Untitled

Abstract

The effect of sodium alginate in supersaturated solutions of calcium carbonate was investigated under plethostatic conditions. The rates of crystal growth measured in the presence of sodium alginate at concentrations as low as 0.83 x 10(-7) mol dm(-3) were drastically reduced. Kinetic analysis according to a Langmuir-type adsorption isotherm led to the calculation of an affinity constant Kaff = 999.8 x 10(-4) mol dm(-3). The apparent order found from kinetic data was 3.0+/-0.2 suggesting a surface nucleation mechanism.

The inhibition of calcium carbonate crystal growth by the cysteine-rich Mdm2 peptide

“…Besides the above limitations, the kinetic Langmuir model continues to describe a lot of physisorption and not phenomena [49,50] in a better manner than the other models, because the active sites used by the adsorption process are almost energetically equivalent, and the correction factor α ads was added. The crystal surface contains active sites Table 3 Comparative data on the inhibition of calcite precipitation based on the ratio of the rate constants for adsorption and desorption, K aff = k a /k d with different energy such as kinks, steps, and terraces, but for the adsorption process only a small fraction of the available active sites are used with similar adsorption energy [22,32,[49][50][51]. The presence of Mdm2 in the supersaturated solutions only affect the crystallization kinetics of calcite, causing no changes in the mechanism of crystal growth or favoring the formation of another calcium carbonate polymorph such as aragonite [52], vaterite [53], or hydrated calcium carbonate [54,55].…”

“…The reproducibility of the precipitation rates, R calcite , was better than 8% (mean of 5 experiments). In the present work, the rate of crystal growth at the time of the onset of precipitation (i.e., at time zero) were used for the kinetic treatment in order to avoid taking into account the fact than the crystals formed may serve as seed crystals, thus accelerating the rate of precipitation [22][23][24][29][30][31][32]. Finally, in order to maintain all parameters constant during each experiment (plethostatic conditions), an amount of inert electrolyte (KNO 3 ) was added in the working solution for the constancy of the ionic strength.…”

“…Natural organic polyelectrolytes are effective crystal growth inhibitors of calcium carbonate, and there are computational models to evaluate the chemical potential of such substances acting as inhibitors [19]. Extensive studies of several additives and their effects have been performed recently [20][21][22][23][24].…”

Nanoscale detection of organic signatures in carbonate microbialites

“…4), the morphology of Lake Van aragonite crystals is unusual compared with the morphology of crystals that are usually synthesized experimentally in the absence of organics. The presence of a widespread organic-rich matrix may thus explain the stabilization of the ACC layer as well as the clustering and submicrometer-size of the aragonite crystals, because organic molecules can promote the formation of numerous nucleation sites (36) and inhibit crystal growth by poisoning their surfaces (37). The widespread occurrence of EPS down to the nanometer-scale evidenced in this study may explain the micritic texture of Lake Van microbialites and more generally the micritic texture usually observed in carbonate microbialites (4).…”

Effect of Alginate from Chilean Lessonia nigrescens and MWCNTs on CaCO3 Crystallization by Classical and Non-Classical Methods

“…Rounded calcite crystals have been obtained through gas diffusion (GD) method by using ALG [19]. ALG does not alter the typical rhombohedral calcite form on CaCO 3 crystallization [20] and it has shown inhibiting capacity by adsorption onto the active growth sites of the crystal surface [21]. Also, "rosette-like" CaCO 3 aggregates have been obtained by direct mixing of Ca 2+ and CO 3 2− ions in the presence of sodium ALG [22].…”