Enhanced solar desalination with photothermal hydrophobic carbon nanotube-infused PVDF membranes in air-gap membrane distillation

• Published in: Desalination 2024-12, Vol.592, p.118142, Article 118142
• Main Authors: Nassar, Lobna, Hegab, Hanaa M., Kharraz, Jehad A., An, Alicia Kyoungjin, Al Marzooqi, Faisal, El Fadel, Mutasem, Hasan, Shadi W.
• Format: Article
• Language: English
• Subjects: Hydrophobic multiwalled carbon nanotubes; Oleylamine; Photothermal membrane distillation; Solar; Temperature polarization
• ISSN: 0011-9164
• DOI: 10.1016/j.desal.2024.118142

This work aims to increase the efficiency of the solar powered-air gap membrane distillation (SP-AGMD) process; a desalination method driven by solar energy, providing an eco-friendly and sustainable approach to addressing global water shortages. The innovation lies in integrating photothermal hydrophobic multiwalled carbon nanotubes (h-MWCNTs), in varying weight percentages from 5 % to 60 %, into polyvinylidene fluoride (PVDF) membranes using the phase inversion membrane fabrication technique. The h-MWCNTs were synthesized through oxidation and functionalization with oleylamine (OL) to improve their photothermal properties. Their successful integration was confirmed via scanning electron microscopy (SEM), thermogravimetric analysis (TGA), Fourier transform infrared spectroscopy (FTIR), and Raman spectroscopy. The h-MWCNTs-based SP-AGMD membranes were further evaluated for wettability, liquid entry pressure (LEP), surface temperature, and solar absorbance, demonstrating significant solar light absorption and localized surface heating. This generated the necessary driving force for the AGMD process. Performance metrics such as vapor flux, salt rejection, specific thermal energy consumption, photothermal efficiency, and temperature polarization (TP) coefficient were significantly improved, especially with a 20 % h-MWCNTs addition, which tripled the solar-energy-driven flux and increased photothermal efficiency by 326 % under standard solar conditions, compared to unmodified membranes. All h-MWCNTs-based SP-AGMD membranes achieved over 99 % salt rejection. Lastly, the membranes were tested with real seawater to confirm their applicability for desalination. This photothermal approach offers a scalable, sustainable solution for water purification, making a significant advancement in membrane distillation technology. [Display omitted] •Photothermal h-MWCNTs improve SP-AGMD membrane efficiency for solar desalination.•Adding 20 % h-MWCNTs triples solar-driven flux and boosts efficiency by 326 %.•All modified membranes achieved over 99 % salt rejection in desalination tests.•Evaluations confirm high solar absorption and effective localized surface heating.