Portable Raman Spectrometer for in situ analysis of asbestos and fibrous minerals

Asbestos inhalation is associated with fatal respiratory diseases and raises concerns from the perspective of workplace safety and environmental impacts. Asbestos and asbestos-like minerals naturally occur in rocks and may become airborne when outcrops or soils are disturbed by anthropic activities. In situ detection of these minerals is a crucial step for the risk evaluation of natural sites. We assess here whether a portable Raman spectrometer (pRS) may be used in the identification of asbestos and asbestos-like minerals at the mining front during exploitation. pRS performance was tested at three geologically different mining sites in Italy and New Caledonia and compared with a high-resolution micro-Raman spectrometer (HRS). About 80% of the overall in situ analyses at the mining front were successfully identified by pRS, even when intermixed phases or strongly disaggregated and altered samples were analyzed. Chrysotile and tremolite asbestos, asbestos-like antigorite, and balangeroite were correctly detected during surveys. The major difficulties faced during in situ pRS measurements were fluorescence emission and focussing the laser beam on non-cohesive bundles of fibers. pRS is adequate for discriminating asbestos and asbestos-like minerals in situ. pRS may support risk assessment of mining sites to better protect workers and environmen

Modelling the Fenton reaction of amphibole asbestos

In this work a sample of UICC crocidolite and a sample of fibrous tremolite were leached up to 1 week both in a simplified Gamble’s solution at acidic pH and in a phosphate buffered medium at neutral pH, in presence of H2O2. Surface chemical modifications were monitored by XPS spectroscopy. Subsequently, the generation of HO• radicals following reaction of both pristine and leached fibres with H2O2 (Fenton reaction) was investigated by spin trapping/EPR spectroscopy, with the aim of better clarifying the relationships between possible surface alteration occurring in vivo and chemical reactivity of amphibole asbestos. Moreover, the generation of HO• radicals was monitored on thermally treated fibres after leaching in phosphate buffered medium at neutral pH and in presence of H2O2 to investigate how chemical reactivity may be modulated by Fe oxidation state. Results showed that, for both amphibole asbestos, the surface alteration following incubation in the modified Gamble’s solution does not alter HO• radical generation. Interestingly, leaching in phosphate buffered solution in presence of H2O2 induced a progressive increase in HO• release for crocidolite fibres, whereas a strong reduction was observed for asbestos tremolite. This behaviour is likely due to the quicker alteration of the crocidolite surface due to the interaction with H2O2, as indicated by XPS analysis. In particular, the oxidation induced by H2O2 promotes the dissolution of the first atomic layer of the crocidolite structure and the following occurrence on its surface of new reactive Fe centres, particularly under the form of Fe(II), of which the bulk is richer than the oxidized surface. Accordingly, the heated samples showed a reduced, but not suppressed by thermal oxidation, chemical reactivity, with no significant evolution following incubation in phosphate buffered medium at neutral pH and in presence of H2O2

Evaluation of the Photocatalytic Activity of a Cordierite-Honeycomb-Supported TiO2 Film with a Liquid–Solid Photoreactor

Anatase nanoparticles in suspension have demonstrated high photoactivity that can be exploited for pollutant removal in water phases. The main drawback of this system is the difficulty of recovering (and eventually reusing) the nanoparticles after their use, and the possible interference of inorganic salts (e.g., sulfates) that can reduce the performance of the photocatalyst. The present work describes the development of a cordierite-honeycomb-supported TiO2 film to eliminate the problems of catalyst recovery. The catalyst was then tested against phenol in the presence of increasing concentrations of sulfates in a specially developed recirculating modular photoreactor, able to accommodate the supported catalyst and scalable for application at industrial level. The effect of SO42− was evaluated at different concentrations, showing a slight deactivation only at very high sulfate concentration (≥3 g L−1). Lastly, in the framework of the EU project Project Ô, the catalyst was tested in the treatment of real wastewater from a textile company containing a relevant concentration of sulfates, highlighting the stability of the photocatalyst

Altération des minéraux asbestiformes sous le climat subtropical : surveillance minéralogique et géochimie. L'exemple de la Nouvelle-Calédonie.

Under humid tropical to sub-tropical conditions, weathering processes and supergene mineralization are the main responsible for genesis and release of asbestos fibres. The New Caledonia is one of the largest world producers of Ni ore that is formed by the alteration of ultramafic rocks. Almost all outcrops of geological units and open mines contain serpentine and amphibole, also as asbestos varieties. Mining companies must therefore deal with the health concerns related to environmental exposure to mineral fibres. At present, there is not a technique capable to instantly characterize an asbestos fibre in situ, providing information about size and distribution, morphology, chemical composition and alteration grade. However, the acquisition of all these parameters is necessary for determining the health risk associated to fibre exposition. The employment of specialized tools such as Polarized Light Microscopy associated to Dispersion Staining (PLM/DS) and portable Raman spectroscopy has proved extremely effective in the improvement of performance and rapidity of data acquisition and interpretation, even in the presence of strongly fibrous and altered samples. Regardless of the alteration state, a great variability in morphology was observed (SEM investigation). Preliminary geochemical analyses have proved that the physical-mechanical effect of fluid circulation within the porous of fibres and lamellae, associated to chemical elemental exchange at rock/waters interface, favoured the dissociation of fibres and their release in the environment. A focus was set on fibrous antigorite, recognized as asbestos only by Caledonian legislation, but still not by European law.Sous climat humide tropical ou subtropical, les processus d'altération supergène sont les principaux responsables de la formation et de la libération des fibres d'amiante dans l’environnement. Plus du tiers de la Nouvelle Calédonie est recouvert d’unités ultrabasiques altérées, riches en minerai de Ni. L’exploitation minière du Ni doit composer avec la présence d’affleurements d’amiante et de minéraux fibreux de type serpentine et amphibole. Dans ce contexte, les sociétés minières doivent prévenir les risques sanitaires liés à l'exposition environnementale aux fibres minérales. Actuellement, il n'existe pas de technique analytique capable de caractériser instantanément une fibre d'amiante in situ, en fournissant des informations sur la distribution de taille, la morphologie, la composition chimique et le degré d'altération associés. Cependant, la connaissance de tous ces paramètres est nécessaire pour évaluer le risque sanitaire associé à l'exposition. L'utilisation des dispositifs portable tels quels la Microscopie Optique à Lumière Polarisée (MOLP) et la spectrométrie Raman représente la stratégie la plus efficace pour améliorer l'acquisition et l'interprétation des données, y compris pour les échantillons fortement fibreux et altérés. De plus, des analyses géochimiques préliminaires ont révélé que l'effet mécanique de la circulation des fluides entre les fibres et lamelles, associé à la lixiviation chimique des éléments à l'interface roche/eau, favorisent la dissociation des fibres et leur libération dans l'environnement. Un focus a été réalisé sur l'antigorite fibreuse, reconnue comme amiante uniquement dans la réglementation calédonienne

Amiante et bonnes pratiques. Rapport scientifique final

- Le programme « ABP, Amiante et bonnes pratiques », a proposé une étude intégrée et pluridisciplinaire depuis l’identification jusqu’au caractère pathogène des fibres issues des minéraux amiantifères présents en secteur minier néo-calédonien.- Au travers d’un échantillonnage d’un panel représentatif des asbestes présents (famille des serpentinites et des amphiboles), les minéralogies, les propriétés physico-chimiques et toxicologiques de ces minéraux amiantifères ont été caractérisées.- À noter que le programme ABP a apporté les premières données toxicologiques sur les fibres d’amiante néo-calédoniennes. Un intérêt particulier est porté sur l’antigorite, minéral fibreux très présent sur le territoire calédonien, notamment en secteur minier, mais non répertorié comme amiante dans la législation hors territoire

Monitoring environmental risk in fibrous minerals in New Caledonia: a comparison between different analytical methods

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