A study of silicon carbide synthesis from waste serpentine

Our plain-English summary of A study of silicon carbide synthesis from waste serpentine, by T.W. Cheng, C.W. Hsu (Chemosphere, 2006).

The study

• Authors: T.W. Cheng, C.W. Hsu
• Journal: Chemosphere
• Published: 2006;64(3):510-4
• Cited by: 2 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

There are 60000 tons of serpentine wastes produced in year 2004 in Taiwan. This is due to the well-developed joints in the serpentine ore body as well as the stringent requirements of the particle size and chemical composition of serpentine by iron making company. The waste also creates considerable environmental problems. The purpose of this study is reutilization of waste serpentine to produce a high value silica powder after acid leaching. These siliceous microstructure products obtained from serpentine would be responsible for high reactivity and characteristic molecular sieving effect. In this study, the amorphous silica powder was then synthesized to silicon carbide with the C/SiO(2) molar ratio of 3. The experiment results show that silicon carbide can be synthesized in 1550 degrees C. The formed silicon carbide was whisker beta type SiC which can be used as raw materials for industry.

In plain English

This Taiwanese technical note described a laboratory experiment, not a health study. It does not mention asbestos, chrysotile, workers or disease. The authors aimed to turn mining waste serpentine into silicon carbide, an industrial ceramic. Undersized waste serpentine was ground and soaked in sulfuric acid under different conditions. At 60 degrees C the serpentine structure stayed intact. At 80 degrees C it was destroyed and became partly amorphous. Raw serpentine contained 40.94% silica. After 48 hours in 5 M acid, the residue contained 76.22% silica at 60 degrees C, 88.95% at 80 degrees C and 90.66% at 90 degrees C. For silicon carbide synthesis, silica extracted at 80 degrees C in 5 M acid for 48 hours was mixed with carbon black and heated. The most silicon carbide formed at a carbon-to-silica molar ratio of 3. With that ratio and 5 hours of sintering at 1550 degrees C, almost all phases had turned into silicon carbide. The product was whisker beta type silicon carbide. The authors concluded that it is feasible to produce silicon carbide from silica extracted from serpentine waste.

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 materials-processing experiment (technical note): acid extraction of silica from waste serpentine, followed by high-temperature synthesis of silicon carbide
• Who was studied: No people or animals were studied. The material was waste serpentine from mining in Taiwan. The samples were collected from undersized raw material (less than 6 mm), while the oversized material was supplied to China Steel.
• Exposure: No human exposure was studied. The serpentine was treated with sulfuric acid (H2SO4). For silicon carbide synthesis, the silica was extracted at 80 degrees C in 5 M sulfuric acid for 48 hours, then mixed with carbon black and sintered.
• Main results:
  • The silica (SiO2) content went from about 41% in the raw serpentine to about 91% in the extracted residue. Table 1 gives 40.94% for raw serpentine. After 5 M sulfuric acid for 48 hours, the residue contained 76.22% at 60 degrees C, 88.95% at 80 degrees C and 90.66% at 90 degrees C.
  • Silica content in the residues rose as extraction temperature increased.
  • At 80 degrees C extraction, the serpentine structure was destroyed and the residue showed a partly amorphous phase.
  • Surface area of the treated particles decreased with increasing extraction temperature. Table 1 values: 182.3 m2/g at 60 degrees C, 166.5 m2/g at 80 degrees C and 107.8 m2/g at 90 degrees C, against 3.8 m2/g for raw serpentine.
  • At 1550 degrees C for 5 hours, the maximum amount of silicon carbide formed at a carbon-to-silica molar ratio of 3.
  • With a sintering time of 5 hours and a carbon-to-silica molar ratio of 3, almost all phases had turned into silicon carbide when the temperature reached 1550 degrees C. The authors stated that sintering for at least 5 hours was needed.
  • The silicon carbide produced was of the whisker beta type.
• The authors' conclusion: The authors concluded that it is feasible to produce silicon carbide from amorphous silica extracted from serpentine waste, and that the product can be used as an industrial raw material.

Topics

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

Medical terms in this study, explained in our Lexicon: Serpentine Group.

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• Pulmonary response, in vivo, to silicon carbide whiskers — G.L. Vaughan, S.A. Trently, et al. (1993)
• In vitro activity of silicon carbide whiskers in comparison to other industrial fibers using four cell culture systems — N.F. Johnson, M.D. Hoover, et al. (1992)
• Pulmonary effects and biopersistence of deposited silicon carbide whisker after 1-year inhalation in rats — I. Akiyama, A. Ogami, et al. (2007)
• Toxicity in vitro of some silicon carbides and silicon nitrides: whiskers and powders — I. Svensson, E. Artursson, et al. (1997)

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