Purifying drinking water

25 May 2021 | Muriel Cozier

‘The challenge for science is to develop more sensitive methods to target hormone molecules.’

Researchers from Karlsruhe Institute of Technology (KIT), Karlsruhe, Germany, have developed a chemical process for removing micro-pollutants, such as steroid hormones, from drinking water. The process uses the mechanisms of photocatalysis and transforms the pollutants into potentially harmless products.

The researchers say that with conventional water treatment technologies, wastewater treatment plants can neither find nor remove micro-pollutants, which contaminate drinking water worldwide and pose a significant threat to human health. Publishing their work in Applied Catalysis B: Environmental, the researchers said that their process was able to reduce the concentration of estradiol, the most biologically active steroid hormone, from 100 to 2 nanograms per litre.

The new photocatalysis process is based on a commercially available large-pore polymer membrane which is coated with Pd(II)-porphyrin, a palladium-containing, light-sensitive molecule that can absorb visible radiation. Exposure to radiation with simulated sunlight leads to the production of a ‘singlet oxygen,’ a highly reactive oxygen species. This singlet oxygen specifically targets the hormone molecules converting them into potentially safe oxidation products. The process is said to make it possible to filter 60 to 600 litres of water per square meter of membrane in one hour.

The European Union has set strict minimum quality standards for safe and clean drinking water, which must be taken into account in the development of new technologies for water treatment. ‘The challenge for science is to develop more sensitive methods to target hormone molecules,’ said Professor Andrea Iris Schäfer, Head of the Institute for Advanced Membrane Technology at KIT. ‘The main problem is that steroid hormones are very hard to detect in water, there is one hormone molecule for every quintillion water molecules. This is an extremely low concentration,’ Schäfer added.

The next goal the researchers say; is to ‘further optimise the photocatalytic process and transfer it to a larger scale, as well as determining issues such whether costly palladium can be replaced by other metals.

DOI: 10.1016/j.apcatb.2021.120097

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