The x-ray identification and crystal structures of clay minerals

Thermal expansion of AlON and γ-Al2O3

There are several known deposits of bentonites in Croatia. Some of them have been used in the oil and casting industry and were thus studied with the focus on their appropriate properties. In the first comprehensive characterisation of the Croatian bentonite deposits mineralogical and petrological characterisation of investigated bentonites was performed leading to conclusions about their genesis. With the advancement of analytical methods and new findings about smectite characterisation in recent years, a demand for a full characterisation of known bentonite deposits occurred. Thirteen samples of bentonites were studied, most of them from Croatia (Poljanska Luka, Bednja, Draga – Gornja Jelenska, Loncarski Vis, Sjenicak, Paripovac, Divoselo and Bunaric - Maovice), but for comparison, samples from Bosnia and Herzegovina (Sipovo), Slovenia (Zaloska Gorica), and Serbia (Vranjska Banja) were also analysed. Their mineralogical and chemical characteristics were analysed using several analytical methods on whole rock and <2µm samples. Mineralogical composition was determined using XRD and IR analyses. Chemical composition was determined using ICP/AES and ICP/MS. Additionally ; thermal analyses have been made, as well as determination of CEC and the exchanged cations. Layer charge was determined both by chemical formulae calculations using chemical analysis data and experimentally, observing the swelling behaviour of potassium saturated samples solvated with ethylene glycol. The results were then compared with the classification system proposed recently. According to this classification scheme, the main mineral component of most of the investigated bentonites is a calcium-rich dioctahedral montmorillonite with experimentally determined low layer-charge deriving from the substitutions mostly occurring in the octahedral sheet with variable share of tetrahedral substitutions. However, three of the investigated samples contain beidellite as the main mineral. All of the bentonites were formed from altered volcanic material, their age ranging from Late Jurassic to Late Miocene. Some samples proved to be difficult to characterise as they contain impurities, both mineralogical impurities and amorphous substances such as volcanic glass, which rendered some of the data obtained by chemical analyses problematic to interpret. Overall, the results present a systematic classification of local bentonites based on latest analytical data and in accordance with widely accepted classification schemes. Inevitably, however, this work opens up questions about the reliability of some analytical methods when dealing with samples containing impurities and the need to complement several different analytical methods in order to obtain accurate results.

methods

Comprehensive characterisation of bentonites from Croatia and neighbouring countries

Natural bentonite clay was treated in order to remove impurities to increase the cation exchange capacity of the montmorillonite and to obtain a more effective radioactive cesium sorption. It was found that the treatment of the clay determines the amount of sorbed cesium. On the other hand it was shown that montmorillonites may retain cesium through several mechanisms which provide strongly retained cations occupying cationic sites into the clay structure or sorbed cesium which may be lost by purification treatments.

Modification of the structure of natural bentonite and study on the sorption of Cs

Etude D'Une Smectite Magnesienne De Transition, A Caracteristiques Di Et Trioctaedriques Et Derivee De L'Evolution Superficielle D'une Trachydolerite De Provence

The x-ray identification and crystal structures of clay minerals

Citations

Thermal expansion of AlON and γ-Al2O3

Comprehensive characterisation of bentonites from Croatia and neighbouring countries

Modification of the structure of natural bentonite and study on the sorption of Cs

Etude D'Une Smectite Magnesienne De Transition, A Caracteristiques Di Et Trioctaedriques Et Derivee De L'Evolution Superficielle D'une Trachydolerite De Provence

Geology of the Blackbutte mercury mine Lane County Oregon

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