“…However, our results showed that the rate of silica gelation could not be explained simply by the low acidity of the leaching slurries. This phenomenon was also reported in a previous study [19].…”
Section: Preparation Of the Monophasic Precursor From Bfssupporting
Previously, mineral carbonation of blast-furnace slag was carried out to sequestrate CO 2 and attain pure CaCO 3 crystals. In this process, amorphous silica-alumina nanoparticles were obtained as a byproduct. In this study, the crystallization of these nanoparticles on calcination at various temperatures in air was examined using TGA-DTA, XRD, MAS-NMR spectroscopy, and FT-IR spectroscopy. The precursor nanoparticles (Si:Al = 78:22 mol %) were prepared using the solution extracted from blast-furnace slag (BFS) with acetic acid at room temperature. The XRD analysis showed that the initial amorphous state was retained up to 800 • C, and decomposition to amorphous silica and mullite started after calcination at 950 • C. At temperatures between 1150 • C and 1250 • C, amorphous silica crystalized to cristobalite, which eventually melted to glassy silica at 1500 • C. The mullite crystals initially adopted a metastable tetragonal phase and transformed to a stable, needle-like orthorhombic phase at higher temperatures. 27 Al MAS-NMR spectroscopy revealed that octahedrally coordinated Al was favored up to a temperature of 800 • C as a result of the dehydration process and transformed into tetrahedrally coordinated Al at higher temperatures. A microstructural examination revealed that the initially randomly-oriented mullite developed into stable, needle-like grains owing to anisotropic grain growth in the presence of a glass phase at high temperatures. This study suggests that the recycling of BFS can be exploited for the procurement of a mullite-type ceramic material.
“…However, our results showed that the rate of silica gelation could not be explained simply by the low acidity of the leaching slurries. This phenomenon was also reported in a previous study [19].…”
Section: Preparation Of the Monophasic Precursor From Bfssupporting
Previously, mineral carbonation of blast-furnace slag was carried out to sequestrate CO 2 and attain pure CaCO 3 crystals. In this process, amorphous silica-alumina nanoparticles were obtained as a byproduct. In this study, the crystallization of these nanoparticles on calcination at various temperatures in air was examined using TGA-DTA, XRD, MAS-NMR spectroscopy, and FT-IR spectroscopy. The precursor nanoparticles (Si:Al = 78:22 mol %) were prepared using the solution extracted from blast-furnace slag (BFS) with acetic acid at room temperature. The XRD analysis showed that the initial amorphous state was retained up to 800 • C, and decomposition to amorphous silica and mullite started after calcination at 950 • C. At temperatures between 1150 • C and 1250 • C, amorphous silica crystalized to cristobalite, which eventually melted to glassy silica at 1500 • C. The mullite crystals initially adopted a metastable tetragonal phase and transformed to a stable, needle-like orthorhombic phase at higher temperatures. 27 Al MAS-NMR spectroscopy revealed that octahedrally coordinated Al was favored up to a temperature of 800 • C as a result of the dehydration process and transformed into tetrahedrally coordinated Al at higher temperatures. A microstructural examination revealed that the initially randomly-oriented mullite developed into stable, needle-like grains owing to anisotropic grain growth in the presence of a glass phase at high temperatures. This study suggests that the recycling of BFS can be exploited for the procurement of a mullite-type ceramic material.
“…Copper leaching reached a maximum when the temperature was 65 °C , but leaching of zinc was lowest. A similar phenomenon was found when Yang et al [23] studied the leaching of aluminum from secondary aluminum dross, and when Hyun et al [24] investigated the leaching of CaO-SiO2 resources. Considering the relative extents of copper and zinc leaching, the optimum temperature was selected as 55 °C .…”
In this work, oxidizing roasting was combined with leaching to separate copper, lead, and zinc from a concentrate obtained by bulk flotation of a low-grade ore sourced from the Jiama mining area of Tibet. The flotation concentrate contained 7.79% Cu, 22.00% Pb, 4.81% Zn, 8.24% S, and 12.15% CaO; copper sulfide accounted for 76.97% of the copper, lead sulfide for 25.55% of the lead, and zinc sulfide for 67.66% of the zinc. After oxidizing roasting of the flotation concentrate, the S content in the roasting slag decreased to 0.22%, indicating that most sulfide in the concentrate was transformed to oxide, which was beneficial to leaching. The calcine was subjected to sulfuric acid leaching for separation of copper, lead, and zinc; i.e., copper and zinc were leached, and lead was retained in the residue. The optimum parameters of the leaching process were: a leaching temperature of 55 °C; sulfuric acid added at 828 kg/t calcine; a liquid:solid ratio of 3:1; and a leaching time of 1.5 h. Under these conditions, the extents of leaching of copper and zinc were 87.43% and 64.38%, respectively. Copper and zinc in the leaching solution could be further separated by electrowinning. The effects of leaching parameters on the extents of leaching of copper and zinc were further revealed by X-ray diffraction and scanning electron microscopy analysis.
“…The influence factor of acid solubility was attributed to the reaction between HF solution and SF. 34,35 In the HF solution, the SF could be dissolved; thus, the weight of composite particles was lost and the acid solubility increased. Figure 8.Acid solubility curves of PMMA/SF composite particles with different SF contents.…”
Polymethyl methacrylate/silica fume composite particles with different silica fume contents were prepared via in situ suspension polymerization. Morphological, mechanical, acid resisting, and thermal performances of the synthesized material were investigated. The results revealed that the polymethyl methacrylate/silica fume composite particles presented 0.6-0.9 mm sphericity in diameter. When the contents of silica fume were about between 20 and 50 wt%, the measurements of apparent density (1.072-1.156 g/cm 3 ) were obviously lower than its theoretical values (1.163-1.278 g/ cm 3 ) due to abundant micron-sized macropores (>50 nm) existing inside the composite particles. Furthermore, the crushing rate and acid solubility of composite particles were all less than 5%, which reached the requirements of the standard of SY/T 5108-2006. With increasing the silica fume content from 0 to 60 wt%, the T g of the composite particles increased from 105.21 to 223.50 C, and the mass loss decreased from 24.46 to 4.25% as the temperature increased to 400 C. The reinforced performances including of spherical millimetric size, light weight, high strength, good acid resistance, and excellent thermal stability confirmed that the polymethyl methacrylate/silica fume composite particles have a great potential application as proppants in petroleum and gas exploration.
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