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The aim of this work is to study the effect of a water-soluble biopolymer, carboxymethyl inulin (CMI), on the crystallization of calcium carbonate. We have investigated the effect of the feed rate of the reactant and the concentration of the biopolymer on the surface area, particle size and size distribution, final morphology and polymorph of calcium carbonate crystals during a precipitation. The produced crystals were characterized by scanning electron microscopy (SEM), Fourier transform infrared spectrometry (FT-IR), X-ray diffraction (XRD), thermal analysis (TGA-DTA) and BET (Brunauer-Emmett-Teller) methods. In the presence of the biopolymer (0.5-1 g L 21 ), the polymorph of the synthesized calcium carbonate crystals changed from pure calcite to a mixture of vaterite and calcite. The formation of a thermodynamically unstable vaterite phase was attained in the presence of the biopolymer.

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Influence of graft copolymers with different architecture on spontaneous batch crystallization of calcium oxalate was investigated. The series of water-soluble polyethyleneglycol methacrylate-vinylsulfonic acid graft copolymers [(PEG-MA)-co-VS] and homopolymer of vinylsulfonic acid have been made, by radical polymerization, with defined molecular weight and structure. The presence of polymers inhibited the crystal growth of calcium oxalate possibly through adsorption onto the active growth sites for crystal growth due to the charge and hydrophilic effects. The higher inhibition efficiency of vinylsulfonic acid homopolymer is related to the maximum surface charge density due to adsorbed polymer. The homopolymer influenced both the morphology and phase transformation of calcium oxalate crystals. Polyelectrolyte effects were interpreted in terms of the adsorption of inhibitors onto the active growth sites on the crystal surface.

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