A new method of full resource utilization of copper slag

Copper slags can hardly be utilized because the fayalite in it produces silica gel during the dissolution process. This work proposes a new process on sulfuric acid treatment of copper slag (Jinchuan Group, Gansu Province, China.). The results show that over 98% of recovery efficiency of Cu 2+ , Co 2+ , Ni 2+ and Zn 2+ was achieved through the whole process cycle. Ammonia was used to control the pH of the solution in order to completely precipitate Fe 2+ , and then produce hematite powder. More than 85% of the non-ferrous metal ions were left in the solution, and the utilization method of stepwise extraction was evaluated. The generation of silica gel during the acid digestion of copper slag was not restricted, and the silica gel in the acid-leach residue was subsequently dissolved with NaOH solution to obtain sodium metasilicate solution. Acidification and other steps were carried out to produce high-purity silica with a purity of 99.9%. Magnetite and pyroxene were obtained by using a simple magnetic separation process to segregate the remaining slag phase. The whole process achieves the full resource utilization of copper slag, and exhibits great potential for the future industrial utilization of copper slag in an economically and environmentally friendly way. • Copper slag has achieved full resource utilization. • The silicon and iron in the copper slag is well-utilized. • The “circulation” leads to an increase of the recovery rate of metal ions.