In acidic conditions, copper extractant (hydroxyl oxime) will be nitrated by nitrate, become to the corresponding nitro aldoxime or nitro ketoxime. The extraction ability of nitrated extraction reagent is very strong, but the back extraction ability is very weak, even use 200 g/L sulfuric acid, it is difficult to take down the loaded copper ion.
In normal back extraction system of electrolyte, nitrated extraction reagent cannot be regenerated, so the extraction ability has been lost absolutely. Nitrate not only make nitration with the extracting reagent, but also can oxidize extraction reagent, accelerate the degradation of extracting reagent. In the condition of higher acidity, the oxidative damage effect of NO3- is very strong for extraction reagent, some extraction reagent will be oxidized degradation before it is nitrated.