Synthesis of Nanoscale CaO-Al2O3-SiO2-H2O and Na2O-Al2O3-SiO2-H2O Using the Hydrothermal Method and Their Characterization

Yang, Jingbin; Li, Dongxu; Yuan, Fang

doi:10.3390/ma10070695

Cited by 27 publications

(18 citation statements)

References 35 publications

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“…In addition, a broad featureless hump caused by amorphous aluminosilicate was observed between 25 • and 35 • 2θ [4]. As the curing temperature increased to 95 • C, all K-A-S-H products remained amorphous at the 1-day age.…”

Section: X-ray Diffraction Analysismentioning

confidence: 97%

“…The proportions of nano-SiO 2 , nano-Al 2 O 3 , KOH, and deionized water are shown in Table 1. Nanoscale K-A-S-H gel was synthesized according to our previous hydrothermal method [3,4]. The samples are named as follows: using K-A-S-H1.0 1 -1d-95 as an example, the K-A-S-H1.0 indicates a K 2 O/SiO 2 ratio in the K-A-S-H system of 1.0, the subscript indicates a SiO 2 /Al 2 O 3 ratio of 1, the 1d indicates a curing time of 1 day, and the 95 indicates that the material was cured at a temperature of 95 • C.…”

Section: Synthesis Of K-a-s-hmentioning

confidence: 99%

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Insights into the Microstructure of Hydrothermal Synthesized Nanoscale K2O-Al2O3-SiO2-H2O Particles

et al. 2019

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K-A-S-H (K2O-Al2O3-SiO2-H2O) gel is a key phase that forms in most alkali-activated binders (eco-friendly binders which utilize a substantial amount of industrial by-product). An in-depth understanding of the microstructure and performance of this nano-sized key phase facilitates better application to alkali-activated binders. However, such studies remain little and undetailed. Therefore, our research aims to provide insights into the microstructure of K-A-S-H particles synthesized with accurate stoichiometric control by the hydrothermal method through thermogravimetric analysis (TG), Fourier transform infrared spectroscopy (FTIR), nuclear magnetic resonance (NMR), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and BET surface area. The results show that for materials prepared at the curing temperature lower than 80 °C, the K-A-S-H products were completely amorphous. With increased curing temperature and time, the K-A-S-H products were transformed from the amorphous phase to the crystalline zeolite phase structure, with a reduction in the specific surface area. The TG results indicate that the crystalline phase contains more non-evaporated water or zeolite water for structural rearrangement. The degree of tetrahedral polymerization slightly decreased with an increase of the K2O/SiO2 ratio as the amount of non-bridged oxygen atoms increased, whereas it gradually increased with an increase of curing temperature and time, as suggested by the FTIR and NMR results. Various K2O/SiO2 ratios resulted in the formation of zeolite K-H and K-G zeolite, both of which exhibited highly polymerized three-dimensional network structures. However, there was no significant effect of the SiO2/Al2O3 ratio on the structure of K-A-S-H products. Overall, these results provide insight into understanding the chemical stability of K-A-S-H.

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Section: X-ray Diffraction Analysismentioning

confidence: 97%

Section: Synthesis Of K-a-s-hmentioning

confidence: 99%

Insights into the Microstructure of Hydrothermal Synthesized Nanoscale K2O-Al2O3-SiO2-H2O Particles

et al. 2019

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“…This study used nanoscale C-A-S-H gel synthesized according to the hydrothermal method listed in literature [ 25 ], with a CaO/SiO 2 ratio of 1.0 a SiO 2 /Al 2 O 3 ratio of 2.0, and a water/solid ratio of 8.0. Figure 1 and Figure 2 show the micromorphology and particle size distribution of the synthetic C-A-S-H gel under scanning electron microscope.…”

Section: Methodsmentioning

confidence: 99%

“…By applying the synthesized C-A-S-H gel to AAS, we can investigate the effect of synthetic C-A-S-H gel on the early-stage shrinkage of AAS mortar. In this research, amorphous C-A-S-H gel powder was prepared by hydrothermal method using nano-SiO 2 and nano-Al 2 O 3 as raw materials [ 25 ]; The powders were then added to the AAS mortar via two different methods. The effect of synthesized C-A-S-H gels on the shrinkage of AAS mortar was studied and a series of tests were performed to determine the autogenous shrinkage and drying shrinkage.…”

Section: Introductionmentioning

confidence: 99%

Effect of a Synthetic Nano-CaO-Al2O3-SiO2-H2O Gel on the Early-Stage Shrinkage Performance of Alkali-Activated Slag Mortars

Bao

Yang

et al. 2018

Materials

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The relatively high shrinkage of the alkali-activated slag (AAS) has restricted its application as a widely-used building material. This research attempts to study the effect of a hydrothermally synthesized C-A-S-H gel, which has a similar composition to that of the main AAS product, on the shrinkage performance of the AAS. The C-A-S-H nano-particles were mixed into AAS mortars in a proportion ranging from 1 wt % to 5 wt % using two different methods, and the drying and autogenous shrinkage ratio of modified AAS mortars were measured at various ages. The effect of C-A-S-H on their microstructures was also characterized. Results obtained indicated that the addition of C-A-S-H gel to AAS mortars had reduced their drying and autogenous shrinkage, with the addition of 3 wt % reaching the maximum reduction. However, the added amount was not directly proportional to the decrease of shrinkage; the proportion of early-stage drying shrinkage of AAS mortars was greater than that of autogenous shrinkage; the dispersion method was slightly better than the dry mixing method in both shrinkage reduction. MIP results suggested that the addition of C-A-S-H gel had reduced the total porosity and the average pore size of AAS mortars, optimized their pore structure distribution, and significantly reduced the volume of mesopores (<0.05 µm) which resulted in high shrinkage, while the adding method had no significant effect on the pore size distribution of AAS mortars. SEM results showed that the addition of C-A-S-H gel can reduce the crack width of mortars, obtain a dense and uniform matrix structure, increase the density, and effectively suppress both shrinkage deformation of the system, whereas the adding method has no obvious effect on the crack width of the mortar. This research provides a novel approach of the AAS shrinkage reduction and structure refinement, shedding lights on nano-material modification of the AAS.

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“…The tensile peak at 887 cm −1 was attributed to Si-O-Na [26]. The spectra also showed a Si-OH stretching peak at 970 cm −1 [27,28], and Si-OH and H-O-H stretching vibrational peaks at 1454 cm −1 and 3450 cm −1 , respectively [29][30][31]. The results indicated that NaOH destroyed Si-O-Si bond under calcination, while Si-OH and Si-O-Na were formed at the same time to activate the silicon.…”

Section: Characterization Of Ashmamentioning

confidence: 97%

A Functionalized Silicate Adsorbent and Exploration of Its Adsorption Mechanism

et al. 2020

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Active silicate materials have good adsorption and passivation effects on heavy metal pollutants. The experimental conditions for the preparation of active silicate heavy metal adsorbent (ASHMA) and the adsorption of Cu(II) by ASHMA were investigated. The optimum preparation conditions of ASHMA were as follows: 200 mesh quartz sand as the raw material, NaOH as an activating agent, NaOH/quartz sand = 0.45 (mass fraction), and calcination at 600 • C for 60 min. Under these conditions, the active silicon content of the adsorbent was 22.38% and the utilization efficiency of NaOH reached 89.11%. The adsorption mechanism of Cu(II) on the ASHMA was analyzed by the Langmuir and Freundlich isotherm models, which provided fits of 0.99 and 0.98, respectively. The separation coefficient (R L ) and adsorption constant (n) showed that the adsorbent favored the adsorption of Cu(II), and the maximum adsorption capacity (Q max ) estimated by the Langmuir isotherm was higher than that of 300 mg/L. Furthermore, adsorption by ASHMA was a relatively rapid process, and adsorption equilibrium could be achieved in 1 min. The adsorbents were characterized by FT-IR and Raman spectroscopy. The results showed that the activating agent destroyed the crystal structure of the quartz sand under calcination, and formed Si-O-Na and Si-OH groups to realize activation. The experimental results revealed that the adsorption process involved the removal of Cu(II) by the formation of Si-O-Cu bonds on the surface of the adsorbent. The above results indicated that the adsorbent prepared from quartz sand had a good removal effect on Cu(II).The amorphous silica structure of active silicate materials makes their reactivity much stronger than that of crystalline silica and confers these materials with excellent adsorption properties for pollutants such as heavy metals [7][8][9]. Studies have shown that the silanol groups (Si-OH) in active silicate materials are the main determinants of surface chemistry [10] and can form covalent bonds and hydrogen bonds with some ions and molecules [11]. Heavy metals such as Cu(II), Cd(II), and Pb(II) in aqueous solution were found to be removed by forming surface adsorption complexes with surface silanol [12,13]. Our team used leaching residue from lead-zinc tailings with high silicon content as a raw material to prepare an active silicate heavy metal adsorbent, which showed a very high adsorption capacity for the heavy metals Cu, Pb, Cd and Zn. The saturated adsorption capacities were 3.40, 2.83, 0.66 and 0.62 mmol/g, respectively [14].Besides, when active silicate materials are applied to the remediation of heavy metals in soil, extractable heavy metals can be transformed into forms with relatively stable valence [15,16], and the heavy metal stress and accumulation in plants can be reduced [17]. Moreover, the active silicates can be absorbed by plants as nutrient elements to form phytoliths, which play an important role in increasing grain yield and enhancing photosynthesis, pest resistance, lodging resistance, and so on...

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Synthesis of Nanoscale CaO-Al2O3-SiO2-H2O and Na2O-Al2O3-SiO2-H2O Using the Hydrothermal Method and Their Characterization

Cited by 27 publications

References 35 publications

Insights into the Microstructure of Hydrothermal Synthesized Nanoscale K2O-Al2O3-SiO2-H2O Particles

Insights into the Microstructure of Hydrothermal Synthesized Nanoscale K2O-Al2O3-SiO2-H2O Particles

Effect of a Synthetic Nano-CaO-Al2O3-SiO2-H2O Gel on the Early-Stage Shrinkage Performance of Alkali-Activated Slag Mortars

A Functionalized Silicate Adsorbent and Exploration of Its Adsorption Mechanism

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