A novel and greener sequential column leaching approach for the treatment of two different Greek laterites

Kostas Komnitsas; Evangelos Petrakis; Georgios Bartzas

doi:10.1016/j.scitotenv.2022.158748

A novel and greener sequential column leaching approach for the treatment of two different Greek laterites

Sci Total Environ. 2023 Jan 1:854:158748. doi: 10.1016/j.scitotenv.2022.158748. Epub 2022 Sep 13.

Authors

Kostas Komnitsas¹, Evangelos Petrakis², Georgios Bartzas³

Affiliations

¹ Technical University of Crete, School of Mineral Resources Engineering, University Campus, Kounoupidiana, 73100 Chania, Greece. Electronic address: kkomnitsas@tuc.gr.
² Technical University of Crete, School of Mineral Resources Engineering, University Campus, Kounoupidiana, 73100 Chania, Greece.
³ School of Mining and Metallurgical Engineering, National Technical University of Athens, 15780 Athens, Greece.

PMID: 36108865
DOI: 10.1016/j.scitotenv.2022.158748

Abstract

Τhe present study investigates, from an environmental protection viewpoint, the efficiency of sequential column leaching of two different Greek laterites, i.e. a limonitic ore from central and a saprolitic ore from northern Greece. First, the most refractory limonitic laterite is leached in the first column for 15 days and the obtained pregnant leach solution (PLS) is further used for the leaching of the easier to treat saprolitic ore in the second column, thus achieving a significantly reduced acid consumption. The main parameters affecting the process efficiency, i.e. acid molarity (1.5 or 3 mol/L H₂SO₄) and addition of sodium sulfite (Na₂SO₃) in the leaching solution were studied. The extraction of Ni, Co, Fe, Al, Mg, Mn and Ca was determined by Atomic Absorption Spectroscopy (AAS), while the characterization of the ores and final residues was carried out by X-ray fluorescence (XRF), X-ray diffraction (XRD), Fourier-transform infrared (FTIR) spectroscopy, thermogravimetric analysis (TGA/DTA), and Scanning Electron Microscopy/Energy Dispersive X-Ray Spectroscopy (SEM-EDS) analysis. The results confirm the efficiency of the proposed green approach, which with the use of leaching solution containing 1.5 mol/L H₂SO₄ and 20 g/L Na₂SO₃ resulted in 73.8 % Ni, 71.6 % Co and 8.4 % Fe extraction after a short period of time (33 days), while the acid consumption, which is a serious environmental concern, was very low and did not exceed 300 kg/t ore. Overall, the proposed process not only improves the efficiency of leaching of different types of laterites for the recovery of both Ni and Co but also reduces the environmental impacts due to the significantly lower acid consumption.

Keywords: Acid consumption; Limonitic/saprolitic laterites; Sequential column leaching; Sodium sulfite; Sulphuric acid.