Cyanide detoxification and iron mineral recycle of cyanide tailings by the sustainable utilization technology of oxidation-reduction roasting: Process optimization and mechanism study

Abstract

The novel cyanide detoxification and resource utilization of cyanide tailings were treated sequentially by the oxidation-reduction roasting. Through a series of conditional experiments, the oxidation roasting realized the content of cyanide decrease to < 0.04 mg/kg (detection limit) with the removal rate reached to 99.99% at the optimum conditions. The reduction roasting realized the main mineral hematite transformed to magnetite and recycled the iron concentrate from the cyanide tailings with iron grade of 59.21% and iron recovery of 89.57%. The migration and transformation paths and decomposition products of cyanide during oxidative degradation process were investigated by the hexacyanoferrate reagents decomposition with the real-time concentration of CO2, XRD and FT-IR. The hexacyanoferrate decomposition reactions were complex, and divided into three stages, such as the room temperature-350 ℃, 350 ℃− 550 ℃, 550 ℃− 800 ℃ respectively. The transformation paths and decomposition products iron-cyanide complex were mainly as follows: K4Fe(CN)6 or K3Fe(CN)6 was oxidized and decomposed into CNO-, and further decomposed into CO3- by the roasting temperature increasing.