Application of polymer coatings and nanoparticles in consolidation and hydrophobic treatment of stone monuments

Application of Inorganic Nanomaterials in Cultural Heritage Conservation, Risk of Toxicity, and Preventive Measures

Nanotechnology has allowed for significant progress in architectural, artistic, archaeological, or museum heritage conservation for repairing and preventing damages produced by deterioration agents (weathering, contaminants, or biological actions). This review analyzes the current treatments using nanomaterials, including consolidants, biocides, hydrophobic protectives, mechanical resistance improvers, flame-retardants, and multifunctional nanocomposites. Unfortunately, nanomaterials can affect human and animal health, altering the environment. Right now, it is a priority to stop to analyze its advantages and disadvantages. Therefore, the aims are to raise awareness about the nanotoxicity risks during handling and the subsequent environmental exposure to all those directly or indirectly involved in conservation processes. It reports the human-body interaction mechanisms and provides guidelines for preventing or controlling its toxicity, mentioning the current toxicity research of main compounds and emphasizing the need to provide more information about morphological, structural, and specific features that ultimately contribute to understanding their toxicity. It provides information about the current documents of international organizations (European Commission, NIOSH, OECD, Countries Normative) about worker protection, isolation, laboratory ventilation control, and debris management. Furthermore, it reports the qualitative risk assessment methods, management strategies, dose control, and focus/receptor relationship, besides the latest trends of using nanomaterials in masks and gas emissions control devices, discussing their risk of toxicity.

Desalination technologies, membrane distillation, and electrospinning, an overview

Water is a critical component for humans to survive, especially in arid lands or areas where fresh water is scarce. Hence, desalination is an excellent way to effectuate the increasing water demand. Membrane distillation (MD) technology entails a membrane-based non-isothermal prominent process used in various applications, for instance, water treatment and desalination. It is operable at low temperature and pressure, from which the heat demand for the process can be sustainably sourced from renewable solar energy and waste heat. In MD, the water vapors are gone through the membrane's pores and condense at permeate side, rejecting dissolved salts and non-volatile substances. However, the efficacy of water and biofouling are the main challenges for MD due to the lack of appropriate and versatile membrane. Numerous researchers have explored different membrane composites to overcome the above-said issue, and attempt to develop efficient, elegant, and biofouling-resistant novel membranes for MD. This review article addresses the 21st-century water crises, desalination technologies, principles of MD, the different properties of membrane composites alongside compositions and modules of membranes. The desired membrane characteristics, MD configurations, role of electrospinning in MD, characteristics and modifications of membranes used for MD are also highlighted in this review.

Application of SiON Coatings in Sandstone Artifacts Conservation

For a long time, a large number of sandstone cultural relics have been exposed to the outdoors, and they are facing unprecedented threats. Curing perhydropolysilazane at varied pyrolysis times results in a series of SiON solids. Fourier transform infrared absorption spectroscopy (FTIR) results show that the Si−H bond disappears at 2163 cm−1, and that the Si−O peaks at 460 cm−1, becoming stronger during the pyrolysis of Perhydropolysilazane (PHPS) to SiON solids. X-ray photoelectron spectroscopy (XPS) results indicate a decrease in the proportion of N atoms from 22.71% to 3.38% and an increase in the proportion of O atoms from 59.74% to 69.1%, indicating a gradual production of SiO2 from perhydropolysilazane. To protect the sandstone, the SiON protective layer and the commonly used protective materials—acrylic resin and polydimethylsiloxane—are applied. When compared to sandstone treated with acrylic resin B72 and polydimethylsiloxane coatings, SiON-coated sandstone effectively reduces porosity and water absorption. Ageing tests have shown that the SiON-coated sandstone is effective in resisting crystalline damage from sodium sulfate. These thenardites can change shape during formation, allowing their widespread distribution in different locations in the sandstone. The surface thenardite of the SiON-treated samples was smaller than that of the polydimethylsiloxane and acrylic resin B72-treated samples, while the untreated samples were flaky with obvious dehydration characteristics.

Remediation of noxious pollutants using nano-titania-based photocatalytic construction materials: a review

Nano-titania (n-TiO₂), due to its unique photocatalytic and hydrophobic properties, can be used to prepare self-cleaning cement-based smart building materials. The n-TiO₂ degrades organic and inorganic pollutants through its photocatalytic action and convert them into non-toxic byproducts, i.e., improves the air quality. In this review, aspects such as methodologies of n-TiO₂ synthesis, approaches for n-TiO₂ loading on cementitious materials, photocatalytic properties, self-cleaning mechanism, and application of n-TiO₂ in cement-based materials have been overviewed. Further, the n-TiO₂ can be used either as coatings or admixtures in pavement blocks, mortars/concrete at zebra crossings, road dividers and linings, and high rise buildings. Moreover, the implications and economic aspects of n-TiO₂ usage in cement-based materials revealed that n-TiO₂ increases the material cost by ~ 27%, (101 to 128.1$) in comparison to conventional building materials. Furthermore, the low-cost carbonized materials such as biochars have been suggested to be used as support of n-TiO₂ to lower the cost and improve the remediation efficiency of photocatalytic concrete.