Nano Sponge On Graphene Can Be Used As High Efficiency Filter For Industrial Wastewater

Engineers at the University of Vienna have developed a new composite material that effectively filters out organic pollutants from water. The system uses super porous "nano sponge" embedded in graphene sheet.

The key to the new filter is a class of materials called covalent organic frameworks (COFS). These structures are very porous, giving them a large surface area in a very small space, which means that they can effectively grab a large number of molecules. Materials known as metal organic frameworks (MOFs) are being studied for carbon capture, desalination or extraction of drinking water from thin air, and COFS may have a series of similar functions.

In the new study, the researchers focused on using COFS to remove organic dyes from water. These chemicals are common pollutants in industrial wastewater and can be toxic and carcinogenic – not to mention difficult to remove.

The team adjusted the COFS to selectively capture organic dye molecules. The molecules of – 8 – 0.6 are attracted to the surface of the dye with a suitable size of negative charge.

But there is another obstacle to overcome. When the material is used in a powdery form, the outer pores are first filled with molecules, while the middle pores are empty and basically useless. So the team developed a method to disperse graphene sheets by planting COFS on them.

The final result is that two nanometers thick COFS layer is formed on the monoatomic layer of graphene, which increases the maximum capacity of the material to accommodate organic dye molecules. Graphene itself has considerable pores, allowing water to flow quickly, while COFS play its role.

"Therefore, the combination of the macropores of the graphene network with the ultra-thin COFS layer and a large number of adsorption points can achieve extremely fast and efficient wastewater treatment," the researchers said

The team said the technology should also be fairly cheap. There is no need to use too much graphene, and COFS can be cleaned out and reused.

The study was published in the Journal Angewandte Chemie.