Hydrometallurgical process for the separ

The Laboratory of Metallurgy of the National Technical University of Athens has developed and patented a novel integrated hydrometallurgical method, suitable to treat low-grade nickel oxide ores efficiently and economically. It involves heap leaching of the ore by dilute sulphuric acid at ambient temperature, purification of the leach liquor and recovery of nickel and cobalt by electrowinning. A typical composition of the pregnant solution produced from heap leaching is the following: Ni2+ = 5 g/L, Co2+ = 0.3 g/L, Fe3+ = 23.0 g/L, Al3+ = 6.0 g/L, Cr3+ = 1.0 g/L, Mn2+ = 1 g/L and Mg2+ = 8 g/L. The proposed hydrometallurgical process for nickel recovery from real sulphate heap liquors consists of six unit operations including the removal of iron, aluminum and chromium by chemical precipitation, extraction of cobalt, manganese and magnesium, and nickel concentration followed by electrowinning. This method demonstrates a systematic approach to efficiently recover nickel from lower-grade ores, showcasing significant advancements in hydrometallurgical processing techniques.