Recovery of Ni matte from Ni-bearing electroplating sludge

Area of Science:

• Metallurgical Engineering
• Environmental Science
• Materials Science

Background:

• Electroplating sludge (ES) is a significant industrial waste containing valuable metals like nickel.
• Traditional methods for nickel recovery from ES are often inefficient or environmentally challenging.
• Developing selective and efficient recovery processes is crucial for resource sustainability.

Purpose of the Study:

• To propose and evaluate a novel two-stage process for the selective recovery of nickel from Ni-bearing electroplating sludge.
• To optimize the carbothermic reduction and smelting stages for maximum nickel recovery and selectivity.
• To characterize the composition of the resulting nickel-iron-sulfur (Ni-Fe-S) matte and slag.

Main Methods:

• Carbothermic reduction of ES with carbon at 1000°C to form Ni-rich phases (Ni3S2, Fe4Ni5S8).
• Smelting of the reduced ES with SiO2 at 1500°C to produce a liquid Ni-Fe-S matte and slag.
• Separation of the matte from slag by gravity.

Main Results:

• Achieved a high nickel recovery ratio of 97.2%, significantly outperforming iron recovery (14.7%).
• Produced a Ni-Fe-S matte with a high Ni/Fe mass ratio of approximately 4.2, compared to 0.7 in the original ES.
• Obtained a final matte composition of 58.5% Ni, 13.8% Fe, and 27.7% S, along with vitrified slag.

Conclusions:

• The proposed two-stage carbothermic reduction and smelting process enables selective nickel recovery from electroplating sludge.
• The high nickel recovery and enhanced Ni/Fe ratio demonstrate the effectiveness of the method.
• The resulting nickel matte is a suitable precursor for producing pure nickel or nickel-based chemicals.