T. Zaremba

Thermal decomposition of different types of asbestos

Given the known carcinogenic effects, asbestos minerals are considered as general health hazard. Therefore, the elimination of asbestos materials from the environment is necessary. Asbestos minerals should be entirely transformed to a non-hazardous material. One of these methods is destructing the fibers structure of asbestos minerals by thermal treatment. Asbestos minerals are naturally occurring hydrous silicates, so that they decompose to release water by heating at high temperatures which may lead to changes in crystal structure and the formation of new phases without the dangerous properties. In this article, thermal behavior of asbestos minerals is investigated to observe the disappearance of this hazardous structure and to characterize products obtained by this way. Ten samples of asbestos minerals (six chrysotile samples from different locations, two samples of crocidolite, one amosite, and one tremolite) from different locations were tested. Mineralogical and morphological data (X-ray diffraction, Fourier transform infrared spectroscopy, and scanning electron microscopy) were obtained before and after differential thermal analysis.

Thermal decomposition of asbestos-containing materials

Asbestos is the common name applied to a group of natural, fibrous silicate minerals, which were once one of the most popular raw materials to be used in building materials. Asbestos was mainly used for the production of assortment asbestos–cement products. Today it is generally known that asbestos belongs to the group of hazardous materials and shows carcinogenic activity. In Poland, asbestos-containing materials are stored in special landfills. This is not the final solution to the asbestos problem because the fibrous structure of asbestos is still maintained. Therefore, methods based on recycling must be found which will be able to destroy asbestos’ dangerous fibrous structure. One of these methods may be thermal decomposition, where chemically combined water is released from the asbestos materials during heating. This leads to changes in the crystal structure and to the formation of new mineral phases. The aim of the preliminary research presented in this study was to determine the thermal behaviour as well as the structural and phase transformations of asbestos–cement materials during heating to high temperature. In the present study, three different types of asbestos-containing materials from Poland were examined. Differential thermal analysis, thermogravimetry with evolved gas analysis, X-ray diffraction, infrared spectroscopy and scanning electron microscopy were used to study the thermal decomposition of asbestos–cement samples. It was found that there were no significant differences between the type of asbestos–cement samples used—their thermal decomposition takes place in a similar way.

Utilisation of cement-asbestos wastes by thermal treatment and the potential possibility use of obtained product for the clinker bricks manufacture

The aim of this study was to investigate the thermal behaviour of cement-asbestos wastes and to determine whether it is possible to use them in the production of building ceramics, e.g. clinker bricks. In the first part of the research, the process of cement-asbestos thermal decomposition was studied. This asbestos material contained the chrysotile and crocidolite variety of asbestos. The results of this study allowed to determine the lowest temperature of thermal treatment that provides asbestos detoxification. The second part of the paper presents the results of a preliminary study on using previously calcined cement-asbestos wastes as an additive to ceramic masses typical for clinker bricks. Green compacts containing various amounts of cement-asbestos wastes were sintered and then ceramic properties were determined. The results of the study indicate that calcined asbestos-containing materials can be used as one of the secondary raw materials in the production of clinker ceramics.

Synthesis of K2Ti4O9 whiskers

Potassium tetratitanate (K2Ti4O9) whiskers were synthesized by the calcination and slow-cooling method. Powder X-ray diffraction (XRD) analysis and differential thermal analysis (DTA) were used to study the formation of K2Ti4O9. In the slow-cooling calcination process, the control of cooling rate was crucial to growth of K2Ti4O9 whiskers. The characterization of the whiskers was carried out by means of scanning electron microscope (SEM).