Determination of La, Ce, Nd, Sm, and Gd in mineral waste from cassiterite beneficiation by wavelength-dispersive X-ray fluorescence spectrometry.

The objective of this study was to establish the best parameters to correct for matrix effects in the chemical analysis of a siliceous geologic material rich in metallic elements of high economic value, such as La, Ce, Nd, Sm, and Gd (rare earth elements), using empirical influence coefficients applied to wavelength dispersive X-ray fluorescence (WDXRF). At present, this material is considered waste derived from the extraction of tin from cassiterite, a special ore from which niobium and tantalum are also processed. In this study, a reliable methodology for the analysis of rare earth elements in a siliceous matrix using the WDXRF technique was developed.

Physical and chemical study of lattice kaolinites and their interaction with orthophosphate.

This study covers the evaluation of the structure and the capacity in adsorbing orthophosphate ions of kaolinites collected from sampling sites in Manaus (Brazil). The kaolinites were obtained using physical fractioning (sieving/siphoning) techniques and chemical treatment with HCl, H2SO4, H2O2 and KCl. The investigation of the kaolinite lattices involved the Hinckley and Plançon indexes determined from X-ray diffraction data, Fourier transformed infrared spectroscopy, scanning electron microscopy and Mössbauer spectroscopy.

Mercury conversion processes in Amazon soils evaluated by thermodesorption analysis.

This paper reports on the speciation study and the Hg redox behavior in Amazon soils not influenced by gold mining and collected near Manaus, AM, Brazil. The samples were incubated by adding Hg(0) and HgCl(2) to dry soil. Solid phase Hg speciation analysis was carried out using a Hg thermodesorption technique with the aim of distinguishing elemental Hg(0) from Hg(II) binding forms.

Speciation and quantification of mercury in Oxisol, Ultisol, and Spodosol from Amazon (Manaus, Brazil).

In order to investigate the content and distribution of Hg in soils from Amazon areas not impacted by gold mining activities, the concentration and granulometric distribution of Hg were determined in three different types of soils. Hg speciation data were obtained by a thermodesorption atomic spectrometry system and the role of physico-chemical and mineralogical characteristics on Hg content were also studied. Hg concentrations found in the soil fraction <2000 microm were similar to values found in other Amazon areas without anthropogenic sources.