In developed countries, nanoparticles derived from natural minerals and high-purity chemicals both are widely studied, while in developing countries like Mongolia, the natural minerals-based nanoparticles have more interest because of the low production cost and applicability of domestic natural minerals for their production. For the synthesis of natural mineral-based nanomaterials, it is important first to define the chemical composition and physical structure of local minerals and their possible processing route. We employed an environmentally friendly alkaline leaching procedure to recover silica from the clay mineral at 90°C for 24 hours. We applied an organic surfactant (CTAB) and a simple coprecipitation approach to form iron-doped silica nanoparticles. Consequently, we used iron-doped silica nanoparticles as a substrate and catalyst for the synthesis of carbon nanosphere at 750 °C for 1 hour in an argon and acetylene gas atmosphere. As a result, vast quantities of superhydrophobic carbon nanospheres (CNS) were obtained. The physicochemical properties of nanosilica substrate, non-functionalized carbon nanosphere, and functionalized carbon nanosphere (CNS) samples were characterized using XRD, XRF, SEM, EDS, TEM, and FTIR spectrometer. Iron-doped mineral-derived nanosilica particles demonstrated high catalytic efficiency and the potential to produce a large amount of value-added carbon nanospheres. Superhydrophobic CNS can be used in a variety of applications, particularly drug delivery; however, to use CNS in both aqueous and non-aqueous media, the superhydrophobic properties of CNS can be modified using different oxidizers. The changes in hydrophobicity of the CNS were examined and suggested possible oxidizing agents.
Mechanical activation is known to greatly influence the reactivity of fly ashes. In this paper, we report a comparative study of the properties of alkali-activated geopolymer materials prepared using both ball-milled and attrition-milled fly ashes. Ball milling was carried out for 30 min and 60 min while attrition milling was carried out continuously in a high-speed attritor. The surface area of the raw fly ash decreased from 4017 cm2/g to 3999 cm2/g and 3912 cm2/g after ball milling for 30 min and 60 min, respectively. By contrast, the surface area of the continuously attrition-milled fly ash increased to 5545 cm2/g. Fly ash processed by continuous attrition milling showed a 50% particle size reduction to 25–38 μm, whereas fly ash ball-milled for 30 and 60 min was reduced in size by 33.4 and 42.9%. The milled fly ash samples were activated with 8 M NaOH solution and cured at 40 °C for 68 h. After curing, the samples were maintained at room temperature, and their 7-, 14-, and 28-day compressive strengths were measured. The compressive strength of the attrition-milled 28-day geopolymer paste was 24.6 MPa; that of the geopolymers ball-milled for 30 and 60 min was 23.37 MPa and 17.58 MPa, respectively; and that of the unmilled control geopolymer fly-ash-based paste was 17 MPa. The improvement in the mechanical properties is attributed to the increased gel formation resulting from the increased surface area (decreased particle size) in the fly ash glass starting material.
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