Sorption of Ni by “lithiophorite–asbolane” intermediates in Moa Bay lateritic deposits, eastern Cuba

The Moa Bay Ni–Co laterite deposits, placed in the so-called Mayari–Baracoa ophiolitic belt (eastern Cuba), are oxide type. Despite its geological relevance and economical impact no detailed studies exist with regards to cristallochemical characterization of Ni incorporated in (or attached to) the main Ni-containing minerals forming the lateritic profile. A sample corresponding to the ore limonite horizon has been studied by microfocus Raman, micro X-ray diffraction (µXRD), electron probe micro analysis (EPMA) and synchrotron radiation microfocus X-ray absorption spectroscopy (XAS) to gain structural and chemical information on Ni. The data obtained has revealed that Ni is preferably accumulated in quantities up to 21 wt.% in “lithiophorite–asbolane” intermediates. The local environment of Ni shows Ni–Mn distances ∼ 3.5 Å suggesting that Ni is sorbed mostly in inner-sphere complexes sitting on Mn vacancies and at the edge of the Mn layers. However it is shown that in the presence of Al the Ni is incorporated within the “lithiophorite–asbolane” intermediate by developing brucite-like interlayers. The understanding of Ni sorption mechanisms within the limonite horizon suggests that combined physicochemical factors such as soil porosity and pH regime have important implications for Ni mobility across the profile.