The Self-sustained High temperature Synthesis (SHS) technology as novel approach in the management of asbestos waste

Our plain-English summary of The Self-sustained High temperature Synthesis (SHS) technology as novel approach in the management of asbestos waste, by L. Gaggero, M. Ferretti (Journal of Environmental Management, 2018).

The study

• Authors: L. Gaggero, M. Ferretti
• Journal: Journal of Environmental Management
• Published: 2018;216:246-256
• Cited by: 2 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

The SHS technique was experimented in chrysotile breakdown. By means of two reactions such as Mg3Si2O5(OH)4 + Fe2O3 + 3 Mg and 2Mg3Si2O5(OH)4 + Fe3O4 + 4 Mg the chrysotile was completely converted into forsterite-rich olivine. Different mixtures of hematite + Mg and magnetite + Mg were tested with chrysotile to establish the maximum chrysotile amount in order to allow the reaction. In comparison with conventional thermal treatments, the SHS process is characterized by a fast reaction, needs low activation energy and the apparatus is simple. For these reasons, the asbestos neutralisation is carried out with positive balance of time and costs of the process. Furthermore, the combustion product can be re-used as secondary material.

Copyright © 2017 Elsevier Ltd. All rights reserved.

In plain English

This was a laboratory experiment testing whether a heat-releasing chemical reaction called Self-sustained High temperature Synthesis (SHS) could break down chrysotile asbestos. The authors used natural chrysotile fibres from a serpentinite vein in Petronio Valley, Eastern Liguria, Italy. They mixed the fibres with iron oxide (hematite or magnetite) and magnesium and pressed them into small pellets. In the pellets listed, chrysotile made up between 45 and 65 percent by weight. For comparison, chrysotile was also heated conventionally in a furnace. After more than 36 hours at 1000 degrees C, the furnace-heated samples had become forsterite and enstatite but still kept their fibrous shape. In the SHS pellets, the reaction took some seconds. The fibrous shape completely disappeared, and the chrysotile was converted into stubby grains of forsterite-rich olivine. X-ray analysis of the hematite-plus-magnesium pellets found no chrysotile left. Reaction temperatures fell as chrysotile content rose. The authors concluded that SHS has advantages over conventional heat treatment in speed, energy and equipment, and that its product could be reused, for example as abrasive or refractory 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: Laboratory experiment on the chemical breakdown of chrysotile. It compared SHS (combustion synthesis) with preliminary conventional step heating. This was not a health study.
• Who was studied: Natural chrysotile fibres from a serpentinite vein in Petronio Valley, Eastern Liguria, Italy. For SHS, the fibres were made into nine listed pellets: eight with mixed reactants and one layered.
• Exposure: Chrysotile was mixed with hematite plus magnesium or with magnetite plus magnesium and ignited by SHS. Chrysotile content in the pellets ranged from 45 to 65 weight percent. For comparison, chrysotile was also heated conventionally in a furnace at 1000 degrees C for 24 to 48 hours.
• Main results:
  • Conventional furnace heating: after more than 36 hours at 1000 degrees C, the samples were composed of forsterite and enstatite but still had a fibrous habit.
  • SHS: with the reactants of both reactions (hematite plus magnesium, and magnetite plus magnesium), the chrysotile was completely converted into forsterite-rich olivine.
  • SHS: after ignition, the fibrous habit completely disappeared, and the new olivine had a prismatic, stubby shape.
  • X-ray analysis of hematite-plus-magnesium pellets after SHS found no chrysotile in either mixed or layered pellets. It had been replaced by forsterite, periclase and iron.
  • SHS pellets lost on average about 4% of their weight. Adjusted for the chrysotile share of the pellet, this corresponds to a loss of 10 to 12%, which the authors linked to dehydroxilation of chrysotile.
  • The SHS breakdown took some seconds in these experiments, compared with conventional thermal treatments.
  • As chrysotile content in the pellets increased, lower reaction temperatures were recorded.
  • Unlike conventional heating, the SHS products did not contain enstatite.
• The authors' conclusion: The authors concluded that, compared with conventional thermal treatments, SHS favours asbestos neutralisation because of its fast reaction time, low activation energy and simple instruments. They also concluded that the product could be re-used, for example as abrasive or refractory material.
• Limitations the authors state:
  • The authors stated that current cost figures for neutralisation methods are not reliable, because they reflect only treatment costs in pilot plants.
  • The authors noted that, because of the large temperature gradients and very fast heating and cooling, non-equilibrium phases could form in the products.

Topics

The National Library of Medicine indexes this study under subjects our site covers: Chrysotile.

Medical terms in this study, explained in our Lexicon: Chrysotile, Forsterite, Olivine, Hematite.

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