Trace metals leaching from rocks

For the precise AMS analysis of Be and A1, Hunt et al. (2008) reported an efficient sample preparation method, where quartz was separated from rocks following a sequence of pulverization, size fractionation, acid etching and leaching, and liquid density separation. This protocol yields pure quartz mineral phase, however, trace-level contamination is expected. Most of the time quartz is contaminated due to lattice imperfections with some combination of native Al, Fe, Ti, alkalis, and alkaline earth metals. 

Reactions (1) and (4) result in strongly acidified solutions which, in addition to dissolve large amounts of Fe(II) and SO, also leach important quantities of many other major and trace metals from the mineralizations and the host rocks, including Al, Mg, and Ca (with minor Na, K, and Ba) from the accompanying aluminosilicates, carbonates, and sulfates, in addition to Cu, Zn, Mn, As, Pb, or Cd from other sulfides (sphalerite, chalcopy-rite, galena, arsenopyrite) and sulfosalts (tetrahedrite-tennantite). Iron and aluminum are usually the most abundant metal cations of those present in AMD [5, 9, 12, 22]. 

Extraction for the analyte from the fuel can be used for sample preparation, which combines the advantages of separating the analyte from the matrix, transferring it to an aqueous phase and may also result in preconcentration. Liquid-liquid extraction procedures present as main advantage for their simplicity. Akinlua and Smith (2010) reported the extraction of trace metals from petroleum source rock by superheated water and the conditions for maximum yield were determined. The optimum temperature for superheated water extraction of the metals from petroleum source rocks was 250°C. The extraction time was 30 min. The leaching of Cd, Cr, Mn and Ni had better yield with superheated water, while V had better yield with acid digestion. 

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