Magnesium Silicate Binding Materials Formed from Heat-Treated Serpentine-Group Minerals and Aqueous Solutions: Structural Features, Acid-Neutralizing Capacity, and Strength Properties

Our plain-English summary of Magnesium Silicate Binding Materials Formed from Heat-Treated Serpentine-Group Minerals and Aqueous Solutions: Structural Features, Acid-Neutralizing Capacity, and Strength Properties, by T.K. Ivanova, I.P. Kremenetskaya, V.V. Marchevskaya, et al (Materials, 2022).

The study

• Authors: T.K. Ivanova, I.P. Kremenetskaya, V.V. Marchevskaya, M.V. Slukovskaya, S.V. Drogobuzhskaya
• Journal: Materials
• Published: 2022;15(24)
• Cited by: 4 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

The influence of structural features of three serpentine-group minerals (antigorite, chrysotile, and lizardite) on the hydration of heat-treated materials and the formation of magnesium silicate binder has been studied. Initial serpentine samples have been fired in the interval 550-800 °C with a step of 50 °C; acid neutralization capacity (ANC) values have been determined for all samples. Antigorite samples (SAP) have exhibited a maximum reactivity at a temperature of 700 °C (ANC 7.7 meq/g). We have established that the acid-neutralizing capacity of chrysotile and lizardite samples in the temperature range of 650-700 °C differ slightly; the capacity varied in the interval of 19.6-19.7 meq/g and 19.6-19.7 meq/g, respectively. The samples obtained at optimal temperatures (antigorite-700 °C, lizardite, and chrysotile-650 °C) have been studied. Heat-treated serpentines have interacted with water vapor for a year; serpentine hydration has been investigated. The strength characteristics of the resulting binder agents were studied after 7, 28, 180, and 360 days. Upon hardening within 7 days, the strengths of the SAP and SCH samples have been almost the same (2.2 MPa), whereas this indicator for the SLH and SLK samples has been significantly lower (0.5 MPa). After hardening for over a year, the chrysotile sample SCH had the highest strength (about 8 MPa), whereas the strength of antigorite SAP was 3 MPa. The samples of initial, heat-treated, and hydrated heat-treated serpentines have been studied using XRD, differential scanning calorimetry, and surface texture analysis. The serpentine structure is crucial in destroying the mineral crystal lattice during heat treatment. In contrast to heat-treated chrysotile and lizardite, antigorite did not adsorb water. Structural features of chrysotile provided the highest compressive strength of the binding agent compared with antigorite and lizardite. The acid-neutralizing ability of lizardite was noticeably higher than antigorite, whereas its compressive strength was lower due to the layered mineral structure and impurities. We have established that the minerals' structural features are crucial for the hydration of heat-treated serpentines; the structure determines material utilization in various environmental technologies.

In plain English

This was a laboratory materials study; it did not examine people, animals or disease. The authors tested four serpentine-mineral samples from Russian deposits: one antigorite, one chrysotile and two lizardites. They ground and heated the samples at 550 to 800 °C and measured how much acid each could neutralize, choosing 700 °C for antigorite and 650 °C for chrysotile and lizardite. At these temperatures the calculated degree of activation was 92% for chrysotile, 72% for one lizardite sample and 38% for antigorite. Heated antigorite did not take up water from the air. Mixed with water, the heated powders hardened into blocks. At 28 days their compressive strength was 3.5 MPa for chrysotile, 2.4 MPa for antigorite and 0.7 MPa for one lizardite sample. After a year, chrysotile reached about 8 MPa and antigorite 3 MPa. The authors concluded that mineral structure was crucial to how the heated material hydrated. They also concluded that chrysotile was suitable for making strong granular material intended for cleaning metal-rich solutions.

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-science experiment (no human or animal subjects)
• Who was studied: Four serpentine mineral samples from Russia: an antigorite sample (SAP) from the Pechenga ore field, a chrysotile sample (SCH) from overburden rock of the Khalilovo magnesite deposit (Orenburg region), and two lizardite samples from the Murmansk region (SLH from the Khabozero olivinite deposit; SLK, with vermiculite and pyroxene impurities, from the Kovdor phlogopite deposit)
• Exposure: No human exposure was studied. The serpentine powders (antigorite, chrysotile, lizardite) were milled to particles under 8 µm and fired for 20 minutes at 550 to 800 °C in 50-degree steps. They were then exposed to water vapor or mixed with water and hardened for 7, 28, 180 and 360 days.
• Main results:
  • The highest acid-neutralizing capacity was 7.7 meq/g for antigorite (SAP), 18.9 meq/g for lizardite (SLH) and 19.7 meq/g for chrysotile (SCH).
  • The calculated degree of activation was 92% for chrysotile, 72% for lizardite (sample SLH) and 38% for antigorite.
  • Heat-treated antigorite did not adsorb water from the air. Heat-treated lizardite and chrysotile did take up water vapor.
  • Leaching with 8 wt.% hydrochloric acid removed close to 100% of the magnesium from heat-treated chrysotile, and 82 to 84% from lizardite and antigorite.
  • Compressive strength after 28 days of hardening was 3.5 MPa for chrysotile, 2.4 MPa for antigorite and 0.7 MPa for lizardite (SLH). After 7 days, Table 6 gives 2.0 MPa for SAP, 2.2 MPa for SCH and 0.5 MPa for both SLH and SLK.
  • After hardening for over a year, chrysotile (SCH) had the highest strength (about 8 MPa; 7.9 MPa in Table 6) and antigorite (SAP) reached 3 MPa. Lizardite SLH rose to 1.1 MPa, and lizardite SLK stayed at 0.5 MPa.
  • The authors found no relation between compressive strength and the content of the binder precursor in the heat-treated serpentines. They attributed this mainly to mineral structure, in particular the layered structure of lizardite.
• The authors' conclusion: The authors concluded that the structural features of the serpentine minerals were crucial to the hydration of the heat-treated material. They judged chrysotile suitable for producing high-strength granular materials, and judged that lizardite's layered structure and impurities reduced binder strength.

Topics

Medical terms in this study, explained in our Lexicon: Silicate, Serpentine Group, Antigorite, Chrysotile, Lizardite.

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