Membrane surface modification to enhance membrane hydrophobicity
Date of Issue2010
School of Civil and Environmental Engineering
Membrane distillation (MD) is an emerging technology which is being studied as a low cost, energy saving alternative to conventional separation process such as distillation and reverse osmosis for seawater desalination. However, the MD technology has not be used for practical applications in industries due to some barriers which include membrane pore wetting, low permeate flux and flux decline. Therefore, extensive studies on these aspects are being carried out worldwide, aiming on improving MD performance. This report documents the modification of commercial membranes to improve its hydrophobicity and change its pore structure for better application in the MD process. Surface modification was carried out on commerical PVDF hollow fiber membrane by using reagent A and reagent B, and a fluoro-compound. (As this work is in the process of filing patent, the chemicals were not released in this report). During the modification process, rinsing was done using isopropanol, water, ethanol, acetic acid and acetone. Despite the decrease in porosity and permeate flux, the modified membrane was observed to have better mechanical properties and hydrophobicity. Among all of the modified hollow fibers, a high contact angle value of 124° has been achieved. The same modification was also carried out on PVDF-HFP polymer in powdered and pellets form before fabrication into flat sheet membranes. The contact angle values of the PVDF-HFP membranes obtained from modified powder and pellets are 98.4 ± 3.1 and 103.9 ± 1.2, respectively, both showing an increase of hydrophobicity as compared to the original membrane. Thus it was concluded that the modification method developed in this study is a useful means to enhance membrane hydrophobicity, which favours the performance improvement of the MD process.
Final Year Project (FYP)
Nanyang Technological University