Engineers from Washington University in St. Louis have created graphene oxide sheets that transform dirty water into drinking water, and also can desalinate salt water.

The researchers’ nanoparticle biofoam uses graphene oxide incorporated into nanocellulose foam. Using bacteria-produced cellulose and graphene oxide, they created a bi-layered biofoam with a relatively simple process. The material changes water from the bulk (dirty) to the evaporative surface, minimizing the heat coming down in a single step.

Nanoparticle biofoam. Image credit: Washington University in St. LouisNanoparticle biofoam. Image credit: Washington University in St. LouisThe researchers say that a novel design of the material initiates the process: a bi-layered structure with light-absorbing graphene oxide filled nanocellulose is at the top with simple nanocellulose at the bottom. When suspended over water, the water reaches the top surface where evaporation occurs. The cellulose at the bottom draws the water up to the graphene oxide where rapid evaporation occurs.

The fresh water that results is collected from the top of the sheet. The process relies on sunlight, which heats the top because of the graphene oxide. The heat is confined to the top layer, where evaporation is occurring, because the bulk water is protected by the nanocellulose layer.

Because cellulose is readily producable on a large scale and graphene oxide is relatively inexpensive, the team envisions sheets that could be made at scale to address the need for clean water.