Characterization of Nickel in Chromite Beneficiation Tailings by Mineral Liberation Analysis and Its Recovery by H2SO4 Leaching Followed by Oxalic Acid Precipitation

Abstract

This study investigated the recovery of nickel from tailings (0.2% Ni) obtained in a chromite beneficiation plant using H2SO4 leaching followed by oxalic acid precipitation. The tailings were characterized using mineral liberation analysis. Ni was found as Fe-Ni, Fe-Ni-Co sulfide minerals, which were encapsulated in serpentine, olivine, pyroxene and clinochlore. Liberated fine chromite minerals benefited from magnetic separation followed by Falcon concentrator. A chromite product with a grade > 37% was obtained. The effect of leaching conditions including acid concentration, temperature, time and solid-to-liquid ratio on the leaching behavior of Ni was investigated based on the Taguchi approach. It was possible to extract Ni with a rate of > 98% from the tailings using the following conditions: H2SO4 concentration of 3 M, solid-to-liquid ratio of 1:20 and ambient temperature for 2 h. Finally, Ni was precipitated as an oxalate form with a precipitation rate of 72%. It is believed that implementing additional purification methods like solvent extraction may be essential to obtain a high-purity nickel product from the leach solution of oxalate precipitate. Experimental results indicate that the tailings used in this study are a good alternative as Ni resource in the near future.