Anàlisi i control de cianurs i productes relacionats presents en aigües residuals i dissolucions de processos industrials mitjançant electroforesi capil.lar

Esta tesis consiste en la aplicación de la electroforesis capilar (CE) a la separación y cuantificación de especies cianuradas y al estudio del comportamiento de estas especies y de su destino final. Como material de estudio se han seleccionado distintos procesos industriales (lixiviación de minerales y arenas auriferas, disoluciones de proceso en industrias de recubrimientos electrolíticos, lixiviación intensiva en autoclave de convertidores de automóvil) donde los cianuros tienen aplicación. En la primera parte de la tesis se ha realizado un estudio detallado de las características de la técnica CE, y posteriormente se ha optimizado una metodología para aplicarla a los distintos problemas que se recogen en el resto de la memoria. La segunda parte de la tesis se ha dedicado a la aplicación de la ce al estudio de la lixiviación con NaCN de los metales preciosos y estratégicos presentes en minerales auriferos (Au, Ag) y en convertidores de automóviles (PT, PD, RH), obteniendo finalmente un método analítico capaz de ser utilizado para el seguimiento de este tipo de procesos. En la tercera parte de la tesis se ha realizado la determinación del cianuro libre, del débilmente ligado y del total en aguas procedentes de la industria de los recubrimientos electrolíticos y en disoluciones de cianuros oxidadas con hipoclorito, que es el método mas extendido para tratar las aguas industriales. Para analizar estas formas de cianuros, se han planteado dos soluciones, basadas en la detección indirecta y en la derivatización.La problemática de la detección del cianuro libre (CN- y HCN (aq)) y de especies relacionadas (CNO-, SCN-, NO3, CI-, SO42- y CIO-) resuelto con la utilización de la fluorescencia indirecta con un detector prototipo con fuente láser.La determinación de cianuros en muestras reales de disoluciones de recubrimientos electrolíticos se ha conseguido mediante su derivatizacion a NI(CN)42- utilizando una disolución de NI(II)-NH3

Environmental risk assessment of silver nanoparticles in 2 aquatic ecosystems using fuzzy logic

The rapid development of nanotechnology has stimulated the use of silver nanoparticles (AgNPs) in various fields that leads to their presence in different ecosystem compartments, in particular aquatic ecosystems. Several studies have shown that a variety of living organisms are affected by AgNPs. Therefore, a methodology to assess the risk of AgNPs for aquatic ecosystems was developed. The methodology is based on fuzzy logic, a proven method for dealing with variables with an associated uncertainty, as is the case with many variables related to AgNPs. After a careful literature search, a selection of relevant variables was carried out and the fuzzy model was designed. From inputs such as AgNPs’ size, shape, and coating, it is possible to determine their level of toxicity which, together with their level of concentration, are sufficient to create a risk assessment. Two case studies to assess this methodology are presented, one involving continuous effluent from a wastewater treatment plant and the second involving an accidental spill. The results showed that the accidental spills have a higher risk than WWTP release, with the combination of Plates–BPEI being the most toxic one. This approach can be adapted to different situations and types of nanoparticles, making it highly useful for both stakeholders and decision makersPostprint (published version

Environmental risk assessment of silver nanoparticles in aquatic ecosystems using fuzzy logic

The rapid development of nanotechnology has stimulated the use of silver nanoparticles (AgNPs) in various fields that leads to their presence in different ecosystem compartments, in particular aquatic ecosystems. Several studies have shown that a variety of living organisms are affected by AgNPs. Therefore, a methodology to assess the risk of AgNPs for aquatic ecosystems was developed. The methodology is based on fuzzy logic, a proven method for dealing with variables with an associated uncertainty, as is the case with many variables related to AgNPs. After a careful literature search, a selection of relevant variables was carried out and the fuzzy model was designed. From inputs such as AgNPs’ size, shape, and coating, it is possible to determine their level of toxicity which, together with their level of concentration, are sufficient to create a risk assessment. Two case studies to assess this methodology are presented, one involving continuous effluent from a wastewater treatment plant and the second involving an accidental spill. The results showed that the accidental spills have a higher risk than WWTP release, with the combination of Plates–BPEI being the most toxic one. This approach can be adapted to different situations and types of nanoparticles, making it highly useful for both stakeholders and decision makers.This research was funded by the Spanish Ministry of Science, Innovation and Universitiesand Agencia Estatal de Investigación/European Regional Development Plan (grant CGL2017-87216-C4-3-R). Authors want to thank Fundación Carolina and Universidad Tecnológica del Chocófor thePhD research grant given to Mr. Ramírez.Peer ReviewedPostprint (published version

Water-air volatilization factors to determine volatile organic compound (VOC) reference levels in water

The goal of this work is the modeling and calculation of volatilization factors (VFs) from water to air for volatile organic compounds (VOCs) in order to perform human health risk - base d reference levels (RLs) for the safe use of water. The VF models have been developed starting from the overall mass - transfer coefficients ( K overall ) concept from air to water for two interaction geometries (flat surface and spherical droplets) in indoor a nd outdoor scenarios . For a case study with five groups of risk scenarios and thirty VOCs , theoretical VFs have been calculated by using the developed models. Results showed that K overall values for flat and spherical surface geometries were close to the m ass transfer coefficient for water ( K L ) when Henry ’s law constant ( K H ) was high. I n the case of s pherical drop geometry , the fraction of volatilization ( f V ) was asymptotical when increasing K H with f V values also limited due to K overall . VFs for flat surfa ces were calculated from the emission flux of VOCs , and results showed values close to 1000 K H for the most conservative indoor scenarios and almost constant values for outdoor scenarios. VFs for spherical geometry in indoor scenarios followed also constant VFs and were far from 1000 K H . The highest calculated VF values corresponded to the E2A, E2B, E3A and E5A scenarios and were compared with experimental and real results in order to check the goodness of flat and sphere geometry models. Results showed an ov erestimation of OPEN ACCESS Toxics 2014 , 2 277 calculated values for the E2A and E2B scenarios and an underestimation for the E3A and E5A scenarios. In both cases , most of the calculated VFs were from 0.1 - to 10 - times higher than experimental /real valuesPeer ReviewedPostprint (published version

Activation process of air stable nanoscale zero-valent iron particles

Nanoscale Zero Valent Iron (nZVI) represents a promising material for subsurface water remediation technology. However, dry, bare nZVI particles are highly reactive, being pyrophoric when they are in contact with air. The current trends of nZVI manufacturing lead to the surface passivation of dry nZVI particles with a thin oxide layer, which entails a decrease in their reactivity. In this work an activation procedure to recover the reactivity of air-stable nZVI particles is presented. The method consists of exposing nZVI to water for 36 h just before the reaction with the pollutants. To assess the increase in nZVI reactivity based on the activation procedure, three types of nZVI particles with different oxide shell thicknesses have been tested for Cr(VI) removal. The two types of air-stable nZVI particles with an oxide shell thickness of around 3.4 and 6.5 nm increased their reactivity by a factor of 4.7 and 3.4 after activation, respectively. However, the pyrophoric nZVI particles displayed no significant improvement in reactivity. The improvement in reactivity is related mainly to the degradation of the oxide shell, which enhances electron transfer and leads secondarily to an increase in the specific surface area of the nZVI after the activation process. In order to validate the activation process, additional tests with selected chlorinated compounds demonstrated an increase in the degradation rate by activated nZVI particles.Postprint (author's final draft

Assessment of the water chemical quality improvement based on human health risk indexes: Application to a drinking water treatment plant incorporating membrane technologies

A methodology has been developed in order to evaluate the potential risk of drinking water for the health of the consumers. The methodology used for the assessment considered systemic and carcinogenic effects caused by oral ingestion of water based on the reference data developed by the World Health Organisation (WHO) and the Risk Assessment Information System (RAIS) for chemical contaminants. The exposure includes a hypothetical dose received by drinking this water according to the analysed contaminants. An assessment of the chemical quality improvement of produced water in the Drinking Water Treatment Plant (DWTP) after integration of membrane technologies was performed. Series of concentration values covering up to 261 chemical parameters over 5 years (2008–2012) of raw and treated water in the Sant Joan Despí DWTP, at the lower part of the Llobregat River basin (NE Spain), were used. After the application of the methodology, the resulting global indexes were located below the thresholds except for carcinogenic risk in the output of DWTP, where the index was slightly above the threshold during 2008 and 2009 before the upgrade of the treatment works including membrane technologies was executed. The annual evolution of global indexes showed a reduction in the global values for all situations: HQ systemic index based on RAIS dropped from 0.64 to 0.42 for surface water and from 0.61 to 0.31 for drinking water; the R carcinogenic index based on RAIS was negligible for input water and varied between 4.2 × 10- 05 and 7.4 × 10- 06 for drinking water; the W systemic index based on the WHO data varied between 0.41 and 0.16 for surface water and between 0.61 and 0.31 for drinking water. A specific analysis for the indexes associated with trihalomethanes (THMs) showed the same pattern.Peer ReviewedPostprint (author's final draft

Customized screen-printed electrodes based on Ag-nanoseeds for enhanced electroanalytical response towards Cd(II), Pb(II) and As(V) in aqueous samples

Electrochemical analysis based on screen-printed electrodes (SPEs) represents a great alternative to conventional analytical methods such as ICP-MS or LC-MS due to their portability, sensitivity, selectivity, and cost-effectiveness. In addition, the functionalization of SPEs with nanomaterials has been reported to provide an enhanced analytical performance. In this regard, silver nanoparticles (AgNPs) were synthesized and appropriately characterized, showing spherical silver nanoseeds (Ag-NS) with a diameter of 12.20 ± 0.04 nm. Using the drop-casting methodology, the synthesized AgNPs were used to modify screen-printed carbon nanofiber electrodes (SPCNFEs). Ag-NS deposition onto the electrode surface was confirmed by scanning electron microscopy (SEM). Furthermore, the analytical response of the modified electrodes (Ag-NS-SPCNFE) was evaluated for the determination of trace Pb(II), Cd(II), and As(V) using differential pulse anodic stripping voltammetry (DPASV), obtaining detection limits of 3.3, 3.7, and 2.6 µg L-1, for Pb(II), Cd(II) and As(V), respectively. Finally, Ag-NS-SPCNFE was tested towards the determination of As(V) in a spiked tap water sample, showing a good agreement with concentrations determined by ICP-MS.Peer ReviewedPostprint (published version

Subsurface nitrate reduction under wetlands takes place in narrow superficial zones

This study aims to investigate the depth distribution of the Nitrate Reduction Potential (NRP) on a natural and a re-established wetland. The obtained NRP provides a valuable data of the driving factors affecting denitrification, the Dissimilatory Nitrate Reduction to Ammonium (DNRA) process and the performance of a re-established wetland. Intact soil cores were collected and divided in slices for the determination of Organic Matter (OM) through Loss of Ignition (LOI) as well as Dissolved Organic Carbon (DOC) and NRP spiking nitrate in batch tests. The Nitrate Reduction (NR) was fitted as a pseudo-first order rate constant (k) from where NRPs were obtained. NR took place in a narrow superficial zone showing a dropping natural logarithmic trend along depth. The main driving factor of denitrification, besides depth, was OM. Although, DOC and LOI could not express by themselves and absolute correlation with NRP, high amounts of DOC ensured enough quantity and quality of labile OM for NR. Besides, high concentration of LOI but a scarce abundance of DOC failed to drive NR. DNRA was only important in superficial samples with high contents of OM. Lastly, the high NRP of the re-established wetland confirms that wetlands can be restored satisfactorily.Preprin

Direct As(V) Determination Using Screen-Printed Electrodes Modified with Silver Manoparticles

Carbon-nanofiber-based screen-printed electrodes modified with silver nanoparticles (Ag-NP-SPCNFEs) were tested in a pioneering manner for the direct determination of As(V) at low µg L–1 levels by means of differential pulse anodic stripping voltammetry. Screen-printed electrodes were modified with two different types of Ag-NPs, nanoseeds (NS), and nanoprisms (NPr) and characterized both microscopically and electrochemically. Furthermore, after optimizing the direct voltammetric determination of As(V), the analytical performance of considered sensors was compared for the direct determination of As(V). These results suggest that Ag-NS offer a better analytical response compared to Ag-NPr, with a detection and quantification limit of 0.6 and 1.9 µg L–1, respectively. The proposed methodology was validated using a spiked tap water sample with a very high reproducibility and good agreement with inductively coupled plasma - mass spectrometry (ICP-MS) measurementsPeer ReviewedPostprint (published version

Tailored carrier/bacteria technology for rehabilitation of areas with pesticide-containing pollution – AQUAREHAB WP2

Postprint (published version