A new approach to the decontamination of asbestos-polluted waters by treatment with oxalic acid under power ultrasound.
A suspension of chrysotile asbestos fibres in aqueous 0.5M oxalic acid was subjected to power ultrasound with the aim to disrupt and detoxify the mineral by the leaching action of oxalic acid on its structural cations acting simultaneously with a vigorous acoustic cavitation. Sonication was performed in a "cavitating tube", a vertical hollow vibrating cylinder made of titanium, operating at 19.2 kHz and 150 W. Treatment lasted from 2.5 to 21 h. Scanning electron microscopy (SEM) showed that the joint action of the chelating agent and ultrasound (though not of either when applied independently) mostly converted asbestos fibres into micrometric aggregates and nano-sized debris, whose morphology totally differed from asbestos fibres. When treated suspensions were filtered through CA membranes (pore size 0.20 microm), more than half of the asbestos went through the filter because it had either been brought in solution or dispersed in the form of extremely small particles. Most of the structural metal ions were brought into solution (ICP-AES). After the treatment the BET surface area of the recovered solid was tenfold greater than the original. The crystalline fraction of residual solids, though resembling the original sample in XRD, was shown by micro-Raman spectra to be made of antigorite, a polymorph form of serpentine. Furthermore, as the length of these antigorite fibrils lay outside the fibre range rated as a health hazard under worldwide regulations, our procedure can be employed for the decontamination of chrysotile-polluted waters and sediments.
Turci
Francesco
F
Dipartimento di Chimica IFM, Interdepartmental Centre "G. Scansetti" for Studies on Asbestos and Other Toxic Particulates and Centre of Excellence of Nanostructured Interfaces and Surface (NIS), University of Torino, Via Pietro Giuria 7, 10125 Torino, Italy.
Tomatis
Maura
M
Dipartimento di Chimica IFM, Interdepartmental Centre "G. Scansetti" for Studies on Asbestos and Other Toxic Particulates and Centre of Excellence of Nanostructured Interfaces and Surface (NIS), University of Torino, Via Pietro Giuria 7, 10125 Torino, Italy.
Mantegna
Stefano
S
Dipartimento di Scienza e Tecnologia del Farmaco, University of Torino, Via Pietro Giuria 9, 10125 Torino, Italy.
Cravotto
Giancarlo
G
Dipartimento di Scienza e Tecnologia del Farmaco, University of Torino, Via Pietro Giuria 9, 10125 Torino, Italy. Electronic address: giancarlo.cravotto@unito.it.
Fubini
Bice
B
Dipartimento di Chimica IFM, Interdepartmental Centre "G. Scansetti" for Studies on Asbestos and Other Toxic Particulates and Centre of Excellence of Nanostructured Interfaces and Surface (NIS), University of Torino, Via Pietro Giuria 7, 10125 Torino, Italy. Electronic address: bice.fubini@unito.it.
D017632:Asbestos, Serpentine / Q000737:chemistry* / Q000528:radiation effects*; D007202:Indicators and Reagents; D008274:Magnesium / Q000737:chemistry; D013058:Mass Spectrometry; D008855:Microscopy, Electron, Scanning; D019815:Oxalic Acid / Q000737:chemistry* / Q000528:radiation effects*; D010316:Particle Size; D019163:Reducing Agents; D013059:Spectrum Analysis, Raman; D013499:Surface Properties; D014465:Ultrasonics; D014874:Water Pollutants, Chemical / Q000737:chemistry* / Q000528:radiation effects*; D014961:X-Ray Diffraction
D017632:Asbestos, Serpentine; D007202:Indicators and Reagents; D019163:Reducing Agents; D014874:Water Pollutants, Chemical; D019815:Oxalic Acid; D008274:Magnesium