Hydrophobic membrane development for membrane distillation (md) application and process study of effective md application

• Main Author: Hengki, Setiadi Siah
• Other Authors: Wang Rong
• Format: Final Year Project
• Language: English
• Published: 2014
• Subjects: DRNTU::Engineering
• Online Access: http://hdl.handle.net/10356/61043
• Institution: Nanyang Technological University

Membrane distillation (MD) is a thermal-driven membrane process and considered as a promising alternative approach for seawater desalination which could use low grade waste heat as thermal source. However, MD still has little acceptance in industry because of some barriers, including absence of specially designed MD membrane with high hydrophobicity, high porosity, competitive flux, long term stability, and robust mechanical strength. Another major obstacle in the MD process is the phenomenon of membrane fouling. There are only few works dedicated to investigate membrane scaling and cleaning behavior in MD process. Hence this research aims to study: 1) Fabrication of carbon nanotube (CNT) incorporated PVDF nanofiber membranes by electrospinning for MD application to enhance permeate flux 2) Effects of scaling and cleaning on MD process performance The obtained experimental data claimed that incorporation of hydrophilic CNT into the pristine PVDF nanofibers membrane enhanced permeation flux in MD process. The controlled PVDF nanofiber membrane, hydrophilic CNT incorporated membranes exhibited permeation flux of 20 and 48 kg/m²h, respectively. Besides, experimental data showed a decline in contact angle and pore sizes but improvement in mechanical strength of the modified membranes due to the incorporation of CNT. Among all the cleaning procedures implemented, only 24 hours chemical treatment with sodium hydroxide was able to restore productivity of the MD process up to 95-100%. FTIR and SEM analysis showed that 24 hours NaOH cleaning could not completely remove the scalant from the surface of PTFE and PVDF membrane. In contrast to PVDF membrane, which demonstrated gradual increase in permeate conductivity after chemical cleaning, PTFE membrane filtrate demonstrated a constant unchanged permeate conductivity over time. Besides, addition of sodium alginate into the scaling solution increased the productivity of PTFE membrane by 1.75 times while it was found that alginate did not increase the evaporation rate of water in the MD process.