Publication: Kalsiyum Karbonatın Polimorfik Faz Dönüşümünün Prolin Varlığında _x000D_
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Bu çalışmada, kalsiyum karbonatın polimorfik faz dönüşümü katkı maddesi olarak kullanılan prolin varlığında incelenmiştir. Deneyler 1L kapasiteli çift ceketli kristalizörde, 30 C sıcaklık ve pH 8,5’da yürütülmüştür. 50 ve 100 ppm olmak üzere iki farklı katkı konsantrasyonunda deneyler gerçekleştirilmiştir. Reaktan olarak kalsiyum klorür dihidrat ve sodyum karbonat kullanılmıştır. Deney süresince belirli zaman aralıklarında numuneler alınarak, kristallerin yapısı, fonksiyonel grupları, morfolojisi, tane boyutları ve yüzey yüklerinin değişimi belirlenmiştir. XRD ve FTIR analiz sonuçları, kalsiyum karbonat kristallerinin prolin varlığında kalsit formundan vaterit formuna dönüştüğünü göstermiştir. SEM görüntüleri saf ortamda üretilen kalsit kristallerinin kübik formda olduğunu buna karşın prolin varlığında kristallerin yuvarlak görünümlü vaterit morfolojisine sahip kristallere dönüştüğünü göstermiştir. Ayrıca, prolinin kalsiyum karbonat kristallerinin yüzey alanına ve yüzey yüküne olan etkisi BET analizi ve zeta potansiyeli ölçümleri yapılarak belirlenmiştir. Saf ortamda üretilen kalsit kristallerinin BET yüzey alanı ve zeta potansiyeli değeri sırasıyla 0,7 m2/g ve –8,0 ± 2,1 mV olarak ölçülmüştür. Buna karşın, 100 ppm prolin varlığında kristallerin BET yüzey alanı 3.7 $m^2$/g’a yükselmiş ve prolinin kristallerin yüzeyine fiziksel olarak adsorplanmasından dolayı zeta potansiyel değerleri daha negatif (–24,0 ± 2,6 mV) hale gelmiştir. Sonuç olarak, katkı maddesi olarak kullanılan prolinin kalsiyum karbonatın hem fiziksel hem de morfolojik özelliklerini önemli ölçüde değiştirdiği gösterilmiş ve farklı formlarda kalsiyum karbonat kristallerinin üretilmesine imkân sağlayacağı tespit edilmiştir.
In this study, the polymorphic phase transformation of calcium carbonate was analyzed in the presence _x000D_ of proline used as an additive. The experiments were carried out in a 1-litre double-jacketed crystallizer_x000D_ at 30 C and pH 8.5. The experiments were performed at two different concentrations of 50 and 100 _x000D_ ppm. Calcium chloride dihydrate and sodium carbonate were used as the reactants. During the _x000D_ polymorphic transformation process, the samples were withdrawn from the crystallizer at regular time _x000D_ intervals and the structure, functional group, morphology, particle size and surface charges of the _x000D_ calcium carbonate were determined as a function of the time. XRD and FTIR results showed that calcium _x000D_ carbonate crystals transformed from calcite to vaterite structures in the presence of proline. SEM _x000D_ images indicated that the calcium carbonate crystals prepared in pure media was cubic shaped crystals_x000D_ and the morphology transformed into spherical like vaterite crystals in the presence of proline._x000D_ Moreover, the effects of proline on the surface area and surface charge of calcium carbonate were_x000D_ investigated by BET and zeta potential analysis. BET surface area and zeta potential for calcite crystals _x000D_ prepared in pure media were 0.7 m2/ g and - 8.0 ± 2.1 mV, respectively. By the addition of proline to _x000D_ the crystallization media, BET surface area increased to 3.7 $m^2$/g, and the surface became more _x000D_ negative (- 24.0 ± 2.6 mV).
In this study, the polymorphic phase transformation of calcium carbonate was analyzed in the presence _x000D_ of proline used as an additive. The experiments were carried out in a 1-litre double-jacketed crystallizer_x000D_ at 30 C and pH 8.5. The experiments were performed at two different concentrations of 50 and 100 _x000D_ ppm. Calcium chloride dihydrate and sodium carbonate were used as the reactants. During the _x000D_ polymorphic transformation process, the samples were withdrawn from the crystallizer at regular time _x000D_ intervals and the structure, functional group, morphology, particle size and surface charges of the _x000D_ calcium carbonate were determined as a function of the time. XRD and FTIR results showed that calcium _x000D_ carbonate crystals transformed from calcite to vaterite structures in the presence of proline. SEM _x000D_ images indicated that the calcium carbonate crystals prepared in pure media was cubic shaped crystals_x000D_ and the morphology transformed into spherical like vaterite crystals in the presence of proline._x000D_ Moreover, the effects of proline on the surface area and surface charge of calcium carbonate were_x000D_ investigated by BET and zeta potential analysis. BET surface area and zeta potential for calcite crystals _x000D_ prepared in pure media were 0.7 m2/ g and - 8.0 ± 2.1 mV, respectively. By the addition of proline to _x000D_ the crystallization media, BET surface area increased to 3.7 $m^2$/g, and the surface became more _x000D_ negative (- 24.0 ± 2.6 mV).