Researchers from the Technion – Israel Institute of Technology have developed innovative technology to remove dangerous pollutants from drinking water.
The technology effectively removes and destroys synthetic organofluorine chemical compounds (PFAS). PFAS are a family of problematic pollutants, also known as “eternal chemicals” due to their chemical stability and persistence in the environment.
There are thousands of PFAS chemicals, and they are found in many different consumer, commercial, and industrial products. It is therefore difficult to study and assess the potential risks to human health and the environment. These substances can be found in air, water, soil and food, as well as in a wide range of products, including Teflon stove coating, fire-fighting foam, flame retardants and water repellent additives. They reach groundwater in a variety of ways, including agricultural irrigation using treated wastewater and fire-fighting substances seeping into the soil. Due to their chemical stability, they remain intact for a long time in the soil, leading to significant contamination of watering sources, which greatly increases human exposure.
“Lately, it has become clear that these chemicals pose a serious health and environmental hazard – so finding ways to remove and destroy them is of great importance,” said Dr Adi Radian. , assistant professor at the Technion, at NoCamels.
Dr. Radian, head of the soil and environmental chemistry laboratory in the Department of Civil and Environmental Engineering, led the study with his postdoctoral student, Dr. Samapti Kundu. Their findings were published in the Chemical Engineering Journal.
Exposure to PFAS can lead to many health risks, including cancer, heart and liver disease, fertility problems, birth defects, and damage to the immune system. In 2017, the International Agency for Research on Cancer (IARC) classified the polyfluoroalkyl substance (PFAS) as a possible human carcinogen based in part on limited epidemiological evidence of associations with kidney and testicular cancers in highly exposed subjects.
These substances have been controlled in Israel. Last summer, the Israel Fire and Rescue Authority stopped using fire-retardant foam containing two toxic substances from the PFAS family, fearing that these chemicals could seep into groundwater, reports the Israeli daily Haaretz. A few months earlier, the Ministry of Health had discovered a source of drinking water polluted by these chemicals located in the suburbs of Haifa Bay. They speculated that the pollution came from the use of this fire retardant foam at a fuel storage facility in the area. The extraction of drinking water in the Krayiot region was stopped following the discovery of this high concentration of PFAS.
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Haaretz reported that there is currently no standard in Israel for the maximum allowable concentration of PFAS in drinking water, but the Standards Institution is in the process of formulating a standard for fire-fighting foam which will also include toxicity levels, including a ban on the use of two PFAS compounds. and a restriction on the concentration of another.
Nowadays, the removal of these substances from drinking water is done by relatively simple and inexpensive adsorption techniques. (Adsorption is the adhesion of atoms, ions or molecules of a gas, liquid or dissolved solid to a surface. This process creates a film of adsorbate on the surface of the This process differs from absorption, in which a fluid – the absorbent – is dissolved by or permeates a liquid or solid – the absorbent). These methods are not efficient enough and only transfer pollutants from the water to the adsorbent material – requiring additional purification steps to get rid of adsorbed toxic substances. Moreover, these methods are not selective. They can also eliminate substances essential to a person’s health.
The new research looked at the possibility of combining the two methods – separating pollutants with special polymers and then using advanced oxidation processes to remove them. The results indicate that good planning leads to high efficiency in a wide range of acidity (pH) and salinity.
The method described in the study shows the removal of seven types of PFAS – even when they are all in the same unit of fluid – at a level of efficiency approaching 90%, and that in a matter of minutes.
“Our proposed platform has two advantages,” says Dr. Radian, “First, it acts as a sorbent – removing PFAS
quickly and efficiently from contaminated water at the source. Once the filter has reached capacity, we can easily regenerate it by adding hydrogen peroxide, which breaks down adsorbed contaminants and refreshes the sorbent for continued use.
Another big advantage of the method, says Dr. Radian, is that the adsorbent material is based on clay, iron oxides and cyclodextrins – all non-toxic and durable materials that can be easily removed once they are no longer needed.
Clay-iron-polymer composites act as accelerators that confine the PFAS to the surface and then accelerate the oxidation process that breaks down the pollutants into non-toxic substances (fluoride ions, water and carbon dioxide). This combination effectively removes PFAS and does not release unwanted substances into the water used for drinking.
The researchers show that this system makes it unnecessary to carry out additional processes such as heating, UV radiation and the use of sound waves, which make the task more complicated and more expensive.
Dr. Radian says the platform has been validated with a variety of toxic pollutants, not just PFAS. “We hope to improve the technology over the coming year and test it with real water from contaminated sites in Israel. I am hopeful that this technology will become an applied and sustainable product.
“I believe that basic science and engineering studies, like what is pursued in our department, are the building blocks of technologies that are applicable in the field,” Dr. Radian told NoCamels, “strengthening the links between the industry, government and academia will provide innovative technologies in the field of environmental engineering.