Micropollutants

The increasing contamination of water with contaminating substances will be one of the most urgent environmental problems in the coming decades. Such substances can be detected in low but increasing concentrations in surface water, groundwater, drinking water and in wastewater. Because of their low concentrations, typically in the range of µg L^-1 to ng L^-1, these substances are referred to as micropollutants. They also show toxic or otherwise negative effects at concentrations in the ppt or ppb range.

For their separation, we are developing so-called membrane adsorbers at the IGB, which allow filtration and adsorption to be combined in a single process. This concept has so far been used mainly in downstream processing in biotechnology to separate low concentrations of small molecules using microfiltration – especially when one can only work at low pressure. At Fraunhofer IGB, we are working on transferring this concept for the treatment of water.

Tailored membrane adsorbers by embedding sub-micrometer particles with specific binding sites

To this end, we are developing sub-micrometer particles with special binding sites for various substances. By embedding such particles in the membrane, customized membrane adsorbers can be produced. The particles can be produced e.g. by mini emulsion polymerization. Subsequently, we disperse the particles in a polymer solution, from which a porous membrane is then precipitated via a phase inversion process.

Combined membrane adsorbers with high retention rate

Membrane adsorbers are now available that can be used to separate different micropollutants such as diclofenac, sulfamethoxazole, metoprolol and carbamazepine together.

For diclofenac, we have achieved adsorption capacities of up to 9.8 g m^-2, retaining more than 99% of the diclofenac before breakthrough.

In addition, we have developed particles with ion exchange capabilities, thiourea groups and chelate groups for the separation of metal ions. With such membrane adsorbers, valuable metals such as silver, copper or rare earths can be recovered from water.

• Studies on the separation of micropollutants or metals with available membrane adsorbers
• Design of customized membrane absorbers according to customer specifications
• Feasibility studies for the separation of desired substances

1. Niedergall, K., Kopp, D., Besch, S., & Schiestel, T. (2016). Mixed-Matrix Membrane Adsorbers for the Selective Binding of Metal Ions from Diluted Solutions. Chemie Ingenieur Technik, 88(4), 437-446. https://doi.org/10.1002/cite.201400144.
2. Niedergall, K., Bach, M., Hirth, T., Tovar, G. E. M., & Schiestel, T. (2014). Removal of micropollutants from water by nanocomposite membrane adsorbers. Separation and Purification Technology, 131, 60-68. https://doi.org/10.1016/j.seppur.2014.04.032.
3. Sarah Uebele, Tobias Goetz, Mathias Ulbricht, Thomas Schiestel, Mixed-Matrix Membrane Adsorbers for the Simultaneous Removal of Different Pharmaceutical Micropollutants from Water (2022) https://doi.org/10.1021/acsapm.1c01546