Column leaching of low-grade saprolitic laterites and valorization of leaching residues

Kostas Komnitsas; Evangelos Petrakis; Georgios Bartzas; Vassiliki Karmali

doi:10.1016/j.scitotenv.2019.01.381

Column leaching of low-grade saprolitic laterites and valorization of leaching residues

Sci Total Environ. 2019 May 15:665:347-357. doi: 10.1016/j.scitotenv.2019.01.381. Epub 2019 Jan 30.

Authors

Kostas Komnitsas¹, Evangelos Petrakis², Georgios Bartzas³, Vassiliki Karmali²

Affiliations

¹ Technical University of Crete, School of Mineral Resources Engineering, University Campus, Kounoupidiana, 73100 Chania, Greece. Electronic address: komni@mred.tuc.gr.
² Technical University of Crete, School of Mineral Resources Engineering, University Campus, Kounoupidiana, 73100 Chania, Greece.
³ National Technical University of Athens, School of Mining and Metallurgical Engineering, 9 Heroon Polytechniou str., 157 80 Zografos, Athens, Greece.

PMID: 30772565
DOI: 10.1016/j.scitotenv.2019.01.381

Abstract

Socio-economic data on nickel and cobalt show their importance throughout the entire metal value chain, from mining to end use, disposal and recycling. Thus, the extraction of both metals from primary and secondary raw materials as well as from wastes is currently considered strategically important for the industry and the society. In this paper heap leaching of Greek low-grade saprolitic laterites, with Ni content 0.97%, was investigated. The main parameters studied involved the strength of the H₂SO₄ solution used (49 and 147gL^-1) and the effect of adding sodium sulfite (Na₂SO₃) in the leaching medium. The pregnant leach solution (PLS) was recycled several times during leaching in order to minimize acid consumption. The experimental results showed that within a period of 25days, and under the optimum conditions (147gL^-1 H₂SO₄ and 20gL^-1 Na₂SO₃), i) Ni and Co extractions were 72.5% and 47.4%, respectively and ii) Fe and Al co-extractions were 8.7% and 31.3%, respectively. Furthermore, valorization of the leaching residues through alkali activation using NaOH and Na₂SiO₃ and the addition of metakaolin (MK) for the production of inorganic polymers (IPs) was explored. X-ray fluorescence (XRF), X-ray diffraction (XRD), Fourier-transform infrared (FTIR) spectroscopy, Differential scanning calorimetry (DSC/TG) and Scanning electron microscopy (SEM-EDS) were used to characterize the ore, its leaching residues and the IPs. The IPs produced demonstrated high compressive strength, almost 40MPa and are suitable for a wide range of applications in the construction sector.

Keywords: Column leaching; Inorganic polymers; Saprolitic laterites; Sodium sulfite; Sulfuric acid.