Selective leaching of arsenic and valuable metals in copper smelting soot strengthened by ball milling pretreatment

The high-efficiency separation of arsenic and valuable metals in copper smelting soot strengthened by the ball milling pretreatment were investigated. The results show that the ball milling pretreatment alone can inhibit the leaching of As in soot. Compared with the unmilled soot, the leaching efficiency is reduced from 56.01% to 32.85%. However, the addition of NaOH can significantly increase the As leaching efficiency from 56.01% to 78.52%. The optimal process parameters are as follows: the mass ratio of NaOH to ash (mNaOH:mAsh) of 0.5:1, activation time of ball mill of 60 min (after ball milling pretreatment for (50±5) min in alkaline medium, and then milling with ethanol in sequence), the rotation speed of 600 r/min. Besides, Cu, Zn, Pb and Cd in the soot is basically not leached after treatment by this method, and the As content in the leaching residual solid is reduced from 5.74% to 0.13%. The SEM and particle size analysis show that ball milling can create defects on the surface of the particles, reduce the particle size of the soot, increase the specific surface area of the reaction and promote the mass transfer of the interface. Therefore, the leaching efficiency of As is dramatically enhanced. The results of XRD and XPS show that high temperature and high pressure are generated in the specific area during the ball milling process, inducing the solid-solid reaction: the oxidation state of As2O3 after reacting with NaOH converges into soluble arsenate, finally. And decomposition of parts of PbSO4 into PbO in a local high temperature environment, which further enhances the efficient separation of As and valuable metals during the leaching process. This study provides a theoretical basis for the harmlessness, and the resource utilization of arsenic-containing materials is produced by copper smelting industry. © 2020, Science Press. All right reserved.