New chemical interaction utilizes photocatalytic layer to eliminate steroid hormones

Overview

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• Source: Karlsruher Institut für Technologie (KIT)


• Date: 22 May,2021

Micropollutants like steroid hormones contaminate drinking water worldwide and pose a substantial threat to human health and the environment even in smallest quantities. Until today, readily scalable water treatment technologies that remove them economically and sustainably have been lacking.

It takes advantage of the mechanisms of photocatalysis and transforms the pollutants into possibly safe oxidation products. The group reports on this in the scientific journal Applied Catalysis B: Environmental.

Specifically, the steroid hormones estrone, estradiol, progesterone, and testosterone may cause biological damage in wildlife and humans.

The European Union has therefore set strict minimum quality criteria for clean and safe drinking water, which should also be taken into account in the creation of new technologies for water treatment. The main problem is that steroid hormones are extremely hard to detect in water. “There is one hormone receptor for every quintillion water molecules. This is an extremely low concentration,” explains the specialist.

Detecting – and removing – micropollutants
With conventional water treatment technologies, wastewater treatment plants can neither find nor eliminate micropollutants. Researchers in the IAMT and the KIT Institute of Microstructure Technology (IMT) are therefore working on new methods to not only detect and measure micropollutants, but also remove them. A new, photocatalytic process turns out to be promising.

The scientists coated a commercially available large-pore polymer membrane with Pd(II)-porphyrin, a palladium-containing, light-sensitive molecule which can absorb visible radiation. Exposure to radiation with simulated sunlight initiates a chemical process that produces so-called singlet oxygen, an extremely reactive oxygen species.

The singlet oxygen especially”strikes” 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, increasing the surface area of attack.”

Roman Lyubimenko, Scientist, Advanced Membrane Technologyand KIT Institute of Microstructure Technology

Significant reduction of the estradiol concentration
The chemical decomposition of steroid hormones and the filtration of different micropollutants can be accomplished in a single module. With this procedure, filtering of 60 to 600 liters of water per square meter of membrane is possible 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.

“This means that we’re already very close to the EU target value of one nanogram per liter,” emphasizes Schäfer. The next aim of this research team is to further optimize the photocatalytic process and transfer it to a larger scale. Open issues are to find out how much light intensity and how much porphyrin is going to be needed and whether the costly palladium in the platinum group of metals could be replaced by other compounds. (sur)