A major problem with water purification filtration devices is that, over time, bacteria accumulate on the surface of the material, resulting in a gradual deterioration of the effect. But researchers at the University of Washington in Saint Louis have developed a new type of filtration membrane. It uses graphene to proactively destroy bacteria to reduce biological contamination. More interestingly, it also uses the power of bacteria flexibly. During the manufacture, the researchers first fed a sugary substance to bacillus acetate (Gluconacetobacter hansenii). Bacteria will then produce nano-cellulose in the water.
At the same time as the fiber grew, the team added graphene oxide flakes to increase the stability and durability of the filter membrane.”It’s like 3D printing with microbes, and we can add anything we like to the growth of a bacterium’s nano-cellulose. We have observed it under different pH conditions. “, said Young-Shin June, one of the study’s leading co-authors.
Compared with the filter membranes prepared by vacuum filtration or rotary coating, the characters of graphene oxide biofilm are more stable. “After using the bacteria, the researchers executed the Bacillus acetate, which produced cellulose, through an alkali solution. At the same time, the oxygen groups are removed and the graphene oxide is ‘ restored ‘. ” The treated graphene biofilm reacts to light to destroy other bacteria that stick to the membrane. “If you want to use microbes to clean water, the reduced graphene oxide in the membrane absorbs sunlight, heats the membrane and inactivate bacteria,” said Srikanth Singamaneni, co-author of the study.
To test the bactericidal capacity of the membrane, the researchers exposed it to Escherichia coli. “It was found that just three minutes of light was enough to heat the membrane above the 70°C (158°F) and easily inactivate the pathogenic microbes. Under high pressure, the sterilization film can filter water at twice the speed of the ordinary membrane. ”
In contrast, if there is no reductive oxidation of graphene, the prepared filter membrane does not effectively inactivate Escherichia coli. “It is worth mentioning that the relatively low cost of the new process has helped people in millions of developing countries to drink clean drinking water. ”