Extraction of uranyl nitrate.

A 20 wt% solution of uranyl nitrate (UN) in water is to be treated with tributyl phosphate (TBP) to remove 90% of the uranyl nitrate in batchwise equilibrium contacts. Assuming water and TBP are mutually insoluble, how much TBP is required for 100 g of solution if, at equilibrium, (g UN/g TBP) = 5.5(g UN/g H2O)

(d) an infinite number of crosscurrent stages is used.

Make balances of matter and procedure of the result, please.