Simultaneous extraction of metals from nickel concentrate via NH 4 HSO 4 roasting-water leaching process and transformation of mineral phase

Low -temperature NH 4 HSO 4 roasting-water leaching process was proposed to extract Ni, Cu and Co from Jinchuan nickel concentrate simultaneously. The effects of some factors on the metal extraction in the process of sulfation roasting and water leaching were systematically investigated. The results showed that 95.7% Ni, 98.9% Cu and 96.8% Co were extracted under optimized roasting and water leaching conditions. The transformation evolution of mineral phases was determined through the means of DTA-TG, XRD, SEM and EDS. The valuable metals were effectively extracted by being transformed to water-soluble metal-ammonium complexes under the sulfation reaction of NH 4 HSO 4 and decomposed SO 3 and NH 3 . Iron impurities in the leach solution can be removed by elevating leaching temperature to combine iron ions with ammonium ions to form NH 4 [Fe 3 (SO 4 ) 2 (OH) 6 ] precipitate. The volatiles collected in the roasting process were determined to be (NH 4 ) 2 SO 4 and (NH 4 ) 2 SO 3 , which can be used as reagents for sulfation roasting.