Circular hydrometallurgy for energy-transition metals

Introduction

CIRMET will lead to a new approach to hydrometallurgy, called “circular hydrometallurgy”, with a focus on the design of energy-efficient flowsheets or unit processes that consume a minimum amount of reagents and produce virtually no waste.

Goals of CIRMET

CIRMET has the ambitious goal to replace the traditional, linear hydrometallurgical flowsheets for extraction and refining of the “energy-transition” metals cobalt and nickel into a next-generation, circular flowsheet, which:

1. Consumes no chemicals other than (green) hydrogen, water, and carbon dioxide (taking advantage of the unique chemical properties of carbon dioxide).
2. Uses the acid for the leaching process as a “catalyst” that is continually regenerated rather than consumed.
3. Reduces the net consumption of acids and bases to virtually zero through ingenious manipulations of chemical equilibria via solvent extraction.
4. Comprises a virtually zero discharge of solid and liquid waste streams.

As such, CIRMET can drastically reduce the environmental footprint of hydrometallurgical processes.

Theoretical Framework

To enable such circular flowsheets, a new theoretical chemical thermodynamic framework for multiphase electrolyte equilibria involving two immiscible liquids and innovative unit operations for sustainable metal and sulphur recovery are developed.

Methodology

Hydrometallurgical processes are approached from a molecular level. Liquid-liquid equilibria are modelled by Gibbs-energy-minimisation (GEM) methods, rather than by solving law-of-mass action (LMA) equations.

Proof of Concept

The proof of concept of circular flowsheets is demonstrated for metal recovery from real, complex (rather than synthetic), impurity-bearing input streams:

• Nickel laterites
• Cobalt-nickel sulphide ores
• Mixed hydroxide precipitate (MHP)
• Mixed sulphide precipitate (MSP)

Innovation Spheres

Only by combining these three mutually supporting spheres of innovation can CIRMET be successful:

1. The “thermodynamic framework”
2. The “unit process level”
3. The “general flowsheet” sphere