Researchers from the Faculty of Civil and Environmental Engineering at the Technion-Israel Institute of Technology have developed an innovative technology for removing dangerous pollutants from drinking water.

The technology efficiently removes and destroys synthetic organo-fluorine chemical compounds (PFAS) very efficiently. The research was headed by Dr. Adi Radian and her post-doctoral student Dr. Samapti Kundu and was published in Chemical Engineering Journal.

PFAS is a family of problematic pollutants also known as “forever chemicals” because of their chemical stability and environmental persistence.

These substances can be found in a large range of products, including Teflon pan coating, fire-fighting foam, flame retardants and water-repellent additives. They reach the groundwater in various ways, including agricultural irrigation using treated wastewater and fire-fighting substances seeping into the soil. As a result of their chemical stability, they remain intact in the ground for a long time, leading to extensive contamination of drinking sources, which, in turn, significantly increases human exposure.

Dr. Adi Radian. Credit: Courtesy.

International studies have demonstrated the many health risks posed by exposure to PFAS, including cancer, heart and liver disease, fertility problems, birth defects and damage to the immune system. Consequently, Israel has begun monitoring these substances. In fact, last summer the extraction of potable water in the Krayiot region was stopped following the discovery of a high PFAS concentration.

Removing these substances from drinking water is accomplished through relatively simple and inexpensive adsorption techniques. However, these methods are not sufficiently efficient, and, most importantly, they only transfer the pollutants from the water to the adsorbent material, which requires additional purification steps to get rid of the toxic adsorbed substances. Furthermore, these methods are not selective; they can also remove substances essential for people’s health.

Two new and promising solutions include using oxidation processes and targeted polymers that efficiently adsorb the polluting substances. Yet until now, these technologies have not exhibited satisfactory results.

The new research examined the possibility of combining these two methods—separating the pollutants with special polymers and then using advanced oxidation processes to eliminate them. The findings indicate that proper planning leads to high efficiency under a wide range of acidity (pH) and salinity.

Dr. Samapti Kundu. Credit: Courtesy.

The method shows the removal of seven types of PFAS, even when all of them are found in the same unit of fluid, at a level of efficiency that approaches 90 percent, and it does so within a few minutes.

The system described is based on natural materials that are both safe and inexpensive.

The researchers used ubiquitous soil minerals—iron oxides and clays, together with cyclodextrin polymers. The clay-iron-polymer composites act as accelerators that confine the PFAS on the surface and then accelerate the oxidation process that destroys the pollutants into non-toxic substances (fluoride ions, water and carbon dioxide). The combination efficiently removes the PFAS and does not release unwanted substances in water used for drinking.

The research, which was conducted in the Soil Chemistry Laboratory in the Faculty of Civil and Environmental Engineering, shows that this system makes it unnecessary to carry out complementary processes such as heating, UV radiation and using sound waves, which make the task more complicated and more expensive.

How the system works: 1. The pollutants are separated from the water and confined to the surface of the clay-polymer composite; 2. The pollutants are oxidized to create non-toxic substances (water, CO2 and fluoride ions); 3. The system is regenerated; at the end of the oxidation process, a new cycle of removal and degradation can begin. Credit: Courtesy.

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