About 20% of the cobalt is still not recovered in one section of the cobalt precipitation process, and this process uses lime neutralization and precipitation to recover the cobalt in the liquid after one section of cobalt precipitation:
At the same time, under the alkaline environment, part of magnesium sulfate will react with lime to form magnesium hydroxide.
The operating conditions are: under the condition of 60℃ and constant stirring, a slurry of cooked lime (slurry concentration ~20%) is continuously added to the second stage cobalt precipitation reaction tank. In order to ensure the complete precipitation of cobalt recovery, the solution endpoint pH should be controlled at about 8.
The cobalt slurry produced after the second-stage cobalt precipitation is filtered, mixed with the extracted residue to adjust the slurry and sent to the iron removal process to re-enter the process.
The typical composition of the second stage cobalt precipitation solution and the second stage cobalt slag are shown in Table 5 and Table 6, respectively.
The second stage cobalt precipitation liquid mainly contains magnesium, manganese and other metal ions, and direct discharge will cause water pollution, so magnesium precipitation treatment is required. This process uses lime to adjust the pH of the solution so that magnesium and manganese ions can be removed by precipitation.
Its operating conditions are: at 60℃, under the condition of constant stirring, add the slurry of cooked lime (slurry concentration ~20%) to the magnesium sink reaction tank. To ensure that the magnesium, manganese ions precipitation completely, the solution end pH should be controlled above 11.
Table 7 shows the main technical indicators obtained in May 2014 according to the trial production of this process.