Developing an inexpensive system to purify water from arsenic compounds

Chinese and American chemists have developed a cheap system for purifying water from arsenic compounds based on manganese oxide and titanium dioxide nanoparticles.

They tested it successfully in the state of New Jersey and in a village located in Yingchuan Province in northern China. The results of testing the operation of this system were published in an article in the journal Nature Water.

“We have developed a drinking water purification system based on an oxidant made of activated carbon and manganese oxide, as well as an adsorbent based on titanium dioxide nanoparticles. This system, as our practical tests in two different regions of the globe have shown, is able to effectively purify water from arsenic, and at the same time, the cost of purifying one liter of water is less than one US cent,” the article reads.

This water purification system was developed by a team of Chinese and American chemists led by Chinese researcher Zheng Yang, a professor at the Southern University of Science and Technology in Shenzhen. It is a traditional three-stage filter for water purification. It contains three components, namely activated carbon with the addition of manganese oxide and a powder made of titanium dioxide nanoparticles, in addition to regular activated carbon, which purifies water from organic materials, microbes, and suspended materials.

As the chemists explained, in the first stage, manganese oxide molecules interact with arsenic ions and move them from the +3 oxidation state to +5, where the atoms of this chemical element begin to actively interact with titanium dioxide nanoparticles in a second filter container. In addition, arsenic in the +5 oxidation state is tens of times less dangerous to the human and animal bodies, which reduces the risk of pure water to the health of potential consumers.

The operation of this system was tested during relatively short-term experiments conducted in an area of ​​the North American state of New Jersey, where the water contains significant amounts of arsenic, as well as during a two-year trial in a rural area of ​​Inchuan Province with a similar concentration of arsenic compounds in groundwater. During these experiments, the researchers tracked how the concentration of these toxins changed over time, and they also measured the rate of water purification.

The chemists’ measurements showed that their filter could purify nearly five cubic meters of water before the arsenic content in the treated water reached 10 parts per billion, the maximum allowed by the World Health Organization and relevant US and Chinese environmental agencies. In that case, the researchers concluded, the filter could be restored to working condition by treating the titanium nanoparticles with hydrochloric acid, making such an arsenic-free water purification system available to even the poorest regions of the world.

High levels of lead, arsenic and other elements in water lead to the development of severe disorders in the functioning of the human brain and body. In some countries, such as India and Bangladesh, about a quarter of the water sources contain very high levels of arsenic compounds, which has a very negative impact on the lives of local residents and forces scientists to develop technologies to purify water from arsenic.