Generally, lateritesLaterites and sulfides ores are the major sources of nickelNickel (Ni) and cobaltCobalt (Co) and contain impurities metalsMetals including Fe, Al and Cr. Ni and Co are extensively used in lithiumLithium-ion batteryBattery manufacturing as a critical element in cathode materials, requiring high-purity metalMetals salts as a precursor. Hydrometallurgical processesHydrometallurgical processes including sulfuric acidAcid high-pressure leachingHigh pressure leaching, nitric acidAcid pressure leachingLeaching, atmospheric leachingLeaching, and the sulfation-roasting-leachingLeaching processes have high recovery rates of valuable Ni & Co along with low value/waste Fe. These processes typically have high capital & operating costs (i.e., autoclavesAutoclave) due to aggressive operating conditions (250–270 °C; 4–5 MPa). Iron is typically the main impurity in the ores and adds to the operating costs due to additional acid consumptionAcid consumption during leachingLeaching, slow Fe extractionExtraction process, costly processes to recover Fe as a by-product to offset process costs (i.e., Fe pyrohydrolysis or hydro-hydrolysis), or waste disposal issues of iron hydroxides. The purpose of this study was to develop a modified hydrometallurgical approach that maximizes Ni, Co, and Cu recovery, while minimizing Fe co-dissolutionDissolution through selective leachingSelective leaching. The first part of the study was performed on a Cu-Ni sulfide concentrate which was ground to – 140 mesh and mixed with various additives which included Na2SO4 for a sulfation reaction, NH4Cl for a chlorination reaction, and roasted at temperatures of between 250 °C and 650˚C for a specified residence time and heating rate. Following the roasting process, the treated ore was leached with deionized (DI) water and in several cases with additives at 65–95 °C for 5 h. Under certain sulfidation conditions, it was found that the leachingLeaching efficiencies for Co, Cu & Ni were 100.0%, 89.2% & 68.0%, respectively, with little to no Fe extractionExtraction in the leach solution. For chlorinated ores improved leachingLeaching efficiencies for Co, Cu, and Ni were observed with 100.0%, 95.0%, and 98.8% extractionExtraction respectively with 3.8% Fe extracted in the leach solution. During roasting, conversion of Fe (II) into Fe (III), which inhibited iron dissolutionDissolution in water leachingLeaching such that Co, Cu, and Ni are selectively leached over trivalent metalsMetals.