New research in the Netherlands points to a more effective way of removing nitrates from drinking water through the use of a catalyst.
Nitrate concentrations in groundwater become elevated as a result of human activities, such as excessive use of fertilizers. Regulations can help tackle the problem at source, reducing the contamination, but it is still necessary to treat the mains water supply.
One option is biological conversion, with bacteria converting the nitrate to nitrogen gas, but this is a slow process. A faster method uses palladium to catalyze the conversion of nitrate to nitrogen, but this reaction produces ammonia, a harmful by-product.
Yingnan Zhao of the University of Twente's MESA+ Institute for Nanotechnology studied the process and found that this drawback can be eliminated by using palladium nanoparticles as a catalyst and by carefully controlling their size.
The amount of ammonia produced appears to depend on the method used to prepare the palladium and on the catalyst's physical structure, the University of Twente reported.
Zhao used nanometer-sized colloidal palladium particles, as their dimensions can be easily controlled. These particles are fixed to a surface, so they do not end up in the water supply, and stabilizers such as polyvinyl alcohol are added to stop them clumping together. These stabilizers tend to shield the surface of the palladium particles, which reduces their effectiveness as a catalyst. However, by introducing additional treatments, Zhao managed to fully expose the catalytic surface once again or to manipulate it in a controlled manner.
This resulted in palladium nanoparticles that can catalyze the conversion to nitrogen, while producing very little ammonia.
Zhao's research brings the further development of catalytic water treatment — for example, in compact devices for home use — one step closer, the university said.