Production of high purity magnetic nickel powder from spent DRI catalyst via cementation method

Abstract

In the present study, a novel two-step method was developed to synthesize high purity magnetic nickel from spent direct reduction of iron (DRI) catalyst. Initially, nickel was leached from spent DRI catalyst by hydrochloric acid and the effect of important parameters including temperature (25–85 °C), leaching time (30–210 min), acid concentration (1–5 M) and average catalyst particle size (111–325 μm) were studied using design of experiments (DOE) approach. 100% Ni extraction with negligible Al dissolution (<0.5%) could be achieved at a temperature of 46 °C, leaching time of 172 min, the acid concentration of 4 M and particle size of 111 μm. Next, the nickel cementation by aluminium powder was investigated thoroughly by considering solution initial pH, aluminium particle size and its addition method, pH adjustment method and temperature as important variables. The structural properties of cemented nickel were characterized by FESEM, XRD and EDX analysis. It was observed that through treating of the optimal leached liquor with 2 M sodium hydroxide, more than 96% of Ni could be recovered by gradual addition of excess Al powder to the solution with initial pH of 0.2. The purity of cemented Ni would be 98.5% if the cementation process was performed at 80 °C.