Micropollutants

Challenge: contamination of water with 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.

Solution: separation of micropollutants with membrane adsorbers

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.

SEM image of porous adsorber particles
© Fraunhofer IGB
SEM image of porous adsorber particles
SEM image of a mixed matrix membrane adsorber.
© Fraunhofer IGB
SEM image of a mixed matrix membrane adsorber.
Breakthrough curves of membrane adsorbers filled with different particles for diclofenac.
© Fraunhofer IGB
Breakthrough curves of membrane adsorbers filled with different particles for diclofenac

Recovery of metal ions with membrane adsorbers

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.

Services

  • 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

Publications

  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

Reference projects

Duration: March 2017 – February 2020

POLINOM – polyvalent separations by flexible integration of active surfaces in membranes

 

In this project, new coating materials and particulate additives for filtration membranes are developed with the aim to generate membranes which – in addition to their filtration function – can adsorptively bind dissolved substances in water.

 

Duration: July 2011 - October 2014

Molecular Sorting – recovery of metals

 

The recycling of special metals is of high importance due to their value (precious metals), their availability (rare earths) or their toxicity (heavy metals), both for industrial production and for the environment. Process and wastewater streams, e.g. from leaching baths in the electroplating industry, or even landfill leachates can contain significant amounts of dissolved metals. To close material cycles, there is a great need for technologies that can be integrated in order to recover various metals efficiently.

 

 

Mixed-matrix membranes for wastewater treatment

 

Fraunhofer IGB has investigated the development of mixed-matrix membranes with optimized separation efficiencies suitable for use in a membrane bioreactor for the downstream treatment of decentrally treated wastewater. By integrating such a downstream membrane process, aerobically stabilized sludge could be dried and hygienized on site so that it can be reused for agricultural purposes.