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

• Published in: The Science of the total environment 2023-01, Vol.854, p.158748, Article 158748
• Main Authors: Komnitsas, Kostas, Petrakis, Evangelos, Bartzas, Georgios
• Format: Article
• Language: English
• Subjects: Acid consumption; atomic absorption spectrometry; electron microscopy; energy-dispersive X-ray analysis; environment; environmental protection; fluorescence; Greece; laterites; Limonitic/saprolitic laterites; Sequential column leaching; Sodium sulfite; Sulphuric acid; thermogravimetry; X-radiation; X-ray diffraction
• ISSN: 0048-9697; 1879-1026; 1879-1026
• DOI: 10.1016/j.scitotenv.2022.158748

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. [Display omitted] •A novel heap leaching process for treating different low-grade laterites is proposed.•Sequential leaching tests are carried out to maximize Ni/Co extraction.•Leaching residues are characterized with the used of several analytical techniques.•Acid consumption is much lower (295 kg/t) compared to other similar processes.•Lower environmental footprint is potentially achieved.