Passivation of the calcite surface with malonate ion

Passivation of the calcite surface with phenylmalonate and benzylmalonate ions

“…For both dicarboxylic acids an increase was observed in the absolute value of the surface charge at pH ∼ = 7.00 compared to other experimental pH values. This is in agreement with the position of the maximum value of the surface charge between the experimental range reported for pure calcite in aqueous solution, which was around pH 7.45 [5].…”

“…We have shown previously [5] the determination of the surface charge of marble powder in aqueous media as a function of pH. The isoelectric point (IP) was found to occur at pH 6.45 and the point of zero charge (PZC) at pH 8.20, which are close values compared to those reported in other works [4,33,36].…”

“…In general, the procedure was similar to our previous work [5]; however, the results showed interesting differences among malonic, phenylmalonic, and benzylmalonic acids as candidate agents of passivation of marble and limestone in cultural heritage.…”

“…In a preview paper [5] we studied the characteristics of calcium carbonate regarding the affinity to malonic acid. The goal was to apply this dicarboxylic acid as a passivant agent in the conservation of cultural heritage built from marble and limestone, keeping the original appearance of the object and trying to be gentle to the surface.…”

Molecular models of a hydrated calcite mineral surface

“…The ð10 14Þ calcite surface is charge neutral, which assures that there is no significant polarization associated with any of the interfaces (calcite-water, water-vacuum, and calcite-vacuum) created by the slab model (Duckworth et al, 2003). At circumneutral conditions, the calcite surface is approximately neutral with charge separation (van Cappellen et al, 1993;Pokrovsky et al, 1999Pokrovsky et al, , 2000Fenter et al, 2000;Pokrovsky and Schott, 2002;Duckworth et al, 2003;Salinas-Nolasco et al, 2004). Assuming equilibrium conditions for the calcite, protonated surface and solvated metal and bicarbonate species were omitted from the simulation cell.…”