Fe Migration and its Influence on the Oxidative Leaching of Low-Grade Ni-Cu-Fe-Bearing Sulfide Ores in Sulfuric Acid Solutions

摘要

The migratory characteristic of iron and its effects on the oxidative dissolution of low-grade polymetallic Ni-Cu-Fe-bearing sulfide ores in sulfuric acid solutions were investigated. This study involved three parts. First, the influence of Fe on the Ni and Cu leaching efficiencies was measured using leaching tests. It was revealed that the dissolution of Fe-bearing sulfide limits the dissolution of Ni-Cu sulfide to a certain extent, the leached Fe3+ ion significantly affects Ni and Cu leaching, and the Fe3+ ion has a synergistic impact with hydrogen and alkali-metal ions in the solutions. Second, this work presents the thermodynamic solution status and mineralogical phase transformation of the Fe species. Fe sulfide tends to oxidize into Fe3+ ions, precipitating into Fe oxide/sulfate sediment. Third, the electrochemical test results illustrate that a lower reduction potential leads to the preferential dissolution of Fe sulfide relative to Ni-Cu sulfides; the dissolved Fe3+ ion results in a better exchange efficiency of Fe3+/Fe2+ and a higher potential and conductivity of the Fe3+-containing solution, increasing the Ni and Cu dissolution rates by a factor of 3.65 and 2.92 times at pH 0.8, relative to that of Fe3+-free solutions, respectively. Furthermore, the coupling of Fe(3+)with Na+/Mg(2+)ions slows down the Ni-Cu leaching rate by more than 10% compared to that of Fe3+ ions in acidic solutions. Based on these results, the influence of Fe migration on the Ni-Cu oxidative leaching was significantly affected by the acidity and ionic state of the lixivium. This study elucidates the effect of ionic migration, which is related to the metallurgical return water, on the Ni-Cu oxidative extraction for the low-grade Ni-Cu-Fe sulfide ore.