Characterization and leaching behaviour of lizardite in Yuanjiang laterite ore

摘要

Lizardites in Yuanjiang laterite ore were characterized using X-ray diffraction (XRD), X-ray energy dispersive spectroscopy (EDS) and Fourier transform infrared spectroscopy (FTIR). Their leaching behaviour in sulphuric acid was investigated. XRD patterns show that there are two different lizardite polytypes in Yuanjiang laterite ore: lizardite-1T and lizardite-1M. The crystal order of the lizardites between soil and rock samples was different, which was demonstrated by XRD and FTIR spectrum analyses. The obvious change of the crystal cell volume was observed in the lizardite-1T of soil sample, with higher iron content, whereas the crystal cell varied little for the lizardite-1T of rock sample, with higher aluminum content. FTIR spectrum, EDS analyses and the leaching experiments show substitution of octahedral nickel, iron and aluminum, as well as tetrahedral aluminum. Iron occurred as ferrous and ferric iron in the lizardite-1T of rock sample, mostly as ferrous iron in the lizardite-1M and as ferric iron in the lizardite-1T of soil and rock fragment samples. The results from leaching experiments also show that the leachability of lizardite-1T in sulphuric acid decreases in the following sequence: lizardite-1T of laterite soil>lizardite-1T of rock frag-ments>lizardite-1T of rocks. Lizardite-1M leached faster than lizardite-1T of rock fragments. The leaching behaviour differences of lizardites in Yuanjiang laterite ore may be explained by the various crystal structures resulting from the weathering process of laterite ores and the substitution of metal cations such as Ni~(2+), Fe~(2+), Fe~(3+) and Al~(3+). It is concluded that rapid dissolution occurs preferentially for the lizardite with low crystal order, low aluminum content and high iron content while acid leaching laterite ores.