Document Detail

A biomimetic approach to the chemical inactivation of chrysotile fibres by lichen metabolites.
MedLine Citation:
PMID:  17295378     Owner:  NLM     Status:  MEDLINE    
Some lichens were recently reported to modify the surface state of asbestos. Here we report some new insight on the physico-chemical modifications induced by natural chelators (lichen metabolites) on two asbestos samples collected in two different locations. A biomimetic approach was followed by reproducing in the laboratory the weathering effect of lichen metabolites. Norstictic, pulvinic and oxalic acid (0.005, 0.5 and 50 mM) were put in contact with chrysotile fibres, either in pure form (A) or intergrown with balangeroite, an iron-rich asbestiform phase (B). Mg and Si removal, measured by inductively coupled plasma atomic emission spectrometry (ICP-AES) and scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDS), reveals an incongruent dissolution for pure chrysotile (A), with Mg removal always exceeding that of Si, while chrysotile-balangeroite (B) follows a congruent dissolution pattern in all cases except in the presence of 50 mM oxalic acid. A much larger removal of Mg than Si in the solutions of 0.5 and 50 mM oxalic acid with chrysotile (A) suggests a structural collapse, which in the case of chrysotile-balangeroite (B) only occurs with 50 mM oxalic acid; in these cases both samples are converted into amorphous silica (as detected by X-ray diffraction (XRD)). Subsequent to incubation, some new phases (Fe(2)O(3), CaMg(CO(3))(2), Ca(C(2)O(4)) x H(2)O and Mg(C(2)O(4))2 x H(2)O), similar to those observed in the field, were detected by XRD and micro-Raman spectroscopy. The leaching effect of lichen metabolites also modifies the Fenton activity, a process widely correlated with asbestos pathogenicity: pure chrysotile (A) activity is reduced by 50 mM oxalic acid, while all lichen metabolites reduce the activity of chrysotile-balangeroite (B). The selective removal of poorly coordinated, highly reactive iron ions, evidenced by NO adsorption, accounts for the loss in Fenton activity. Such fibres were chemically close to the ones observed in the field. Chrysotile-rich rocks, colonised by lichens, could be exposed to a natural bioattenuation and considered as a transient environmental hazard.
Francesco Turci; Sergio E Favero-Longo; Maura Tomatis; Gianmario Martra; Daniele Castelli; Rosanna Piervittori; Bice Fubini
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  Chemistry (Weinheim an der Bergstrasse, Germany)     Volume:  13     ISSN:  0947-6539     ISO Abbreviation:  Chemistry     Publication Date:  2007  
Date Detail:
Created Date:  2007-05-24     Completed Date:  2007-06-19     Revised Date:  2009-08-04    
Medline Journal Info:
Nlm Unique ID:  9513783     Medline TA:  Chemistry     Country:  Germany    
Other Details:
Languages:  eng     Pagination:  4081-93     Citation Subset:  IM    
Dipartimento di Chimica IFM, Centre of Excellence of Nanostructured Interfaces and Surfaces (NIS), University of Torino, via Pietro Giuria 7, 10125 Torino, Italy.
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MeSH Terms
Asbestos, Serpentine / antagonists & inhibitors*,  chemistry
Lichens / chemistry*
Molecular Mimicry*
Plant Extracts / pharmacology*
Spectrum Analysis / methods
Reg. No./Substance:
0/Asbestos, Serpentine; 0/Plant Extracts

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