Study of ground and unground leached vermiculite

0340225 - ÚACH 2010 RIV NL eng J - Journal Article
Maqueda, C. - Perez-Rodriguez, J. L. - Šubrt, Jan - Murafa, Nataliya
Study of ground and unground leached vermiculite.
Applied Clay Science. Roč. 44, 1-2 (2009), s. 178-184. ISSN 0169-1317. E-ISSN 1872-9053
Grant - others:CICYT(ES) AGL-2005-0164
Institutional research plan: CEZ:AV0Z40320502
Keywords : vermiculite * amorphous silica * acid leaching
Subject RIV: CA - Inorganic Chemistry
Impact factor: 2.784, year: 2009

Grinding of clays modifies their surfaces and can significantly affect their leaching behaviour. The acid reaction of vermiculite from Santa Olalla (Huelva, Spain) with HCl at various concentrations was affected by grinding and acid concentration. The acid leaching of ground vermiculite for 3 min with 1 M HCl solution at 80 degrees C for 24 h removed MgO and Al2O3 almost completely, leaving a residue containing SiO2 and Fe2O3. X-ray diffraction analysis showed the presence of akaganeite (beta-FeOOH) and an amorphous phase (silica). Porosity studies showed a very high specific surface area for ground samples compared with unground vermiculite samples, attributed to the presence of iron in the residue coming from structural iron. High resolution transmission electron microscopy (HRTEM) confirmed the presence of iron oxyhydroxides embedded in the silica material. The particle morphology of the iron oxides corresponded well to akaganeite microcrystals precipitated from solution.
Permanent Link: http://hdl.handle.net/11104/0183512