This document summarizes research on developing forward osmosis membranes for water purification. It presents two studies: 1) evaluating the impact of spacers and flow rates on an SW30XLE membrane, finding that spacers with higher pore size provide higher water and salt permeability; and 2) evaluating three impregnated membranes with different compositions, finding the membrane with 80% PEGDA and 20% zwitterionic monomer had the highest water permeability and lowest salt permeability. The document outlines the experimental methods, results, and conclusions from both studies and development of impregnated forward osmosis membranes for water purification applications.

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?