In the refining process of copper, cobalt and nickel ore in the Democratic Republic of the Congo, a two-stage leaching process is often used. Hebei Messi Biology Co., Ltd. stated that the purpose of adopting two-stage leaching is to achieve a higher leaching rate of copper, nickel and cobalt in the ore, especially the indispensable role of magnesium oxide.
Two-stage cobalt precipitation: First stage cobalt precipitation, add 5% to 15% magnesium oxide to the cobalt-containing solution 3, control the pH value to 7.90 to 8.15, and precipitate the cobalt for 240 to 300 minutes. After the reaction, the solid-liquid separation is completed to obtain cobalt hydroxide product and cobalt precipitation liquid 1; Second stage cobalt precipitation: add lime milk to the cobalt precipitation liquid 1, control the pH value to 8.40 to 8.60, continue the cobalt precipitation reaction for 60 to 120 minutes, and after the reaction, the solid-liquid separation is completed to obtain the second stage cobalt precipitation slag and cobalt precipitation liquid 2. The cobalt precipitation liquid 2 is discharged after the treatment meets the standard; the oxidant used for manganese removal is oxidant a plus oxidant b, prepared in a molar ratio of oxidant a: oxidant b = 1:1 to 3. The oxidant a is composed of two elements, hydrogen and oxygen.
The oxidant b is composed of three elements, hydrogen, oxygen and sulfur. The magnesium oxide used for the two-stage cobalt precipitation should be intermittently milked to increase the activity, milking once every 15 to 25 minutes, and each milking time is 3 to 5 minutes. The reducing agent used for leaching in step (1) is any one of sodium sulfite, sodium pyrosulfite, sulfur dioxide, and sulfide. The leached slag leached in step (1) and the supernatant of the manganese removal slag storage slurry reservoir in step (3) are returned to step (1) for leaching, which can reduce the amount of concentrated sulfuric acid and reducing agent. The low-grade cobalt ore contains 0.2 to 0.5% cobalt, less than 0.5% copper, and 5 to 20% alkaline gangue.