Thermal treatment of mechanochemically activated kaolinite

Horváth, Erzsébet; Frost, Ray L.; Makó, Éva; Kristóf, János; Cseh, Tamás

doi:10.1016/s0040-6031(03)00184-9

Cited by 117 publications

(72 citation statements)

References 25 publications

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“…It was observed that enthalpy of dehydroxylation (∆H dehy ) decreased as grinding time increased ( Figure 5). This implies that partially dehydroxylation already occurred during the grinding process as observed for kaolinite [59]; montmorillonite [58] and sepiolite [61]. This dehydroxylation is related with the loss of some OH groups through a prototropic mechanism based on the concept of protons migration during grinding and their consequent combination with hydroxyl groups to form water molecule.…”

Section: Discussionmentioning

confidence: 85%

“…However, the decrease in temperature is stronger in amosite ground for 5 min than in crocidolite and chrysotile, thus proving that amosite is less resistant to grinding and thus markedly damaged. Furthermore, in crocidolite, grinding treatment for 5 and 10 min produces: (i) a disappearance of the first event at 374 • C related to the loss of hydrogen ions and electrons to give oxy-crocidolite [46] since the dehydrogenation process from a strongly altered structure had already been completed during grinding process as occurs for other silicates [58,59]; (ii) a decrease in second endothermic effect due to easier dehydroxylation from a strongly altered structure. Chrysotile and amosite decomposition took place essentially in one main endothermic effect.…”

Section: Discussionmentioning

confidence: 98%

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Effect of Grinding on Chrysotile, Amosite and Crocidolite and Implications for Thermal Treatment

2018

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Nowadays, due to the adverse health effects associated with exposure to asbestos, its inertization is one of the most important issues of waste risk management. Based on the research line of mechano-chemical and thermal treatment of asbestos containing materials, the aim of this study was to examine the effects of dry grinding on the structure, temperature stability and fibre size of chrysotile from Balangero (Italy), as well as standard UICC (Union for International Cancer Control) amosite and standard UICC (Union for International Cancer Control) crocidolite. Dry grinding was accomplished in an eccentric vibration mill by varying the grinding time (30 s, 5 and 10 min). Results show a decrease in crystallinity, the formation of lattice defects and size reduction with progressive formation of agglomerates in the samples after the mechanical treatment. Transmission electron microscopy (TEM) results show that the final product obtained after 10 min of grinding is composed of non-crystalline particles and a minor residue of crystalline fibres that are not regulated because they do not meet the size criteria for a regulated fibre. Grinding results in a decrease of temperature and enthalpy of dehydroxylation (∆H dehy ) of chrysotile, amosite and crocidolite. This permits us to completely destroy these fibres in thermal inertization processes using a lower net thermal energy than that used for the raw samples.

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Section: Discussionmentioning

confidence: 85%

Section: Discussionmentioning

confidence: 98%

Effect of Grinding on Chrysotile, Amosite and Crocidolite and Implications for Thermal Treatment

2018

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“…The objective of this work is to undertake a comparative study of the thermal stability of wheatleyite and moolooite using a combination of high resolution thermogravimetry coupled to evolved gas mass spectrometry [51][52][53][54].…”

Section: Introductionmentioning

confidence: 99%

“…Thermal analysis has been used extensively for testing the stability of minerals [29][30][31][32][33][34][35][36][37][38][39][40][41][42][43][44][45][46]. To the best of the authors knowledge no thermoanalytical studies of halotrichites have been undertaken; although differential thermal analysis of some related minerals has been published [47][48][49][50].The objective of this work is to undertake a comparative study of the thermal stability of wheatleyite and moolooite using a combination of high resolution thermogravimetry coupled to evolved gas mass spectrometry [51][52][53][54]. …”

mentioning

confidence: 99%

Thermogravimetric analysis of wheatleyite Na2Cu2+(C2O4)2·2H2O

Frost

Locke

Martens

2008

J Therm Anal Calorim

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Evidence for the existence of primitive life forms such as lichens and fungi can be based upon the formation of oxalates. These oxalates form as a film like deposit on rocks and other host matrices. The anhydrous oxalate mineral moolooite CuC 2 O 4 as the natural copper (II) oxalate mineral is a classic example. Another example of a natural oxalate is the mineral wheatleyite Na 2 Cu 2+ (C 2 O 4 ) 2 .2H 2 O. High resolution thermogravimetry coupled to evolved gas mass spectrometry shows decomposition of wheatleyite at 255°C. Two higher temperature mass losses are observed at 324 and 349°C. Higher temperature mass losses are observed at 819, 833 and 857°C. These mass losses as confirmed by mass spectrometry are attributed to the decomposition of tennerite CuO. In comparison the thermal decomposition of moolooite takes place at 260 °C. Evolved gas mass spectrometry for moolooite shows the gas lost at this temperature is carbon dioxide. No water evolution was observed, thus indicating the moolooite is the anhydrous copper (II) oxalate as compared to the synthetic compound which is the dihydrate.Keywords: oxalate, wheatleyite, moolooite, copper(II) oxalate, Raman spectroscopy, high resolution thermogravimetry, evolved gas mass spectrometry IntroductionThe presence of oxalates is widespread in nature. These minerals form as the result of expulsion of heavy metals from fungi, lichens and plants [1][2][3]. The production of simple organic acids such as oxalic and citric acids has profound implications for metal speciation in biogeochemical cycles [4]. The metal complexing properties of the acids are essential to the nutrition of fungi and lichens and affects the metal stability and mobility in the environment [4]. Lichens and fungi produce the oxalates of heavy metals as a mechanism for the removal of heavy metals from the plant [5].Thermal analysis has been used for a long time for the analysis of oxalates [6][7][8][9][10][11][12][13][14][15]. Many of these analyses were undertaken many years ago [16][17][18][19][20][21]. The development of technology in thermal analysis has meant that high resolution studies with evolved gas mass spectrometry can now be undertaken to study both synthetic and natural oxalates [22][23][24][25][26][27]. A mineral commonly found in the drier parts of Australia is the mineral moolooite which is the anhydrous copper(II) oxalate. The mineral has been formed through the expulsion of copper from primitive plant forms. These primitive plant forms have been found on host rocks which contain copper. The presence of• Author to whom correspondence should be addressed (r.frost@qut.edu.au) 2 oxalates is widespread in nature, not only in plants but also as naturally occurring minerals. Among these minerals is the sodium copper oxalate mineral wheatlyite [28].The thermal stability of minerals such as the natural oxalates is important to test for life on Mars.. Thermal analysis has been used extensively for testing the stability of minerals [29][30][31][32][33][34][35][36][37][38][39][40][41][42...

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“…-O segundo pico se refere à perda de hidroxilas de constituição da caulinita, ilita, flogopita e merlionita podendo atingir temperaturas superiores a 500ºC dependendo da cristalinidade (SANTOS, 1975;GRIM, 1953;HORVÁTH et al, 2003;COSTA et al, 2004) 500-700 --Perda de hidroxilas da muscovita (RAMACHANDRAN et al, 2003 A parcela hidratada ou carbonatada não variou significativamente entre as frações granulométricas selecionadas, sendo aproximadamente 50% de cada parcela, apesar do aumento de área de pasta de cimento ou de cal endurecida exposta nas frações granulométricas miúdas e finas. A diferença da perda de massa acima de 750 ºC representa a fração de CO 2 da calcita bem cristalizada proveniente de rochas calcárias.…”

Section: Termogravimetria -Antes E Após O Ataque Com Hcl 33%unclassified

Caracterização de agregados de resíduos de construção e demolição reciclados e a influência de suas características no comportamento de concretos.

Angulo¹,

John²,

Kahn³

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Thermal treatment of mechanochemically activated kaolinite

Cited by 117 publications

References 25 publications

Effect of Grinding on Chrysotile, Amosite and Crocidolite and Implications for Thermal Treatment

Effect of Grinding on Chrysotile, Amosite and Crocidolite and Implications for Thermal Treatment

Thermogravimetric analysis of wheatleyite Na2Cu2+(C2O4)2·2H2O

Caracterização de agregados de resíduos de construção e demolição reciclados e a influência de suas características no comportamento de concretos.

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