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Sample Problem #5: An ore containing 10 percent CuSO4, 85 percent insoluble gangue, and 5 percent moisture will be extracted with water. The final underflow sludge will contain only 0.15 percent CuSO4. The underflow sludge retains 0.8 lb of solution per pound of gangue. Calculate the percent extraction if two countercurrent equilibrium stages are used to process 1000 lb/hr of ore with 4000 lb/hr of water.

Solution: % extraction = ? V1 SLE1 L0 1000 lb/hr 10% CuSO4 85% gangue 5% H20

Modified Prob5.10 Foust

4000 lb H20 V3 SLE2 L2 0.8 lb soln lb gangue 0.15% CuSO4

Solution (contd): • in L2: solution retained

= 0.8( 0.85 )( 1000 ) = 680 lb/hr

• L2: (1-0015)L2 = H2O + gangue ( 1− 0.0015)L 2

= ( 680− 0.0015L 2 ) + 0.85( 1000)

∴ L2 = 1530 lb/hr • total balance: V1 - L0 = V3 – L2 V1 - 1000 = 4000 – 1530 = 3470 lb/hr • CuSO4 balance:

y1A V1 − x 0AL 0 = y 3A V3 − x 3AL 3 y1A ( 3470) − 0.10( 1000) = 0( 4000) − 0.0015( 1530) y1A

V1 = 97.7 lb/hr

Modified Prob5.10 Foust

Solution (contd): • % extraction: =

y1A V1 0

x A L0

( 100) =

97.7 ( 100) = 97.7% 0.10( 1000)

Modified Prob5.10 Foust