Georgia Tech scientists have fabricated graphene oxide (GO) membranes that could help make paper production less energy-intense and greener too.
Said to work effectively in industrial applications, GO – a chemically resistant material based on carbon – allows water to get through it much faster than through conventional membranes.
However, making these membranes work in realistic conditions with high chemical concentrations haven’t fetched results the industry is looking forward to.
Now a team led by Georgia Tech professor Sankar Nair and his colleagues, Meisha Shofner and Scott Sinquefield, has utilized new fabrication techniques that allow them to control the microstructure of GO membranes.
This in turn ensures that water is filtered out continuously even at higher chemical concentrations.
To create the new membranes, researchers Zhongzhen Wang, Chen Ma, and Chunyan Xusuch, sandwiched large aromatic dye molecules in between GO sheets.
These molecules strongly bound themselves to the GO sheets in multiple ways – including stacking one molecule on another, resulting in ‘gallery’ spaces between the GO sheets, with the dye molecules acting as ‘pillars.’
Water molecules easily filter through the narrow spaces between the pillars, while chemicals present in the water are selectively blocked based on their size and shape.
The membrane’s microstructure can be further tuned vertically and laterally, allowing them to control both the height of the gallery and the amount of space between the pillars.
According to the scientists, the GO nanofiltration membranes were scaled up to 4 feet in length and demonstrated their operation for more than 750 hours in a real feed stream derived from a paper mill.
This is revolutionary as paper mills accounts for having one of the most energy-intensive chemical processes.
They not only consume large quantities of water to produce cellulose pulp from trees, but also rely on power gulping, steam-fed evaporators that reuse water and chemicals left behind by the pulping process.
Pointing to how their membranes improve sustainability, Nair opines that their GO product could save the paper industry more than 30% in energy costs of water separation.
Image and content: Tamturbo/Georgia Tech