Thermal and Infrared Studies of Garnierite from the Soroako Nickeliferous Laterite Deposit, Sulawesi, Indonesia

Abstract

Mineralogical characterisation of some garnierite samples from Soroako have been conducted using XRD, thermal analysis and FTIR spectroscopy. X ray diffraction patterns reveal the samples mainly containing the mixture of kerolite (talk-like phase) and serpentine with minor smectite, sepiolite and silica. Thermal analyses of garnierite samples indicated by DTA curves are in good agreement with patterns that have been reported in literature. Three endothermic peaks normally occurring within the ranges between 58oC and <800oC illustrate three steps weight losses: adsorbed, bound, and hydroxyl/crystal water. One additional weight loss in low temperature region of sepiolite is corresponding to the lost of zeolitic water. Infrared spectra appeared in 3800 – 3200 cm-1 region generally exhibit broad absorption bands, indicating low crystallinities of studied samples and they may be assigned to the presence of hydroxyl group bonded to octahedral coordination mainly Mg atom. The bands observed at 1660 cm-1, 1639 cm-1, 1637 cm-1 and 1633 cm-1 in all samples indicate water molecules. FTIR spectra displaying the strong bands at 1045 cm-1, 1038 cm-1, and 1036 cm-1 could be related to the presence Si-O-Si bonds linking to tetrahedral coordination. The strong absorption bands appeared at 511 cm-1, 505 cm-1, 499 cm-1, and 496 cm-1 in respective samples are atributed to divalent cation bonds (e.g. Mg,Ni-O). It is shown that both TG/DTA and FTIR seem to be the powerful tool in diagnosis the crystal chemistry of garnierite which is mainly composed of phyllosilicate minerals. Key