Preparation of amorphous calcium carbonate nanoparticles from impure dolomitic marble with the aid of poly(acrylic acid) as a stabilizer

• Impure dolomitic marbles are used to synthesize pure CaCO3 nanoparticles.
• Poly(acrylic acid) is used as the stabilizer of amorphous CaCO3.
• The bubbling method is employed for the preparation of CaCO3.
• The carbon dioxide bubbling efficiency is improved by designing a column.
• The yields of final products are enhanced by the proposed bubbling method.

Nanomaterials of Precipitated Calcium Carbonate (PCC) such as Amorphous Calcium Carbonate (ACC) nanoparticles are highly demanded industrial products. These products are prepared in industrial scale, using pure CaCO3 natural resources such as pure carbonate rocks, cockle shells, corals, and pearls. Such natural resources could be consumed rapidly due to their excessive use in PCC industries. Therefore, the development of novel procedures to prepare nanoparticles of PCC using impure minerals is desirable. Herein, we report a simple, novel and economical method to synthesize poly(acrylic acid) (PAA) stabilized ACC nanoparticles using extensively distributed impure dolomitic marbles in place of natural pure CaCO3 raw materials. The yields of final ACC products are enhanced using a bubbling column which can produce small bubbles to improve bubbling efficiency. The average particle sizes of final calcium carbonate products are in the range 21–53 nm. The best conditions to produce ACC, among the conditions used in the proposed method, are temperature of 40 °C, pH of 4.5 and PAA concentration of 10−2 M. One or more crystalline phase(s) of PCC is associated with ACC in each product and its nature depends on the conditions used in the synthesis of these products. The unstable vaterite form of PCC is formed when the PAA concentration is less than 0.5 M and at lower temperatures such as room temperature. The stability of the vaterite phase decreases when the temperature and the PAA concentration are increased. The synthesized ACC nanoparticles are in required purity and quality to be suitable for industrial applications.

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