Microwave thermal inertisation of asbestos containing waste and its recycling in traditional ceramics

Our plain-English summary of Microwave thermal inertisation of asbestos containing waste and its recycling in traditional ceramics, by C. Leonelli, P. Veronesi, D.N. Boccaccini, et al (Journal of Hazardous Materials, 2006).

The study

• Authors: C. Leonelli, P. Veronesi, D.N. Boccaccini, M.R. Rivasi, L. Barbieri, F. Andreola, I. Lancellotti, D. Rabitti, G.C. Pellacani
• Journal: Journal of Hazardous Materials
• Published: 2006;135(1-3):149-55
• Cited by: 33 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Asbestos was widely used as a building material prior to the 1970's. It is well known that asbestos is a health hazard and its progressive elimination is a priority for pollution prevention. Asbestos can be transformed to non-hazardous silicate phases by microwave thermal treatment. The aim of this investigation is to describe the microwave inertization process of asbestos containing waste (ACW) and its recycling in porcelain stoneware tiles, porous single-fired wall tiles and ceramic bricks following industrial manufacture procedure. Inertised asbestos powder was added in the percentages of 1, 3, and 5 wt.% to commercially available compositions and then fired following industrial thermal cycles. Water absorption and linear shrinkage of the obtained industrial products do not present significant variations with additions up to 5 wt.% of microwave inertised ACW.

In plain English

This Italian study of materials, not people or animals, tested whether microwave heating could make asbestos containing waste non-fibrous and reusable in ceramics. Bricks were made and fired at an industrial plant; other work was laboratory-based. The waste was almost pure serpentine asbestos building insulation with a little organic binder. Heat analysis showed at least 803 degrees C was needed to lose the fibrous form. After 13 minutes of microwaving, X-ray analysis showed a new mineral, forsterite, and microscopy showed complete loss of fibrous structure. A 25-minute treatment heated samples well above 1200 degrees C and made them glassy. The treated powder was added at 1, 3 and 5 percent by weight to porcelain stoneware tiles, porous single-fired wall tiles and bricks. Water absorption changed little, falling slightly in bricks; shrinkage stayed within industrial tolerance. Using their 1.2 kW unit and Italian electricity prices of 6 October 2005, the authors estimated running costs at 0.04 to 0.12 euro per kg, excluding installation. They concluded that the forsterite, which they called harmless, suited tile and brick making as a raw material.

We wrote this plain-English summary from the full article with the help of AI, and a second AI model checked each sentence against the article. It is not the authors' wording; the abstract and the article are their own account.

What the study did and found

• Design: Materials experiment: microwave heat treatment of asbestos containing waste and tile test firings in the laboratory, with brick samples made and fired at an industrial plant. No human or animal subjects.
• Who was studied: Samples of asbestos containing waste (almost pure serpentine asbestos with a small amount of organic binder, used for building insulation), supplied by ENEA, Italy. The number of samples is not stated.
• Exposure: Microwave irradiation at 2.45 GHz for 13 minutes (inertisation) or 25 minutes (vitrification). The treated material was then added at 1, 3 and 5 wt.% to ceramic mixes. Bricks were fired in an industrial kiln at 950 degrees C.
• Main results:
  • Thermal analysis of untreated waste showed a peak at 803 degrees C marking the change from fibrous to crystalline structure. The authors stated that samples must be heated at least to this temperature.
  • After 13 minutes of microwave treatment, X-ray diffraction showed formation of a new crystalline phase, forsterite.
  • Electron microscopy showed complete loss of the fibrous structure in the treated samples.
  • With 25 minutes of treatment, the temperature rose well above 1200 degrees C and the samples vitrified (became glassy).
  • Adding the treated waste did not change the water absorption of the ceramics to a great extent.
  • Bricks showed a slight decrease in water absorption compared with the standard.
  • Porcelain stoneware tile results agreed with ISO 13006, which sets water absorption at 0.05% or less.
  • Linear shrinkage values were within industrial tolerance for all materials.
  • The cost estimate was based on the 1.2 kW multimode applicator used in this investigation.
  • Using Italian electricity prices of 6 October 2005, the estimated running cost of microwave treatment was about 0.04 to 0.12 euro per kg.
  • The authors estimated that Italy's 30 million tons of asbestos containing waste could be eliminated in 57 years at a 5 wt.% addition to products.
• The authors' conclusion: The authors concluded that forsterite derived from microwave-treated asbestos waste was a suitable secondary raw material for ceramic tiles and bricks. They also estimated that recycling costs were 10 times lower than disposal as toxic waste.
• Limitations the authors state:
  • The cost estimate covered only running costs, not initial installation costs.

Topics

Medical terms in this study, explained in our Lexicon: Silicate.

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