I have decided to use the probe sonication for making a homogeneous MPD solution and g-c3n4 as the nanopaticle to coat for TFN. But whenever I use the Probe sonication, once I start the process, a milky foam is created on the top of the solution. Although, the foam is reduced after a time but never disapear. Is it normal or is there any same experience for anyone for trying to remove the foam?

Thank you.