Recovery of polymetallic elements from cyanide tailings via reduction smelting
(School of Minerals Processing and Bioengineering, Central South University, Changsha 410083, China)
Abstract: A process for treating cyanide tailings was proposed. The process essentially implicates reduction smelting which involves volatilizing silver, lead, and zinc in the cyanide tailings at high temperatures. Meanwhile, gold and copper combine with the reduced iron to form a metal phase, allowing for the simultaneous recovery of polymetallic elements. The experimental results indicate that the process works optimally with a coke powder of 7.5 wt.%, an alkalinity of 1.0, a melting temperature of 1450 °C, and a melting time of 60 min. Under these conditions, more than 99% of gold, 77% of copper and 94% of iron are incorporated into pig iron. In the meantime, the volatilization rate of silver exceeds 90%, while lead and zinc are essentially completely volatilized. The primary component of the by-product smelting slag is akermanite, which exhibits lower leaching toxicity than the national standard and belongs to general solid waste. Additionally, taking the trapping process of iron to copper as a case study, the mechanism of iron trapping is methodically examined and divided into three processes: smelting reduction, migration capture, and condensation deposition.
Key words: cyanide tailings; gold tailings; reduction smelting; valuable element recovery