Abstract:Acid-extracting residue of circulating uidized bed (CFB) y ash is still underutilized leaving disposal problems. In fact, high silica content inside this material opens a possibility to become a potential zeolites precursor. In this study, ne particles of acid residues have been reused to prepare zeolite Na-X and Na-P with high purity and intensity. Acid residue was used to synthesize zeolite Na-X and Na-P using a single-step hydrothermal process. The effects of crystallization time, temperature and sodium hyd… Show more
“…When the hydrothermal time was increased to 12 h (Ht 2), the diffraction peak strength of C 2 S weakened, and the diffraction peak of the zeolite phases significantly increased in intensity. When the hydrothermal time was further extended to 24 h (Ht 4), the peak strength and peak type did not significantly change, indicating that the growth and dissolution of crystals reached dynamic equilibrium at this time 31 . Figure 7 XRD patterns of hydrothermal products with different hydrothermal times; Ht 1: hydrothermal time at 6 h, Ht 2: hydrothermal time at 12 h, Ht 3: hydrothermal time at 18 h, Ht 4: hydrothermal time at 24 h. …”
Section: Resultsmentioning
confidence: 97%
“…Hydrothermal temperature also has a significant influence on the formation of zeolite. Higher temperatures can improve the concentration of chemical groups in the sol, which is conducive to zeolite crystallization 31 . Figure 8 shows the XRD patterns of zeolites prepared at different hydrothermal temperatures.…”
In this study, geopolymers were prepared using ladle furnace slag (LFS) and fly ash (FA), and hydrothermal treatment was then used to synthesize bulk zeolite molecular sieves with gismondine, zeolite-P1, and sodalite phases. The effect of the synthesis conditions on the crystalline phases of the zeolite molecular sieves was investigated by XRD. The results showed that the best zeolite molecular sieves were prepared with an LFS: FA ratio of 4: 6, a curing temperature of 40 °C, a curing time of 12 h, a sodium silicate modulus (Ms) of 1.4, a NaOH concentration of 4 mol/L, a hydrothermal temperature of 120 °C, and a hydrothermal time of 12 h. On this basis, the products were analyzed by SEM, N2 adsorption, and FT-IR. The results showed that the synthesized zeolite molecular sieves had mesoporous properties, and the degree of polymerization and cross-linking of the silica-aluminate gel were enhanced after hydrothermal treatment. In addition, the formation mechanism of the zeolite molecular sieves was explored through the changes of the silica-alumina during zeolite formation. This paper is the first to use the hydrothermal conversion of zeolite molecular sieves from LFS-FA based polymers to provide some guidance for the resource utilization of LFS and FA.
“…When the hydrothermal time was increased to 12 h (Ht 2), the diffraction peak strength of C 2 S weakened, and the diffraction peak of the zeolite phases significantly increased in intensity. When the hydrothermal time was further extended to 24 h (Ht 4), the peak strength and peak type did not significantly change, indicating that the growth and dissolution of crystals reached dynamic equilibrium at this time 31 . Figure 7 XRD patterns of hydrothermal products with different hydrothermal times; Ht 1: hydrothermal time at 6 h, Ht 2: hydrothermal time at 12 h, Ht 3: hydrothermal time at 18 h, Ht 4: hydrothermal time at 24 h. …”
Section: Resultsmentioning
confidence: 97%
“…Hydrothermal temperature also has a significant influence on the formation of zeolite. Higher temperatures can improve the concentration of chemical groups in the sol, which is conducive to zeolite crystallization 31 . Figure 8 shows the XRD patterns of zeolites prepared at different hydrothermal temperatures.…”
In this study, geopolymers were prepared using ladle furnace slag (LFS) and fly ash (FA), and hydrothermal treatment was then used to synthesize bulk zeolite molecular sieves with gismondine, zeolite-P1, and sodalite phases. The effect of the synthesis conditions on the crystalline phases of the zeolite molecular sieves was investigated by XRD. The results showed that the best zeolite molecular sieves were prepared with an LFS: FA ratio of 4: 6, a curing temperature of 40 °C, a curing time of 12 h, a sodium silicate modulus (Ms) of 1.4, a NaOH concentration of 4 mol/L, a hydrothermal temperature of 120 °C, and a hydrothermal time of 12 h. On this basis, the products were analyzed by SEM, N2 adsorption, and FT-IR. The results showed that the synthesized zeolite molecular sieves had mesoporous properties, and the degree of polymerization and cross-linking of the silica-aluminate gel were enhanced after hydrothermal treatment. In addition, the formation mechanism of the zeolite molecular sieves was explored through the changes of the silica-alumina during zeolite formation. This paper is the first to use the hydrothermal conversion of zeolite molecular sieves from LFS-FA based polymers to provide some guidance for the resource utilization of LFS and FA.
“…It is reported that special templates or structure-directing agents were beneficial for the formation of zeolite during the hydrothermal condition . In this study, a self-made structure-directing agent was used for zeolite synthesis.…”
Section: Resultsmentioning
confidence: 99%
“…It is reported that special templates or structure-directing agents were beneficial for the formation of zeolite during the hydrothermal condition. 28 In this study, a self-made structure-directing agent was used for zeolite synthesis. Figure 2 shows the XRD patterns of the Si/Al-gel and synthesized zeolites with different amounts of structuredirecting agent added (90 °C, NaOH concentration of 2.5 mol•L −1 , stirring for 3 h, and aging for 12 h).…”
CO2 mineral sequestration is one of the most promising
strategies for combating global warming. However, its industrial applications
of CO2 mineral carbonation are limited due to the concerns
of energy and cost consumption. Simultaneously, recovery of valuable
byproducts is essential for favorable economic viability during the
mineralization process. In this study, a novel process combining CO2 mineral sequestration and zeolite synthesis by using blast
furnace slag was proposed. Si/Al-gel was first prepared by leaching
and precipitation of the slag, followed by hydrothermal reaction to
synthesize faujasite type zeolite. The process optimization and CO2 net-emission reduction evaluation of the proposed route were
conducted in this study. A sole phase faujasite zeolite with high
specific surface area (721 m2/g) was successfully synthesized
under the optimal hydrothermal conditions. The Si/Al-depleted precipitated
mother liquid (rich in MgSO4) together with the CaSO4·0.5H2O leaching residue was used to mineral
sequestrate CO2. The total amount of CO2 sequestrated
by processing one ton slag was 398 kg. Preliminary evaluation of CO2 net-emission reduction indicated that 52 kg of CO2 can be permanently stored for 1000 kg of slag processing after deducting
the CO2 released in this process. The major component of
blast furnace slag was fully utilized in this process, realizing the
double benefits of CO2 emission reduction and solid waste
disposal as well as exhibiting great potential for industrial application.
“…According to Ostwald rule of stages, the synthesis process of zeolites often undergoes the structural transformations from one metastable form to more thermodynamically stable form 24 . FAU‐type zeolite possesses the similar synthesis ratio with zeolite P. When crystallization T was 120°C, FAU‐type zeolite as a metastable phase would be preferentially crystallized in the Si‐rich synthesis system formed by the solubility of the raw materials 25 . When crystallization T was 130°C and 140°C, the metastable FAU‐type zeolite was dissolved and transformed to more thermodynamically stable zeolite P particles 26 .…”
A facile, rapid, and energy‐saving gel‐like‐solid method was applied to prepare zeolites from natural minerals. Using potassic rocks (PRs) activated by the alkali fusion decomposition method together with silica‐alumina xerogel as silicon‐ and aluminum‐species, zeolite P has been successfully synthesized via gel‐like‐solid phase method. The effects of crystallization time (t), crystallization temperature (T), m (PRs)/m (xerogel) ratios, and n(H2O)/n (SiO2) ratios on the crystallinity and morphology of zeolite P were investigated. The optimal synthesis conditions were m (PRs)/m (xerogel) of 0.185, n(H2O)/n (SiO2) of 28.12, crystallization t of 3 h, and crystallization T of 140°C. The synthesized zeolite P featuring high crystallinity possessed spherical morphology aggregated by small grains and was applied in the ion exchange for Ca2+ and Mg2+ ions. The maximum Ca2+ and Mg2+ ions exchange capacities of zeolite P could reach 415 mgCaCO3·g−1 and 162 mgMgCO3·g−1, respectively. Compared with other published materials, the synthesized zeolite P exhibited satisfactory Ca2+ and Mg2+ ions exchange capacities. The above results demonstrated that the gel‐like‐solid phase method could shorten the crystallization t and enhance the crystallinity of zeolites synthesized from natural minerals and solid waste, showing a great potential in actual applications.
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