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 Scurve 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 S-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 valueadded metals from fire assay waste is exceptionally high, integrating recycling and repurposing of value-added base metals to promote a circular economy.

Separation and Characterization of Nickel Hydroxide from Waste Solution Using Ca(OH)2 Precipitation in Chloride Media

“…Figure 3a illustrates the SEM imaging, a stratified granule composed of approximately pure brucite crystalline phase in spherical morphology particles, which is characteristic of β-Ni(OH) 2 . This finding supports the findings of prior research [15]. The coarse texture may be indicative of elevated levels of oxides on the surface of Ni, while the uneven clustering is also characteristic of the typical formations that occur during the precipitation process.…”

“…Indeed, at pH 2.5, Ni co-exists with Fe, as explained by this group in Ref. [15]. In addition, the EDX is shown in Figure S3, which verifies the presence of Ni and Fe in the precipitate.…”

“…The synthesis of Ni(OH) 2 involved two distinct steps: (1) preparation of the precursor solution (2) and synthesis of Ni(OH) 2 . As outlined in the referenced literature [15], with minor adjustments, the pregnant waste solution (WPS) harbored valuable copper (Cu) that could be extracted using solvent extraction (SX). In this method, WPS was introduced into a 1000 mL separating flask at an organic/aqueous ratio of 1:5.…”

“…This experimental study was conducted under conditions designed at pH 6.5, which represents the optimal pH for precipitating Ni 2+ ions [15] from PWS. After precipitation, the solution was characterized by ICP-OES.…”

“…Specifically, the utilization of elevated temperatures has an impact on decreasing the amount of Ni precipitated (Ni loss) during the Fe precipitation procedure at pH 2.5, as illustrated by this group in Ref. [15]. Thus, this study confirmed the precipitation process of Ni 2+ ions operates optimally at a temperature of 60 • C and a pH of 6.5, as indicated in Table 2, which resulted in 600 ppm Ni in solution from 62,700 ppm Ni in the pregnant waste solution (Table 1).…”