Removal of Nickel from Nickel Sulfite-Fire Assay Dissolution Filtrate Through Precipitation

Abstract

This study responds to stringent environmental regulations and increasing focus on resource conservation by exploring economically viable refining technologies through recycling. With the rising costs of filtrate disposal, there is a significant emphasis on removing and recycling valuable constituents, particularly nickel and copper (Ni and Cu). Herein, we employ analytical techniques with the aim of investigating an alternative method for recovering Ni and other valuable metals from a nickel sulfide-fire assay filtrate using <i>S</i>-curve precipitation under optimal conditions. The waste from the fire assay procedure contains substantial amounts of Ni and other critical metals, with concentrations of 62.7 g/L of Ni and 3.87 g/L of Cu. Prior to precipitation, traditional solvent extraction was used for Cu extraction, selectively removed before separating primary impurities such as iron (Fe). A pivotal aspect of this research involves applying <i>S</i>-curve precipitation with precise parameters at different pH levels. Analytical techniques reveal a minor depletion occurs as Ni is separated from Fe at a pH of 2.5, resulting in the formation of a refined Ni stream that is then refined into a mixed hydroxide Ni(OH)₂ product. The efficiency of 5,8-diethyl-7-hydroxydodecan-6-oxime (LIX 63-70) in extracting value-added metals from fire assay waste is exceptionally high, integrating recycling and repurposing of value-added base metals to promote a circular economy.