Filter & Membrane Testing Technology - Benelux Scientific · penetration pressure allows to...

POROLUXTM – the standard in porometry

Filter & Membrane Testing Technology

POROLUXTM – the standard in porometry Porometer NV

Capillary Flow Porometry

Dr. Angels Odena

Ing. Danny Pattyn

www.porometer.com

March 2015


http://www.porometer.com/


Who are we?

• POROMETER is a Belgian-German membrane and filter characterisation equipment manufacturer.

• Many years of experience with porometers: • Sales and service: Coulter I and II, Xonics 3G, Porometer4 (Porvair), PMI. • Supported customers in Europe and Asia.

• True understanding of porometers and their applications: most porometers had

significant limitations which customers were often not aware of.

• In 2007 POROMETER and IB-FT - a German engineering company with a solid track record of engineering and manufacturing test equipment for the filter industry – joined forces to develop the POROLUX™ range.

• POROMETER commercialises instruments based on capillary flow porometry to measure

pore size distribution and gas permeability.


Introduction: where are porometers used?

• An accurate determination of pore size and pore size distribution is important for media used in filtration and separation processes.

• In classical filtration: used to design filters for automotive and industrial applications. • Porometers are also increasingly used to characterise the pore structure of polymeric

and ceramic membranes in applications such as:

- Water treatment (waste water recycling, desalination, micro pollutants and organics removal, etc.)

- Energy: fuel cells (proton exchange fuel cell), biorefinery - Blood treatment & purification of bio-molecules - Sustainable processes: organic solvent filtration, gas separation (biogas

purification, air separation, hydrogen recovery)

• Other important fields of use: • technical textiles, • nonwovens, • paper.


• (Mercury) Intrusion Porosimetry

- The pressurised mercury is forced into the

cavities of the porous material. The penetration pressure allows to calculate the pore dimensions.

- Pore size range: 900 µm – 3.6 nm

• Physisorption

- An inert gas (N2) kept a liquid N2 temperature is adsorbed on the surface of a porous solid material. This allows to calculate the surface area and dimensions of the pores of the material.

- Pore size range: 0.35 – 200 nm

Different techniques measure different pores


• Capillary Flow Porometry

- An inert gas is used to displace wetting liquid

from pores and gas flow rate is normally measured using flow meters

- Pore size range: 300 µm – 15 nm

• Liquid-liquid Porometry

- The wetting liquid is displaced from pores by

another wetting liquid having higher surface tension. The very low liquid flow rates are measured using a liquid flow meter or a microbalance.

- Pore size range: 0.5 µm – 2 nm

Different techniques measure different pores


Source: ThermoFisher


• An inert gas is used to displace a wetting liquid

from pores. The gas flow rate achieved at a certain

pressure is measured using flow meters.

• Measurable pore size range: 500 µm – 15 nm

• Only measures through pores



What diameter is measured with porometry?

p ( ) 1

D


Theory of capillary flow porometry (CFP) 1

The method depends upon the capillary rise created by surface tension. A wetted capillary or pore immersed in a liquid draws liquid up the capillary until equilibrium with the force of gravity is obtained. The equilibrium conditions can be expressed as: 2π r γ cos θ = r² π h ρ g .....(1) Where: r= radius of the capillary (or pore) D= diameter of the capillary (or pore) h= height of column of liquid γ= surface tension of liquid ρ= density of liquid θ= contact angle between the liquid and capillary wall g= acceleration due to gravity


Theory of capillary flow porometry (CFP) 2

2π r γ cos θ = r² π h ρ g .....(1) and since pressure (P) = hρg, equation 1 becomes 2π r γ cos θ = r² π P …..(2) 2 γ cos θ = r P …..(3) Equation 3 is sometimes referred to as the Young-Laplace equation. With D = 2 r, this equation can be rewritten as: P = 4 γ cos θ / D …..(4) If the liquid that is used fully wets the capillary and has a zero contact angle with virtually all materials, than cos θ = 1, so that (4) may be restated as P = 4 γ / D …..(5)


• A wetted capillary or pore immersed in a liquid draws liquid up the capillary until

equilibrium with the force of gravity is obtained.

• The mathematical relationship between pressure and diameter is given by the

Young-Laplace equation:

P = 4 * γ *cos (θ) / D

γ: surface tension of liquid, θ: contact angle between liquid and capillary wall

• Larger pores are emptied at lower pressure, smaller pores are emptied at higher

pressure

• This equation assumes “ideal pores”: cylindrical and straight. Corrections can be

made for non-cylindrical pores (shape factor).

Theory of capillary flow porometry (CFP) Summary


How is a sample measured? Liquid displacement technique to measure the pore size distribution of a sample:

• Sample is wetted with a liquid of low surface tension and low vapour pressure, consequently all pores are filled with the liquid.

• Wetted sample subjected to increasing pressure

• When P gas > surface tension of the liquid in the largest pores: pushes liquid out.

• Increasing P further: gas flows through smaller pores until all the pores are emptied.

• Wet run: monitor pressure of gas applied and the flow of gas when liquid is being expelled.

• Dry run: test of the sample without liquid in its pores.

• Pore size distribution: calculated by comparing the flows on the 'wet' with the 'dry' run.

• What happens inside the porometer?

v20porometer.mp4

../Dropbox/Porometer/Marketing/Presentations/inside the porometer.pptx











Measured parameters 1

First Bubble Point (FBP) Maximum pore diameter

Smallest pore size At pressure where the dry curve meets the wet curve

Mean flow pore diameter At the pressure that the wet and the half dry curve (obtained by dividing the flow of the dry curve by 2) meet. Half of the flow is through pores larger than this diameter.

Gas permeability The dry curve: sample does not contain wetting liquid



Half of the flow is through pores larger than this diameter

Flow rate through a wet sample A differential pressure displaces the wetting

liquid from the porous network

Flow rate through a sample that does not contain wetting liquid



Cumulative filter flow (CF(n)) = Wet Flow (n)/Dry Flow (n) ... Filter efficiency

Differential filter flow (DF(n)) = (CF(n) - CF(n-1))... Corrected differential filter flow Flow changes are divided by size changes and normalised to 100%. Pore size distribution.


Porometer technology

1. Pressure scan method

• A single valve is continuously being opened during the measurements.

• Continuous measurement of both pressure and gas flow.

• Fast and typically very reproducible results.

• Very suited for QC work.

• Drawback: samples with complex pore paths are difficult to measure.

• Less accurate at higher pressures.

Instruments: POROLUX™ 100 series

Pre

ssure

/ b

ar

Time / min


POROLUX™ 100/100NW/100FM/500: Pressure scan

• A single valve is continuously opened during the measurements.

• Continuous measurement of both pressure and gas flow.

• Fast an typically very reproducible results.

• Very suited for QC work.

• Less accurate at higher pressures and therefor limited to 7 bar / 100 psi

The software allows the user to select the speed of pressure increase and the number of pressure steps. This way the user can easily obtain more data point and thus improve the resolution for the pore size distribution for a wide range of samples


POROLUX™ pressure scan: Product range

Product overview POROLUX™

100

POROLUX™

100NW

POROLUX™

100FM

POROLUX™

500

Max pressure 0.7 MPa/100 psi 0.15 MPa/22 psi 0.25 MPa/36 psi 3.5 MPa/500 psi

Min pore(2) 0.091 µm 0.427 µm 0.250 µm 13 nm

Max pore(2) 500 µm 500 µm 500 µm 500 µm

Max flow 100 l/min 200 l/min 200 l/min 200 l/min

Sample holders 25 mm 25 mm 25mm 25 mm

Pressure

sensors(3) 8 bar 2 bar 3 bar 0.5-5-50 bar

Flow sensors(3) 5-100 l/min 10-200 l/min 10-200 l/min 10-200 l/min

Calculated FBP Yes Yes Yes Yes

Measured FBP No No No No


POROLUX™ 100: Reproducibility


POROLUX™ 100: Effect of analysis time

Initial pressure (bar) 0.5

Final pressure (bar) 2.5

Wet measurements 30

Pressure slope (s/bar) 500 180 60 30

Run time " 33:15" " 11:23" " 4:47" " 2:53"

(slow) (fast)

Bubble point flow (l/min) 0,02

Bubble point pore size (um) 0.7407 0.7268 0.6894 0.6642

MFP size (um) 0.5252 0.4887 0.3999 0.3879

Smallest pore size (um) 0.4647 0.392 0.3047 0.2781


50

0

5

10

15

20

25

30

35

40

45

Diameter (um)

0,750,25 0,3 0,35 0,4 0,45 0,5 0,55 0,6 0,65 0,7

45

0

5

10

15

20

25

30

35

40

Pressure (bar)

2,60 0,2 0,4 0,6 0,8 1 1,2 1,4 1,6 1,8 2 2,2 2,4

slow

fast

slow

fast


Porometer technology

2. Pressure step/stability method

• A large needle valve opens with very accurate and precise movements.

• A data point is recorded when the defined stability algorithms are met for both pressure and flow.

• The porometer detects when a pore empties at a certain pressure and waits until all pores of the same diameter have been completely emptied before accepting a data point.

• Very accurate measurement of pore sizes and calculation of real pore size distribution.

Instruments: POROLUX™ 1000 series

Pre

ssure

/ b

ar

Time / min


Stability algorithms for flow and pressure:

Samples have complex mixtures of pores (e.g. shape and/or length)

Consider 2 pores with the same diameter:

• A straight pore (S) with a pore length of 1

• A tortuous pore (T) with a pore length of 1.5.

Analysis with the pressure scan method:

• Pores open at a different pressure: T has more resistance, opens later in time and thus at a higher pressure.

• Pore T shows up as a pore with a smaller diameter than pore S.

Analysis with the pressure step/stability method:

• Pore S and pore T open at a different time but due to the stability algorithms still at the same pressure.

• Pore S and pore T will be shown as pores with the same diameter.

(S) (T)


Stability algorithms for flow and pressure

A data point is only taken when the chosen pressure and the resulting flow are stable within certain criteria.

Criteria are defined by the user as a stability window for pressure and for flow:

• Wait shorter or longer time: time 1 > time 2

• Accept a different % in variation of the nominal value

1 % 5 %

Time 1

Time 2


Pressure scan vs. pressure step/stability

Pressure scan Pressure step/stability

Stability algorithms No Yes, for pressure and gas

flow

Measurements Immediate

Continuously Only after meeting criteria for

stability

Advantages

For QC work

For samples where all pores

are identical

Essential when analyzing

samples with a complex pore

structure

Disadvantage

Pressure regulation is not

linear over the entire pressure

range Slower measurements

Key words Speed and reproducibility Precision and accuracy


Measured and calculated First Bubble Point (FBP)

POROLUX 1000 POROLUX 1000

POROLUX 100


0

0.02

0.04

0.06

0.08

0.1

0.12

0.14

1.1 1.2 1.3 1.4 1.5 1.6

Flo

w r

ate

(l/m

in)

Pressure (bar)

Calculated FBP Defined at 100 ml/min

Measured FBP

Measured and calculated first bubble point (FBP)

Measured FBP Calculated FBP

Criteria Defined at the pressured required to achieve a deviation

of 20% in the slope of the linear pressure increase. Defined at the pressured required to achieve a

100 ml/min flow rate.

Pressure 1.398 bar 1.509 bar

Flow rate 4 ml/min 100 ml/min

FBP size 458 nm 425 nm


Options for calculated first bubble point (FBP)

Criteria Description

Size at “x” ml/min. Defined at the pressured required to achieve a

predefined “x” ml/min flow rate.

Differential size accounting

Based on a differential calculation of the wet curve. Defined at the pressure corresponding to the steepest

point after the first flow is detected.

Requires enough measurement points in order to calculate correctly the steepest point.

Size for flow rate above “x” ml/min Defined at the pressure corresponding to the first measured point after a flow level of “x” ml/min is

achieved

X= 30 ml, 50 ml or 100 ml/min


Measured and calculated first bubble point (FBP)

Measured first bubble point Calculated first bubble point

Defined at the pressure at which a deviation from the linear pressure increase occurs.

The porometer “senses” the largest pore by applying a low, constant flow rate that is used to increase the pressure.

Defined at the pressure at which a certain flow is detected.

The user defines the criteria to influence the sensitivity of this bubble point detection.

The user decides to take the bubble point at e.g. 30, 50, 100 ml/min or first flow via a mathematical determination

More accurate, correct Faster but less accurate, simulation

Can be measured before running the wet measurement. Can only be calculated once the wet measurement has been completed.


POROLUX™ 1000: Pressure step/stability

• Control of the pressure increase and the pressure with a very accurate entry pressure regulator and the specially designed needle valve.

• Very accurate measurement of the pore size: flow measured with the best flow meters on the market.

• Besides the calculated FBP at multiple flow rates, the POROLUX™ 1000 also offers the user to detect the measured FBP.

• The software allows the user to set up stability criteria for pressure and flow in a very intuitive way thus giving an insight of the complexity of the pore structure.

• The resolution can easily be enhanced by choosing a larger number of pressure steps.


POROLUX™ 1000: Product range POROLUX™

1000

POROLUX™

1000LP

POROLUX™

1000LF

Measuring principle Pressure Step Pressure Step Pressure Step

Max pressure 35 bar 8 bar 35 bar

Min pore (1) 13-15 nm 80 nm 18 nm

Max pore (2) 500 µm 500 µm 500 µm

Max flow 200 l/min 100 l/min 10 l/min

Sample holders 13-25-47 mm 25 mm 13-25-47 mm

Pressure sensors 2-50 bar 1-10 bar 2-50 bar

Flow sensors 10-200 l/min 5-100 l/min 0,5-10 l/min

FBP regulator 5-30 ml/min 5-30 ml/min 5-30 ml/min

Measured FBP Yes Yes Yes

Calculated FBP Yes Yes Yes

Liquid permeability Option Option Option

Hydrohead Option Option Option

Comfort kit Option Option Option

Large sample sample holder Option Option Option

Hollow fibers sample holder Option Option Option (1) Using Porefil (2) Using silicone oil


Sample ID "PES2" AVG STD RSD

Bubble point pressure (bar) 0.9972 0.9889 1.027 1.005 1.005 1.0065 0.0142 1.4%

Bubble point flow (l/min) 0.01338 0.01059 0.01618 0.009094 0.009126

Bubble point pore size (nm) 641.8 647.2 623 636.8 636.5 637.06 8.99 1.4%

MFP pressure (bar) 1.148 1.14 1.148 1.143 1.145 1.1448 0.0034 0.3%

MFP size (nm) 557.4 561.3 557.7 559.9 558.7 559.00 1.62 0,3%

Smallest pore pressure (bar) 1.182 1.19 1.2 1.196 1.187 1.1910 0.0071 0.6%

Smallest pore size (nm) 541.4 537.7 533.1 535 539.1 537.26 3.28 0.6%

Run time " 21:22" " 22:46" " 21:56" " 22:03" " 22:39"

(1) Repetitive measurements on the SAME sample

POROLUX™ 1000: Reproducibility (1)


POROLUX™ 1000: Reproducibility 16

0

2

4

6

8

10

12

14

Pressure (bar)

40 0,5 1 1,5 2 2,5 3 3,5

100

0

10

20

30

40

50

60

70

80

90

Diameter (um)

0,40,1 0,125 0,15 0,175 0,2 0,225 0,25 0,275 0,3 0,325 0,35 0,375


POROLUX™ 1000: Effect of analysis time

fast

slow

40

0

5

10

15

20

25

30

35

Pressure (bar)

1,40 0,1 0,2 0,3 0,4 0,5 0,6 0,7 0,8 0,9 1 1,1 1,2 1,3

100 data points – 30 min 35 sec – MFP 0.74 µm @ 0.86 bar

30 data points – 23 min 57 sec – MFP 0.72 µm @ 0.88 bar

slow

fast


• There is no universally accepted reference material. • SEM images are limited to the surface: no information

about the inside of membrane. Inside pores can get wider, thinner, tortuous, can merge with other pores.

• Closest to perfect cylindrical pores: track etched

membranes. They have a narrow pore distribution but as seen on the SEM image some of the pores merge.

• We recommend to use a material that has been

analyzed many times and for which statistical data for FBP (first bubble point) mean and min pore is available.

Reference Material / Calibration


Interaction of porous material with liquid

In theory, many different wetting liquids can be used. In order to obtain a good wetting of the sample, the wetting liquid should have the following physical properties:

- Zero contact angle - Low surface tension - Low vapor pressure

The wetting liquids also has to be chemically inert and should not cause swelling of the sample.


Water:

• It will only wet hydrophilic pores

• Tends to evaporate at increased flow through the large pores of the sample

• Surface tension 72 dyn/cm

It is recommended to use liquids with low vapor pressure

Porefil and Galpore:

• Low vapor pressure and low surface tension (16 dyn/cm).

Silicone oils:

• High viscosity, low surface tension and low vapor pressure.

• Disadvantage: hard to clean, residual silicone oil can contaminate subsequent tests

Wetting liquids


Agfa

ARCI India

BARC India

Baxter

Brita

Donaldson

Dräger

DSM

Eastern Liaoning University – Dandong

Eaton Filtration

Edwards Lifesciences

EMPA

FLSmidth

Foshan Jinhui

Fraunhofer Institute

Fresenius Medical care

Fuji

GE Healthcare

GMT Membrantechnik

Grundfos

Guangzhou Institute of Fibre

Some of our customers

HAW Hamburg

Hengst

Hydrogenics

Indian Institute of Technology - Dehli

INHA University

nnovation Centre of Nanotechnology - Dubna

Johnson & Johnson Medical

KAUST

Kazan University

Kyemyung University

Leibnitz Institute Hannover

Lotte Chemical

NITRA – Northern India Textile Research Association

Macopharma

Mahle

MEET – Uni Münster

Microdyn Nadir

Millipore

Pall

Paul Fitration

Polymer Group Inc.

Procter & Gamble

RCEES Beijing

Reicofil

Roki Techno

RWTH Aachen (Prof. M. Wessling)

SAFT

Samsung

Sanitec

Sartorius Stedim

SARI – Shanghai

Sichuan University

Solvay Solexis

STFI Chemnitz

Tianjin institute of Seawater Desalination

University of Twente (European Membrane Institute)

Universidad Complutense de Madrid

Université Claude Bernard

USM Malaysia

VIAM – Russian Research Institute of Aviation Materials

VITO

Waseda University


• Self-assembly of TiO2 nanoparticles around the pores of PES ultrafiltration membrane for mitigating organic fouling, Journal of Membrane Science, Vol. 467, 2014 , P, 226-235. Xin Li, Xiaofeng Fang, Ruizhi Pang, Jiansheng Li, Xiuyun Sun, Jinyou Shen, Weiqing Han, Lianjun Wang.

• Preparation and properties of PVDF composite hollow fiber membranes for desalination through direct contact membrane distillation. Journal of Membrane Science 405– 406, 2012, p. 185– 200. Hou et al.

• Tubular macro-porous titanium membranes. Journal of Membrane Science, Volume 461, 2014, pages 6139-

145. O. David, Y. Gendel, M. Wessling.

• Neck-size distributions of through-pores in polymer membranes Journal of Membrane Science, Vol. 415–416, 2012, p. 608-615. C. Agarwal, A. K. Pandey, S. Das, M. K. Sharma, D. Pattyn, P. Ares, A. Goswami

• Fabrication of electrospun nanofibrous membranes for membrane distillation application Desalination and Water Treatment, Vol. 51, Issue 7-9, 2013, p. 1337-1343. L. Francis, H. Maab, A. Al-Saadi, S. Nunes, N. Ghaffour, G. L. Amy.

• Preparation of mixed-matrix membranes for micellar enhanced ultrafiltration based on response surface methodology Desalination, Vol. 293, 2012, p. 7-20. H. P. Ngang, A.L. Ahmad, S.C. Low, B.S. Ooi

• Interaction of isothermal phase inversion and membrane formulation for pathogens detection in water Bioresource Technology, Vol. 113, 2012, p. 219-224. S.C. Low, A.L. Ahmad, N. Ideris, Q. H. Ng

• Synthesis of polyvinylidene fluoride (PVDF) membranes for protein binding: Effect of casting thickness Journal of Applied Polymer Science. Vol. 128, Issue 5, 2013, p. 3438–3445. A. L. Ahmad, N. Ideris, B.

S. Ooi, S. C. Low, A. Ismail.

• Synthesis and fabrication of nanostructured hydrophobic polyazole membranes for low-energy water recovery. Journal of Membrane Science, Vol. 423-424, 2012, p. 11-19. H. Maab, L. Francis, A. Al-Saadi, C. Aubru, N. Ghaffour, G. Amy, S. P. Nunes.

Publications


Thank you for your attention

www.porometer.com


http://www.porometer.com/

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