Aluminum Concentrate Prepared by Activated Roasting-Secondary Alkaline Leaching Desilication of Pyrite Tailings

This is an essay in the field of metallurgical engineering. Content of alumina in pyrite tailings in the southwest China is higher than 46%, and the alumina is of high recycling value. However, SiO₂ with high content and stable crystal structure exists in aluminosilicate minerals in tailings, resulting in a low aluminosilicate ratio of Al₂O₃/SiO₂ (A/S) of tailings, which is only 1.72. To realize the separation of aluminum and silicon, and obtain aluminum concentrate for recycling of the tailings, the SiO₂ with stable structure is transformed into amorphous SiO₂ by activated roasting. And then the calcine is leached twice with NaOH solution for desilicating to obtain the aluminum concentrate. The results show that under the optimum conditions of roasting time of 35 min, roasting temperature of 1140 ℃, the concentration of NaOH 140 g/L in primary alkaline leaching, leaching temperature of 110 ℃, leaching time of 30 min, the ratio of liquid to solid 16, the aluminum-silicon ratio (A/S) increases to 4.11. Under the optimum conditions of NaOH concentration 140 g/L in secondary alkaline leaching, leaching temperature 105 ℃, leaching time 30 min, and leaching liquid to solid ratio 10, the aluminum-silicon ratio (A/S) of 5.11 is obtained, which lays a good foundation for comprehensive utilization of the tailings.