Molecular Crystallization Inhibitors for Salt Damage Control in Porous Materials: An Overview

Abstract

The use of inhibition chemicals holds the prospect of an efficient strategy to control crystallization in porous materials, thereby potentially contributing to the prevention or mitigation of the salt decay phenomenon in modern as well as historical building materials in a more sustainable manner. In this review, we first provide an essential background on the mechanism of salt crystallization and on the factors influencing this phenomenon; next, we illustrate the mechanism at the basis of the action of crystal growth inhibitors, and critically discuss the major advances in the development of different families of inhibitors, particularly focusing on their influence on salt transport and crystallization within the structure of porous media. Specifically, correlations between the crystallization inhibition processes in porous materials and variables, such as porous substrate composition and properties, contaminant salt type and concentrations, microclimatic conditions, inhibiting solution concentration and properties, and application methods, will be highlighted. Environmental aspects, limitations, and problems associated with some inhibition chemicals are also taken into account. Finally, a survey and a discussion on the most representative experimental techniques and instrumentation available to assess qualitatively and quantitatively the inhibitor effectiveness, as well as recently developed modelling tools are given out.

Principal Component Analysis (PCA) Combined with Naturally Occurring Crystallization Inhibitors: An Integrated Strategy for a more Sustainable Control of Salt Decay in Built Heritage

“…Porosimetry measurements indicates in fact that soll exhibits lower overall porosity compared to bajda and safra (29.8% vs. 30.4% and 35.6%, respectively). For the soll, the maximum concentration of distribution of pores is in the ranges 1-0.6 µm and 1-2 µm, whereas franka has a higher percentage of large pores (2-4 µm) [1,13,20]. Similarly, within the group of limestones from South Eastern Sicily, the somewhat different grouping for Noto and Palazzolo varieties (N and P, respectively) reflects small differences in terms of chemical composition (P limestone has a larger silicate component compared to N counterpart, i.e., 5.4% vs. 3.5%) and porous structure (P limestone exhibits a higher percentage (32.5%) of large pores (2-4 µm) relative to N (20.1%)) [14].…”

“…It is generally understood as a temperature/humidity dependent weathering process arising from: (1) the presence of salt crystals on the surface of porous materials, which generally results in an aesthetic rather than mechanical damage (i.e., efflorescence), or (2) mechanical stresses introduced by salt crystals deposited within the material pores (i.e., sub-florescence or crypto-florescence), which may undermine the structural safety of the materials as well as cause widespread loss of (sometimes precious) surface. Despite having acquired significant knowledge of the decay mechanisms, several relative fundamental issues have not yet been fully understood [1][2][3]. Accordingly, adequate prevention or mitigation strategies are often lacking.…”

“…Classical desalination techniques usually involve washing with water and application of poulticing using highly absorbent materials; other approaches include chemical cleaning, salt extraction by barium compounds, electromigration, the creation of chemical barriers, and the employment of a variety of consolidants and surface coatings, such as water repellents. However, the classical desalination approaches are sometimes ineffective or too expensive, therefore justifying the need to find new approaches [1][2][3].…”

“…Heritage 2021, 4 221 In the last two decades, there has been an ever growing attention to the development of organic crystallization inhibition chemicals as an innovative strategy for controlling salt crystallization in porous materials, which, ultimately, may provide a means of conserving modern/historical buildings, and protecting heritage sites in a sustainable manner [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20]. It is commonly understood that inhibitors act through two different mechanisms [1], i.e., preventing or delaying the formation of stable nuclei, and so causing salt precipitation delay or modifying crystal behavior by adsorption on specific faces of a growing crystal, which decreases its growth rate.…”

Isolation and Characterization of Bacteriophages with Lytic Effect Against Waste Water Bacterial Pathogens

“…was survival in UV exposure for 80 minutes. Other studies revealed to phages were fоund in envirоnments with high UV irradiation and heat as the Sahara ( Pachepsky et al, 2014) or hоt springs ( Percival et al, 2014) or in envirоnments with various pH values and ionic strengths like in food (Kausar and Qamer, 2016), cheese factories ( Bracciale et al, 2020), humans (Bach et al, 2005, soil ( Carla et al, 2020), and sewage (Iliadis et al, 2018). Moreоver, maintenance of phage pоpulations usually requires the presence of the bacterial hоst, which is alsо influenced by envirоnmental factоrs ( Yang et al, 2020).…”