A method and mechanism for extracting Cu, Co, and Zn from limonite tailings

The development of green methods to process and use iron tailings is crucial due to the accumulation of tailings, which poses significant environmental and human health risks. In this study, a scheme of extracting Cu, Co and Zn from limonite tailings by sulfuric roasting with ammonium sulfate and then water leaching was proposed. Most of the Fe is converted to jarosite and enriched in the leaching residue. Ferric iron is present in the leaching residue in the form of jarosite and can be reused as an adsorbent. The impact of various factors, including roasting temperature, time, ammonium sulfate dosage, leaching temperature, and liquid-to-solid ratio, on the metal leaching rate was investigated. The findings indicated that when the roasting temperature was set at 400 degrees C, the roasting time was 120 minutes, the quantity of ammonium sulfate was 1.5 times the original amount, the leaching temperature was 70 degrees C, and the liquid-to-solid ratio was 10:1, the leaching rate of Fe was as low as 34.20 %, and the leaching rates of Cu, Co, and Zn were 81.25 %, 91.35 %, and 89.35 %, respectively. A mechanistic analysis indicates that during the calcination process, the phase transitions of Fe are (NHa)3Fe(SOa)3, NHaFe(SOa)2, and Fe2(SOa)3, and the phase transformations of Cu, Co, and Zn are in accordance with these changes. A higher leaching temperature makes it easier for iron to form jarosite, which reduces the leaching rate of iron. This study has a simple, efficient, and environmentally friendly method for extracting valuable metals from limonite tailings.