Micropollutants such as steroid hormones contaminate drinking water around the world and pose a significant risk to human health and the environment, even in the smallest amounts. Up until now, there has been a lack of easily scalable water treatment technologies with which they can be removed efficiently and sustainably. Scientists at the Karlsruhe Institute of Technology (KIT) developed a new chemical process for removing hormones. It uses the mechanisms of photocatalysis and converts the pollutants into potentially safe oxidation products. The team reports on this in the journal Applied Catalysis B: Environmental.
Organic pollutants such as pharmaceuticals, pesticides and hormones contaminate drinking water – even in nanoscale concentrations – in a way that poses a significant risk to humans, animals and the environment. In particular, the steroid hormones estrone, estradiol, progesterone and testosterone can cause biological damage in humans and wild animals. The European Union has therefore set strict minimum quality standards for safe and clean drinking water, which must also be taken into account when developing new technologies for water treatment. “The challenge for science is to develop more sensitive methods to target the hormone molecules,” says Professor Andrea Iris Schäfer, head of the Institute for Advanced Membrane Technology (IAMT) at KIT. The main problem is that steroid hormones are very difficult to detect in water. “There is one hormone molecule for every trillion water molecules. This is an extremely low concentration,” explains the expert.
Detect and remove micropollutants
With traditional water treatment technologies, sewage treatment plants cannot find or remove micropollutants. Researchers at the IAMT and at the KIT Institute for Microstructure Technology (IMT) are therefore working on new methods to not only detect and measure micropollutants, but also to remove them. A new photocatalytic process is showing great promise. The scientists coated a commercially available polymer membrane with large pores with Pd (II) porphyrin, a light-sensitive molecule containing palladium that can absorb visible radiation. Irradiation with simulated sunlight triggers a chemical process that creates so-called singlet oxygen, a highly reactive oxygen species. The singlet oxygen specifically “attacks” the hormone molecules and converts them into potentially safe oxidation products. “It is crucial that we coat the surface of each pore with the photosensitizer molecule in order to enlarge the target area,” explains Roman Lyubimenko, scientist at IAMT and IMT.
Significant reduction in estradiol concentration
The chemical decomposition of steroid hormones and the filtration of other micropollutants can be realized in a single module. With this process, it is possible to filter 60 to 600 liters of water per square meter of membrane in one hour. The scientists were able to reduce the concentration of estradiol, the most biologically active steroid hormone, by 98 percent from 100 to 2 nanograms per liter. “We are already very close to the EU target of one nanogram per liter,” emphasizes Schäfer. The next goal of the research team is to further optimize the photocatalytic process and transfer it to a larger scale. The open questions are to find out how much light intensity and how much porphyrin is required and whether the expensive palladium from the platinum group of metals can be replaced by other metals.
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Materials provided by Karlsruhe Institute of Technology (KIT). Note: The content can be edited by style and length.
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