Chrysotile asbestos detoxification with a combined treatment of oxalic acid and silicates producing amorphous silica and biomaterial

Our plain-English summary of Chrysotile asbestos detoxification with a combined treatment of oxalic acid and silicates producing amorphous silica and biomaterial, by A. Valouma, A. Verganelaki, P. Maravelaki-Kalaitzaki, et al (Journal of Hazardous Materials, 2016).

The study

• Authors: A. Valouma, A. Verganelaki, P. Maravelaki-Kalaitzaki, E. Gidarakos
• Journal: Journal of Hazardous Materials
• Published: 2016;305:164-170
• Cited by: 18 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

This study was primarily imposed by the ever increasing need for detoxification of asbestos and asbestos containing materials (ACM), with potential application onsite. The present work investigates potential detoxification of pure chrysotile (Chr) asbestos via a combined treatment of oxalic acid dihydrate (Oxac) (Η2C2Ο4·2Η2Ο) with silicates, such as tetraethoxysilane (TEOS) (SiH20C8O4) and pure water glass (WG) (potassium silicate) (K2SiO3). These reagents used in the experimental procedure, do not cause adverse effects on the environment and are cost effective. The results of FTIR, XRD, optical and scanning microscopy coupled with EDS analyses indicated that all of the applied treatments destructed the Chr structure and yielded silica of amorphous phase and the biomaterial glushinskite from the Oxac reacted with brucite [Mg(OH)2] layer. Each of the proposed formulations can be applied for the detoxification of asbestos, according to priorities related to the specific products of the recovery treatment. Therefore, Oxac acid leaching followed by the TEOS addition is preferred in cases of glushinskite recovery; TEOS treatment of asbestos with subsequent Oxac addition produced amorphous silica production; finally Oxac acid leaching followed by WG encapsulated the asbestos fibers and can be used in cases of onsite asbestos and ACM detoxification.

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In plain English

This laboratory study tested chemical treatments meant to break down pure chrysotile asbestos collected from asbestos mines in Northern Greece. The authors used three mixtures at room temperature. AOxT was oxalic acid followed by tetraethoxysilane (TEOS). ATOx was TEOS followed by oxalic acid after 5 days. AOxWG was oxalic acid followed by potassium silicate ("water glass"). Chrysotile in distilled water served as a reference sample. Changes were tracked with infrared spectroscopy, X-ray diffraction and microscopy. By day 30, chrysotile fibers could no longer be told apart under the stereoscope in any treated sample. The X-ray signals typical of chrysotile disappeared after 30 days in every treatment except AOxT. Only ATOx showed full transformation into amorphous material. All treatments formed the magnesium oxalate mineral glushinskite. In AOxWG, a glassy coating encapsulated the fibers. The authors concluded that AOxT suits glushinskite recovery, ATOx suits amorphous silica production, and AOxWG suits onsite detoxification. They judged detoxification from these mineral analyses. The article describes no tests on cells or animals.

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 chemistry experiment comparing three chemical treatments of chrysotile, with an untreated reference sample
• Who was studied: pure chrysotile asbestos collected from asbestos mines in Northern Greece. A reference sample of chrysotile mixed with distilled water was kept on a shaker for comparison. The amount of chrysotile used is not stated.
• Exposure: Three treatments of chrysotile. AOxT: oxalic acid, then TEOS in isopropanol (molar ratio Chr/Oxac/TEOS 1/9/124). ATOx: TEOS first, with oxalic acid added after 5 days (Chr/TEOS/Oxac 1/124/9). AOxWG: oxalic acid, then potassium silicate water glass (Chr/Oxac/WG 1/18/250). All were run at about 26 to 26.5 degrees C.
• Main results:
  • Stereoscope, day 30: all treated samples looked compact and homogeneous, and chrysotile fibers could not be distinguished.
  • X-ray diffraction: the main chrysotile signals disappeared after 30 days in all treatments except AOxT.
  • Infrared spectroscopy: in all treatments, the main chrysotile absorptions at 3878, 962 and 612 cm−1 fell markedly within 10 days and disappeared after 20 days.
  • All treatments formed magnesium oxalate (glushinskite). It formed faster and in larger quantity with AOxT than with ATOx.
  • AOxWG: under electron microscopy the fibers were no longer visible and appeared encapsulated. Surface elemental analysis found only silicon and potassium, with no magnesium.
  • Only ATOx showed full transformation of chrysotile into an amorphous material by X-ray diffraction. The authors selected it as the optimum treatment.
• The authors' conclusion: The authors concluded that all three treatments destroyed the chrysotile structure and yielded amorphous silica. They selected ATOx as the optimum treatment. Each formulation could be chosen according to the desired product: AOxT for glushinskite recovery, ATOx for amorphous silica production, and AOxWG for onsite asbestos detoxification.

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, Silicate, Brucite.

Related studies

• A new approach to the decontamination of asbestos-polluted waters by treatment with oxalic acid under power ultrasound — F. Turci, M. Tomatis, et al. (2008)
• The combination of oxalic acid with power ultrasound fully degrades chrysotile asbestos fibres — F. Turci, M. Tomatis, et al. (2007)
• Magnesium oxide production from chrysotile asbestos detoxification with oxalic acid treatment — A. Valouma, A. Verganelaki, et al. (2017)
• Chrysotile asbestos is progressively converted into a non-fibrous amorphous material by the chelating action of lichen metabolites — S.E. Favero-Longo, F. Turci, et al. (2005)
• The effects of naturally occurring acids on the surface properties of chrysotile asbestos — E.P. Holmes, L.M. Lavkulich (2014)
• Microwave-assisted acid treatment for the mineral transformation of chrysotile as an alternative for asbestos waste management — S. Essih, L. Pardo, et al. (2024)

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