I have a mixture of HNO3 (aq), H2C2O4 (aq) (oxalic acid) and H2O. Is there anyway to remove oxalic acid from the other two components to produce two products oxalic acid (S) and HNO3/H2O mixture?

You already have oxalic acid. Cannot separate acid form as oxalic acid is very soluble in water. You could possibly try to convert the oxalate into a precipitate but that may well remove the nitrate too. Converting into Nitrate salts won't work since they are all very water soluble. Calcium oxalate is insoluble, work on that end.