The researchers have developed a method that uses the chemical reaction between carbon nanotubes (CNTs) and a hypochlorite compound to easily and effectively remove CNTs from industrial wastewater containing CNTs.

Easy removal of CNTs from wastewater containing CNTs using a hypochlorite compound (NaClO)

Nanocarbon materials have an extremely small size and special shapes, so there are concerns about adverse effects on the environment and living organisms. CNTs are thought to have low acute toxicity, but the long-term risks remain unclear. Therefore, it is important to prevent exposure of CNTs to the environment.

The developed technology is used to treat CNT-dispersed aqueous solution by adding a solution of sodium hypochlorite (1.25%) and then maintaining the temperature at 37°C. The results showed that the black color of all tested CNT-dispersions gradually faded, and became completely clear in 96 hours, indicating the CNTs were removed. It is hoped that this technology will lead to realization of a cost-efficient industrial treatment method for wastewater containing CNTs, which will help prevent exposure of CNTs to the environment and contribute to development of a safe and secure CNT industry.

The researchers will use the developed technology to treat wastewater containing CNTs from CNT-application development companies and other sources to confirm the effectiveness of the method, and further refine it.