Why is zinc not extracted from zinc oxide through reduction using CO?

Explanation

`DeltaG^(@)` for the conversion of Zn into ZnO is approx. -650 kJ and for the conversion of CO into `CO_(2)` is approx. -450 kJ, i.e,
`2Zn+O_(2) to 2ZnO, DeltaG^(@)= -650 kJ`
`2CO +O_(2) to 2CO_(2) , DeltaG^(@)= -450 kJ`
For the reaction,
`2ZnO + 2CO to 2Zn + 2CO_(2), DeltaG^(@) =+200 kJ`
Positive value of `DeltaG^(@)` shows that the reaction is not feasible. That.s why, CO cannot be used for the reduction of ZnO into Zn.