 | Researchers from KFUPM (led by Dr. Turki Baroud chairman of the Materials Science and Engineering Department) and ARAMCO (led by Dr. Hasan Al-Abdulqader) joined forces to maximize the value of the waste stream. In the oil industry, produced water is a term used to describe water that is produced as a byproduct during the extraction of oil and natural gas. This water is very challenging to treat due to the high salinity (>70,000 ppm) along with the high concentration of oil and minerals. Membrane distillation is a promising technique where it needs a relatively small amount of energy to operate. The challenge comes in the form of developing a membrane that prevents water with high salt content and low surface contaminants to pass through while only water vapor is allowed to pass from the hot side to the cold side where it condensates to form pure and clean water. Thus, membranes need porous and specific surface chemistry and energy that only allow water vapor to cross the membrane. |
Both teams were inspired by the hydrophobic effects of lotus flowers (caused by the microscale roughness of these leaves, which forms air pockets that prevent water droplets from passing through) and the non-stick properties of Teflon (PTFE) coating
observed in cooking utensils. This "non-stick" characteristic is induced by PTFE's extremely low surface energy, which results in low molecular interactions, particularly with adhesive molecules. To mimic such phenomena, both teams developed
novel Superhydrophobic and Omniphobic (oleophobic and superhydrophobic) membranes for air-gap distillation via a simple and scalable approach that will help desalinate the highly saline wastewater (produced water) produced by the oil and gas
industry. In this project, a sandpaper substrate was utilized to create a highly efficient textured membrane material, yielding a superhydrophobic material that is excellent at rejecting water. This texturing approach takes advantage of its
simplicity and outperforms the more expensive and sophisticated photolithography-based patterned mold substrate. Additionally, long chains of fluorine-containing functional groups were grafted on the membrane surface. The fluorine atoms in
these chains lower the surface energy. The resultant PVDF semi-crystalline fluoropolymer has a very low surface and repels practically all other molecules, preventing them from adhering to the membrane material.
The developed membranes demonstrated excellent and stable performance with high salt rejection (over 99.99% ), and high vapor flux. Interestingly, the developed membranes in this project outperformed commercially available PVDF and PTFE membranes tested in Air Gap Membrane Distillation (AGMD) systems under similar operating conditions.
“This work will guide in terms of better design and development of cost-effective porous membranes, and ultimately pave the way for practical applications for wastewater desalination and treatment,” says Dr. Baroud.
This study exemplifies how ideas and solutions may emerge from anywhere, from plant leaves to everyday mundane household appliances like nonstick pans. Both teams field 13 patents as a result of their study, as well as publication in the Desalination journal (IF : 9.501), and more will be published soon. In the words of Dr. Baroud, “This project was a collaborative endeavor that involved individuals from academia and industry with diverse expertise and backgrounds with the passion to save our environment”.