Comparative experimental study on the harmless treatment of cyanide tailings through slurry electrolysis

摘要

In this work, the cyanide tailings were treated with slurry electrolysis technology. The removal of cyanide and the regularity of the oxidative dissolution of the main minerals in tailings during direct electrolysis (ET), air electrolysis (ETA), and NaCl electrolysis (ETC) were compared and analyzed. X ray diffraction, backscattered electron analysis, mineral liberation analysis, and other analytical methods were performed to analyze and characterize the mineral composition and interlocking relationship of cyanide tailings. Results indicated that cyanides and typical minerals, such as pyrite and pyrrhotite, in cyanide tailings would undergo a certain degree of oxidation and dissolution in the ET, ETA, and ETC systems, and the processing effect of the ETC system was more obvious than that of other systems. After the treatment, the mass loss of cyanide tailings could reach 8.62%, which was 5.10% and 1.36% higher than the mass loss in ET and ETA, respectively. The removal rates of CNT, CN-, Cu, Zn, and Fe were 92.07%, 97.17%, 86.31%, 98.24%, and 93.03%, respectively. The relative contents of pyrite and pyrrhotite decreased by 8.82% and 4.65%, respectively. The particle size occupancy rates of pyrite greater than 50 mu m and pyrrhotite greater than 15 mu m were 0.24% and 3.36%, respectively. The mineral liberation degrees of typical minerals increased significantly, and the mineral liberation degrees of pyrite and pyrrhotite increased by 16.46% and 13.20%, respectively. The oxidation of cyanides and minerals in cyanide tailings under the ETC system mainly involved electrochemical indirect oxidation. Cl- migrated to the anode through electrogeneration to generate Cl-2/ClO- in situ. CN- and metal cyanide ions that migrated near the anode were oxidized by Cl-2/ClO- to produce CO2, N-2, and metal cations. Metal cations returned to the cathode where they were reduced and deposited. Pyrite, pyrrhotite, and other minerals in cyanide tailings could also be oxidized and dissolved by ClO-. Therefore, the particle size of minerals decreased, and the degree of mineral liberation increased. As electrolysis proceeded, the interlocking relationship between the minerals was destroyed, and more minerals were exposed in the form of monomers. These phenomena provided favorable conditions for the subsequent comprehensive recovery of valuable metals from cyanide tailings.