Photothermal efficiency of carbon nanotubes-embedded polysulfone membranes for direct contact membrane distillation

Abstract

Membrane distillation (MD) is a highly promising method for desalinating water with high salt content. However, a major challenge faced by this technology is its high energy consumption, which is caused by the need to heat up the saline feed solution. Hence, this study aimed to incorporate multi-walled carbon nanotubes (MWCNTs) into the polysulfone (PSF) matrix to fabricate composite photothermal MD membranes. These membranes have the capability to function independently without the need for an external energy source. Various quantities of MWCNTs ranging from 0.5 to 1.5% (by weight) were added to the PSF casting solution. This led to the creation of composite membranes with improved photothermal characteristics. The PSF and PSF/MWCNTs composite membranes were analyzed using scanning electron microscopy (SEM), FTIR spectroscopy, thermal gravimetric analysis, and contact angle measurements. The concentration of MWCNTs that yielded the highest photothermal efficiency was found to be 1% (by weight). The membranes were assessed using a photothermal membrane distillation (PMD) device, where the operational conditions and parameters were investigated. The presence of MWCNTs resulted in an increase in the surface temperature of the membrane to 67 °C when placed 10 cm away from a 200 W light source. In addition, the inclusion of MWCNTs led to a rise in the contact angle measurement from 80° to 112°, as well as an improvement in the liquid entry pressure (LEP) from 25.5 to 52 psi. Moreover, it significantly impacted the improvement of membrane production in the presence of light, while also exhibiting a high degree of operational efficiency.

Graphical Abstract