Dithionite Inhibits Iron(III) (Hydr)oxide Formation during Olivine Dissolution Advancing Simultaneous CO₂...

Area of Science:

• Geochemistry and Materials Science
• Environmental Engineering
• Sustainable Energy Technologies

Background:

• Rising CO2 levels necessitate carbon-neutral energy transitions, increasing demand for critical elements like nickel and cobalt.
• Depleting high-grade ores and impurities in low-grade minerals like olivine (e.g., iron) impede efficient critical element recovery and CO2 mineralization.
• Addressing these challenges requires innovative methods for simultaneous CO2 capture and resource extraction.

Purpose of the Study:

• To investigate the dissolution of nickel and magnesium from San Carlos olivine under high CO2 pressure and temperature.
• To evaluate the effectiveness of sodium dithionite (Na2S2O4) as a reducing agent in overcoming iron-related dissolution hindrances.
• To enhance the efficiency of CO2 mineralization and critical element recovery from low-grade olivine ores.

Main Methods:

• Experimental dissolution of San Carlos olivine at elevated temperatures and CO2 pressures.
• Utilizing sodium dithionite (Na2S2O4) to prevent the formation of iron(III) (hydr)oxide layers.
• Conducting multiple dissolution cycles with solution replacement to assess long-term recovery rates.
• Quantifying magnesium (Mg) and nickel (Ni) dissolution using analytical techniques.

Main Results:

• Iron(III) (hydr)oxide formation was identified as a key impediment to olivine dissolution.
• The addition of sodium dithionite significantly improved Mg and Ni dissolution rates, increasing them by 2.85-fold and 2.66-fold, respectively, within 24 hours.
• Over seven cycles, 98.9% of total Mg and 84.6% of total Ni were recovered.
• The use of Na2S2O4 effectively prevented iron passivation, enhancing mineral accessibility.

Conclusions:

• Sodium dithionite is a highly effective agent for improving olivine dissolution and critical element recovery.
• This integrated approach enhances CO2 mineralization potential while addressing the sustainable supply of critical elements.
• The findings present a promising strategy for circular economy principles in mining and carbon capture technologies.