IN SITU CHARACTERISATION OF CALCITE GROWTH AND INHIBITION USING ATOMIC FORCE MICROSCOPY

Abstract

Real time in situ monitoring of calcite growth and inhibition on the cleavage plane (1014) is investigated using atomic force microscopy (AFM). Calcite growth and inhibition were studied using a Molecular Imaging microscope in contact mode, equipped with an in situ fluid cell. As has been reported previously, it is observed that calcite growth from aqueous solution is by motion of mono-molecular steps, and dissolution by a combination of step motion and etch pit expansion. The measured step heights were between 2.7 to 3 A. Our aim is to study the effects of a range of phosphonate-based crystal growth inhibitors of related structure, in order to provide insight into the mechanism of inhibition as a function of the additive structure. Results of this study demonstrate the effect of inhibitors on the growth steps and terraces on the (1014) surface of calcite in real time. The organic additives bind to the crystal surface, with selective binding to the step edges particularly evident in some cases. In other cases, it appears that the additive acts by binding to the terraces on the crystal surface, resulting in inhibition by coating the surface. Efforts to correlate the observations made by atomic force microscopy with bulk crystallization experiments have been made.

Growth modification of seeded calcite using carboxylic acids: Atomistic simulations

“…Experimental observations of calcite surfaces [12,54] show a high density of steps, where carbonate dissolution at the pH of interest (around nine) is more favorable [55], which is also predicted by theory [56]. Even stable surfaces such as the ð1 0 1 4Þ surface have been shown to reconstruct in moist air via pit formation and film growth [57], making it reasonable to consider defective stepped surfaces in our simulations.…”

“…One way to gain this level of control is the use of growth modifying additives during the precipitation of calcite from the aqueous phase. It has been shown in the past that the adsorption of many types of polymers such as hydrophilic block copolymers [6,7], polycarboxylic acids [8][9][10][11], phosphonates [12,13] and polyamino acids [14][15][16][17] during precipitation or dissolution can modify calcite particle size and morphology. It was also shown that polycarboxylic acids can promote a very particular growth mechanisms [18], during which agglomeration of small primary particles results in a very high overall specific surface area.…”

The interaction of EDTA with barium sulfate

“…Work within our group has focused on trying to understand, at a fundamental level, the interactions of inhibitor molecules with the surfaces of barium sulfate [4][5][6][7]. In addition, we have sought to take useful information from molecular modelling and see whether it correlates with inhibition and vice versa, thus undertaking several studies employing both computational and experimental techniques [8,9].…”

Adsorption and precipitation of an aminoalkylphosphonate onto calcite

“…At low concentrations, the adsorption of phosphate and phosphonate on calcite has been studied in detail [3][4][5][6][7][8][9][10][11][12][13][14][15]. Several in situ atomic force microscope (AFM) [3][4][5]15] and X-ray photoelectron spectroscopy [6] studies showed that phosphonate and phosphate are adsorbed to the growth sites (kink 0021-9797/$ -see front matter  2004 Elsevier Inc. All rights reserved. doi:10.1016/j.jcis.2004.08.054 site, step edges, and terraces) and further growth of calcite is therefore inhibited.…”