Browsing by Author "Feijoo, Jorge"

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    Addition of ferrocyanide-based compounds to repairing joint lime mortars as a protective method for porous building materials against sodium chloride damage
    (Materials and structures, 2021) Feijoo, Jorge; Duygu, Ergenç; Fort, Rafael; Buergo, Mónica Álvarez de
    Soluble salts are considered one of the main agents in weathering of porous materials used in building constructions. In this work, a comparison in terms of protection against the damage caused by salts, durability and harmful effects of the application of a joint lime repair mortar, with and without K4Fe(CN)6 in its composition, for bonding sandstone blocks contaminated with NaCl was evaluated. Results show that the introduction of ferrocyanide allowed: 1) to protect the mortar during the curing process, hindering the entry of salts into its pores during drying; 2) to improve the carbonation of the mortar and its adhesion to the porous materials´ surface and 3) to remove chlorides from the surrounding materials, reaching percentages of reduction close to 100%. All of these without causing aesthetic damage to the materials and maintaining a protective capacity against NaCl over time that allows considering this treatment not only as a shock treatment but also as a preventive measure.
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    Biochar Amendments and Phytoremediation: A Combined Approach for Effective Lead Removal in Shooting Range Soils
    (Toxics, 2024) Maceiras, Rocío; Pérez-Rial, Leticia; Alfonsín, Víctor; Feijoo, Jorge; López, Ignacio
    The increasing contamination of soil with heavy metals poses a problem to environmental sustainability. Among these pollutants, lead is particularly concerning due to its persistence in the environment, with harmful effects on human health and ecosystems. Various strategies that combine phytoremediation techniques with soil amendments have emerged to mitigate lead contamination. In this context, biochar has gained significant attention for its potential to enhance soil quality and remediate metal-contaminated environments. This study aims to investigate the combined effect of biochar amendments on the phytoremediation of lead-contaminated shooting range soils. A series of experiments were conducted to determine the impact of the amount and distribution of biochar on lead removal from soil. Soil samples were incubated with biochar for one week, after which two types of seeds (Brassica rapa and Lolium perenne) were planted. Plant and root lengths, as well as the number of germinated seeds, were measured, and a statistical analysis was conducted to determine the influence of the amendments. After one month, the Pb concentration decreased by more than 70%. Our results demonstrate that seed germination and plant growth were significantly better in soil samples where biochar was mixed rather than applied superficially, with the optimal performance observed at a 10% wt. biochar amendment. Additionally, the combined use of biochar and phytoremediation proved highly effective in immobilizing lead and reducing its bioavailability. These findings suggest that the combination of biochar, particularly when mixed at appropriate concentrations, and Brassica rapa significantly improved lead removal efficiency.
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    CO2 Capture via Adsorption Using Silica Gel
    (European Journal of Sustainable Development, 2024) Pérez-Rial, Leticia; Alfonsín, Víctor; Maceiras, Rocío; Feijoo, Jorge; Vallejo, Javier P.
    This paper investigates the potential of silica gel as an effective adsorbent for CO2 capture. The study explores the adsorption mechanisms, the efficiency of CO2 uptake, and some factors influencing the adsorption capacity of silica gel. The experimental results demonstrate the significant potential of silica gel for CO2 adsorption under various conditions. The adsorption capacity was found to be highly dependent on parameters such as gas flow rate and the particle size of silica gel. The findings suggest that with optimized conditions, silica gel could be a viable material for reducing atmospheric CO2 levels. This research contributes to the development of sustainable and efficient technologies for mitigating climate change through carbon dioxide capture and storage.
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    Construction and Building Materials Electroprecipitation of inorganic borates, with different solubility, within monumental
    (Construction and building materials, 2023) Feijoo, Jorge; Gómez-Villalba, L.S.; Ríos, A. de los; Fort, R.
    Biodeterioration is a serious threat to the preservation of cultural heritage. Currently, the chemical treatments used to combat it must fulfil a series of restrictions to ensure that they are not harmful to humans or the environment. Borates satisfy these conditions but due to its high degree of leaching its application is limited to indoor areas. The use of electroprecipitation may to increase the range of applicability by allowing to precipitate, along the entire section of the stony materials, of a mixture of boron salts with different solubility (zinc, magnesium, and sodium borates) to cover a wide range of moisture conditions. The results obtained show that electroprecipitation not only increases the penetration depth of boron compounds but also allows the formation of compounds of different solubility, which allows the treatment to last over time. Furthermore, the treatment increased the mechanical properties and reduced the porosity of the stones treated, all without causing significant aesthetic changes.
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    Effects of paraffin additives, as phase change materials, on the behavior of a traditional lime mortar
    (Construction and building materials, 2022) Feijoo, Jorge; Álvarez-Feijoo, M.A.; Fort, Rafael; Arce, Elena; Duygu, Ergenç
    This study refers to the inclusion of phase change materials (PCMs) in porous building materials as an alternative means of improving their thermal behavior, assessing the changes caused in their physical-mechanical and durability properties. Specifically, an organic paraffin wax was selected for direct incorporation into lime mortars using different concentrations by weight. The results show that PCMs improve the thermal properties of the mortar while reducing its accessible porosity. This increases the mortars’ resistance to water and soluble salts. However, excessive PCM content causes stresses within the mortar that can jeopardize its structure.
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    Electroosmotic permeability in kaolinite and CaCO3 poultice mixtures
    (Journal of Cultural Heritage, 2024) Eslami, Naser; Feijoo, Jorge; Paz-García, Juan M.; Franzoni, Elisa; Ottosen, Lisbeth M.
    Electrokinetic treatment of masonry for desalination or electroosmotic dewatering depends on a poultice, in which the electrodes are placed, which fulfills several purposes. Poultice composed of kaolinite and CaCO3 have been shown to have good workability and high pH buffering capacity. In this work, the elec- troosmotic (EO) permeability is studied in different kaolinite - CaCO3 mixtures. In addition, the effect on EO of using NaCl as a mixing solution is investigated. A special cell is used to test the EO in the speci- mens. A phenomenological approach, based on the potential gradient and the flux of solution, was used to calculate the EO flow rate and EO permeability coefficient. Results showed that by increasing the con- centration of CaCO3 in the poultice mixture, the EO flow rate decreased and the poultice with 80 % CaCO3 and more did not have any EO flow. Furthermore, the ionic strength in the mixing solution decreases the EO flow rate.
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    Evaluation of the Suitability of Electrokinetic Treatment to Desalinate the Limestone of the Tomb of Cyrus, a UNESCO World Heritage Site in Iran
    (Heritage, 2023) Eslami, Naser; Feijoo, Jorge; Aly, Nevin
    The tomb of Cyrus the Great, founder of the Persian Empire, is considered one of the most important monuments of Iran. Its advanced state of deterioration motivated the need to carry out a study focused on analyzing the possible damage caused by the presence of soluble salts, and to assess the suitability of an electrokinetic treatment for their extraction. Preliminary diagnostics carried out on stone samples taken from the tomb confirmed that it is affected by the action of soluble salts, and especially by the presence of nitrates and sulfates. The effectiveness and possible harmful effects caused by electrokinetic treatment were evaluated, under laboratory conditions, using the same limestone that makes up the tomb. The obtained results show that this treatment, in a short period of time, reduces the ionic content, reaching high percentages of anion extraction, without causing any damage, which indicates that it is suitable for this type of stone.
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    Experimental study of electroosmosis and (Cl-) diffusion in fired-clay bricks
    (Construction and building materials, 2024) Eslami, Naser; Ottosen, Lisbeth M.; Feijoo, Jorge; Franzoni, Elisa; Paz-García, Juan Manuel
    Electroosmosis (EO) is considered as a base for methods in drying moist masonry. EO and the other transport mechanisms, namely electromigration and diffusion, that can influence EO in the bricks, were studied in four Danish bricks with different manufacturing years and locations. Brick cubes were cut from each brick type and then saturated in NaCl 0.1 M solution. A cell with four electrodes was used to measure the electroosmotic permeability coefficient using a phenomenological approach based on non-equilibrium thermodynamics. The effective diffusion coefficient for chloride and electromigration coefficient were calculated. Results showed that the EO flux obtained in the bricks did not follow either the magnitude of zeta potential or ionic content present in the bricks. It was observed that there was a correlation between the EO coefficient and the porous structure of the brick, especially with the pore connectivity, since the bricks with higher pore connectivity and, therefore, with higher effective diffusion coefficient had a higher electroosmotic coefficient.
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    In-situ electrochemical synthesis of inorganic compounds for materials conservation: assessment of their effects on the porous structure
    (Ceramics International, 2021) Gómez Villalba, Luz Stella; Feijoo, Jorge; Rabanal, María Eugenia; Fort, Rafael
    This study refers to the application of in-situ electrochemical synthesis as an alternative method to improve the properties of porous materials against harmful external agents that deteriorate them. It is oriented to an understanding of the effects of crystallisation on the pore structure of different compounds commonly used in the restoration and conservation of porous materials (historic ceramics, building walls, sculptures, or biomedical applications). It analyses the microstructural, chemical details, and stability of the neo-formed phases that modify the pore network. The electrochemical synthesis was carried out at ambient temperature (20°C), over high porous sandstone for crystallising Ca carbonate, Mg carbonate, Ca phosphate, and Ca oxalate compounds. Based on the neo-formed minerals, a comparison was made depending on their specific properties defining how they affected the pore structure. The characterisation included polarised light optical microscopy, environmental and field emission scanning electron microscopy, digital image analysis, cathodoluminescence(CL-ESEM),energydispersive X-ray spectroscopy, and X-ray microdiffraction. Aragonite, hydromagnesite, hydroxyapatite, and whewellite were identified as the majority phases depending on the treatment. Phase transformation, dehydration, and dissolution-re-precipitation processes suggested different degrees of stability, including aragonite/calcite (CaCO3 treatment) and hydromagnesite/magnesite (MgCO3 treatment) transformations and simultaneous crystallisation of brushite/hydroxyapatite ((Ca 3 (PO 4 ) 2 treatment). Electrocrystallisation induced changes in inter-granular porosity, the development of secondary porosity inherent to the minerals, and differences in pore cementation depending on its mineralogy. Among the treatments, Mg carbonate reduced porosity most effectively, followed in descending order by calcium carbonate and calcium phosphate, being the calcium oxalate the less effective.
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    Influence of Activated Carbon Granulometry on H2 Purification in Glycerol Reforming Syngas: Adsorption and Kinetic Analysis
    (Energies, 2024-11-29) Maceiras, Rocío; Feijoo, Jorge; Pérez-Rial, Leticia; Álvarez-Feijoo, Miguel A.; Eslami, Naser
    This study investigates the adsorption performance of granular activated carbon (GAC) and pelletized activated carbon (PAC) for the purification of syngas produced from glycerol reforming, focusing on the removal of CO2, CO, and CH4. The adsorption process was studied at two different flow rates (0.5 L/min and 1 L/min) to assess the impact of particle size and gas flow rate on adsorption capacity. The results indicate that GAC exhibits superior multi-gas adsorption, particularly at lower flow rates, effectively capturing CO2, CO, and CH4, while PAC exhibits lower adsorption performance. Kinetic analysis revealed that the pseudo-second-order and Avrami models fit well with both adsorbents, though GAC aligns more closely with the Avrami model, reflecting its multi-step adsorption mechanism and greater pore diffusion efficiency. These findings highlight the importance of adsorbent size and flow rate in optimizing hydrogen purification processes, with GAC emerging as a highly efficient adsorbent for industrial-scale syngas treatment.
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    Measuring the Electro-osmotic Permeability Coefficient in Single Bricks
    (Journals of materials in civil engineering, 2024) Eslami, Naser; Feijoo, Jorge; Paz García, Juanma; Franzoni, Elisa; Ottosen, Lisbeth M.
    The transport process electroosmosis (EO) has been suggested to be used for dewatering damp brick masonry for decades. Still, it is debated whether EO can be obtained in bricks. By use of an advanced EO laboratory cell, this paper reports that an EO flow can be generated in two types of Danish bricks. The electroosmotic permeability coefficient was shown to be dependent on both intrinsic properties of bricks, such as pore size distribution, and extrinsic properties, such as zeta potential. Results showed that the brick with a higher pore volume but with a lower surface charge the EO permeability coefficient is lower.
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    Preparation of Synthetic Slays to Remove Phosphates and Ibuprofen in Water
    (Water 2021, 13, 2394, 2021) Devesa-Rey, Rosa; Val, Jesús del; Feijoo, Jorge; González-Coma, José P.; Castiñeira, Gonzalo; González-Gil, Lorena
    The main objective of this study consists in the synthesis of a layered double hydroxide (LDH) clay doped with magnesium and aluminum in order to test the removal of phosphates and ibuprofen in water. Two different LDH composites are assessed: oven-dried (LDHD) and calcined (LDHC). Single adsorptions of phosphate and ibuprofen showed up to 70% and 58% removal in water, when LDHC was used. A poorer performance was observed for LDHD, which presented adsorption efficiencies of 52% and 35%, respectively. The simultaneous removal of phosphate and ibuprofen in water showed that LDHC allows a greater reduction in the concentration of both compounds than LDHD. Phosphate adsorption showed a close agreement between the experimental and theoretical capacities predicted by the pseudo-second-order model, whereas ibuprofen fitted to a first-order model. In addition, phosphate adsorption showed a good fit to an intraparticle diffusion model and to Bangham model suggesting that diffusion into pores controls the adsorption process. No other mechanisms may be involved in ibuprofen adsorption, apart from intraparticle diffusion. Finally, phosphate desorption could recover up to 59% of the initial concentration, showing the feasibility of the recuperation of this compound in the LDH.