9.4 Selective nitrate/chloride separation from process water

Selective separation of nitrate from water is highly relevant for many applications. Nitrate levels in drinking water should be kept low to minimize the risk of nitrite formation in bottle-fed infants. Nitrate needs to be removed from brines from production or regeneration processes in order to enable the discharge or recycling of the brine. Contrary, in agricultural applications, the aim is to keep the nitrate in the water but to remove chloride, e.g. in recirculating water used in closed horticulture systems. Also in the production process of fertilizers, chloride needs to be removed from a rather nitrate-rich aqueous stream. Currently used electrochemical and biological methods deal either with safety or high capital expenses and hence alternative approaches have to be considered.

Research challenge

In this project it is first aimed to develop advanced materials that can be used in membrane and/or adsorption technologies to obtain nitrate/chloride selectivity. The main challenge in nitrate/chloride selectivity is related to the small differences between the two equally charged nitrate and chloride ions in terms of their size and dehydration energy. This requires the incorporation of subtle differences in the chemical structures of the new materials to tune their interaction with nitrate and chloride ions.

The second aim of the project is the implementation of the selected configuration(s) into a process for the removal of the respective ions out of aqueous salt solutions. When applied in a membrane, the selectivity should go along with a high permeation. This combination is not trivial as in general selectivity (implying interaction) slows down transport through the membrane. In the case of adsorption technologies the main challenge, next to achieving selectivity, is related to the regeneration of the adsorption materials. Ideally, this requires no chemicals and the energy consumption is low.


The ideal MSc candidate has solid knowledge and skills in both (synthetic) chemistry and chemical engineering. A strong interest (or preferentially experience) in polymer chemistry is essential. A deep understanding of physical and chemical properties is a must to be able to design, make and apply the new materials.


The research project is part of the Wetsus research theme Desalination/Salt. The following companies are part of the theme: Friesland Campina, Esco Salt, Shell, Vitens, DMT, Yara, Van der Knaap, Water Future

Intended promotors: Dr. ir. Louis de Smet and Prof. Dr. Han Zuilhof (Wageningen University)

For more information contact Dr. Henk Miedema () or Dr. ir. Louis de Smet ().

9th call is closed. You can no longer apply.

Wetsus, Leeuwarden, The Netherlands

combining scientific excellence with commercial relevance