Arsenic distribution and speciation in the bauxitic Fe-Ni-laterite ore deposit of the Patitira mine, Lokris area (Greece)

Bauxitic Fe-Ni-laterite ore from the Patitira mine in Lokris area (Greece) contains assemblages of unusual As-bearing goethite-type phases in samples with significant organic matter. The material was initially characterized by bulk ICP-MS and SEM-EDS. Furthermore, the distribution and speciation of As were studied by Synchrotron Radiation (SR) spectroscopic techniques, for first time in the literature. The SR μ-XRF elemental maps and the As K-edge μ-XAFS spectra revealed that As is exclusively correlated to Fe, occurring as As5+ in the form of arsenate anions (AsO43−). However, the arsenate anions, being considered as sorbed species on goethite-type phases, exhibit -at molecular scale- a disordered structural environment, resembling locally to the configuration of such anions in natural hydrated Ni arsenates (annabergite) rather than to natural hydrated ferric arsenates (scorodite). The metalloid element in study, possibly derived from As-mineralizations or volcanic rocks, has been transferred in the environment of the laterite re-deposition, where arsenates could interact with the aforementioned Fe-phases.