Competitive Adsorption on Wollastonite:  An Atomistic Simulation Approach

Abstract

Atomistic simulation techniques are used to simulate surface structure and adsorption behavior of scarcely floatable wollastonite mineral in the presence of molecular and dissociated water, methanoic acid, and methylamine. The latter two additives represent the two widely used collector head-group molecules. The static energy minimization code METADISE was used to perform the simulation to obtain pure surface energy and adsorption energy in the presence of added molecule. The hydroxylation was performed on those surfaces where low-coordinated silicon was made to saturate by bonding with hydroxyl group, and the subsequent charge neutralization was maintained by adding proton on single-coordinated surface oxygen. A comparison of surface energies revealed that all the surfaces become stabilized in the presence of added molecules; however, the presence of methylamine decreased the surface energy to lower values. Adsorption of dissociated water is preferred by the {100} and {102} surfaces, whereas the {001} surface preferred methylamine adsorption, because these show highly negative adsorption energies. In terms of molecular adsorption, the preferred adsorption sequence for all the surfaces is methylamine > methanoic acid > water without considering coadsorption. For the {100} and {102} surfaces, the adsorption energy values of carboxylic acid and amine are more negative than that of water and therefore we conclude that both carboxyl and amine head-group molecules adsorb preferably on wollastonite. Our simulation verify usability of carboxylic acid head group as widely used collectors for wollastonite flotation and, at the same time, it predicts the use of amine head-group collectors as possible modifiers, which corresponds well with our experimental findings.

Advances in atomistic simulations of mineral surfaces

“…Similar classical simulations, making use of the METADISE computer code, have been performed to describe the (100) (001) and ( 102) surfaces of the CaSiO 3 low temperature polymorph awollastonite, a member of the inosilicate family with a triclinic crystal structure (space group P 1). 128,129 The (100) surface is the best cleavage plane. It contains one lone oxygen per 2D unit cell, while the (102) surface contains double lone oxygens.…”

From lime to silica and alumina: systematic modeling of cement clinkers using a general force-field

“…The present force field generalizes and simplifies the stateof-the-art force fields usually used to model cement clinker and pastes [16][17][18][19][20] in three important ways: (i) non-bonded interactions (repulsive contacts and dispersive) are modeled via the Lennard-Jones potential instead of the Buckingham potential usually employed for minerals; (ii) only pair potentials are considered (no three-body terms are included); and (iii) fixed partial charges are used instead of core-shell models.…”

“…Some of these potentials have been built to describe the interactions between the different types of atoms within a given crystal, which means that the transferability of the corresponding parameters is generally not possible when considering other (analogous) systems. Historically, most of the potentials used to model cement clinker phases (and even the corresponding hydrated systems) have been based on Buckingham-type potentials, 3,4,[15][16][17][18][19][20][21] some originally developed for silicates and alumino-silicate materials, where different three-body interaction terms are generally introduced to account for the bond-hybridization around particular atom types such as silicon and oxygen. 17 Polarizability effects can also be taken into account using coreshell approaches instead of relying on fixed partial-charge models.…”

“…In order to analyze the distribution of silica aggregates in the amorphous calcium silica systems, one can use eqn (16) to calculate the probability of finding a particular atom (Si or O) in a silicate aggregate of size n a , 67 P n a ð Þ ¼…”

Atomistic simulation studies of magnetite surface structures and adsorption behavior in the presence of molecular and dissociated water and formic acid

“…Computational techniques are well placed to investigate at the atomic level, not only the surface structure but also the interactions between solid and adsorbate. Atomistic simulation techniques are useful for constructing, interpreting and predicting surface structures [2], morphology [3] and adsorption behavior [4].…”