Ammonium monoethyloxalate (AmEtOx): a new agent for the conservation of carbonate stone substrates

M. Carla Aragoni
Primo
Membro del Collaboration Group
;
Laura Giacopetti
Secondo
Membro del Collaboration Group
;
Massimiliano Arca
;
Stefano Columbu;Francesco Isaia;Vito Lippolis
Membro del Collaboration Group
;
Paola Meloni
Membro del Collaboration Group
;
Enrico Podda;Anna Pintus
Ultimo
Membro del Collaboration Group
2021

Abstract

The ammonium salt of monoethyloxalate (AmEtOx) was investigated as a novel precursor for the conservation of carbonate stone substrates, such as biomicritic limestone and marble. Full characterization of treated and untreated authentic stone samples was carried out by means of SEM, X-ray powder diffraction, synchrotron tts-mXRD measurements, mercury intrusion porosimetry, determination of water transport properties, and pull-off tests. The improved solubility (1.49 M, 20.1% w/w) of AmEtOx as compared to that of ammonium oxalate (AmOx; 0.4 M, 5% w/w) results in the formation of microcrystalline phases 30–50 and 200–500 mm thick of calcium oxalate mono-(whewellite) or dihydrate (weddellite), on marble and biomicrite samples, respectively, after treatment with AmEtOx 5% and 12% w/w aqueous solutions. As a result, a reduction in the porosity of the stone samples and an enhancement of their cohesion are observed. DFT calculations, carried out to investigate the hydrolysis reaction leading from AmEtOx to AmOx, showed that the localization of the Lowest Unoccupied Molecular Orbital (LUMO) and the natural charge distribution account nicely for the tendency to hydrolyse observed experimentally, eventually leading to the formation of whewellite and weddellite on the stone surface.
Inglese
45
12
5327
5339
13
https://pubs.rsc.org/en/content/articlelanding/2021/nj/d0nj06001a#!divAbstract
Esperti anonimi
internazionale
scientifica
synthesis; marble; DFT; conservation; limestone; XRD; oxalate
Carla Aragoni, M.; Giacopetti, Laura; Arca, Massimiliano; Carcangiu, Gianfranco; Columbu, Stefano; Gimeno, Domingo; Isaia, Francesco; Lippolis, Vito; Meloni, Paola; Navarro Ezquerra, Antonia; Podda, Enrico; Rius, Jordi; Vallcorba, Oriol; Pintus, Anna
1.1 Articolo in rivista
info:eu-repo/semantics/article
1 Contributo su Rivista::1.1 Articolo in rivista
262
14
reserved
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