Carbon-nanotube process evolved for membrane distillation desalination

A new architecture for the membrane distillation process which immobilizes carbon nanotubes in the membrane pores has been developed by Professor Somenath Mitra of chairman of the department of chemistry and environmental science of the New Jersey Institute of Technology, USA.

The process is outlined in a paper Water Desalination Using Carbon Nanotube Enhanced Membrane Distillation by Prof Mitra and doctoral students Ken Gethard and Ornthida Sae-Khow in the current issue of the American Chemistry Society’s Applied Materials & Interfaces.

The novel architecture not only increases vapor permeation but also prevents liquid water from clogging the membrane pores. Test outcomes show dramatic increases in both salt reduction and water production.

“The biggest challenge,” said Mitra, “is finding appropriate membranes that encourage high water vapor flux but prevent salt from passing through.”

The new process can facilitate membrane distillation at a relatively lower temperature, higher flow rate and higher salt concentration. Compared with a plain membrane, this new distillation process demonstrates the same level of salt reduction at a 20°C lower temperature, and at a flow rate six times greater.

For a salt concentration of 34,000 mg/L and at 80 °C, the nanotube incorporation led to increases of 1.85 and 15 times in flux and salt reduction, respectively.

“Together these benefits lead to a greener process which could make membrane distillation economically competitive with existing desalination technologies and we hope could provide potable water where it is most needed,” said Mitra.