1. Forward Osmosis Membranes for
Water Purification
Ken He
Advisor: Dr. Haiqing Lin
Mentor: Junyi Liu
Department of Chemical and Biological Engineering
SUNY at Buffalo
12/11/2015

2. 2
Outline
1. Introduction
2. Experimental Work
3. Result and Discussion
4. Conclusions

3. 3
1.1 Introduction of Forward Osmosis
• Forward osmosis (FO), is an osmotic process that uses a semi
permeable membrane to effect separation of water from dissolved
solutes
• Driving force: Osmotic pressure difference
• Feed Solution: Waste water
• Draw Solution: Salt water
• Advantages:
• High energy efficiency
• Low cost

4. 4
1.2 Introduction of FO Membrane
Commercial FO membrane Impregnated membrane
• Thickness: ~200 μm
• Thin composite membrane
• Three layers
• Thickness: ~50 μm
• Combines the selective layer with
the support layer
• Could potentially increase water
permeability by eliminating the
internal concentration polarization

5. 5
1.3 Theoretical Models for Water Transport in Membranes
1. 𝐽 𝑊 = 𝐴 𝑊∆𝜋 =
𝑃 𝑊
𝑙
𝑉 𝑊
𝑅 𝑔 𝑇
(𝜋 𝐷 − 𝜋 𝐹)
𝐽 𝑊, water flux (L/m2 hour or LMH) 𝑉 𝑊, molar volume of water (18 cm3/mol)
𝐴 𝑊, water permeance (LMH/bar) 𝑅 𝑔, gas constant (83.1 cm3 bar/mol K)
∆𝜋, osmotic pressure difference across the membrane (bar) 𝑇, temperature (K)
𝑃 𝑊, water permeability (cm2/s)
𝑙, membrane thickness (cm)
2. 𝐽𝑆 = 𝐵 𝐶𝑆,𝐷 − 𝐶𝑆,𝐹 =
𝑃 𝑆
𝑙
(𝐶𝑆,𝐷 − 𝐶𝑆,𝐹)
𝐽𝑆, salt flux (g/m2 hour or gMH)
𝐵, salt permeance in the membrane (cm/s)
𝑃𝑆, salt permeability (cm2/s)
𝐶𝑆,𝐷, salt concentration in the draw solution (g/cm3)
𝐶𝑆,𝐹, salt concentration in the feed solution (g/cm3)

6. 6
1.4 Rational Performances of FO system
Desired attributes:
• High water permeability
• Low salt permeability
Impact factors for the system:
• Spacers (flow channels)
• Peristaltic pump flowrates

7. 7
2.1 Preparation of Impregnated Membrane
Impregnated Membrane
Solutes
(70wt%)
Solvent
(30wt%)
Initiator
(0.1wt%)
Support
1 100% PEGDA 0% ZI
Water HCPK Porous hydrophobic support2 80% PEGDA 20% ZI
3 60% PEGDA 40% ZI

8. 8
2.2 FTIR for Impregnated Membrane
• Lack of peaks at 810 cm-1 and 1408 cm-1 indicate that
essentially 100% conversion of acrylate groups was achieved
C=C
C=C

9. 9
2.3 Experimental Methods
Study 1:
• Evaluation of impact factors with SW30XLE
 Feed solution: 4 L of de-ionized water
 Draw solution: 1.5 L of 1M NaCl in de-ionized water
 Spacers used: Permeate Carrier vs Medium Foulant
 Membrane used: SW30XLE
 Peristaltic pump flowrate settings: 38 cm/s vs 68 cm/s for both feed and
draw solutions

10. 10
2.3 Experimental Methods (Cont.)
Study 2:
• Evaluation of impregnated membrane
 Feed solution: 4 L of de-ionized water
 Draw solution: 1.5 L of 1M NaCl in de-ionized water
 Spacers used: Permeate Carrier
 Membrane used: 3 impregnated membranes
 Peristaltic pump flowrate settings: 38 cm/s for both feed and draw
solutions
Both studies obtain water flux, salt flux and salt concentration of
the feed solution as a function of time

11. 11
3.1 Result and Discussion
Study 1: Evaluation of impact factors with SW30XLE
• Experiment 1 and 2 are compared for effect of spacers
• Experiment 1 and 3 are compared for effect of peristaltic pump flowrates
Experiment Membrane
Flowrate Setting
(cm/s)
Spacers
Water permeability
(cm^2/s)
Salt permeability
(cm^2/s)
1 SW30XLE 38/38
Permeate
Carrier
2.3E-03 5.5E-07
2 SW30XLE 38/38
Medium
Foulant
2.7E-03 1.0E-06
3 SW30XLE 68/68
Permeate
Carrier
2.5E-03 4.8E-06

12. 12
3.1 Result and Discussion (Cont.)
Study 2: Evaluation of impregnated membrane
• Impregnated membrane with 80% PEGDA and 20% Zwitterionic monomer
has the highest water permeability and lowest salt permeability
Experiment Membrane
Thickness
(μm)
Flowrate
Setting
(cm/s)
Spacers
Water
permeability
(cm^2/s)
Salt
permeability
(cm^2/s)
1 IM-100%PEGDA 48 38/38
Permeate
Carrier
1.4E-04 3.3E-06
2 IM-80%P20%ZI 50 38/38
Permeate
Carrier
2.0E-04 2.5E-06
3 IM-60%P40%ZI 52 38/38
Permeate
Carrier
1.6E-04 3.0E-06

13. 13
4.1 Conclusion
Study 1:
• Spacers with higher pore size provide higher water
permeability and higher salt permeability
• Effect of peristaltic pump flowrates on the system
has to be studied further
Study 2:
• Successfully prepared the impregnated membrane
with PEGDA and Zwitterionic monomer
• Obtained preliminary data for impregnated
membrane

14. Questions?