The Interaction of Diphosphonates with Calcitic Surfaces:  Understanding the Inhibition Activity in Marble Dissolution

Abstract

The rates of dissolution of calcitic Carrara marble have been reported to be significantly reduced in alkaline pH (pH 8.25) at 25 degrees C in the presence of (1-hydroxyethylidene)-1,1 diphosphonic acid (HEDP). The adsorption takes place at the calcite/water interface at the double layer through the interaction of charged surface species with the charged solution species of the adsorbate. The present work focused on obtaining a better understanding of the interaction of the calcite surface with HEDP. Calculations were performed according to the triple layer model, assuming the formation of surface complexes between the charged surface species of calcite and the species of HEDP dominant at pH 8.25. According to the model, the adsorbed species are located at the inner Helmholtz plane of the electrical double layer. Strong lateral interactions between the adsorbed species were suggested and were corroborated from the calculation of the respective energy, which was equal to 69 kJ mol(-1). The adsorption isotherm was consistent with the proposed model at low surface coverage values, while discrepancies between the values experimentally measured and the predicted were found at higher adsorbate concentrations. The deviations from the predicted values were attributed to the fact that HEDP adsorption on calcite resulted in the formation of multiple layers. The model explained adequately the changes in the zeta-potential values of calcite in the presence of HEDP in the solution which resulted in charge reversal upon adsorption.

From Nanoparticles to Gels: A Breakthrough in Art Conservation Science

“…Finally, colloids are being increasingly developed and proposed for the protection of works of art, i.e., preventing damage and alterations by either acting on the works’ surfaces (remedial conservation) or devising tools to neutralize environmental degradation agents before they reach the artifacts (preventive conservation). , Among the latest applications, we mention here multifunctional halloysite nanotubes, the use of graphene veils to prevent the fading of colors, colloidal semiconductor photocatalyst or nanocrystals for self-cleaning and degradation prevention, , soil colloids as templates to protect jade, antioxidant bionanocomposites or antifouling coatings, , sol–gel or nanocarriers to protect bronze from corrosion, , mesoporous silica nanoparticles for the controlled release of antimicrobials, cellulose nanocrystals or lignin nanoparticles as UV absorbers, and organic–inorganic composites or metal organic frameworks to absorb volatile acids in enclosures. − These are all key studies to show the vast potential impact of nanoparticles and nanocomposites in cultural heritage conservation, thanks to properties that surpass those of conventional restoration materials. Current challenges involve scaling up the production of these innovative systems, implementing green synthetic processes, transferring the best products to the conservation market, and linking with transversal sectors that can benefit from the new materials.…”

“…Finally, colloids are being increasingly developed and proposed for the protection of works of art, i.e., preventing damage and alterations by either acting on the works’ surfaces (remedial conservation) 81 or devising tools to neutralize environmental degradation agents before they reach the artifacts (preventive conservation). 9 , 10 Among the latest applications, we mention here multifunctional halloysite nanotubes, 82 the use of graphene veils to prevent the fading of colors, 83 colloidal semiconductor photocatalyst or nanocrystals for self-cleaning and degradation prevention, 84 , 85 soil colloids as templates to protect jade, 86 antioxidant bionanocomposites or antifouling coatings, 87 , 88 sol–gel or nanocarriers to protect bronze from corrosion, 89 , 90 mesoporous silica nanoparticles for the controlled release of antimicrobials, 91 cellulose nanocrystals or lignin nanoparticles as UV absorbers, 92 and organic–inorganic composites or metal organic frameworks to absorb volatile acids in enclosures.…”

Reverse Flotation Separation of Fluorite from Calcite: A Novel Reagent Scheme

“…1-Hydroxyethylidene-1,1-diphosphonic acid (HEDP or H 4 L) is widely used in water treatment as an anti-scaling reagent due to its outstanding properties such as high efficiency, low cost, low-temperature resistance and environmental friendliness [17][18][19][20]. HEDP can chelate with metal ions (especially Ca salts from aqueous solutions) to form six-membered ring complexes, providing for its anti-scaling properties [18,[21][22][23]. There have been reports of stronger interaction between HEDP and Ca ions, so it is anticipated that HEDP can serve as a depressant of calcium-containing minerals such as fluorite or calcite.…”

Biomimetic fluorapatite films for conservation of historic calcareous stones

“…Coatings of synthetic polymers such as acrylics, epoxides, and organosilicon compounds have been extensively used in the conservation of historic stones in the past [5][6][7]. Surfactants such as oleates and organic phosphates [8] have also been explored for the conservation of calcareous stones. These organic protective materials work to a certain extent, but they have inherent disadvantages such as short lifetimes [9,10], poor compatibility with the stones, and they cause color changes of [11] the stones.…”