Development of solar absorbing nanoporous membranes for direct solar seawater desalination

Because of the abundance of solar energy, solar-based desalination is an attractive technology to meet the ever-increasing water demand. In this study, we develop efficient, low cost, and optimized nanoporous membranes for direct solar desalination of seawater. Our objective is to develop a black-body like membrane that maximizes solar absorption via the structure design and coating. To fabricate our envisioned solar absorbing membranes, we developed two different and distinct approaches, the first being a flat-sheet membrane via phase inversion and the second via chemical vapor deposition. The absorbance for each membrane was measured using a UV(vis) spectrometer. The structures of the prepared membranes were characterized and observed by scanning electron microscopy and atomic force microscopy. The meanflow pore size, bubble point pore size and pore size distribution were measured using a capillary flow porometer. Also, the porosity was calculated experimentally using a gravimetric method using Salwick as a wetting liquid. Contact angle measurements were also performed to know the hydrophobic/hydrophilic nature of the membranes. In CNT, the absorption and the porosity increase as the PVDF concentration decreases while the contact angle increases as the PVDF concentration increases. The contact angle measurements for the AC and graphene membranes with different rates decrease with the increase of the activated carbon and graphene percentage in the membrane. The graphene has the highest absorption form all the membranes approximately 97%.