Research projects
Research area A: Adsorber materials
Research area A focuses on the synthesis of new materials for the recovery of phosphates from wastewater down to a low residual concentration (< 0.5 mg/L, preferably < 0.1 mg/L). To this end, various materials with high ion affinity are being developed, produced and tested for their selective binding of phosphates. These are adsorber materials based on microporous zeolites and organometallic framework compounds (project A3), mesoporous silica gels (project A1) and macroporous neutral polymers or ion exchangers (project A2). In addition to high selectivity and absorption capacity, these materials should also allow efficient reversible adsorption and desorption. Novel materials are being synthesized in all three projects. In addition, the physical relationships between their adsorption and desorption properties and the microstructure and surface properties of the materials produced are being investigated.
Supervisor: Prof. Werner R. Thiel
PhD: Marco Wagen
Separation of solutes by ion exchange is an important step in the extraction of valuable substances from aqueous media. At the Thiel group, specifically functionalized mesoporous silica gels have been synthesized and characterized for many years. Until now, the application of such materials has been limited mainly to catalysis.
In this project, mesoporous silica gels for the separation of phosphate from wastewater are now to be synthesized, characterized and tested for their efficiency. For this purpose, the pore surface of these materials shall be functionalized with phosphate-selective groups that are covalently, i.e. irreversibly, bound to the surface.
Supervisor: Prof. Wolfgang Kleist
PhD: Sven Schaefer
In this project, microporous adsorbents based on zeolites, zeolitic imidazolate frameworks (ZIFs) and metal-organic frameworks (MOFs) will be developed. Zeolites with different topologies will be synthesized in order to investigate the influence of pore geometries (cages vs. channels) and pore diameters on the adsorption of phosphates. The surfaces of the zeolite structures will be specifically modified to enable or improve the adsorption of negatively charged phosphate species.
Furthermore, multivalent cations such as La3+ or Ca2+ will be introduced into the pore structures by cation exchange in order to improve the interaction with phosphates. In addition to the above-mentioned cations, other main and transition metal cations will also be used to elucidate which metals are best suited for this application.
In addition to zeolites, structurally related microporous systems will also be investigated in this project. For this purpose, ZIFs or MOFs will be modified with cationic functionalities by means of post-synthetic modification reactions. All synthesized materials will be thoroughly characterized with regard to their crystalline structure and surface properties in order to investigate correlations with the absorption capacity.
Supervisor: Prof. Stefan Kubik
PhD: Katerina Moschidi
This project aims to develop polymeric adsorber materials based on molecularly imprinted polymers that selectively remove phosphate from wastewater and allow the release of the bound phosphate in a subsequent step for recovery. The polymers will be synthesized from functionalized monomers designed to interact with phosphate anions, appropriate crosslinkers, a template to create cavities in the polymer matrix for phosphate incorporation, and a porogen to ensure mass transport in the final materials. The type of monomers, their ratio and the polymerization conditions will be systematically varied to optimize the performance of the products. The obtained materials will be characterized in terms of composition and morphology. In addition, batch and flow experiments will be performed to quantify the phosphate adsorption capacity and to identify suitable conditions for phosphate adsorption and desorption, as well as for polymer recycling. Finally, the materials will be tested in a pilot wastewater treatment plant to evaluate the feasibility of the developed process.