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This study aims to evaluate the potential for extracting critical metals from Cu-Ni-Co metallurgical slag using various acids.

May 11, 2026Open Access

Resource potential of Cu-Ni-Co metallurgical slag: Quantitative mineralogy and critical metals extraction using different acids

Key Points

This study aims to evaluate the potential for extracting critical metals from Cu-Ni-Co metallurgical slag using various acids.
Utilized mineralogical characterization techniques like XRD, SEM-EPMA, LA-ICP-MS, and automated mineralogy.
Conducted laboratory extraction tests with different acids (sulfuric, methanesulfonic, and citric) under varied conditions.
Tested extraction efficiencies on both original and finely milled slag at different temperatures and leaching durations.
Achieved extraction efficiencies of up to 89% for Co, 71% for Cu, and 46% for Ni from the original granulated slag.
Identified the primary host phases for metals as silicate phases, and noted that extraction of Cu and Ni was limited by adsorption into new phases.
Concluded that alternative leaching agents showed no improvement over sulfuric acid for metal recovery.

Abstract

Dumps of waste metallurgical slags can store large quantities of critical raw materials. This study examined the granulated slag from a Ni Cu smelter, containing 0.30 wt% Cu, 0.11 wt% Ni, and 0.086 wt% Co. A combination of mineralogical characterization techniques (XRD, SEM-EPMA, LA-ICP-MS, and automated mineralogy) was employed to investigate the phase composition and distribution of target elements to provide the key information for the possible reprocessing of this material on a quantitative basis. The major constituents are silicate glass (84 area%) and fayalite (15 area%), while entrapped matte (sulfide inclusions) accounts only for 0.2 area%. The silicate phases are also the primary hosts for the target elements, accounting for 98%, 74%, and 66% of the total Co, Cu, and Ni, respectively. Our results indicate that acid leaching and hydrometallurgical processing are the preferred strategies for the potential metal recovery. Laboratory extraction tests were conducted under the following conditions: original slag without comminution and finely milled; sulfuric acid, methanesulfonic acid (MSA), and citric acid; liquid/solid ratios of 10 and 20 L/kg; ambient and elevated (70 °C) temperatures; 2 and 6 h of leaching. For the original granulated slag, extraction efficiencies up to 89% for Co, 71% for Cu, and 46% for Ni were reached. The extractions of Cu and Ni were limited by adsorption or incorporation into newly formed phases. Considering the current prices of MSA and citric acid and the lack of improvement in the extraction efficiency, their use for metal recovery instead of sulfuric acid appears unlikely. • Granulated slag from a Ni Cu smelter is a potential source of critical elements. • This study quantified the distribution of Co, Cu, and Ni among sulfides, olivine, and glass. • Hydrometallurgical reprocessing can be a suitable approach for metal recovery. • Alternative leaching agents (MSA and citric acid) did not prove superior to H 2 SO 4.

Resource potential of Cu-Ni-Co metallurgical slag: Quantitative mineralogy and critical metals extraction using different acids

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Abstract

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