How to control the scaling of CaCO3: a “fingerprinting technique” to classify additives

Abstract

A titration set-up coupling ion selective electrodes with pH adjustment was used to analyze the effects of additives present during precipitation of calcium carbonate. Besides industrially well-established antiscalants (sodium triphosphate, citrate, polyacrylate and poly(aspartic acid)), also functional polymers being active in morphosynthesis (polystyrene sulfonate and poly(styrene-alt-maleic acid)) were analyzed. Interestingly each additive acts in its specific way, suggesting the notation "fingerprinting" for a complex interplay of up to five "solution modes" of influencing CaCO(3) precipitation and crystallisation. The results provide new insights into the modes of additive controlled crystallisation, and in the long run, the insights may facilitate the design of precipitation systems that yield complex and tailor-made crystals.

The multiple effects of amino acids on the early stages of calcium carbonate crystallization

“…The slope of the increase of free calcium prior to nucleation bears important information as it directly reflects interactions between additives and prenucleation species [45,46]. Generally, a steeper slope implies that less calcium is bound in prenucleation clusters, indicating that they are destabilized by the particular additive, whereas flattening of the prenucleation regime in turn suggests cluster stabilization, as reported e.g.…”

“…Generally, a steeper slope implies that less calcium is bound in prenucleation clusters, indicating that they are destabilized by the particular additive, whereas flattening of the prenucleation regime in turn suggests cluster stabilization, as reported e.g. for citrate [46]. However, there are Amino acids in calcium carbonate crystallization caveats as a flatter pre-nucleation slope can also result from activity effects due to increased ionic strength at high additive contents, as reported recently [49].…”

“…For this purpose, a titration assay was employed that had previously been used to investigate the nucleation process [44] as well as the effect of distinct additives on precipitation scenarios [45][46][47]. As in earlier work, experiments were carried out by continually dosing 10 mM CaCl 2 solution into an excess of 10 mM sodium (bi)carbonate buffer, where the pH was kept constant at 9.75 by counter-titration of 10 mM NaOH.…”

Mineralization and non-ideality: on nature’s foundry

“…The activities of these biomolecules condition the pre-nucleation and early mineralization stages, for instance by regulating supersaturation and pH. Such biomolecules can also modulate the stability of mineral precursors as well as regulate nucleation and phase transitions reflecting the multiple roles of (bio)molecules as additives in mineralization processes (Verch et al 2011;Rao et al 2014). Here, multiple properties of biomolecular additives such as charge, amino acid/glycan/lipid composition, covalent modifications, conformations, and self-assembly propensity as well as intermolecular synergy play mechanistic roles (Arias and Fernández 2008;Bentov et al 2010;Chang et al 2016a, b;Rao et al 2013Rao et al , 2015.…”

“…For instance, silicateins from the axial filaments of siliceous skeletons catalyze hydrolysis of silicon alkoxides and self-assemble to form filamentous templates that spatially direct silica deposition (Murr et al 2009). Certain synthetic macromolecules fulfill multiple roles during mineralization (Verch et al 2011) so that the multifunctionality of certain mineral-associated biomolecules appears to be no exception.…”