@anon42519203 They (Whatman, et al) make even simple gravity filter papers that are hydrophylic and hydrophobic, based on whatever filtering you need to do. It is a brilliant idea, honestly, but you can easily make your own, even by accident, using other media, too… if you pour water over a cotton ball in your funnel, then pour the entire volume of a water w/ supernatant non-polar partition over it, all the water and stuff it’s carrying will flow through the cotton ball and the non-polar (such as hexane, toluene, and all its stuff) will stop right on top of the cotton ball as if it were a solid plug! @Beaker I love the fact that you are using grit as your alumina source! Check out sandblasting materials at Harbor Freight for bulk. But if you want pure laboratory grade white alumina, you might want to try Jaxon’s stuff: Activated Alumina, Activated Alumina filters adsorb acids and other products of oxidation from hydrocarbon and synthetic oils. Filtration Media Jaxon 
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