Influence of pH and citrate on the formation of oxalate layers on calcite revealed by in situ nanoscale imaging

Tunable Manipulation of Mineral Carbonation Kinetics in Nanoscale Water Films via Citrate Additives

“…The citrate-mineral interactions in nanoscale adsorbed water films are qualitatively similar to those in bulk aqueous fluids and provide valuable insight into reactions that take place in interpore environments in rocks, soils, and engineered materials. Tunable manipulation of crystallization via additives also has applications for antiscaling, , stone conservation, and toxic metal immobilization. , This type of quantitative information may be used to parametrize multiphase models that predict the fate and transport of subsurface CO 2 , where organic ligands and biomass-associated carboxylated surfaces have potential to dynamically influence carbonation kinetics. Utilization of organic additives, including citrate, to tailor growth rates and products may lead to innovative strategies for anthropogenic carbon sequestration.…”

Formation of Strontianite and Witherite Cohesive Layers on Calcite Surfaces for Building Stone Conservation

“…This type of treatment has been successfully applied, both in situ and in the laboratory, to calcite crystals, on whose surface a micrometric thick layer is replaced by a cohesive layer of calcium oxalate after interaction with oxalatebearing fluids. 5,6,9,10 Due to the large positive molar volume change (more than 50%) associated to this mineral replacement reaction, the so-formed calcium oxalate cohesive layer effectively protects the calcite substrates since it is virtually devoid of porosity.…”

“…A good adhesion between the substrate and the overgrowing cohesive layer is a key factor that determines how effectively the cohesive layer can preserve the building stone from alteration. 5,6,9 Indeed, the fragility of calcium oxalate cohesive layers and their proneness to detach from the calcitic substrates constitutes the main problem of this building stone treatment. Commonly, the existence of crystallographic relationships between the overgrowth and the substrate facilitates the formation of more strongly attached and less fragile overgrowths.…”

“…One of these treatments consists of promoting the formation of mineral cohesive layers on the surfaces of the mineral grains that constitute the outermost external layers of the building stones. ,,, These cohesive layers reduce the porosity of the building stones and, as a result, its exposure to potential alteration vectors (microorganisms, pollution, and acid atmospheres). This type of treatment has been successfully applied, both in situ and in the laboratory, to calcite crystals, on whose surface a micrometric thick layer is replaced by a cohesive layer of calcium oxalate after interaction with oxalate-bearing fluids. ,,, Due to the large positive molar volume change (more than 50%) associated to this mineral replacement reaction, the so-formed calcium oxalate cohesive layer effectively protects the calcite substrates since it is virtually devoid of porosity.…”

“…A good adhesion between the substrate and the overgrowing cohesive layer is a key factor that determines how effectively the cohesive layer can preserve the building stone from alteration. ,, Indeed, the fragility of calcium oxalate cohesive layers and their proneness to detach from the calcitic substrates constitutes the main problem of this building stone treatment. Commonly, the existence of crystallographic relationships between the overgrowth and the substrate facilitates the formation of more strongly attached and less fragile overgrowths. − However, epitactic overgrown cohesive layers can also develop cracks due to accumulated tensile stress. − Though these cracks originate within the cohesive layer, they can often also penetrate the substrate, irreversibly damaging it and making its interior accessible to alteration vectors that can further increase the damage .…”