Method for reducing COD (Chemical Oxygen Demand) of P507 raffinate in nickel-cobalt hydrometallurgy process through reverse extraction

The invention provides a method for reducing COD (Chemical Oxygen Demand) of P507 raffinate in a nickel-cobalt hydrometallurgy process through reverse extraction. The method comprises the following steps: 1, preparing an acidified organic phase; 2, carrying out reverse extraction on the P507 raffinate and the acidified organic phase in an extraction tank according to a certain phase ratio; and 3, the P507 subjected to reverse extraction enters a subsequent wastewater treatment process, an organic phase is recycled, and the process is opened to a nickel-cobalt wet smelting extraction process after the organic phase is recycled for enough times. Through the treatment of the steps, the COD of the P507 raffinate is reduced by more than 500mg/L. Wherein the acidified organic phase is selected from one of kerosene, kerosene + P204 and kerosene + P507; the P507 raffinate is selected from one or a mixed solution of a nickel extraction separation line P507 raffinate and a cobalt extraction separation line P507 raffina