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Browsing by Author "Osman Adam Osman, Ahmed"

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    Master Thesis
    Effect of ions on particle size and morphology in calcium carbonate (CaCO3) crystallization
    (01. Izmir Institute of Technology, 2021-12) Osman Adam Osman, Ahmed; Özdemir, Ekrem
    The particle sizes of calcium carbonate (CaCO3) produced by the chemical crystallization method were reported to be almost always larger than 3 µm. Our recent studies in our lab has shown that the nano-CaCO3 particles can be obtained when calcium hydroxide (Ca(OH)2) solution was used as a stabilizer. In this study, an experimental setup was developed to crystalize CaCO3 from sodium carbonate (Na2CO3) and calcium chloride (CaCl2) solutions in a plug flow reactor (PFR) with a retention time of 9 seconds and added into a stabilizing solution. The CaCO3 particles of about 30% of vaterite and 70% of calcite were produced with a size larger than 13 µm in the PFR tubular reactor. The influence of cations and anions on the particle size and morphology were investigated. The hydroxide form of sodium (Na+), potassium (K+), calcium (Ca++), ve barium (Ba++) were used as the stabilizer solution containing cations. Totally calcite particles at sizes larger than 2 μm were produced with homogenous size distribution in the presence of Na+ and K+ ions. Nano-calcite particles were produced in solution containing Ca++ ions. A new crystalline form, Barytocalcite (BaCa(CO3)2), and whitherite (BaCO3) particles were produced in solution containing Ba++ ions. The sodium form sulfate (SO4=), nitrate (NO3-), carbonate (CO3=) and bisphosphate (HPO4=) were used as the stabilizer solution containing anions. The size and morphology of vaterite and calcite particles were seen almost the same and did not change with the particles synthesized in the PFR tubular reactor in the presence of SO4=, NO3-, and CO3= ions. A different form of particles such as monetite (CaHPO4) and hydroxyapatite (Ca5(PO4)3OH) were synthesized in the presence of HPO4= ion in the stabilizer solution. These formations clearly indicated that the CaCO3 particles synthesized in the PFR tubular reactor were dissolved and recrystallized in the stabilization solutions. It was successfully demonstrated that the synthesis of CaCO3 in nano sizes with the chemical method was achieved and devised a novel technique for the continuous production of nano-CaCO3. It was demonstrated that nano-calcite particles of about 350 nm were produced by the chemical method not previously reported in the literature.