Efficient recovery of valuable metals from low-grade zinc residue by ultrasonic strengthening

Abstract

As zinc ore resources continue to dwindle, the exploitation and utilization of secondary zinc-containing resources have garnered significant attention. This thesis presents an innovative methodology referred to as the ultrasound synergistic manganese dioxide oxidizing acid leaching process, specifically designed for treating complex acid leaching residues obtained from primary zinc oxide ore. ICP-OES analysis revealed that the zinc leaching residues contain 4.57 % zinc, 55.81 % oxygen, 13.51 % calcium, 11.33 % sulfur, 4.39 % iron, 3.23 % silicon, and 0.62 % lead. Optimal operational parameters were determined through a one-factor experimental design under ultrasonication, which included a manganese dioxide concentration of 11.11 g/L, an initial acidity of 160 g/L, a liquid-solid ratio of 7 mL/g, ultrasonic power set at 420W, and leaching conducted at a temperature of 85°C for a duration of 30 min, achieving a zinc leaching rate of 95.68 %. Characterization studies demonstrated that the synergistic effect of ultrasonic waves and manganese dioxide not only disintegrated the mineral surfaces, opened mineral inclusions and released encapsulated zinc but also accelerated the reaction, ultimately enhancing the leaching rate of zinc. Compared to existing methods, this ultrasonic-assisted oxidizing acid leaching process can improve zinc recovery by 10 % and cut the leaching time down to 30 min.