Green Approach to Clean Marble Surfaces

In the field of cultural heritage restoration, the removal of iron corrosion stains is a difficult problem to deal with, especially in porous stone materials. Many studies in recent years have been aimed at finding simple and reliable methods using non-toxic chelating compounds. The search for natural compounds is therefore of great relevance, especially in the restoration of cultural heritage, where the use of toxic chemical compounds often involves risks for the environment and human health. Following this trend, the purpose of this preliminary work was to verify the use of two natural proteins, Lactotransferrin (Ltf) and Ovotransferrin (Ovt), for the removal of iron-based stains on marble surfaces. The two proteins, whose high affinity for iron "in vivo" has been widely documented, were extracted from their natural matrices. The protein extracts were then immobilized using a common cellulose pulp. The poultices obtained were spread on the surfaces of artificially stained marble specimens and, after a set time, were easily removed. The effectiveness of the removal, visually evident, was detected by spectrocolorimetry and image analysis. The surface analyses, before and after the treatment, carried out by X-ray photoelectron spectroscopy (XPS), confirmed that both proteins have a selective and effective complexing capacity for the ferric ions of rust stains.

Alleviation of Iron Corrosion in Chloride Solution by N,N′-bis[2-Methoxynaphthylidene]amino]oxamide as a Corrosion Inhibitor

The alleviation of iron corrosion in 3.5% NaCl sodium chloride solution using N,N′-bis[2-methoxynaphthylidene]amino]oxamide (MAO) as a corrosion inhibitor has been reported. The work was achieved using various investigation techniques. Potentiodynamic cyclic polarization (PCP) displayed a powerful inhibition for the corrosion via reducing the iron’s cathodic and anodic reactions. This was reflected in reduced corrosion currents and increased polarization resistances in the presence and upon the increase of MAO concentration. The electrochemical impedance spectroscopy results indicated that MAO molecules provoke the corrosion resistance via increasing polarization resistance. The power of MAO on decreasing pitting attack was also investigated through measuring the change of current with time at −0.475 V(Ag/AgCl). Scanning electron microscopy images were taken of the surface after the current–time measurements were performed in the absence and presence of MAO. The current-time experiments indicated that MAO highly mitigates the corrosion of iron. The energy dispersive X-ray analyzer reported the products found on the tested surfaces. The effect of extending the exposure time from 1 h to 48 h was also tested and was found to alleviate the corrosion of iron, whether MAO molecules are absent or present.

Simulating the feedback between corrosive gas generation and water availability for the evaluation of radionuclide mobility in the context of radioactive waste disposal

It has been recently recognized that the availability of liquid water may be a controlling factor in the feedback between the physical processes of variably saturated liquid and gas flow on the one hand, and various chemical processes such as metal corrosion in an underground storage facility for radioactive waste on the other hand (e.g., Huang et al., 2021, and reference therein). Iron corrosion in anoxic conditions produces hydrogen gas and consumes water, as expressed by the following stylized chemical equation (e.g., Diercks and Kassner, 1988; Senior et al., 2021): 3Fe+4H2O⟶Fe3O4+4H2 Since water is an educt the corrosion reaction may be suspended or suppressed by the scarcity of water near the corroding surfaces. At the same time, gas pressure build-up through hydrogen generation may limit further water ingress. We developed a model that focuses on the close coupling between gas generation through iron corrosion and water availability. The feedback between iron corrosion, gas generation and liquid phase flow is considered by implementing the corrosion reaction in the subsurface flow and transport simulator PFLOTRAN (Hammond et al., 2012; Lichtner et al., 2015, 2020) making use of its coding provisions to implement source/sink terms for water and gas. These source/sink terms reflect the kinetics of the iron corrosion and its dependence on the educts, where the availability of water is approximated by the local liquid saturation. The model was applied to evaluate the mobility of radionuclides in, and their release from a hypothetical geological storage facility for radioactive waste. The radionuclides are traced through the emplacement chambers and drift by means of advective and diffusive transport. Parameter variations illustrate the influence of crucial modelling parameters on the simulation results.

Twenty years of research on spent nuclear fuel in the context of final disposal at KIT-INE in multinational collaborative projects

Disposal of spent nuclear fuel (SNF) in deep geological repositories is considered a preferential option for the management of such wastes in many countries with nuclear power plants. With the aim to permanently and safely isolate the radionuclide inventory from the biosphere for a sufficient time, a multibarrier system consisting of technical, geotechnical and geological barriers is interposed between the emplaced waste and the environment. In safety assessments for deep underground repositories, access of water, followed by failure of canisters and finally loss of the cladding integrity is considered in the long-term. Hence, evaluating the performance of SNF in deep geological disposal systems requires process understanding of SNF dissolution and rates as well as quantification of radionuclides release from SNF under reducing conditions of a breached container. In order to derive a radionuclide source term, the SNF dissolution and alteration processes can be assigned to two steps: (i) instantaneous release of radionuclides upon cladding failure from gap and grain boundaries and (ii) a long-term release that results from dissolution of the fuel grains itself (Ewing, 2015). In this context, research at KIT-INE has focused for more than 20 years on the behavior of SNF (irradiated UO2 and MOX fuels) under geochemical conditions (pH, redox and ionic strength) representative of various repository concepts, including the interaction of SNF with backfill material, such as bentonite as well as the influence of iron corrosion products, e.g. magnetite and radiolytic reactions on SNF dissolution mechanisms. Since 2001, KIT-INE has contributed with experimental and theoretical studies on the behavior of SNF under repository relevant conditions to six Euratom projects viz SFS (2001–2004), NF-PRO (2004–2006), MICADO (2006–2009), RECOSY (2007–2011), FIRST-Nuclides (2012–2014) and DISCO (2016–2021). Moreover, since 2007, overall 4 consecutive projects for the Belgian waste management organization, ONDRAF-NIRAS, were performed on the behavior of SNF under conditions representative of the Belgian “Supercontainer” concept. In this contribution, we summarize major achievements of theses research projects to understand and quantify the radionuclide release from dissolving SNF under repository conditions. In particular, the dependence of radionuclide release on the chemical composition of the aqueous and gaseous phase in the proximity of repositories in different types of host rock is discussed.

Recommendations for Departmental Collections Policies

An aged and heavily corroded horizontal iron rim lock for the left side of a door was examined at the request of Anson (“Tuck”) Hines, Director of the Smithsonian Environmental Research Center (SERC). The lock was reportedly found by a contractor on SERC’s property during renovation, and the iron corrosion is typical of exposure to the elements. It was anticipated that the lock would date from the time of the oldest part of the Sellman/Kirkpatrick-Howat house constructed in 1735 or its Greek Revival enlargement in 1841. Examination of the lock included x-radiography. A recommendation was made to not conduct further conservation treatment, such as removal of iron corrosion, because it would threaten the structural integrity of the object. Instead it was advised that the lock be exhibited in a case with conditioned silica gel and regularly monitored, which should keep it in stable condition.

Examination and Treatment Report for a Carpenter & Co. Lock Found at SERC: Museum Conservation Institute #6955

An aged and heavily corroded horizontal iron rim lock for the left side of a door was examined at the request of the director of the Smithsonian Environmental Research Center (SERC). The lock was reportedly found by a contractor on SERC’s property during renovation, and the iron corrosion is typical of exposure to the elements. It was anticipated that the lock would date from the time of the oldest part of the Sellman/Kirkpatrick-Howat house constructed in 1735 or its Greek Revival enlargement in 1841. Examination of the lock included x-radiography. A recommendation was made to not conduct further conservation treatment, such as removal of iron corrosion, because it would threaten the structural integrity of the object. Instead it was advised that the lock be exhibited in a case with conditioned silica gel and regularly monitored, which should keep it in stable condition.