Success stories

Recycling of nitrates from mixed acid pickling by electrodialysis

Nitrate emissions to water cause problems for two reasons. Nitrates contribute to eutrophication and they are harmful to humans in larger concentrations. The mixed acid pickling process will in a foreseeable future be difficult to replace by nitrate free pickling. Today´s treatment systems for nitric acid containing wastewater are not working sufficiently as it regards nitrate separation.

Therefore a system for nitric acid recycling with electrodialysis (ED) has been developed and tested on site in pilot-scale experiments by Avesta-Sheffield (now: AvestaPolarit) and the Swedish Environmental Research Institute (IVL). The goal was the reduction of nitrate discharges and the possibility to gain nitric acid that can be used in the pickling process. The pilot experiments showed that it is possible to separate more than 85 per cent of the nitrates by ED-treatment while getting a nitric acid with sufficient concentration to be used in the pickling process.

The project is now continued based on the results of the pilot-scale experiments. A full-scale demonstration plant will be integrated into the existing system and optimised. Results of the project will be disseminated.

For more information please contact: uwe.fortkamp@ivl.se