Lead sorbed onto volcanic ashes investigated by x-ray absorption spectroscopy and complementary techniques

Abstract

We report on the investigation of lead sorbed onto volcanic ashes using x-ray absorption spectroscopy (XAS) and complementary techniques such as x-ray diffraction (XRD), scanning electron microscopy (SEM), and energy dispersive x-ray spectroscopy (EDS). The ashes from Cameroon volcanic line are used for adsorption applications to remove lead in aqueous solutions. SEM and EDS revealed a heterogeneous structure with particles of different sizes, distributions and the presence of lead on the samples sorbed onto volcanic ashes. The obtained maximum adsorption capacity of the volcanic ashes was 7.60 mg·g−1 at pH 5. According to our results, a mixture of Pb chemical species and a strong interaction with the volcanic ashes surface was found. The XAS results showed that the lead removal occurred mainly by microprecipitation of lead acetate and carbonate (cerussite) and ion exchange. Additionally, it is shown that XAS can be applied to solve adsorption mechanisms.