A Radical Way To Purify Water Using Light

Scientists in China have developed an energy-efficient technique for purifying water using graphitic carbon nitride sheets. Their results are reported in the journal Chem.

Contaminated water contains not only chemicals but also living microorganisms that could cause health problems when ingested. Typically, ultraviolet light, chlorine or ozone is used to purify water.

In the present study, scientists led by Professor Wang Da of the Institute of Process Engineering at the Chinese Academy of Sciences disinfected water using graphitic carbon nitride sheets, an ultra-thin two-dimensional material with the right electronic properties to absorb sunlight and generate reactive oxygen.

The configuration of the material helped produce high concentrations of hydrogen peroxide, which efficiently kills bacteria by oxidizing their cell walls and damaging their chemical structures. The researchers demonstrated that their photocatalyst killed more than 99.9999 percent of bacteria in contaminated water, meeting China’s requirements for clean drinking water.

Unlike metal-based photocatalytic disinfectants, the graphitic carbon nitride sheets do not leave behind secondary pollution or heavy-metal-ion residues, making them a more environmentally-friendly option of water purification.

“The future application of photocatalytic disinfection technology can significantly relieve clean-water scarcity and global energy shortage,” said Wang.

The team believes that their technology should be relatively easy to develop on a larger scale due to the simplicity of its design and the low cost of its manufacture. Going forward, the researchers plan to improve the efficiency of their system by expanding the material’s ability to absorb photons, developing antibacterial fibers and refining the nanosheet preparation process.

However, Wang acknowledges that this bacteria-killing system is not intended to single-handedly purify water.

“Purification needs other devices for removing heavy-metal ions, adjusting pH, and removing residue,” he said. “We need to combine our system with others to meet water-purification requirements.”

Read more from Asian Scientist Magazine at: https://www.asianscientist.com/2019/02/tech/graphitic-carbon-nitride-water-purification/