http://hdl.handle.net/10498/6823 Thu, 05 Nov 2026 09:27:08 GMT 2026-11-05T09:27:08Z http://hdl.handle.net/10498/40523 A dual solid and liquid solvent bar microextraction coupled with portable X-ray fluorescence for lead determination in seawater Cuervo Novas, Senia; Mendiguchía Martínez, Carolina; Moreno Aguilar, Carlos Trace metals play a crucial role in many biogeochemical processes in water. Due to their low concentrations and the complexity of the matrix, analysing these metals in seawater is a complex task that usually requires a previous preconcentration step. We present a simple two-step method for determining lead concentration in seawater. In the first step, we use a two-phase solvent bar microextraction system (2-SBME), previously prepared with a polypropylene hollow fiber. The extracted metal is then measured directly within the solid fiber using a portable X-ray fluorescence spectrometer. The 2-SBME contains two different extraction reagents: one liquid (Cyanex 272) and one solid (carbon nanotubes functionalized with carboxylic groups (CNT-COOH)). Two different microextraction processes are then carried out simultaneously: a LPME and a SPME, achieving a synergistic effect in the separation process. Efficiency was evaluated in terms of the percentage of lead extracted, with optimum conditions obtained at 0.06 mol L−1 of Cyanex 272, 10 mg mL−1 of CNT-COOH, a stirring rate of 50 rpm and an extraction time of 90 min. The influence of X-ray exposure time was also studied. Under optimal conditions, the LOD and LOQ were 0.061 mg L−1 and 0.203 mg L−1, respectively. Finally, the greenness of the new method was evaluated using the AGREEprep and SPMS methods. The method was successfully used to determine the lead concentration in fortified real seawater samples from three different locations, thus demonstrating its applicability. Using portable X-ray fluorescence equipment avoids the re-extraction step, and opens the possibility of in situ analysis. Thu, 01 Jan 2026 00:00:00 GMT http://hdl.handle.net/10498/40523 2026-01-01T00:00:00Z http://hdl.handle.net/10498/40513 A new polymer inclusion membrane-based system to separate and determine copper ions in saline waters Perales Pérez, Ángela; Pinto Ganfornina, Juan José; Moreno Aguilar, Carlos We present a new system to separate and determine copper concentration in saline samples. It is based on the use of a polymer inclusion membrane (PIM) to separate and preconcentrate the copper ions from the saline aqueous matrix to a receiving acidic solution. The influence of the composition and thickness of the PIM has been studied and optimised, by varying the concentration of the base polymer, extractant reagent, and plasticizer, as well as the total volume of solution used to prepare the membrane. The thinner PIM exhibited the best transport of metal ions, with the optimal thickness of 20.5 ± 1.8 μm and the composition being 30% (w/w) of cellulose triacetate (CTA), 60% (w/w) of di(2-ethylhexyl) phosphoric acid (DEHPA), and 10% (w/w) of tris(2-ethylhexyl) phosphate (TEHP). In addition, we studied the influence of the physico-chemical variables on copper transport across the membrane. Optimum results were obtained for a sample pH of 5 and a stripping phase containing 0.1 mol L−1 HNO3. The variation of copper concentration was monitored on-line by using a colorimetric reagent containing 6.67x10−5 mol L−1 of 4-(2-pyridylazo) resorcinol (PAR) in a flow injection analysis (FIA) system. A second-order mathematical relationship was obtained between the extraction time and the percentage of copper separation, enabling the application of the method to real seawater samples with different copper concentrations at the ppm and sub-ppm levels. Thu, 01 Jan 2026 00:00:00 GMT http://hdl.handle.net/10498/40513 2026-01-01T00:00:00Z http://hdl.handle.net/10498/40453 Defects engineering of Au@MoS2 nanostructures for conventional and plasmon-enhanced hydrogen evolution reaction Quintana González, Juan José; Medina Olivera, Antonio Jesús; Manzorro Ureba, Ramón; Pardanaud, Cedric; Hungría Hernández, Ana Belén; Cubillana Aguilera, Laura; Palacios Santander, José María; Hernández Garrido, Juan Carlos; Lajaunie, Luc Cyrille Jacques The influence of thermal treatment under reducing conditions on the structural and hydrogen evolution reaction (HER) properties of Au@MoS2 structures is reported in this work. After a thermal treatment at 800 °C under H2 atmosphere, the Au@MoS2 nanostructures exhibit remarkable performance with an overpotential of 203 mV vs reversible hydrogen electrode (RHE) at 10 mA/cm2 and a Tafel slope of 55 mV/dec which is similar to the value reported for edges sites in MoS2. The samples were investigated by combining ex-situ and in-situ aberration-corrected transmission electron microscopy (TEM) experiments under controlled atmosphere, Raman and XPS spectroscopies. (S) TEM characterization highlights the formation of the core-shell system as well as the decrease of the number of shell layers up to incomplete layers induced by the thermal treatments. The plasmonic-assisted HER performances of these nanostructures under LED illumination are also explored and an enhancement by about 10 % of the current density, depending on the wavelength used, is also reported. These results open new avenues for the design of core shell nanostructures based on transition metal dichalcogenides for the hydrogen evolution reaction. Tue, 02 Jan 2024 00:00:00 GMT http://hdl.handle.net/10498/40453 2024-01-02T00:00:00Z http://hdl.handle.net/10498/40329 Dinámica de gases de efecto invernadero en la bahía de Cádiz: importancia de aportes terrestres López Alonso, Laura Se ha caracterizado la distribución espacial y la reactividad biogeoquímica de los gases de efecto invernadero, así como sus flujos agua-atmósfera, en el parque natural bahía de Cádiz (saco externo e interno de la bahía - BCE y BCI, Río San Pedro - RSP, caño de Sancti Petri – CSP y estuario del Guadalete - GT). El estudio tuvo lugar durante julio del 2025 y se determinaron diversas variables como la temperatura, la salinidad, la alcalinidad total, el pH, el carbono orgánico e inorgánico disuelto, la clorofila-a, los sólidos en suspensión, los nutrientes inorgánicos disueltos, pCO2 y las concentraciones de CH4 y N2O en 54 estaciones distribuidas en los cinco sistemas. La bahía mostró una variabilidad reducida, con valores de pCO2 más elevados en el saco externo (624 ± 146 µatm) que en el interno (483 ± 93 µatm) y concentraciones de CH4 y N2O similares en toda la bahía (60 ± 25 nM y -0,2 ± 0,6 nM, respectivamente). En los sistemas costeros la variabilidad fue mucho mayor, y los tres gases aumentaron hacia las zonas más internas. Los valores máximos se han observado en GT (5141 µatm pCO2, 3726 nM CH4 y 622 nM N2O), coincidiendo con la zona afectada por los vertidos de la estación depuradora de aguas residuales (EDAR Jerez de la Frontera). La pCO2 se relacionó positivamente con la salinidad en RSP y CSP, y negativamente en GT, lo que indica un aumento en de los procesos de degradación de la materia orgánica en las zonas internas de estos sistemas. La concentración de CH4 no responde a los procesos de mezcla en cada uno de los sistemas, lo que apunta a un origen bentónico desacoplado de la respiración en la columna de agua. La distribución del N2O se encuentra relacionada con la disponibilidad de nitrógeno inorgánico, lo que sugiere una producción por nitrificación. Por medio de un análisis de la distribución de pCO2, pH y carbono inorgánico disuelto se ha confirmado el carácter heterotrófico de los cinco sistemas. Los flujos agua-atmósfera muestran que el conjunto de la bahía de Cádiz actúa como una fuente neta de estos gases invernadero hacia la atmósfera, con una intensidad de emisión creciente desde la bahía (5,7 mmol CO2 m-2 d-1, 59,7 µmol CH4 m-2 d-1 y -0,2 µmol N2O m-2 d-1) hacia el interior de los sistemas costeros (39 mmol CO2 m-2 d-1, 740,2 µmol CH4 m-2 d-1 y 102,6 µmol N2O m-2 d-1).; The spatial distribution and biogeochemical reactivity of greenhouse gases, together with their air-water fluxes, were characterized in the Bahía de Cádiz Natural Park (outer and inner bay – BCE and BCI, Río San Pedro creek – RSP, Sancti Petri channel – CSP, and the Guadalete estuary – GT). The study was conducted during July 2025, when temperature, salinity, total alkalinity, pH, dissolved organic and inorganic carbon, chlorophyll-a, suspended solids, dissolved inorganic nutrients, pCO2, and CH4 and N2O concentrations were determined at 54 stations distributed across the five systems. The bay exhibited limited variability, with higher pCO2 values in the outer bay (624 ± 146 µatm) than in the inner bay (483 ± 93 µatm), and similar CH4 and N2O concentrations throughout the bay (60 ± 25 nM and −0.2 ± 0.6 nM, respectively). In the coastal systems, variability was considerably greater, with all three gases increasing toward the innermost zones. Maximum values were recorded in GT (5141 µatm pCO2, 3726 nM CH4, and 622 nM N2O), coinciding with the area affected by discharges from the Jerez de la Frontera wastewater treatment plant (WWTPs). pCO2 was positively correlated with salinity in RSP and CSP, and negatively correlated in GT, indicating an intensification of organic matter degradation processes in the innermost zones of these systems. CH4 concentrations did not respond to mixing processes within each system, pointing to a benthic origin decoupled from water-column respiration. The distribution of N2O was related to inorganic nitrogen availability, suggesting production via nitrification. Analysis of the distribution of pCO2, pH, and dissolved inorganic carbon confirmed the heterotrophic character of all five systems. Air-water fluxes show that the Bahía de Cádiz as a whole acts as a net source of these greenhouse gases to the atmosphere, with emission intensity increasing from the bay (5.7 mmol CO2 m-2 d -1 , 59.7 µmol CH4 m-2 d -1 , and −0.2 µmol N2O m-2 d -1 ) toward the interior of the coastal systems (39 mmol CO2 m-2 d -1 , 740.2 µmol CH4 m-2 d -1 , and 102.6 µmol N2O m-2 d -1 ). Tue, 01 Sep 2026 00:00:00 GMT http://hdl.handle.net/10498/40329 2026-09-01T00:00:00Z