Freshwater only accounts for 2.5% of all water on earth, and the rest is saltwater. The portion of freshwater readily accessible to humans is even smaller (< 1%), as about two-thirds of freshwater is trapped in frozen ice caps.
While water demand for agriculture, industry and domestic use is skyrocketing, freshwater supply is dwindling as a result of climate change-induced drought, ever worsening pollution, and contamination of the environment due to discharge of heavy metals, chemicals, pesticides and pharmaceuticals, just to name a few.
“It is urgent to remove contaminants from water both effectively and efficiently," says Baoxia Mi, CEE Assistant Professor and Director of the Membrane Innovation (MI) Laboratory. “Membrane process are among the most powerful strategies for achieving this goal.”
“We may think of the membrane as a sieve,” she explains. “Properly designed, it will block out all larger-sized unwanted species while allowing water to pass through.”
Students in the MI lab are exploring the use of graphene, an emerging two-dimensional carbon nanomaterial, as building blocks to make a new type of membrane for drinking water purification and wastewater reuse.
“Membranes currently available in the market rely on appropriately sized pore structure as the water pathway,” says Mi. “In contrast, our new membranes use the inter-spacing between stacked graphene nanosheets to filtrate water.”
“Our membrane is something like a window blind, with slightly tilted slats to create space for water to pass through,” adds CEE graduate researcher Sean Zheng, “while the current membranes are more like lotus roots.” (Images at left.)
“Graphene is a wonder material that offers an unprecedented opportunity to make new membranes that are smart and multifunctional,” continues Mi, “and it could revolutionize the way we treat water.”
“Another nice thing about graphene membranes is that a lot of operating energy may be saved thanks to the superfast flow of water within the membrane. This advantage could make it more feasible to generate clean water from unconventional sources, such as wastewater, heavily polluted water, and seawater.”
In a recently renovated lab, Mi and her students are busy unpacking piles of boxes to set up their experiments. The new lab will soon become the home of next-generation membrane technologies.
“I cannot wait to continue my experiments on graphene membranes,” says Zheng. “I have got tons of new ideas to try out once the lab is operational, although I do enjoy the abundant sunshine outside.”
“Hopefully, one day, our membranes can help fight the drought that has been so badly affecting the lives of Californians,” concludes Mi.
Baoxia Mi - Assistant Professor