Ligand-promoted dissolution of serpentine in ultramafic nickel ores

• Ligands investigated for leaching Mg from ultramafic ores at pH 7 and 10.
• Catechol, EDTA and tiron effective leaching agents, citrate and oxalate less so.
• Catechol, EDTA and tiron may enhance aqueous mineral carbon sequestration.

The ligands catechol, citrate, EDTA, oxalate and tiron were investigated for their ability to improve the dissolution of serpentine in ultramafic nickel ores at neutral to alkaline pH to enhance mineral carbon sequestration. It is desirable to leach magnesium from serpentine in ores at neutral to alkaline pH so that leaching and carbonation can be conducted at the same pH value, and ultimately so that the reagent requirements of mineral carbon sequestration can be reduced. Both solution modeling and experimental work were conducted. The solution modeling revealed that each of the ligands studied is able to enhance the solubility of magnesium at the desired pH, with the order of effectiveness being EDTA > tiron > citrate > catechol > oxalate. Experimentally it was shown that the ligands studied could improve both the total amount and rate of magnesium leaching from ultramafic nickel ores. The order of ligand effectiveness based on the experimental work for the Pipe ore was EDTA ⩾ tiron > catechol > oxalate ⩾ citrate. For the OK ore, the order was tiron > EDTA = catechol > oxalate > citrate. Overall, the ligands studied in this work, particularly EDTA, tiron, and catechol, appear promising for enhancing the dissolution of serpentine in ultramafic nickel ores at neutral to alkaline pH.