Extracting iron oxide from ceramics waste
Assuming the iron oxide is just mixed and has not been fused with the other oxides you could use a magnet to pull it from the other oxides.

If it is fused with the other oxides, you could smelt the iron out with carbon. This will also smelt out the tin, which mixes with iron quite well. If you re-oxidized the iron in a furnace with air the iron will selectively oxidize first leaving tin metal when done. This is likely an impractical and cost-inefficient procedure as iron oxide is incredibly cheap relative to the cost of separation.