Desalination and Water Purification Research and Development Program Report No. 57 Characterization of the Hydrophobicity of Polymeric Reverse Osmosis and Nanofiltration Membranes: Implications to Membrane Fouling U.S. Department of the Interior Bureau of Reclamation Technical Service Center Denver, Colorado May 2000 Form Approved REPORT DOCUMENTATION PAGE OMB No. 0704-0188 The public reporting burden for this collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing the collection of information. Send comments regarding this burden estimate or any other aspect of this collection of information, including suggestions for reducing the burden, to Department of Defense, Washington Headquarters Services, Directorate for Information Operations and Reports (0704-0188), 1215 Jefferson Davis Highway, Suite 1204, Arlington, VA 22202-4302. Respondents should be aware that notwithstanding any other provision of law, no person shall be subject to any penalty for failing to comply with a collection of information if it does not display a currently valid OMB control number. PLEASE DO NOT RETURN YOUR FORM TO THE ABOVE ADDRESS. 1. REPORT DATE (DD-MM-YYYY) 2. REPORT TYPE 3. DATES COVERED (From - To) May 2000 Final September 2011 to January 2013 4. TITLE AND SUBTITLE 5a. CONTRACT NUMBER Characterization of the Hydrophobicity of Polymeric Reverse Osmosis and Agreement No 98-FC-81-0057 Nanofiltration Membranes: Implications to Membrane Fouling 5b. GRANT NUMBER 5c. PROGRAM ELEMENT NUMBER 6. AUTHOR(S) 5d. PROJECT NUMBER Amy Childress, Johnathan Brandt 5e. TASK NUMBER Task A 5f. WORK UNIT NUMBER 7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES) 8. PERFORMING ORGANIZATION REPORT University of Nevada, Reno NUMBER 9. SPONSORING/MONITORING AGENCY NAME(S) AND ADDRESS(ES) 10. SPONSOR/MONITOR'S ACRONYM(S) Bureau of Reclamation Reclamation U.S. Department of the Interior 11. SPONSOR/MONITOR'S REPORT Denver Federal Center NUMBER(S) PO Box 25007, Denver, CO 80225-0007 DWPR Report No. 57 12. DISTRIBUTION/AVAILABILITY STATEMENT Available from the National Technical Information Service, Operations Division, 5285 Port Royal Road, Springfield VA 22161 13. SUPPLEMENTARY NOTES Report can be downloaded from Reclamation Web site: http://www.usbr.gov/pmts/water/publications/reports.html 14. ABSTRACT As fresh water supplies dwindle and awareness of contaminants rises, the need for effective water treatment technologies increases. For this reason, membrane processes for drinking water treatment are receiving increased attention. This study develops a methodology for determining membrane hydrophobicity and investigates the relationship between hydrophobicity and membrane fouling. It establishes a protocol for measuring contact angles on both cellulose acetate and thin-film composite reverse-osmosis and nanofiltration membranes. It then uses these contact angle measurements in the Lifshitz-van der Waals/Acid-Base approach to quantitatively calculate the surface energetics of the membranes. 15. SUBJECT TERMS Reverse osmosis, nanofiltration, membrane fouling, hydrophobicity, water treatment, desalination 16. SECURITY CLASSIFICATION OF: 17. LIMITATION 18. NUMBER 19a. NAME OF RESPONSIBLE PERSON OF ABSTRACT OF PAGES Scott Irvine a. REPORT b. ABSTRACT a. THIS PAGE 49 19b. TELEPHONE NUMBER (Include area code) U U U 303-445-2253 Standard Form 298 (Rev. 8/98) Prescribed by ANSI Std. Z39.18 Desalination and Water Purification Research and Development Program Report No. 57 Characterization of the Hydrophobicity of Polymeric Reverse Osmosis and Nanofiltration Membranes: Implications to Membrane Fouling Prepared for the Bureau of Reclamation Under Agreement No. 98-FC-81-0057 by Amy Childress, Ph.D., and Jonathan A. Brant University of Nevada, Reno U.S. Department of the Interior Bureau of Reclamation Technical Service Center Denver, Colorado May 2000 MISSION STATEMENTS The U.S. Department of the Interior protects America’s natural resources and heritage, honors our cultures and tribal communities, and supplies the energy to power our future. The mission of the Bureau of Reclamation is to manage, develop, and protect water and related resources in an environmentally and economically sound manner in the interest of the American public. Disclaimer The views, analysis, recommendations, and conclusions in this report are those of the authors and do not represent official or unofficial policies or opinions of the United States Government, and the United States takes no position with regard to any findings, conclusions, or recommendations made. As such, mention of trade names or commercial products does not constitute their endorsement by the United States Government. Acknowledgments This research was funded by the U.S. Department of the Interior, Bureau of Reclamation, Desalination and Water Purification Research and Development Program. The assistance of Kim Linton throughout the study is greatly appreciated. RO and NF Membrane Hydrophobicity CONTENTS Page 1 Introduction ....................................................................................................... 1 2 Background and Related Research ................................................................... 3 2.1 Definition of Contact Angle ...................................................................... 3 2.2 Methods of Measuring Contact Angles ..................................................... 3 2.2.1 Sessile Drop ................................................................................... 3 2.2.2 Immersion Method ........................................................................ 4 2.2.3 Captive Bubble Method ................................................................. 5 2.3 Types of Contact Angles ........................................................................... 6 2.4 Theory of Contact Angle and Hydrophobicity .......................................... 6 2.4.1 Free Energy of Interaction ............................................................. 6 2.4.2 Young’s Equation .......................................................................... 7 2.4.3 Fowkes’ Approach ........................................................................ 8 2.4.4 Lifshitz–van der Waals/Acid-Base Approach ............................... 9 2.4.5 Deviations from Young’s Equation ............................................. 12 2.4.6 Defining Hydrophobic Interactions ............................................. 13 2.5 Hydrophobicity and Membrane Performance ......................................... 14 2.6 Previous Studies on the Determination of Membrane Surface Energetics .......................................................................................... 15 2.7 Previous Studies Correlating Contact Angle and Membrane Surface Energetics with Membrane Performance .......................................... 16 3 Experimental ................................................................................................... 18 3.1 RO and NF Membranes ........................................................................... 18 3.1.1 Thin Film Composite Membranes ............................................... 18 3.1.2 Cellulose Acetate Membranes ..................................................... 18 3.2 Hydrophobicity Measurements ............................................................... 19 3.2.1 Automated Goniometer ............................................................... 19 3.2.2 Syringe and U-Shaped Needle .................................................... 21 3.2.3 Probe Liquids .............................................................................. 21 3.2.4 Bubble Volume ............................................................................ 22 3.2.5 Parafilm® Standard ..................................................................... 22 3.2.6 Contact Angle Measurement Procedure ...................................... 23 3.2.7 Preliminary Contact Angle Measurements for Ultrapure Water ........................................................................................... 24 3.2.8 Preliminary Contact Angle Measurements for Glycerol ............. 25 3.2.9 Preliminary Contact Angle Measurements for Diiodomethane ............................................................................ 26 3.3 Membrane Performance Tests ................................................................. 26 3.3.1 Membrane Test Unit .................................................................... 26 v Contents 3.3.2 Solution Chemistries ................................................................... 27 3.3.3 Performance Test Protocol .......................................................... 28 3.3.4 Performance Analysis .................................................................. 28 4 Results and Discussion ................................................................................... 30 4.1 Hydrophobicity of Clean Membrane Coupons ....................................... 30 4.1.1 Sample Calculation ...................................................................... 31 4.2 Membrane Performance Trials ................................................................ 33 4.3 Surface Energetics of Membranes Following Surfactant and Humic Performance Experiments ................................................................. 34 4.4 Hydrophobicity Versus Contact Angle with Water ...............................