this experiment used 1.4*10-3 M2.

6.7 Explanations on Premise

Viscosity of yeast solution was assumed to viscousness of H2O. This was due to most of the barm cells deposited on membrane and the filtrate would be H2O merely. The reading from mass balance was mensurating the mass of filtrate ( H2O ) . Therefore, it would easier to presume that viscousness of yeast solution was same with H2O. On top of that, the tortuousness was assumed as 1 and used in Equation ( 3 ) . Tortuosity was defined as ratio of membrane porousness and effectual pore length. Without microscopy aid ( Scaning Electron Microscope ) , microstructure of membrane could non be determined. On top of that, the new membrane was assumed as cleaned and non contaminated. Handss could non touch or keep the membrane due to custodies might incorporate some micro foreign affairs and by chance rub off the micro construction on membrane surface. Tranmembrane force per unit area ( TMP ) was assumed to coerce applied from gas cylinder. It was defined as the mean force per unit area between provender and membrane sides. TMP involved provender, retentate and filtrate force per unit areas. In order to simplify the computation, it could be assumed TMP was same with force per unit area from gas cylinder. In order to cipher specific bar opposition, cake mass formed per unit volume of filtrate was assumed as 1. This was due to this experiment deficit of informations on mass fraction of solids in suspension and in bar. The bar was assumed as incompressible. Under changeless applied force per unit area, the force per unit area opposition increased proportionately to coat tallness and therefore flux decreased over clip.

6.8 Mistake Analysis

Mistake computations and statistical analysis were applied from a book whose writers were Hibbert, D.B & A ; Gooding J.J ( 2006 ) . All the mistakes were in 95 % assurance interval. Specifications of membrane and belongingss of H2O did non incorporate any mistake due to they were measured under standard conditions.

Decision

In a nutshell, dead terminal membrane filtration is a good method to extinguish H2O out if coveted merchandise is collected from membrane surface. Although it is really expensive and requires high applied force per unit area to keep filtration public presentation, it is able to bring forth high quality and concentrated merchandise. From H2O and yeast solution testings, membrane and bar opposition could be estimated. This experiment besides could look into filtration behavior and macromolecular system based on informations aggregation. The filtrate volume as a map of clip was used to look into the fouling theoretical account on membrane. In this experiment, the bar was incompressible due to flow diminishing over clip.

Mention

ANDREA SCHAFER. 2001. Natural Organics Removal Using Membranes: Principles, Performance, and Cost. CRC Press.

BE, J. N. M. 2008. DEAD-END AND CROSSFLOW MICROFILTRATION OF YEAST AND BENTONITE SUSPENSIONS: EXPERIMENTAL AND MODELLING STUDIES INCORPORATING THE USE OF ARTIFICIAL NEURAL NETWORKS. [ Accessed 24 August 2012 ] .

CRISTIANA LUMINITA GIJIU, R. D. , RALUCA DANIELA ISOPESCU. 2012. Membrane Fouling in Dead-end Microfiltration of Yeast Suspensions.

HIBBERT, D. B. , & A ; GOODING, J. J. 2006. Data analysis for chemical science: an introductory usher for pupils and research lab scientists. Oxford, Oxford University Press.

J. Zhang, H.C. Chua, J. Zhou, A.G. Fane, Factors impacting the membrane public presentation in submersed membrane bioreactors, Journal of Membrane Science, Volume 284, Issues 1-2, 1 November 2006, Pages 54-66.

LI, N. N. , FANE, A. G. , HO, W. S. W. & A ; MATSUURA, T. 2011. Advanced Membrane Technology and Applications. John Wiley & A ; Sons.

MILLIPORE. 2012. What is TMP, how do you cipher it, and what is its importance? [ Online ] . Germany: Merck. Available: hypertext transfer protocol: //www.millipore.com/faqs/tech1/faq123 [ Accessed 25 August 2012.

MILLIPORE. 2012. DuraporeA® Membrane Filters [ Online ] . Germany: Merck. Available: hypertext transfer protocol: //www.millipore.com/catalogue/module/c7631 # 0 [ Accessed 25 August 2012.

MUNIR, A. 2006. Dead End Membrane Filtration. Laboratory Feasibility Studies in Environmental Engineering.

SOUHAIMI, M. K. & A ; MATSUURA, T. 2011. Membrane Distillation: Principles and Applications, Elsevier Science.

SUNG-SAM YIM, S.-S. Y. S.-S. Y. 2001. Effectss of Pore Size, Suspension Concentration, and Pre-Sedimentation on the Measurement of Filter Medium Resistance in Cake Filtration. Korean J. Chem. Eng, 18, 741-749.

WU, J. , HE, C. , JIANG, X. & A ; ZHANG, M. 2011. Modeling of the submersed membrane bioreactor fouling by the combined pore bottleneck, pore obstruction and coat formation mechanisms. Desalination, 279, 127-134.

YIM, S.-S. 1999. A theoretical and experimental survey on bar filtration with deposit. Korean Journal of Chemical Engineering, 16, 308-315.

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