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Proof-of-concept for innovative phosphate recovery
In 2022, the MAD (Magnetic Adsorption Desorption) project started, an ambitious study to filter phosphate directly from water, without creating additional waste flows and with minimal addition of chemicals. Now, after two years, we can answer the question: does it really work? Researchers Norbert Kuipers and Ronald Vroon have an answer: technically yes, but commercially it’s not a done deal. Yet.
What was the research about again? WUR sees magnetic seperation as an effective method for filtering phosphate from wastewater. Magnetic filtering is not only more environmentally friendly, but also offers opportunities to reuse the phosphate. The filter is done by adding magnetite particles to the wastewater. Phosphate ions bind to the magnetite and a magnet then removes these particles, including phosphate, from the water. Magnetite and phosphate can then be separated again for reuse of the magnetite and recovery of the phosphate.
Insights along the way
At the end of the project and after testing, the practice turns out to be slightly more complex than expected. “The magnetite we initially had in mind did not bind enough phosphate,” Kuipers explains. “We needed a lot to remove a certain amount of phosphate from the water, which made it unfeasible from a economic point of view.”
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Yet the researchers are far from disappointed. Kuipers: “This is what research is about, gaining insight. And fortunately we have found a good solution in a different type of magnetite. In our research we were able to use the results of a study in which the functionality of this other type of magnetite was described.”
“The great thing is that we now have a proof-of-concept,” adds Vroon. “Although the previous magnetite was not ideal, with the developed and validated model for three companies and their wastewater, we can make relevant predictions for the implementation of this process. We can then validate this experimentally with the new magnetite.”
Follow-up research
So that is exactly what the researchers would like to do in the future: investigate how the improved magnetite performs. Vroon: “We know that it can adsorb more phosphate, but we do not yet know how stable it is. Can we use it for about 30 to 50 cycles? And do all parts of the process work well enough? I mean, we add magnetite to the water and for a profitable process, this must not be achieved by 99%, but by 99.9% or more. Otherwise we lose too much magnetite, which ends up in the wastewater and has to be replenished again and again.”
In short, there is still plenty to investigate in the future. Because not only the sustainable filtering of phosphate is important, but also the reuse of the substance. The researchers are excited for future experiments. Vroon: “This could be the start of a valuable innovation for processing manure with phosphate.”