Nanofiber membrane makes seawater drinkable in minutes. Credit: Pixabay
Safe and readily available water is important for public health, whether it is used for drinking, domestic use, food production, or recreational purposes. Despite the vast quantity of water on Earth, just 2.5% of it is freshwater, and an estimated 785 million people lack a clean source of drinking water. Desalination of seawater could be a vital technology to meet the world’s drinking water needs.
Now, Korean engineers have developed a new desalination technique that takes just minutes to make seawater drinkable. They used a new nanofiber membrane distillation process that could desalinate water with 99.99% efficiency. Engineers believe that commercializing such technology could help humankind cope with the shortage of fresh drinking water in the future.
Amongst the most challenging issues in membrane distillation is membrane wetting that causes the pollution of permeate, reduction in vapor production, and finally, reduction in the performance of the membrane. If a membrane exhibits wetting during membrane distillation operation, the membrane must be replaced.
Engineers at the Korea Institute of Civil Engineering and Building Technology (KICT) have developed co-axial electrospun nanofiber membranes fabricated by an alternative nano-technology, which is electrospinning. It can prevent wetting issues and also improve the long-term stability of the membrane distillation process.
The co-axial electrospinning technique is one of the most favorable and simple options to fabricate membranes with three-dimensional hierarchical structures. In scientific terms, the engineers used poly (vinylidene fluoride-co-hexafluoropropylene) as the core and silica aerogel mixed with a low concentration of the polymer as the sheath to produce a composite membrane with a superhydrophobic surface. This allows them to produce a filter that had a higher surface roughness and lower thermal conductivity.
During the tests, the team was able to maintain stable membrane distillation for 30 days. During those 30 days, the nanofiber membrane obtained by electrospinning maintained a percentage of 99.99% in the rejection of salt. That’s a far longer runtime than other electrospun nanofiber membranes in previous studies that operated for less than 50 hours with high water vapor flux.
“The co-axial electrospun nanofiber membrane has strong potential for the treatment of seawater solutions without suffering from wetting issues and maybe the appropriate membrane for pilot-scale and real-scale membrane distillation applications,” says Dr. Yunchul Woo, lead researcher on the study.
Currently, the main method of desalination of seawater is reverse osmosis. This approach is used in approximately 20,000 specialized factories around the world. Unfortunately, reverse osmosis uses a tremendous amount of energy, and in the process of desalting water in this way, harmful waste is generated, which is usually discharged back into the sea or ocean.