This study investigates the kinetics of the dehydroxylation reaction of chrysotile asbestos, a process crucial for the thermal neutralisation and potential reuse of asbestos-containing waste. Chrysotile, historically the most widely used form of asbestos, a structural transformation upon heating, destroying its fibrous, hazardous form. The reaction was analysed using both non-isothermal thermogravimetry (from 2.5 to 22.5 K·min⁻1) and isothermal calcination (from 823 to 973 K). Activation energy (Ea) was determined using the Friedman isoconversional method and Arrhenius analysis, yielding values of 303 kJ mol⁻1 and 188 kJ mol⁻1, respectively. Despite the variation in Ea due to methodological and experimental differences, both approaches identified diffusion-controlled mechanisms as the rate-limiting step, particularly the diffusion of water vapour from the reaction zone, but only below approximately 900 K. At higher temperatures, the reaction appears to transition to a different kinetic regime. These findings deepen understanding of the reaction kinetics and contribute to the development of effective thermal treatment technologies for managing asbestos waste.
In this research, poly(glycerol adipate) prepolymer (pPGA) was synthetized using enzymatic polymerization of divinyl adipate (DVA) and glycerol in reaction carried out in the presence of Candida Antarctica enzyme. The pPGA was then solved in 1,4-dioxane and mixed with L-lysine diisocyanate (LDI), bioglass, pourged into mold with sodium chloride, cured and freeze-dried. LDI has a dual function in the system: it is a cross-linking agent and also a bioactive agent that is chemically bound to the scaffold. Three types of porous composite scaffolds having 20 wt.% of bioglass and different cross-linking degree (25, 50 and 100 mol% of LDI) were investigated. The scaffolds were characterized by means of porosity, density, SEM. All tested materials were subjected to a quasi - static compression test. Each material was compressed 10 times. It was shown that the materials exhibited a return to their original shape even with a large compression strain of 90%. An imaging study of the scaffolds before and after compression was conducted using computed tomography (CT). The CT study showed that the resulting materials were not significantly mechanically damaged in the multi - compression process.
Asbestos is a general name applied to a group of silicate minerals which naturally occur in fibrous form. It is a natural mineral widely used in the past, especially in the construction industry. Despite its good performance properties, it is currently known that asbestos has carcinogenic properties. The problem of storing asbestos wastes is significant worldwide. This especially applies to countries where the production and use of asbestos products is prohibited by law. One of the possible methods of proceeding and solving the above problem is a thermal treatment, which results in thermal decomposition of dangerous asbestos fibers. The kinetic study of the thermal decomposition process carried out for cement-asbestos has been investigated by ex-situ thermal treatment. Obtained results allow for kinetic interpretation of this thermal transformation. The kinetic analysis of the isothermal data using an Avrami model yields values for the overall reaction order. The apparent activation energy of the thermal decomposition process for tested cement-asbestos sample is about 160 kJ/mol.
Recycling of chrysotile asbestos materials is a global problem. Even though the materials containing asbestos have good properties like resistance to elevated temperatures, high elasticity and mechanical strength, or abrasion resistance, it has been proven to be carcinogenic and banned in over 70 countries. Standard disposal of asbestos products - storing them in appropriately designated areas (landfills) - is a risk-taking method due to the possibility of secondary pollution of the surrounding environment and the waste of natural resources. One of the popular methods of neutralisation asbestos fibres is their thermal treatment. This study aimed to investigate the effect of thermal treatment in the range 25-1000�C in conventional parameters and under reduced pressure of -0.1 and -0.5 bar on the dehydroxylation process of chrysotile. The thermal decomposition course of chrysotile studied by differential thermal analysis (DTA) and thermogravimetric measurements (TG-DTG) showed the possibility of using low pressure to increase the efficiency of the thermal treatment process.
Problems related to the harmfulness and disposal of asbestos materials are well known all over the world. The paper presents the results of research on asbestos waste thermal treatment that is focused on the obtaining of mineral binders. The tests were performed in an electric arc-resistance furnace, in two different ways. The test results have demonstrated that the fibrous structure of asbestos contained in cement-asbestos waste is completely destroyed by thermal treatment, which allows the conversion of asbestos-containing materials into new secondary raw materials without asbestos. Moreover, the so obtained new materials exhibit binding properties close to those of traditional mineral binders, like ordinary Portland cement clinker. The research results indicate that the asbestos waste treatment process is a potential and interesting method of neutralizing this hazardous asbestos waste, enabling the material to be further recycled in the future.
