Mechanochemical treatment to recycling asbestos-containing waste

Our plain-English summary of Mechanochemical treatment to recycling asbestos-containing waste, by P. Plescia, D. Gizzi, S. Benedetti, et al (Waste Management, 2003).

The study

• Authors: P. Plescia, D. Gizzi, S. Benedetti, L. Camilucci, C. Fanizza, P. De Simone, F. Paglietti
• Journal: Waste Management
• Published: 2003;23(3):209-18
• Cited by: 37 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Numerous industrial and experimental facilities have been set up, particularly in the last ten years, as a result of studies and researches on treating asbestos-containing waste (ACW) to stabilise it and to enable its reuse. Some of the stabilisation processes reduce the hazards of ACW by imprisoning in a cement or resonoid matrix. Other processes modify the fibrous structure of asbestos and transform it into an inert substance. One such inactivation process is mechanochemical transformation. This new technology is extremely interesting both economically and industrially, especially in view of the European Directive 1999/3/CE of 24/4/99, which provides for the obligatory treatment of all types of waste material before its disposal.

In plain English

This was a laboratory experiment on waste materials, not a study of people or health. The authors tested whether intense grinding, a 'mechanochemical' treatment, could destroy asbestos fibres. They ground five asbestos-containing waste samples for 12 minutes each in a high-speed ring mill. The samples, including asbestos-cement, contained amosite, chrysotile, crocidolite or mixtures of these. Standard asbestos samples were ground for varying times. Samples were examined by optical and electron microscopy and X-ray diffraction before and after grinding. Afterwards, asbestos fibres were no longer seen in any sample, and the X-ray patterns typical of asbestos were absent. The authors reported that chrysotile tended toward an amorphous (non-crystalline) phase after 4 minutes, while amphiboles were transformed in 8 to 12 minutes. The authors concluded that the process could be successfully applied to asbestos-containing waste on an industrial scale. They noted their mill turned at 250 rpm, against 2000 to 2500 rpm for industrial mills, and that microfibres can be lost into the air during grinding.

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: laboratory experiment: grinding tests on asbestos-containing waste samples and standard asbestos samples, analysed before and after treatment
• Who was studied: five samples of asbestos-containing waste of different origins and types (labelled E1 to E5), plus standard asbestos samples; no people were studied
• Exposure: Mechanochemical treatment by grinding in a Herzog HSM100 ring mill with a tungsten carbide bowl. Waste samples were ground for 12 minutes, and standard chrysotile for several durations. Sample E1 contained amosite. E2 was asbestos-cement sheets with chrysotile and amosite. E3 was asbestos-cement with chrysotile and crocidolite. E4 was calcium carbonate with chrysotile. E5 was asbestos-cement with chrysotile, crocidolite and organic fibre.
• Main results:
  • After grinding, optical (PCM) and electron (SEM) microscopy showed that asbestos fibres had disappeared in all samples
  • X-ray diffraction showed that the main diffraction peaks typical of asbestos were absent in the treated samples
  • Chrysotile tended toward an amorphous phase after 4 minutes of grinding; amphiboles were transformed in 8 to 12 minutes
  • With 20 minutes of grinding, the amorphous material from chrysotile tended to crystallize as another phase, which the authors suggested resembled olivine
  • The larger particles after treatment were mainly aggregates of homogeneous composition (calcium, silicon, magnesium, iron), with a shape ratio different from the 3:1 typical of fibres
• The authors' conclusion: The authors concluded that the mechanochemical process transformed asbestos into an amorphous material, and believed it could be successfully applied to asbestos-containing waste on an industrial scale
• Limitations the authors state:
  • The laboratory mill was slower and had lower impact than industrial machines: 250 rpm compared with 2000 to 2500 rpm
  • Carbon dioxide released from calcite during grinding creates a reducing environment that increases treatment time; grinding conditions need a controlled atmosphere
  • Microfibres can be lost into the air during grinding, so airflows must be filtered and powders recycled

Related studies

• Microwave thermal inertisation of asbestos containing waste and its recycling in traditional ceramics — C. Leonelli, P. Veronesi, et al. (2006)
• Thermal plasma technology for the treatment of wastes: a critical review — E. Gomez, D.A. Rani, et al. (2009)
• Classification and management of asbestos-containing waste: European legislation and the Italian experience — F. Paglietti, S. Malinconico, et al. (2016)
• Neutralization of cement-asbestos waste by melting in an arc-resistance furnace — J. Witek, R. Kusiorowski (2017)
• A study of silicon carbide synthesis from waste serpentine — T.W. Cheng, C.W. Hsu (2006)
• A review of mechanochemistry applications in waste management — X. Guo, D. Xiang, et al. (2010)

Browse more research in Waste Management, or return to medical research.