You might try gravity separation where the material is fed through a wide pipe or wide tube of some sort. Placing a small adjustable air jet, or fan that is adjustable right above a split in the tube where the tube goes from one to two tubes will push the lighter material to one part of the split and go down a different tube from the heavier material which will continue down the other side of the why. It's called forced air separation and is used to very good effect in industry.

I made something like this a few years back for a client, but not one since. If I can find the pictures I'll post them. It will allow for dry separation, and works very well so long as you adjust the air pressure of the air input so as not to blow the heavy material into the lighter material. The key is to get it well separated as it is poured into the tube, and this can easily be done by simply applying a strong fan at the top.

Here is an example of the same concept, a little different. I'm sure if you researched and watched a few videos on the subject you could come up with a solution that better matches the type of separation you are looking for. I feel air separation would better fit your intended purpose and keep water out of your material that could be another problem all together.





Scott