Membrane adsorber

If filtration and adsorption are combined in one unit, a so called membrane adsorber results. This concept was introduced mainly for downstream processing in biotechnology to separate low concentrations of small molecules by microfiltration, where only small pressure must be applied Our aim is to transfer this concept for the treatment of water to separate low concentrations of micropollutants and to close material cycles within production processes and for recycling.

Mixed-matrix membranes adsorber

Mixed-matrix-Membranadsorber.
© Fraunhofer IGB
Mixed-matrix-Membranadsorber.

Our concept is the development of nanoparticles with specific binding sites for different substances. Tailor-made membrane adsorbers can be designed by embedding such particles in membranes. We prepare such particles by miniemulsion polymerization, disperse the particles in the membrane polymer precursor solutions and the particles are embedded in the porous structure of the membrane during phase inversion process.

Enrichment of valuable elements

Binding of silver ions at different membrane adsorbers.
© Fraunhofer IGB
Binding of silver ions at different membrane adsorbers.

For the separation of metal ions we developed particles with ion exchange capabilities, Sulphur containing thiourea groups and chelating groups. With such membrane adsorbers valuable metals such as silver, copper or rare earth can be separated. These developments are a part of the Fraunhofer project »Molecular Sorting«.

Separation of micropollutants

Binding of Bisphenol A and Penicilin G at different membrane adsorbers.
© Fraunhofer IGB
Binding of Bisphenol A and Penicilin G at different membrane adsorbers.

The increasing contamination of water with substances from industrial and natural sources is expected to become one of the key environmental problems in the coming decades. Such compounds are present in surface water, groundwater, drinking water and waste water at low but increasing concentrations. Due to their low level of concentration, which is typically in the lower lg L-1 to the ng L-1 range, these substances are called micropollutants. They show considerable toxic or otherwise negative effects even at concentrations in the ppt or ppb level.

Adsorption experiments with Bisphenol showed that particle-loaded membranes have a higher adsorption capacity in comparison to the blank membranes. In addition, it was demonstrated that the membranes are completely regenerated by a pH shift and therefore can be used multiple times. The prepared membranes show a flux rate as microfiltration membranes and have the capability to selectively adsorb substances with different physico-chemical properties like bisphenol A and penicillin G (potassium salt) in one step. This concept allows the creation of membrane adsorbers with improved or completely new selectivities by embedding various kinds of polymer nanospheres with different chemical affinities into certain substance classes in one membrane.

This concept will be further advanced and will be combined with an additional coating of the porous structure of the membrane to come to an improved flexibility and an increased selectivity. This will be done in the project POLINOM funded by BMBF.

Publications

  • Niedergall, K., et al. (2016). »Mixed-Matrix Membrane Adsorbers for the Selective Binding of Metal Ions from Diluted Solutions.« Chemie- Ingenieur-Technik 88(4): 437-446.
  • Niedergall, K., et al. (2014). »Removal of micropollutants from water by nanocomposite membrane adsorbers.« Separation and Purification Technology 131: 60-68.
  • Niedergall, K., et al. (2013). »Nanostructured Composite Adsorber Membranes for the Reduction of Trace Substances in Water: The Example of Bisphenol A.« Industrial & Engineering Chemistry Research 52(39): 14011-14018.

Reference projects

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.

 

Project duration: March 2017 – February 2020

Membranes for wastewater treatment

 

In this system, aerobic stabilized sludge is generated which can be dried and sanitized on-site and can be used for agricultural purposes. Significant boundary conditions concerning these systems are low costs, ease of use, sustainability, and low maintenance.