engleski

Novel method for precipitation of calcium carbonate polymorphs of unusual morphologies

Precipitation processes of carbonate particles of different size, shape, and surface properties have been intensively investigated due to their importance in geo- and biosciences, and in numerous industrial applications. A novel precipitation process, effectuated through catalytic decomposition of urea at elevated temperatures and by using the enzyme, urease, was employed to precipitate calcium carbonate polymorphs in a reacting solution of calcium salts. The structure and morphology of the obtained precipitates were investigated using scanning electron microscopy (SEM) and X-ray diffraction (XRD). The effects of various experimental conditions on the precipitation processes, such as the concentration of reactants, temperature, aging time, agitation and mixing procedures were investigated. It was found that the formation of different polymorphs of calcium carbonate, characterized by unusual and fascinating morphologies, was effected mostly by agitation and concentration of reactants as well as by mixing procedures. This study also exemplifies recently renewed mechanism in which some of carbonate colloids can be formed through aggregation of preformed nanosize crystalline particles. Understanding the latter processes may lead to new strategies for the synthesis of calcium carbonate precipitates of desirable structural and morphological properties.

calcium carbonate; polymorph; enzyme-catalyzed precipitation; urease; urea

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