Scopus İndeksli Yayınlar Koleksiyonu / Scopus Indexed Publications Collection
Permanent URI for this collectionhttps://hdl.handle.net/11147/7148
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Article Citation - WoS: 7Citation - Scopus: 7Contributory Roles of Concentration and Ph in Caco3 Growth Inhibition for Submicron Particles Synthesis With Additive Ca2+(Elsevier B.V., 2024) Majekodunmi,O.T.; Kilic,S.; Ozdemir,E.Excessive growth of CaCO3 precipitates is inhibited by additive Ca2+. Here, we report the influence of concentration and solution pH on the extent of growth inhibition. Equal volumes of equimolar CaCl2 and Na2CO3 solutions were mixed and continuously dispersed in Ca(OH)2 solution, where Ca2+ irreversibly adsorb on the precipitates. Compared to conditions where additive Ca2+ are absent, this method can produce more than 90% decrease in particle size. We observe the degree of growth inhibition increases as the concentration of additive Ca2+, relative to the volume of precipitates, increases. An unusual role of pH is also revealed: growth inhibition that leads to the synthesis of monodisperse submicron CaCO3 particles is only observed in high alkaline pH conditions. Additive Ca2+ adsorb on CaCO3 precipitates in pH conditions above the isoelectric point (pH ≈ 9), but their ability to limit CaCO3 growth diminishes when pH < 12. © 2024 Elsevier B.V.Article Citation - WoS: 1Citation - Scopus: 1Inhibition of Caco3 Growth and Synthesis of Submicron Particles by Preferential Adsorption of Additive Ca2+ Ions on Fresh Precipitates(Royal Society of Chemistry, 2022) Majekodunmi, Olukayode T.; Kılıç Özdemir, Sevgi; Özdemir, EkremThis study demonstrates a method to inhibit the growth of CaCO3 and synthesize submicron particles in a chemical precipitation process under ambient and high supersaturation conditions. Equimolar CaCl2 and Na2CO3 solutions were mixed in a model tubular reactor at a constant flow rate, and the precipitates were continuously dispersed in stirred 250 mL of 10 mM Ca(OH)2 solution. This approach resulted in the synthesis of colloidally stable submicron CaCO3 particles for a precipitant concentration ≤75 mM. Varying the precipitates’ retention time in the tubular reactor had no significant effects on the particle size and colloidal stability. Time-dependent changes in the mean size, crystal form, morphology and specific surface area of the synthesized particles were also studied. For a precipitant concentration of 75 mM, the particles were monodispersed and porous spindle-like scalenohedral crystals which gradually grew in all faces as more precipitates were fed into the Ca(OH)2 solution. The mean hydrodynamic size of the particles was ∼850 nm at the 8th minute. However, in the absence of additive Ca2+ ions, the particles obtained at the 8th minute were polydisperse mixtures of vaterite and rhombohedral calcite particles greater than 4 μm in size. The results show that free additive Ca2+ ions are irreversibly adsorbed onto the particles as the precipitates dissolve and recrystallize into smaller crystals upon reaching the Ca(OH)2 solution.Article Citation - WoS: 61Citation - Scopus: 66The Use of Metal Piece Additives To Enhance Heat Transfer Rate Through an Unconsolidated Adsorbent Bed(Elsevier Ltd., 2010) Demir, Hasan; Mobedi, Moghtada; Ülkü, SemraThe effects of metal piece additives on effective thermal conductivity and diffusivity of an unconsolidated adsorbent bed in which adsorbent is silica gel were investigated. The metal piece additives were copper, brass, aluminum and stainless steel with two different sizes as 1.0-2.8 mm and 2.8-4.75 mm. The effective thermal conductivity and diffusivity of the mixed bed were predicted by comparison of the experimental results with the solution of dimensionless heat conduction equation for the bed. The performed experiments showed that the addition 15wt% of aluminum pieces with sizes between 1.0 and 2.8 mm enhances the effective thermal diffusivity and conductivity of a pure silica gel bed by 157% and 242%, respectively. © 2010 Elsevier Ltd and IIR.Article Citation - WoS: 4Citation - Scopus: 6The Effect of Additives on Hydrodesulfurization of Dibenzothiophene Over Bulk Molybdenum Sulfide: Increased Catalytic Activity in the Presence of Phenol(Elsevier Ltd., 2008) Gül, Ömer; Atanur, Osman M.; Artok, Levent; Erbatur, OktayThe effect of various additive organic reagents on the activation of MoS3 as molybdenum sulfide catalyst precursor during hydrodesulfurization reaction of dibenzothiophene was studied. It was found that the presence of phenol or 1-naphthol greatly promoted the activity of the catalyst, while tetralin, 9,10-dihydrophenanthrene, ethylbenzene, and pyridine reagents were found to be detrimental for the activity of the catalyst.