Enhanced desalination using carboxylated carbon nanotube immobilized membranes

• Permeate flux reached upto 19.2 kg/m2 h for 3.4% NaCl concentration using the CNIM-f membrane employing SGMD process.
• More than 99% of the salt reduction was achieved with the conductivity of the produced fresh water in the range of 1–2.5 μs/cm.
• The CNIM-f membrane was highly stable over a long operational period.
• This technique represents a new generation of membranes, which can be scaled up for large-scale desalination process.

In carbon nanotube immobilized membrane (CNIM), the nanotubes serve as a sorbent that provides additional pathways for solute transport. In this paper we present that carboxylated nanotubes which are significantly more polar and can increase interactions with the water vapor in CNIM to improve desalination efficiency in membrane distillation (MD). The encapsulation of the nanotubes in PVDF prevented the carboxylated nanotubes from making the overall membrane more hydrophilic and thus retain its performance. Overall, desalination was consistently better with carboxylated nanotubes than with unfunctionalized ones with flux reaching as high as 19.2 kg/m2 h in a sweep gas membrane distillation mode.