Environmental Geology

, Volume 52, Issue 7, pp 1365–1374

Arsenic adsorption on nanocrystalline goethite: the natural example of bolar earths from Mt Amiata (Central Italy)

Original Article

DOI: 10.1007/s00254-006-0579-4

Cite this article as:
Manasse, A. & Viti, C. Environ Geol (2007) 52: 1365. doi:10.1007/s00254-006-0579-4


Bolar earths deposits from Mt Amiata (Central Italy) consist of nanosized pseudo-spherical goethite, with average crystal size of 10–15 nm (as determined by X-ray powder diffraction and transmission electron microscopy observations), possibly associated to amorphous silica and minor sheet silicates, quartz and feldspars. Chemical analyses revealed high As contents (up to 7.4 wt% As2O5), thus indicating the occurrence of a potentially dangerous contaminant. Arsenic doesn’t occur as a specific As phase, but it is strictly associated with goethite nanocrystals. Eh and pH measurements suggest that As occurs as arsenate anions (H2AsO4 and HAsO42−), which are easily and strongly adsorbed to goethite surfaces. The high specific surface area, resulting from goethite nanosize, and the absence of competitive anions explain the extremely efficient adsorption of arsenate and the anomalously high As content in bolar earths. Overall physical/chemical data suggest stable arsenate adsorption, with very limited risk for As release to the environment.


Bolar earthsArsenicAdsorptionGoethite nanocrystalsMt Amiata

Copyright information

© Springer-Verlag 2006

Authors and Affiliations

  1. 1.Dipartimento di Scienze della TerraUniversity of SienaSienaItaly