Synthesis of High Crystallinity 1.13 nm Tobermorite and Xonotlite from Natural Rocks, Their Properties and Application for Heat-Resistant Products

Šiaučiūnas, R.; Smalakys, G.; Eisinas, Anatolijus; Prichockiene, Edita

doi:10.3390/ma15103474

Cited by 10 publications

(8 citation statements)

References 44 publications

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“…In addition, depending on the hydration level, the (002) crystal plane of tobermorite can have different interplanar spacings, i.e., 0.9, 1.1 and 1.4 nm; thus, there are three types of tobermorite [ 18 ]. Numerous studies have synthesized 1.1 nm tobermorite under different hydrothermal conditions and using various raw materials [ 19 , 20 , 21 ]. A pore canal containing some water and Ca 2+ ions is one of the most noticeable structural features of tobermorite [ 22 ].…”

Section: Introductionmentioning

confidence: 99%

Highly Efficient Cd2+ Removal Using Tobermorite with pH Self-Adjustment Ability from Aqueous Solution

et al. 2023

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Cadmium (Cd), as a type of heavy metal, can increase the incidence of many diseases, even in low concentrations. In this study, tobermorite was hydrothermally synthesized and then applied to adsorb Cd2+ from an aqueous solution. The physicochemical characteristics of the synthesized tobermorite were detected, and the results indicated that the well-crystallized tobermorite had a lot of mesopores and a large specific surface area of 140.92 m2/g. It acquired a pH self-adjustment ability via spontaneously releasing Ca2+ and OH- into the aqueous solution. The effects of different factors on Cd2+ removal were investigated. For Cd2+, the removal efficiency could reach 99.71% and the maximum adsorption capacity was 39.18 mg/g using tobermorite. The adsorption data was best fitted with the pseudo-second-order kinetic and Langmuir isotherm models. In addition, there was no strict limit on the solution pH in Cd2+ adsorption because the tobermorite could adjust the solution pH to an alkaline atmosphere spontaneously. The efficient removal of Cd2+ using tobermorite was a result of surface complexation and ion exchange.

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Section: Introductionmentioning

confidence: 99%

Highly Efficient Cd2+ Removal Using Tobermorite with pH Self-Adjustment Ability from Aqueous Solution

et al. 2023

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“…As shown from reactions (1)- (11), when Ca(OH) 2 and SiO 2 are hydrothermally reacted, various calcium silicate compounds may be obtained. While xonotlite is the desired product from reaction (1), tobermorite from reaction (2) is the most common by-product.…”

Section: Thermodynamic Calculations For the Formation Of Xonotlitementioning

confidence: 99%

“…It has the lowest water content in all hydrated calcium silicate crystalline phases and is characterized by good thermal stability, light weight, large specific surface area, and low thermal conductivity [1,2]. Therefore, xonotlite is widely used as an adsorbent [3][4][5], catalyst supports [6], phase change energy storage material matrix [7], photoluminescent material [8], electrode materials [9,10], and thermal insulation in chemical, architectural and metallurgical industries [11,12]. Despite its shape being similar to asbestos fiber, xonotlite has good biocompatibility and will not cause harm to the human body [13,14].…”

Section: Introductionmentioning

confidence: 99%

Thermodynamics of the hydrothermal synthesis of xonotlite

Liu

Huang

et al. 2023

Mater. Res. Express

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Xonotlite, as a new type of inorganic material, has been widely used in the fields of building insulation, friction braking, and bionic composite materials. However, the main method of producing xonotlite, the dynamic hydrothermal method, is regarded as a black box process. While the synthesis mechanism is still unclear, the synthesis conditions could be only optimized through trial-and-error experimentations. In this work, we established a thermodynamic model of the Ca(OH)2-SiO2-H2O system under hydrothermal conditions, and investigated influencing factors of the xonotlite synthesis. The results show that the synthesis reaction of xonotlite is exothermic, and that the standard free energy change comes mainly from the enthalpy change. We also reveal that, for the temperature range of 20 to 220℃, the standard free energy change of xonotlite synthesis reaction is negative, indicating the spontaneous forward reaction. However, due to side reactions, the predicted lowest temperature of xonotlite synthesis is around 170℃. In addition, our studies propose the optimum conditions to synthesis xonotlite with a purity of 99%: reaction temperature, 200℃; Ca/Si ratio, 0.9-1.0; water-solid ratio, no more than 20; pH, 7-8. For xonotlite synthesis with other raw materials, such as Ca(OH)2-SiO2, Ca(OH)2-K2SiO3, Ca(NO3)2·4H2O-Na2SiO3·9H2O and CaCl2·2H2O-Na2SiO3·9H2O, optimum synthesis conditions are also suggested. Those results provide thermodynamics fundamentals to synthesis reaction optimization, which is also an essential guideline to large-scale industrial xonotlite production.

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“…Minerals belonging to the tobermorite group are naturally occurring hydrated calcium silicates resulting from the hydrothermal alteration of calcium carbonate rocks [97], [142]. Typically, tobermorite is synthesized using SiO2-rich materials, such as quartz, silica powder, lime, and silica-rich fly ash [91], [92], [93]. It can be synthesized from dicalcium silicate also [102].…”

Section: X-ray Diffraction (Xrd) Analysismentioning

confidence: 99%

Mitigation Measures of Swelling Characteristics in Alkali-Contaminated Red Earth using Fly Ash and GGBS Blends

Kumar Darapu,

Vindula

2023

IOP Conf. Ser.: Earth Environ. Sci.

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Alkali contamination induces swelling in the inherently non-swelling soils, resulting in heave severely damaging the sub and superstructures. Stabilization measures must be taken in vulnerable areas to prevent such colossal losses. Considerable research has been conducted regarding the swelling behavior of soils contaminated with alkalis and the impact of subsequent stabilization techniques utilizing different industrial byproducts and pozzolanic materials. However, there is a paucity of such studies on the Red Earth (RE) of the Visakhapatnam region. Furthermore, limited attention was given to the effects of extremely low concentrations of alkalis on the swelling behavior of soils. RE in the study area of the Visakhapatnam region predominantly consists of quartz, kaolinite, and hematite. In phase 1 of the experimental analysis, RE was contaminated with a highly dilute NaOH solution (0.05 N), and the resulting swell characteristics were investigated. A free swell of 10% was observed. One-dimensional standard oedometer tests revealed an equilibrium swelling of 5.6%, indicating significant potential for substantial heave and subsequent damage. X-ray diffraction (XRD) analysis revealed the formation of natrolite and analcime zeolites with a hollow structure, which caused the swell. Peaks of silicate minerals like paragonite and ussingite were also observed, indicating the dissolution of authigenic minerals and new precipitations even at lower concentrations of NaOH. In phase 2, swell tests were conducted on a mixture of contaminated red earth (50% w/w), fly ash (25% w/w), and ground granulated blast furnace slag (GGBS, 25% w/w), and it was observed that the swelling was completely arrested. XRD analysis unveiled that even though siliceous zeolites were formed, the development of chrysotile, attapulgite, tobermorite, and dicalcium silicate effectively inhibited the swelling with their pozzolanic behavior.

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Synthesis of High Crystallinity 1.13 nm Tobermorite and Xonotlite from Natural Rocks, Their Properties and Application for Heat-Resistant Products

Cited by 10 publications

References 44 publications

Highly Efficient Cd2+ Removal Using Tobermorite with pH Self-Adjustment Ability from Aqueous Solution

Highly Efficient Cd2+ Removal Using Tobermorite with pH Self-Adjustment Ability from Aqueous Solution

Thermodynamics of the hydrothermal synthesis of xonotlite

Mitigation Measures of Swelling Characteristics in Alkali-Contaminated Red Earth using Fly Ash and GGBS Blends

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