Studies on surface properties of asbestos

Bonneau, L.; Suquet, H.; Malard, C.; Pézerat, H.

doi:10.1016/s0013-9351(86)80187-6

Cited by 43 publications

(12 citation statements)

References 27 publications

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“…In doing so, the precision is improved but water amounts introduced into the system are increased and, consequently, the competition of the adsorption between water and phenanthrene is enhanced. (15). If a C 0 2 molecule is supposed to be sorbed on a basic site (OH group acting as an electron-pair donor), the number of basic sites on the chrysotile-2 surface may be estimated to be about 45% lower than on the chrysotile-1.…”

Section: Results and Discussion (A) Adsorption Properties Phenanthrenmentioning

confidence: 99%

Differences between adsorption properties of two Rhodesian chrysotile samples. Relation with the DTA features introduced by leaching and grinding

Suquet¹

1989

Can. J. Chem.

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H~L~N ESUQUET. Can. J . Chem. 67, 202 (1989). Substantial differences are founded between the absorption properties of two Rhodesian chrysotile samples (-1 and -2), which are, in most chemical and structural aspects, highly similar. The phenanthrene and C 0 2 amounts adsorbed are much less important on chrysotile-2 than on chrysotile-1. This indicates that chrysotile-2 has fewer basic surface sites. DTA and XRD results show that dry grinding and leaching produce a breakdown of the chrysotile structure, yield amorphous silica, and lower the temperature of the dehydroxylation peak. The dehydroxylation peaks of chrysotile-1 and -2 are really doublets. As the low-temperature component of the dehydroxylation peak is greater in chrysotile-2 than in chrysotile-1, the chrysotile-2 contains more ground and (or) leached fibers than chrysotile-l and consequently shows weaker absorption properties.Key words: chrysotile, leaching, phenanthrene adsorption.H~L~N E SUQUET. Can. J. Chem. 67, 202 (1989). On a observe des diffirences importantes dans les propriCtCs d'absorption de deux Cchantillons de chrysotile RhodCsiens (-1 et -2) qui sont, par leurs aspects chimiques et structuraux, trks semblables. Les quantitts de phknanthrkne et de COz qui sont adsorbtes sur la chrysotile-2 sont beaucoup plus faibles que celles adsorbCes sur la chrysotile-1. Ces donnkes indiquent que la chrysotile-2 possede moins de sites basiques. Les rCsultats obtenus par ATD et par DRX montrent que le broyage a sec ainsi que la lixiviation provoquent un effondrement de la structure de la chrysotile qui conduit a de la silice amorphe et a un abaissement de la tempirature du pic de dkhydroxylation. Les pics de dkhydroxylation des chrysotiles-1 et -2 sont en fait des doublets. Comme la composante basse tempCrature du pic de dChydroxylation est plus grande dans la chrysotile-2 que dans la chrysotile-1, on en conclut que la chrysotile-2 contient plus de fibres broyCes et (ou) lixiviCes que la chrysotile-1 et que, en conskquence, elle fait preuve de propriktCs d'adsorption plus faibles.

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Section: Results and Discussion (A) Adsorption Properties Phenanthrenmentioning

confidence: 99%

Differences between adsorption properties of two Rhodesian chrysotile samples. Relation with the DTA features introduced by leaching and grinding

Suquet¹

1989

Can. J. Chem.

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“…Dans notre cas, les sites en cause peuvent Ctre ceux des deux varietes d'amiante puisque nous avons montrC prCcCdemment que ces matkriaux avaient essentiellement un caracthe donneur d'ilectrons (3,4).…”

Section: Discussionunclassified

“…Nos prtcedents travaux sur les amiantes ont mis en evidence la presence dominante de sites donneurs d'electrons sur ces matkriaux. Ces sites sont des groupements O H en basse coordination, situes en frontikre de la phase solide (3,4). De plus, nous avons rev616 le caractkre catalytique des amiantes, notamment dans l'oxydation d'un hydrocarbure polyaromatique, le fluorhe (5).…”

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Hydrodésazotation de l'indole sur catalyseur fer supporté sur amiante

Zalma¹,

Bonneau²,

Fournier³

et al. 1987

Can. J. Chem.

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The aim of this study is to examine hydrodenitrogenation (HDN) of indole on asbestos catalysts (chrysotile and crocidolite) under hydrogen pressure. HDN is carried out according to two competitive pathways, either via ortho-ethylaniline or via ortho-toluidine. This reaction is assisted by increase of temperature and pressure and by pre-reduction of the asbestos. Particles of Fe0on the fibre surface are formed from the original material. Their presence plays a role in the initial breaking of the C—N bond and in the hydrogenation reaction.

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“…A partir do conhecimento da espécie do corante formada durante o processo de adsorção, pode-se caracterizar os diferentes microambientes (sítios de adsorção) presentes em cada tipo de argilas. O conhecimento das características desses sítios tem grande importância, por exemplo, quando se deseja descrever a reatividade de algumas macromoléculas biológi-cas, como enzimas e proteínas, encontradas nos solos 8 , a ação de pesticidas e herbicidas 3,4 , e em geral todos os processos envolvendo solos. A mesma metodologia descrita, empregando corantes como sondas, é também aplicada ao uso de sistemas similares como zeolitas e silicatos 9 .…”

Section: Divulgaçãounclassified

Interações entre corantes e argilas em suspensão aquosa

Neumann¹,

Gessner²,

Cione³

et al. 2000

Quím. Nova

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Recebido em 18/11/99; aceito em 16/3/00 INTERACTION BETWEEN DYES AND CLAYS IN AQUEOUS SUSPENSION.Adsorption of cationic dyes on clays can be used as a model for the interactions between organic compounds and these minerals. Cationic dyes like methylene blue are used to study these interactions because of the spectroscopic changes observed when their molecules are adsorbed on clay surfaces. Depending on the structure and layer charge of the clay particles several processes may occur, like adsorption of dye monomers and aggregates on the external and internal surfaces of the clay tactoids, migration towards internal surfaces, protonation, etc. Under certain conditions the deaggregation-aggregation of the clay particles are accelerated trapping dye species during these processes. A general scheme is proposed for the processes occurring between clays and dyes in aqueous suspensions, which can be used to explain the behaviour of specific systems.Keywords: cationic dyes; clays; clay-dye interactions. DIVULGAÇÃOAs interações de compostos orgânicos com argilas tem sido objeto de numerosas revisões da literatura 1,2 . O interesse nestes processos se direciona principalmente para o comportamento de herbicidas catiônicos 3 , fotoestabilização de complexos pesticidas-argilas 4 , moléculas de corantes orgânicos 5,6 e modificação hidrofóbica das superfícies de argilas.7 Por outro lado, as argilas podem servir como suportes e/ou catalisadores para vários tipos de reações e fotorreações. Cátions orgânicos participam de equilíbrio de troca iônica com a superfície das argilas, além de serem altamente seletivos, como mostram alguns estudos de adsorção competitiva 6 . A utilização de corantes como sondas é bastante interessante, já que são rapidamente adsorvidos pelas argilas e as diferentes espécies formadas após a adsorção são facilmente detectadas por técnicas espectroscópicas clássicas, como UV-VIS e fluorescência. A partir do conhecimento da espécie do corante formada durante o processo de adsorção, pode-se caracterizar os diferentes microambientes (sítios de adsorção) presentes em cada tipo de argilas. O conhecimento das características desses sítios tem grande importância, por exemplo, quando se deseja descrever a reatividade de algumas macromoléculas biológi-cas, como enzimas e proteínas, encontradas nos solos 8 , a ação de pesticidas e herbicidas 3,4 , e em geral todos os processos envolvendo solos. A mesma metodologia descrita, empregando corantes como sondas, é também aplicada ao uso de sistemas similares como zeolitas e silicatos 9 . ARGILAS 10-12A definição clássica designa argila como um material natural, terroso, de granulação fina que quando umedecido com água apresenta plasticidade. Os minerais constituintes das argilas são os argilominerais. Estes compostos são silicatos hidratados que possuem estrutura em camadas constituídas por folhas contínuas formadas por tetraedros de silício (ou alumí-nio) e oxigênio, e folhas formadas por octaedros de alumínio (magnésio ou ferro) e oxigênio e hidroxilas (Figura 1). 11Uma f...

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Studies on surface properties of asbestos

Cited by 43 publications

References 27 publications

Differences between adsorption properties of two Rhodesian chrysotile samples. Relation with the DTA features introduced by leaching and grinding

Differences between adsorption properties of two Rhodesian chrysotile samples. Relation with the DTA features introduced by leaching and grinding

Hydrodésazotation de l'indole sur catalyseur fer supporté sur amiante

Interações entre corantes e argilas em suspensão aquosa

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