Enhanced durability and hydrophobicity of carbon nanotube bucky paper membranes in membrane distillation

Recent work showed that carbon nanotubes could be fabricated into bucky-paper structures as self-supporting membranes and their hydrophobic property used for water desalination by membrane distillation. Carbon nanotube bucky-papers possess very interesting properties such as natural hydrophobicity, high porosity and very high specific surface area, making of them promising candidates for separation applications. However, to inhibit crack formation associated with poor mechanical stability, improved durability structures that retain a high degree of hydrophobicity need to be developed. In this work we chemically modified high purity carbon nanotubes by (i) UV/ozone treatment to create hydroxyl groups and (ii) reacting those groups by substitution with alkoxysilane based groups. The resulting nanotubes presented a silicon content up to 2.5% and the bucky-papers produced had larger contact angle (140° compared to 125°) and liquid entry pressures. We report here on their fabrication and use as membranes in direct contact membrane distillation.

► Fabrication of carbon nanotubes based membranes. ► Alkoxysilane grafting on nanotubes for enhanced hydrophobicity. ► The membranes were characterised and tested in a membrane distillation rig. ► The alkoxysilane modified CNT BP exhibited higher performance and lifespan than the non treated samples.