Browsing by Author "Belaustegui, Yolanda"
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Item Bacterial-cellulose-derived carbonaceous electrode materials for water desalination via capacitive method: The crucial role of defect sites: The crucial role of defect sites(2020-10-15) Belaustegui, Yolanda; Pantò, Fabiola; Urbina, Leire; Corcuera, Maria Angeles; Eceiza, Arantxa; Palella, Alessandra; Triolo, Claudia; Santangelo, Saveria; VALORIZACIÓN DE RESIDUOSElectrosorptive desalination is a very simple and appealing approach to satisfy the increasing demand for drinking water. The large-scale application of this technology calls for the development of easy-to-produce, cheap and highly performing electrode materials and for the identification and tailoring of their most influential properties, as well. Here, biosynthesised bacterial cellulose is used as a carbon precursor for the production of three-dimensional nanostructures endowed with hierarchically porous architecture and different density and type of intrinsic and hetero-atom induced lattice defects. The produced materials exhibit unprecedented desalination capacities for carbon-based electrodes. At an initial concentration of 585 mg L−1 (10 mmol L−1), they are able to remove from 55 to 79 mg g−1 of salt; as the initial concentration rises to 11.7 g L−1 (200 mmol L−1), their salt adsorption capacity reaches values ranging between 1.03 and 1.35 g g−1. The results of the thorough material characterisation by complementary techniques evidence that the relative amount of oxygenated surface functional species enhancing the electrode wettability play a crucial role at lower NaCl concentrations, whereas the availability of active non-sp2 defect sites for adsorption is mainly influential at higher salt concentrations.Item Chromium-free conversion coatings based on inorganic salts(Zr/Ti/Mn/Mo) for aluminum alloys used in aircraft applications(2015-08-01) Santa Coloma, Patricia; Izagirre, Usoa; Belaustegui, Yolanda; Jorcin, J.B.; Cano, F.J.; Lapeña, N.; Belaustegi, Y.; Tecnalia Research & Innovation; INGENIERÍA DE SUPERFICIES; VALORIZACIÓN DE RESIDUOS; MATERIALES PARA CONDICIONES EXTREMAS; SGNovel chromium-free conversion coatings based on Zr/Ti/Mn/Mo compounds were developed at a pilot scale to improve the corrosion resistance of the AA2024-T3 and AA7075-T6 aluminum alloys for aircraft applications. The influence of the presence of Zr and Ti in the Zr/Ti/Mn/Mo conversion bath's formulation on the corrosion resistance of the coated alloys was investigated. The corrosion resistance provided by the conversion coatings was evaluated by salt spray exposure and potentiodynamic sweeps. Optical and scanning electron microscopy coupled with energy dispersive spectroscopy (SEM/EDS) and atomic force microscopy (AFM) operating in the Kelvin Probe mode (SKPFM) were used to provide microstructural information of the coated samples that achieved the best results in the corrosion tests. The salt spray test evidenced the higher corrosion resistance of the coated samples compared to the bare surfaces for both alloys. The potentiodynamic tests showed that the corrosion current density decreased for coated AA7075-T6 and AA2024-T3 alloys, which indicated an obvious improvement of the corrosion resistance with all the processes for both alloys. Although the corrosion resistance of the coated samples appeared to be higher for the alloy AA7075-T6 than for the alloy AA2024-T3, both alloys achieved the best corrosion protection with the coatings deposited from conversion bath formulations containing no titanium salts. The microscopy analysis on the coated AA7075-T6 samples revealed that a local deposition of Zr compounds and, possibly, an oxidation process occurred in the vicinity of the alloy's intermetallic particles. The amount of the Zr deposits at these locations increased with coating's formulations without Ti, which provided the best corrosion resistance. The Cr-free conversion coatings developed in this study for the AA7075-T6 and AA2024-T3 alloys do not meet yet the strict requirements of the aircraft industry. However, they significantly improved the corrosion performance with respect to the bare alloys and could be a good starting point for further studies and optimization.Item Electro-spun graphene-enriched carbon fibres with high nitrogen-contents for electrochemical water desalination(2018-02-15) Belaustegui, Yolanda; Zorita, Saioa; Fernández-Carretero, Francisco; García-Luis, Alberto; Pantò, Fabiola; Stelitano, Sara; Frontera, Patrizia; Antonucci, Pierluigi; Santangelo, Saveria; Tecnalia Research & Innovation; VALORIZACIÓN DE RESIDUOS; ADAPTACIÓN AL CAMBIO CLIMÁTICO; TECNOLOGÍAS DE HIDRÓGENOElectro-spun carbon fibres doped with very high nitrogen concentrations (19–21 wt%) are obtained operating carbonisation at low temperature (500 °C). The as-synthesised fibres are evaluated as electrode materials for the electrochemical desalination of water. The effect of the enrichment of the nitrogen doped carbon fibres with thermally reduced graphene oxide is also investigated. The fibrous electrodes are able to remove amazing amounts of NaCl (17.0–27.6 mg/g) from a salty solution with an initial concentration of 585 mg/L. The nitrogen doping, which dramatically improves the wettability, plays a crucial role in determining the outstanding electro-sorption capacities of the fibres. It allows fully profiting of the more favourable pore size distribution in the graphene-enriched fibres, endowed with higher conductivity and capacitance, for the obtainment of unprecedented electro-sorption capacities via an extremely simple synthesis process, with no need of activation treatments.Item Evaluation of the electrochemical performance of electrospun transition metal oxide-based electrode nanomaterials for water CDI applications(2019-06-20) Santangelo, Saveria; Pantò, Fabiola; Triolo, Claudia; Stelitano, Sara; Frontera, Patrizia; Fernández-Carretero, Francisco; Rincon, Inés; Azpiroz, Patxi; García-Luis, Alberto; Belaustegui, Yolanda; Tecnalia Research & Innovation; TECNOLOGÍAS DE HIDRÓGENO; VALORIZACIÓN DE RESIDUOSComposite fibrous materials based on (graphene-enriched) nitrogen-doped carbon/transition metal oxides were produced by electrospinning and their physicochemical properties were thoroughly investigated by a combination of characterisation techniques. The electrochemical behaviour of the electrodes prepared with them was evaluated in view of their use in the capacitive deionisation of saline water. The morphology of the materials reminded of usnea florida lichens, wheat ears, sea sponges and noodles and depended on the transition metal (Mn, Fe, Ti or Zn). The morphology and the relative amount (14.1–22.2 wt%) of the surface nitrogen and carbon-bonded oxygen functional species, beneficial to wettability and involving pseudocapacitive processes, had strong impact on the specific capacitance (43.7–67.4 F g−1, at 5 m V s−1 scan rate), whereas also the specific micropore volume (0.4–5.6 mm3 g−1) affected the effective areal capacitance of the electrodes (1.2–6.0 F m−2, at 5 mV s−1). Ion storage in the composite materials occurred via a mixed capacitive/pseudocapacitive process. Hence, increasing the content of the oxide (from 24.6 to 56.7 wt%), thanks to the fast-reversible redox reactions at or near surface it involves, partly compensated for the growing hindrance to diffusion encountered by the ions (hampered electrostatic adsorption) as the scan rate increased from 5 to 100 mV s−1.Item Evaluation of the Specific Capacitance of High-Entropy Oxide-Based Electrode Materials in View of Their Use for Water Desalination via Capacitive Method(Multidisciplinary Digital Publishing Institute (MDPI), 2023-01-04) Triolo, Claudia; Santangelo, Saveria; Petrovičovà, Beatrix; Musolino, Maria Grazia; Rincón, Inés; Atxirika, Ainhoa; Gil, Silvia; Belaustegui, YolandaWater pollution and scarcity are serious concerns for the growing world population. To meet the ever-pressing demand of fresh water, a variety of desalting techniques of seawater have been developed. Due to its environmental friendliness, high efficiency, easy regeneration of the electrodes, ambient operating pressure, and low operating potential suitable for the use in remote areas, the capacitive deionization (CDI) method is one of the most sustainable among them. This work focuses on the preparation of high-entropy oxides (HEOs) and carbon/HEO composites and the evaluation of their specific capacitance in view of their possible use as CDI electrode materials. CrMnFeCoNi-HEO, having spinel structure (sHEO), is obtained in the form of nanoparticles (NPs) and nanofibers (NFs) by the sol–gel method and electrospinning, respectively. Composite NFs with embedded sHEO NPs or MgCoNiCuZn-HEO NPs with rock-salt structure (rHEO) are also produced. In the 5–100 mV s−1 scan rate range, the specific capacitance improves in the order C/rHEO NFs (8–32 F g−1) ≅ sHEO NPs (9–32 F g−1) < sHEO NFs (8–43 F g−1) < C/sHEO NFs (12–66 F g−1). The highest capacitance is obtained when the beneficial contributions of the carbon matrix and smaller-sized HEO NPs are synergistically coupled.Item Removal of TiO 2 nanoparticles from water by low pressure pilot plant filtration(2018-03-15) Olabarrieta, Josune; Monzón, Oihane; Belaustegui, Yolanda; Alvarez, Jon-Iñaki; Zorita, Saioa; VALORIZACIÓN DE RESIDUOS; ADAPTACIÓN AL CAMBIO CLIMÁTICORising use of nanoparticles in manufacturing as well as in commercial products bring issues related to environmental release and human exposure. A large amount of TiO2 nanoparticles will eventually reach wastewater treatment plants. Low pressure membrane filtration has been suggested as a feasible treatment of water streams. This study investigated first at laboratory scale the influence of: i) membrane material, ii) pore size and iii) water chemistry on nTiO2 removal. TiO2 retention was governed by the cake layer formation mechanism and significant retention of nanoparticles was observed even for filters having considerably larger pores than nTiO2. PVDF showed a great potential for nTiO2 rejection. Additionally, filtration pilot plant experiments were carried out using PVDF membranes (0.03 and 0.4 μm pore size). The release of nTiO2 in the pilot scale filtration system was always above the instrumental detection limit (> 1.5 μg/L) and in most cases below 100 μg/L regardless of the pore size and applied conditions. The nTiO2 membrane breakthrough predominantly occurred in the first few minutes after backwashes and ceased when the cake layer was formed. Ultrafiltration and microfiltration were comparable with rejection of nTiO2 above 95% at similar permeate flow rates. Nevertheless, ultrafiltration is more promising than microfiltration because it allowed longer operation times between backwash cycles.Item Three-dimensional reduced graphene oxide decorated with iron oxide nanoparticles as efficient active material for high performance capacitive deionization electrodes(2021-05-15) Belaustegui, Yolanda; Rincón, Inés; Fernández-Carretero, Francisco; Azpiroz, Patxi; García-Luís, Alberto; Tanaka, David Alfredo Pacheco; Tecnalia Research & Innovation; VALORIZACIÓN DE RESIDUOS; TECNOLOGÍAS DE HIDRÓGENO; TECNOLOGÍA DE MEMBRANAS E INTENSIFICACIÓN DE PROCESOSA three-dimensional reduced graphene oxide decorated with iron oxide nanoparticles (3D rGO-Fe2O3) material with a suitable porous structure was synthesised using a one-step hydrothermal process in order to fabricate novel electrodes for capacitive deionization (CDI) water desalination. The morphological and structural properties of the as-synthesised compounds were characterised by scanning electron microscopy (SEM), Brunauer-Emmett-Teller (BET), Raman spectroscopy (RS), X-ray diffraction (XRD) and thermal gravimetric analysis (TGA). The CDI electrodes were electrochemically analysed by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). A maximum value of specific capacitance of 345 F g−1 was achieved at 5 mV s−1 scan rate using a NaCl 0.1 mol L−1 solution. The ion removal performance of the CDI electrodes was evaluated with NaCl solutions of different concentrations, showing electrosorption capacities as high as 945 mg g−1 for 11,700 mg L−1 (200 mmol L−1) NaCl solutions, which substantially surpasses results of other carbon-based CDI electrodes.