| Article ID | Journal | Published Year | Pages | File Type |
|---|---|---|---|---|
| 7642644 | Microchemical Journal | 2015 | 7 Pages |
Abstract
A model study on the application of chelating solutions on superficial calcium degradation patinas of wall paintings is presented. For this purpose the solubility of calcium sulfate, carbonate and oxalate in aqueous solutions of the Ca2Â + chelators EDTA and citrate, was evaluated. Both the obtained solutions and their insoluble materials were analyzed by several analytical techniques. These studies revealed that the treatment of solid samples containing calcium sulfate and carbonate as the models of painting patinas resulted in higher solubilities of calcium sulfate and carbonate over that of oxalate. Moreover, our investigations confirmed the higher capacity of EDTA to chelate Ca2Â + compared to that of citrate. All these results were interpreted and discussed on the basis of speciation models, solubility products of the salts and formation constants of the calcium complexes in solution. Finally, we report the characterization of a sodium calcium double citrate salt formed as an unexpected product in the treatment of the calcium sulfate with citrate. Overall our results suggest that the low solubility of calcium oxalate prevents its dissolution upon treatments with chelators, and that the capacity of citrate to dissolve the calcium salts is lower than that of EDTA irrespective of the duration of treatment.
Keywords
Related Topics
Physical Sciences and Engineering
Chemistry
Analytical Chemistry
Authors
Valentina Emanuela Selva Bonino, Matteo Tegoni, Claudio Mucchino, Giovanni Predieri, Antonella Casoli,