Priprava taložnog kalcijeva karbonata šaržnim i semikontinuiranim postupkom

A comparison of the physical-chemical properties of precipitated calcium carbonate (PCC), prepared by batch and semicontinuous processes, is presented. In both processes, PCC, was synthesized by carbonation of slaked lime. In the batch process the experiments were performed by varying the initial mass concentration and temperature, and the semicontinuous process was conducted by varying the initial supersaturation and temperature. Calcite was the only calcium carbonate polymorph that appeared under the experimental conditions investigated. It was found, that in the batch experiments the specific surface area and the average size of calcite particles decreased with the increase of temperature. At the same time, the increase of the initial mass concentration of slaked lime enhanced the degree of precipitate aggregation. PCC prepared by the semicontinuous process, conducted at low temperatures and high supersaturations, was of high specific surface area. By careful tuning of the semicontinuous process parameters, calcite in the form of rhombohedral, scalenohedral or nanosized spherical particles can be producedU ovom su radu uspoređena fizičko-kemijska svojstva taložnog kalcijeva karbonata (TKK) pripravljenog karbonatizacijom vapnenog mlijeka u šaržnom i semikontinuiranom reaktoru. U šaržnom su postupku varirane temperatura i početna masena koncentracija vapnenog mlijeka, dok su u semikontinuiranom mijenjani temperatura i prezasićenost sustava. Pri svim je istraživanim uvjetima nastao kalcit. Utvrđeno je da se specifična površina i prosječni promjer čestica kalcita, pripravljenog šaržnim postupkom, smanjuju s povećanjem temperature, dok se s povišenjem početne masene koncentracije poboljšava stupanj agregiranosti taloga. TKK pripravljen semikontinuiranim postupkom, vođenim pri niskim temperaturama ili visokim prezasićenostima, velike je specifične površine. Odabirom procesnih parametara semikontinuiranog postupka moguće je pripraviti kalcit u obliku romboedarskih, skalenoedarskih ili kuglastih čestica nanometarskih dimenzija