Growth modification of seeded calcite using carboxylic acids: Atomistic simulations

Abstract

a b s t r a c tMolecular dynamics simulations were used to investigate possible explanations for experimentally observed differences in the growth modification of calcite particles by two organic additives, polyacrylic acid (PAA) and polyaspartic acid (p-ASP). The more rigid backbone of p-ASP was found to inhibit the formation of stable complexes with counter-ions in solution, resulting in a higher availability of p-ASP compared to PAA for surface adsorption. Furthermore the presence of nitrogen on the p-ASP backbone yields favorable electrostatic interactions with the surface, resulting in negative adsorption energies, in an upright (brush conformation). This leads to a more rapid binding and longer residence times at calcite surfaces compared to PAA, which adsorbed in a flat (pancake) configuration with positive adsorption energies. The PAA adsorption occurring despite this positive energy difference can be attributed to the disruption of the ordered water layer seen in the simulations and hence a significant entropic contribution to the adsorption free energy. These findings help explain the stronger inhibiting effect on calcite growth observed by p-ASP compared to PAA and can be used as guidelines in the design of additives leading to even more marked growth modifying effects.

Modeling Acid Oil Component Interactions with Carbonate Reservoirs: A First-Principles View on Low Salinity Recovery Mechanisms

“…Some works have been published on the same direction, studying the interaction of acid molecules with calcite surfaces in vacuum and in the presence of water. 22,23 In particular, Sakuma et al 22 studied the first step of the proposed mechanism, concluding that the Ca 2+ replacement by Mg 2+ ion in the presence of SO 4 2− ion is exothermic and that Mg 2+ remains on calcite surface site and not inside the crystal.…”

Electrophoretic deposition of polyacrylic acid and composite films containing nanotubes and oxide particles

“…Polyacrylic acid (PAA) is of great technological interest for applications in biomedical [1][2][3], electrochemical [4,5], electronic [6] and optical [7] devices. PAA has been utilized as a binder and solid electrolyte for lithium ion batteries [8] and supercapacitors [9,10].…”

Interacción entre cementos de diferente composición y aditivos superplastificantes

“…The results reflect the positive effect of calcite on the rheology of the cement. The ability of calcite to adsorb organic admixtures was investigated using molecular dynamic simulations (5). The authors referred to previous work (29)(30) in the formation of stable complexes between negatively charged admixture (polyacrylic acid) and the counter ions in solutions (Ca 2+ ).…”

“…The key parameters which control the adsorption of the polycarboxylates are their ionic charge density, the side chain density and the strength of the electrostatic and steric stabilization (4). The flexibility of the backbone structure may play a significant role in the adsorption process of some adsorbents (5).…”