Alcohol dispersions of calcium hydroxide nanoparticles for stone conservation.

Alcohol dispersions of Ca(OH)2 nanoparticles, the so-called nanolimes, are emerging as an effective conservation material for the consolidation of stone, mortars, and plasters present in old masonry and/or mural paintings. To better understand how this treatment operates, to optimize its performance and broaden its applications, here we study the nano and microstructural characteristics, carbonation behavior, and consolidation efficacy of colloidal alcohol dispersions of Ca(OH)2 nanoparticles produced by both homogeneous (commercial nanolime) and heterogeneous phase synthesis (aged slaked lime and carbide lime putties). We observe that the alcohol not only provides a high colloidal stability to Ca(OH)2 particles, but also affects the kinetics of carbonation and CaCO3 polymorph selection. This is due to the pseudomorphic replacement of Ca(OH)2 particles by calcium alkoxides upon reaction with ethanol or 2-propanol. The extent of this replacement reaction depends on Ca(OH)2 size and time. Hydrolysis of alkoxides speeds up the carbonation process and increases the CaCO3 yield. The higher degree of transformation into calcium alkoxide of both the commercial nanolime and the carbide lime fosters metastable vaterite formation, while calcite precipitation is promoted upon carbonation of the aged slaked lime due its lower reactivity, which limits calcium alkoxide formation. A higher consolidation efficacy in terms of strength gain of treated porous stone is achieved in the latter case, despite the fact that the carbonation is much faster and reaches a higher yield in the former ones. Formation of alkoxides, which has been neglected in previous studies, needs to be considered when applying nanolime treatments. These results show that the use Ca(OH)2 nanoparticle dispersions prepared with either aged slaked lime or carbide lime putties is an economical and effective conservation alternative to commercial nanolimes produced by homogeneous phase synthesis. Ultimately, this study contributes to show that nanotechnology can help saving the built and sculptural heritage.

[1]  C. Rodriguez-Navarro,et al.  Conservation of Ornamental Stone by Myxococcus xanthus-Induced Carbonate Biomineralization , 2003, Applied and Environmental Microbiology.

[2]  J. Marchand,et al.  Solvent Replacement Studies of Hydrated Portland Cement Systems: The Role of Calcium Hydroxide , 1998 .

[3]  M. Chiang,et al.  A very large calcium dialkoxide molecular aggregate having a CdI2 core geometry: Ca9(OCH2CH2OMe)18(HOCH2CH2OMe)2 , 1991 .

[4]  Luigi Dei,et al.  Synthesis of Ca(OH)2 Nanoparticles from Diols , 2001 .

[5]  C. Rodriguez-Navarro,et al.  Bacterially mediated mineralization of vaterite , 2007 .

[6]  L. Alexander,et al.  X-Ray diffraction procedures for polycrystalline and amorphous materials , 1974 .

[7]  Piero Baglioni,et al.  Stable dispersions of Ca(0H)2 in aliphatic alcohols: properties and application in cultural heritage conservation , 2001 .

[8]  Piero Baglioni,et al.  New methodologies for the conservation of cultural heritage: micellar solutions, microemulsions, and hydroxide nanoparticles. , 2010, Accounts of chemical research.

[9]  Piero Baglioni,et al.  Soft condensed matter for the conservation of cultural heritage , 2009 .

[10]  N. Koga,et al.  Thermal behaviors of amorphous calcium carbonates prepared in aqueous and ethanol media , 2008 .

[11]  Paul D'Armada,et al.  Nano-Lime for Consolidation of Plaster and Stone , 2012 .

[12]  Barbara Salvadori,et al.  Nanotechnology in cultural heritage conservation: nanometric slaked lime saves architectonic and artistic surfaces from decay , 2006 .

[13]  S. Tracy,et al.  The growth of calcite spherulites from solution. II. Kinetics of formation , 1998 .

[14]  Piero Baglioni,et al.  Hydroxide nanoparticles for cultural heritage: consolidation and protection of wall paintings and carbonate materials. , 2013, Journal of colloid and interface science.

[15]  V. John,et al.  Carbide lime and industrial hydrated lime characterization , 2009 .

[16]  Shuhong Yu,et al.  Polymorph Discrimination of CaCO3 Mineral in an Ethanol/Water Solution: Formation of Complex Vaterite Superstructures and Aragonite Rods , 2006 .

[17]  Peter Brimblecombe,et al.  Color changes in architectural limestones from pollution and cleaning , 2007 .

[18]  Monica Favaro,et al.  A novel approach to consolidation of historical limestone: the calcium alkoxides , 2008 .

[19]  E. Hansen,et al.  Nanostructure and irreversible colloidal behavior of Ca(OH)2: implications in cultural heritage conservation. , 2005, Langmuir : the ACS journal of surfaces and colloids.

[20]  V. Farmer.  The Infrared spectra of minerals , 1974 .

[21]  M. Rao.  Kinetics and Mechanism of the Transformation of Vaterite to Calcite , 1973 .

[22]  Luigi Dei,et al.  Ca(OH)2 Nanoparticles from W/O Microemulsions , 2003 .

[23]  D. Dysthe,et al.  In situ AFM study of the dissolution and recrystallization behaviour of polished and stressed calcite surfaces , 2006 .

[24]  D. Jacob,et al.  Amorphous, nanocrystalline and crystalline calcium carbonates in biological materials , 2011 .

[25]  S. Martínez-Ramírez,et al.  Raman Spectroscopy: Application to Cementitious Systems , 2011 .

[26]  G. K. WILLIAMSONt,et al.  X-RAY LINE BROADENING FROM FILED ALUMINIUM AND WOLFRAM* , 2002 .

[27]  L. S. Gomez-Villalba,et al.  Structural stability of a colloidal solution of Ca(OH)2 nanocrystals exposed to high relative humidity conditions , 2011 .

[28]  Taylor,et al.  Partial Wetting in Capillary Liquid Absorption by Limestones. , 2000, Journal of colloid and interface science.

[29]  Raymond Siever,et al.  Sand and sandstone , 1972 .

[30]  A. Putnis.  Mineral Replacement Reactions , 2009 .

[31]  Piero Baglioni,et al.  Nanotechnologies for Conservation of Cultural Heritage: Paper and Canvas Deacidification , 2002 .

[32]  Ji-Whan Ahn,et al.  Characteristic of Crystal Transition of Amorphous Calcium Carbonate in H2O, Ethyl and Propyl Alcohol System , 2004 .

[33]  L. Gower.  Biomimetic model systems for investigating the amorphous precursor pathway and its role in biomineralization. , 2008, Chemical reviews.

[34]  D. C. Bradley,et al.  Alkoxo and aryloxo derivatives of metals , 2001 .

[35]  G. K. Williamson,et al.  X-ray line broadening from filed aluminium and wolfram , 1953 .

[36]  Giuliana Taglieri,et al.  Synthesis of Ca(OH)2 nanoparticles with the addition of Triton X-100. Protective treatments on natural stones: Preliminary results , 2012 .

[37]  Yujun Wang,et al.  Calcium Ethoxide as a Solid Base Catalyst for the Transesterification of Soybean Oil to Biodiesel , 2008 .

[38]  Samuel Shaw,et al.  The kinetics and mechanisms of amorphous calcium carbonate (ACC) crystallization to calcite, via vaterite. , 2011, Nanoscale.

[39]  P. Baglioni,et al.  Competitive surface adsorption of solvent molecules and compactness of agglomeration in calcium hydroxide nanoparticles. , 2007, Langmuir : the ACS journal of surfaces and colloids.

[40]  R. Day.  Reactions between methanol and portland cement paste , 1981 .

[41]  Encarnación Ruiz-Agudo,et al.  Influence of Substrate Mineralogy on Bacterial Mineralization of Calcium Carbonate: Implications for Stone Conservation , 2012, Applied and Environmental Microbiology.

[42]  Jayanta Bhattacharya,et al.  Synthesis of Ca(OH) 2 nanoparticles by wet chemical method , 2010 .

[43]  R. Bertoncello,et al.  Silica glass interaction with calcium hydroxide: a surface chemistry approach , 2000 .

[44]  C. Rodriguez-Navarro,et al.  Liesegang pattern development in carbonating traditional lime mortars , 2002, Proceedings of the Royal Society of London. Series A: Mathematical, Physical and Engineering Sciences.

[45]  Piero Baglioni,et al.  Nanoparticles of calcium hydroxide for wood deacidification: Decreasing the emissions of organic acid vapors in church organ environments , 2009 .

[46]  Jeanne Marie Teutonico,et al.  A review of selected inorganic consolidants and protective treatments for porous calcareous materials , 2003 .

[47]  Raimondo Quaresima,et al.  The nanolimes in Cultural Heritage conservation: Characterisation and analysis of the carbonatation process , 2008 .

[48]  Piero Baglioni,et al.  Colloid and materials science for the conservation of cultural heritage: cleaning, consolidation, and deacidification. , 2013, Langmuir : the ACS journal of surfaces and colloids.

[49]  D. Beruto,et al.  Liquid-like H2O adsorption layers to catalyze the Ca(OH)2/CO2 solid–gas reaction and to form a non-protective solid product layer at 20°C , 2000 .

[50]  Jie Zhang,et al.  Comparison of methods for arresting hydration of cement , 2011 .

[51]  Piero Baglioni,et al.  Colloidal Particles of Ca(OH)2: Properties and Applications to Restoration of Frescoes , 2001 .

[52]  S. Gunasekaran,et al.  Raman and infrared spectra of carbonates of calcite structure , 2006 .

[53]  C. Rodriguez-Navarro,et al.  Microstructure and rheology of lime putty. , 2010, Langmuir.

[54]  Sagrario Martínez-Ramírez,et al.  Influence of relative humidity on the carbonation of calcium hydroxide nanoparticles and the formation of calcium carbonate polymorphs , 2011 .

[55]  Piero Baglioni,et al.  A New Method for Consolidating Wall Paintings Based on Dispersions of Lime in Alcohol , 2000 .

[56]  Kerstin Elert,et al.  Lime Mortars for the Conservation of Historic Buildings , 2002 .

[57]  J. Beaudoin.  Validity of using methanol for studying the microstructure of cement paste , 1987 .