For this study the emerging contaminant ß-blocker Metoprolol (MET) has been selected due that it is a highly prescribed pharmaceutical and it has been detected in waste water treatment plants influents, thus, in natural waters. Several studies, focused on the toxicological potential of Metoprolol, indicate its potential environmental relevance and its recalcitrant nature. To remove MET from water, different Advanced Oxidation Processes (AOPs) were used. MET removal was studied, in different reactors with natural and artificial light, by photolysis, UVC/H2O2, photocatalysis, Fenton, photo-Fenton, bicarbonate-activated hydrogen peroxide (with cobalt or iron) processes. The different set-ups and technologies tested have been compared in order to establish the efficiency of the processes. The experiments were normally carried out with 50 mg/L of initial MET in Milli-Q water, free pH, and 25 ± 5 ºC. Thus, photolysis experiments were done in (solarbox (SB), Compound Parabolic Collector (CPC), Black light blue lamps (BLB) and UVC254 nm (UVC) reactors). The best result obtained was 93.5% of MET removal in UVC reactor after 240 minutes. UVC/H2O2 experiments were carried out in UVC reactor. Different H2O2 concentrations and pH were tested and the maximum removals were MET (98%) and TOC (70.7%) for 125 mg H2O2/L. Photocatalysis was carried in SB and CPC with different TiO2 concentrations (0.05, 0.10 and 0.40 g /L). Experiments were also carried out varying the initial MET concentration (25, 50 and 100 mg/L), pH and the water matrix with 0.4 g TiO2/L in SB or adding 25 and 150 mg/L of H2O2. The best results obtained were a complete MET removal and 45.7% of mineralization in SB and 81.5% of MET degradation and 29.2% of mineralization in CPC. The dark-Fenton experiments were carried out at pH in a reactor of 2 L. Two different concentrations of Fe (II) (2.5 mg/L or 10 mg/L) and H2O2 (25 mg/L or 150 mg/L) were used. To improve the Fenton process, the total Iron (II) concentration was divided in equal parts (5) and added at constant periods of time (12 minutes) during 1 hour. With the highest concentrations of iron and H2O2 the maximum MET conversion was 87.0% and mineralization 15.6%. Photo-Fenton experiments were done at pH 3, and temperature of 14 or 25 ºC in four reactors (BLB, SB, CPC and UVC). Two different concentrations of Fe (II) (2.5 mg/L or 10 mg/L) and H2O2 (25 mg/L or 150 mg/L) were used. With the highest iron and H2O2 concentrations, the best results in MET degradation were observed (BLB: 100% in 7 min; SB: 97.3% in 7 min; CPC: 98.3% in 3 min). The dark- Bicarbonate/hydrogen peroxide experiments were carried out with 5 mg/L of MET in drinking water, pH 6.2, and room temperature in a reactor of 0.5 L. To improve the process, cobalt (II) or iron (II) as catalyzer were added in the batch reactor. A complete MET conversion in 40 minutes was achieved. The efficiency of different AOPs and reactors tested was compared from the ratio between accumulated energy and MET eliminated. The energy is better used in CPC (0.065 kJ/mg) than in SB (0.275 kJ/mg). For photo-Fenton process (0.04 kJ/mg) UVC and (0.05 kJ/mg) BLB reactors exhibit a much better performance than (0.30 kJ/mg) SB and (0.26 kJ/mg) CPC reactors. From the intermediates identified, a possible MET fragmentation was proposed for the different processes, where, mainly oxidative attacks were detected. On the other hand, the irradiation in the photocatalytic reactor (SB) was measured by o-NB actinometry, based on pH or o-NB concentration. In addition, this work has demonstrated that the o-NB actinometry, followed by o-NB concentration consumption, could be used in the presence of the catalyst TiO2. / En este trabajo se ha estudiado la eficacia de varios Procesos de Oxidación Avanzada (UVC/H2O2, fotocatálisis, Fenton, foto-Fenton, bicarbonato/H2O2 con y sin catalizador) para degradar el fármaco Metoprolol (MET). Además se ha comparado la eficiencia energética de los diferentes procesos y diferentes instalaciones en la eliminación de MET. Los experimentos se realizaron con 50 mg/L iniciales de MET en agua Mili-Q, pH libre y 25ºC. En el caso de la fotólisis, se usaron cuatro instalaciones (solarbox (SB), concentradores parabólicos compuestos (CPC), lámparas black light blue (BLB) y UVC254 nm (UVC)) y el mejor resultado obtenido fue (UVC: 93,5%). Los experimentos UVC se realizaron a diferentes pH y concentraciones de H2O2 con una eliminación de MET de 98%. Los experimentos de fotocatálisis se llevaron a cabo con luz natural y artificial, variando la concentración de TiO2 (0,05, 0,10 y 0,40 g/L). También se realizaron experimentos con 0,4 g/L TiO2 pero variando la concentración inicial del MET (25, 50 y 100 mg/L), el pH, la matriz acuosa y adicionando peróxido de hidrógeno. Los mejores resultados fueron (CPC: 81,5% y SB: 100%). Los experimentos de Fenton se realizaron a pH 3,0 en un reactor de 2 L. Para mejorar el proceso, la adición del Fe (II) se dividió en 5 adiciones realizadas a intervalos constantes de tiempo durante 60 minutos. La mejor degradación de MET fue 87%. Los experimentos de foto-Fenton se realizaron a pH 3,0 y temperaturas de 14ºC y 25ºC en cuatro instalaciones diferentes (BLB, SB, CPC y UVC). Los mejores resultados obtenidos para la eliminación de MET fueron (BLB: 100%; SB: 97,3% y CPC: 98,3%). Los experimentos con bicarbonato/H2O2 se realizaron con 5 mg/L iniciales de MET en agua potable, pH libre y temperatura ambiental en un reactor de 0,5 L. Adicionalmente se utilizó Co (II) y Fe (II) como catalizadores. Eliminación de MET de 100%. Se realizó la identificación de los diferentes intermedios y se han establecido los posibles caminos de degradación del MET. Finalmente se realizó un estudio de un método actinométrico para poder realizar mediciones de radiación en un reactor fotocatalítico en presencia de un catalizador en suspensión.

Tesi realitzada al Dept. de Química Ambiental de l'IDAEA-CSIC / En aquesta Tesi s’han estudiat les fonts d’emissió de diversos contaminants atmosfèrics, principalment a l’àrea de Barcelona. Els contaminants estudiats han estat l’òxid de nitrogen (NO), compost tòxic que s’emet en grans quantitats pels vehicles a causa de la combustió, l’ozó, que té naturalesa oxidant, i es troba molt relacionat amb la presència d’òxids de nitrogen, i diversos contaminants orgànics presents en el material particulat atmosfèric. Entre els contaminants orgànics estudiats hi ha alguns de més tòxics com són els hidrocarburs aromàtics policíclics (PAH), i d’altres presents al medi, però amb menor impacte sobre la salut, com són els àcids dicarboxílics o els productes derivats de l’oxidació de l’isoprè o l’alfa-pinene. Les taules de dades corresponents a les concentracions de NO i O(3) s’han obtingut a partir de les bases de dades del departament de medi ambient de la Generalitat de Catalunya. Els contaminants orgànics s’han determinat en mostres de material particulat obtingudes de campanyes de seguiment ambiental a les ciutats de Barcelona i Los Angeles. Aquests compostos han estat determinats experimentalment al laboratori, mitjançant la seva extracció i anàlisi amb cromatografia de gasos acoblada a espectrometria de masses. L’ús de la quimiometria ha permès interpretar i simplificar la gran quantitat de dades obtingudes en els estudis de seguiment ambiental realitzats en aquesta Tesi. Depenent de la informació que s’ha volgut obtenir en cada estudi, les taules de dades s’han disposat en matrius de dades augmentades en dos direccions (two-way) i en alguns casos també en estructures en tres direccions (three-way). S’han aplicat diferents mètodes quimiomètrics, entre els que ha destacat el mètode de resolució multivariant de corbes per mínims quadrats alternats (MCR-ALS). L’aplicació d’aquest mètode amb diferents tipus de restriccions com la no-negativitat i la trilinearitat ha permès estimar les fonts d’emissió i de distribució geogràfica i temporal dels contaminants en les regions estudiades. S’ha descrit amb detall els perfils de variació temporal (diària i anual) de les fonts d’emissió de NO i O(3) a la ciutat de Barcelona i a diferents regions de Catalunya. S’ha trobat que les principals fonts d’emissió de contaminants atmosfèrics són antropogèniques, i s’ha confirmat que el tràfic de vehicles és un dels principals emissors dels contaminants estudiats. Altres fonts de contaminació de compostos orgànics trobades en material particulat han estat la crema de biomassa, els productes d’oxidació de l’isoprè i l’alfa-pinene, i els àcids dicarboxílics, que poden tenir tant orígens biogènics com antropogènics. / In this Thesis, emission sources of several air contaminants have been mainly studied in the area of Barcelona. The studied contaminants were nitrogen oxide (NO), ozone (O3), and some organic pollutants in particulate matter. Among the considered organic pollutants, some were toxic, such as polycyclic aromatic hydrocarbons (PAH), and others were present in the environment, but with less impact on human health, such as dicarboxylic acids or oxidation products of isoprene and alpha-pinene. Data corresponding to the concentrations of NO and O3 were obtained from data bases of the Environmental Department of the Generalitat of Catalonia. Organic pollutants were determined in particulate matter samples, acquired in different environmental monitoring campaigns in the cities of Barcelona and Los Angeles. These organic pollutants were analyzed experimentally in the laboratory by ultrasonical extraction and gas chromatography coupled with mass spectrometry. The use of chemometrics allowed interpreting and simplifying the large amount of data obtained in this Thesis from different environmental monitoring studies. Data tables were arranged in two directions (two-way) in augmented data matrices and in some cases in structures in three directions (three-way), depending on the method used for their analysis. In this Thesis, Multivariate Curve Resolution Alternating Least Squares (MCR-ALS) was the more used chemometric method. The application of different types of constraints in MCRALS, such as non-negativity and trilinearity, allowed the estimation of the emission sources of the investigated contaminants and the estimation of their geographical and temporal distribution in the studied regions. Temporal variation profiles (daily and annual) for emission sources of NO and O(3) were described in detail in Barcelona city and in different regions of Catalonia. Contamination sources of organic pollutants found in particulate matter were biomass burning, primary anthropogenic emissions, dicarboxylic acids and oxidation products of isoprene and alpha-pinene. Vehicle traffic was confirmed to be the major anthropogenic source of studied pollutants.

This thesis focuses on the computational study of models for platinum catalysts supported on cerium oxide (CeO2) which are of technological relevance. In these catalysts, ceria is often found acting as a non-inert support, leading to complex metal-support interactions (MSI) that modify the properties of both the oxide and the supported metal. First principles computational methods based on the Density functional Theory (DFT) have been used to study the nature of these interactions and their effect on the atomic and electronic structure and on the chemical activity of these catalytic systems. In particular, charge transfer phenomena have been studied and how the oxygen storage capacity of CeO2 is affected by the presence of deposited Pt particles. The effect of the MSI in the activity towards the WGS has also been addressed, as well as the During the fulfillment of these studies, close collaboration with world leading experimental groups from different countries has been crucial to broaden the understanding of these systems. The interaction of single Pt atoms with the CeO2(111) surface was studied first. By using the DFT+U approach in combination with hybrid functionals the validity of the DFT+U methodology for studying Pt/CeO2 systems was assessed and a suitable value for the U parameter was established for further studies dealing with similar systems. It was found that in its most stable adsorption site, Pt atoms can be found in a neutral form or oxidized to +1 formal oxidation state, with the concomitant reduction of one Ce4+ cation to Ce3+. The formation and stability of Pt dimers on CeO2(111) was studied next. It was shown that Pt atoms can easily diffuse until forming the more stable Pt2 moieties. In turn, the dimers will also diffuse before dissociating, thus describing the initial phase of Pt particle nucleation in Pt/CeO2 catalysts. The effect of the MSI in the reducibility of CeO2 was also addressed. The Oxigen Storage Capacity (OSC) of CeO2 is a consequence of its inherent reducibility, and it is believed that tuning the OSC leads to improving the catalytic performance of ceria-based catalysts. In collaboration with the experimental partners, it was found that the presence of deposited Pt particles facilitates the release of oxygen atoms from ceria by enabling the migration of an oxygen atom from the ceria substrate to the deposited metal. This phenomenon is known as reverse oxygen spill-over mechanism and is only thermodynamically favorable when the ceria substrate is nanostructured. The unprecedented experimental observation of this process and its rationalization through theoretical calculations merited the publication of these results in the prestigious Nature Materials journal. It is also found that very stable cationic Pt2+ species are formed upon the adsorption of Pt atoms on ceria nanoparticles. These adsorption complexes are so stable that they can resist harsh conditions leading to bulk-diffusion and sintering to form larger Pt species. The effect of strong electronic MSI on the activity of Pt/CeO2 catalysts toward the Water-Gas Shift Reaction was also investigated. It was found that the intimate contact between the small metal particles and the oxide substrate triggers electronic perturbations that dramatically enhance the ability of Pt to dissociate water, leading to increased WGS activity. This investigation was performed in collaboration with Jose Rodriguez’s experimental group and was initiated by the research visit that AB carried out to Brookhaven National Laboratory. These landmark results were published in the Journal of the Americal Chemical Society. In addition, the effect of the size and shape of Pt nanoparticles towards their capacity to dissociate water was investigated for lone-standing nanoparticles of different sizes. It was shown that, for Pt particles still under the scalable-to-bulk regime, the size of the particle as well as the type of sites exposed by these play an important role on their reactivity. Smaller particles with uncoordinated corner Pt atoms were found to be most active. / En aquesta tesi s’han utilitzat mètodes teòrics basats en la DFT per estudiar les propietats de sistemes formats per Pt i CeO2. Mitjançant un anàlisi de l’estructura electrònica i geomètrica dels models considerats, s’ha contribuït a la comprensió a nivell microscòpic de les interaccions entre Pt i CeO2. Així, s’han descrit els processos de transferència de càrrega entre diferents espècies de Pt i substrats de CeO2, resultant en l’oxidació de les espècies metàl•liques i la reducció de cations Ce. A més, s’ha demostrat que la presència del platí facilita la reducció de l’òxid de ceri a través de processos de migració (spillover) d’àtoms d’oxigen i que aquest efecte és més pronunciat quan el CeO2 és nanoestructurat. Això ha permès explicar per primera vegada els mecanismes de formació de vacants en catalitzadors basats en Pt i CeO2, que són responsables de la seva capacitat d’emmagatzemar oxigen i per tant, de la seva activitat catalítica. Amb els models de nanopartícules de CeO2, s’ha descrit l’existència de complexos d’adsorció on el Pt es troba dispersat atòmicament i en forma de catió a la superfície de les nanopartícules de cèria. A més, aquestes espècies es poden utilitzar com a electrocatalitzadors en els ànodes de cel•les de combustible, permetent el desenvolupament de dispositius que utilitzin platí de forma més eficient i, per tant, reduint-ne dràsticament els costos. L’estudi de la reactivitat de diferents espècies de Pt envers la reacció WGS mitjançant la determinació del perfil energètic de la dissociació de l’H2O ha permès caracteritzar els efectes que tenen la mida de la partícula de Pt i les interaccions metall-suport amb l’òxid de ceri en l’activitat d’aquests catalitzadors. S’ha demostrat l’excepcional activitat catalítica d’aquests sistemes i s’han identificat les propietats que els fan més reactius, superant en rendiment als catalitzadors que s’utilitzen industrialment per a catalitzar la WGS. Els estudis realitzats durant aquesta tesi han permès descriure detalladament propietats de sistemes formats per Pt i CeO2. Aquesta caracterització serveix per comprendre els sistemes catalítics basats en aquests materials i per guiar el disseny racional de nous materials amb les propietats catalítiques idònies per a cada aplicació.

Coastal areas are very susceptible to contamination due to the interaction of marine and anthropogenic processes. Persistent Organic Pollutants (POPs) are organic compounds very resistent to photolysis and chemical and biological degradation. According to its physicochemical characteristics, POPs are worldwide distributed. These contaminants tend to bioaccumulate through the food webs, so that predators are more sensitive to this contamination. Seabirds are highly exposed to organic pollutants due to their feeding habits and its relatively long life. In this thesis, it has been studied the accumulation of various families of organic pollutants in two species of gulls breeding in the Iberian Peninsula, the yellow-legged gull (Larus michahellis) and Audouin's gull (L. audouinii). Yellow-legged gull is a large gull very common in the Iberian Peninsula. It is an omnivorous and opportunistic species. Audouin's gull is endemic of the Mediterranean region. Few years ago it was endangered but the great population growth made to be considered now as "nearly threatened" species. It is a piscivorous species but it is increasingly exploiting more fishery discards and continental preys. In the first study there are determined 6 families of organic pollutants considered by the Stockholm Convention (PCDD/Fs, PBDEs, PCBs, OCs, PFASs and SCCP) in eggs of the two gull species from the Ebro Delta Natural Park. In the following studies, the analyses are based on the study of PFASs in eggs and blood of both gull species and from different colonies of the Iberian Peninsula (Ebro Delta, Medes Islands, Columbretes Islands, Dragonera Island, Grosa Island, Chafarinas Islands, Atlantic Islands of Galicia and Berlengas Islands). From PFASs levels found in the different matrices the effect of these pollutants on physical (biometric parameters of egg, shell thickness and desiccation index) and hormonal level (through the analysis of the steroid hormones: testosterone and 17ß-estradiol) is studied. It is also assessed the accumulation of these pollutants from the diet of both species (analyzing their own food and through the study of the stable isotopes d13C and d15N, as dietary tracers) and it is estimated the PFASs depuration in blood and its transfer from females to eggs. The results indicate that organic pollutants are present in the populations of yellow-legged and Audouin's gull breeding in the Iberian Peninsula colonies, being OCs and PCBs the families of compounds with higher concentrations. Among PFASs, the main compound detected in all samples was PFOS. The transfer of organic contaminants from mother to offspring is demonstrated with the levels found in eggs of both species. Analysis of PFASs in blood of males and females shows that females discharge a fraction of the compounds accumulated to the eggs, thus females had lower blood PFASs levels than males. However, the study of hormonal level allows the comparison between the levels in both gull species and with other studies and to discuss the influence of the different diet. The analysis of PFASs in albumen and egg suggests that these compounds have more affinity for egg-yolk lipids because they are not detected in albumen. The decreasing concentration of PFOS along the egg sequence shows that females PFOS transfer is higher in the first egg but there is also a good correlation between the levels of PFOS among the 3 eggs from the same clutch. The higher concentrations of some PFASs in 3rd eggs (c), comparing with 1st (a) and 2nd (b), and the differences in d13C values between the a-b and b-c eggs are attributed to the "mother effect". This thesis permits increase the knowledge about the accumulation of POPs in yellow-legged and Audouin's gull from the Iberian Peninsula, to evaluate the differences between the two species and determine the geographical distribution of POPs using eggs as a biomarker of environmental contamination and to study the processes of accumulation and transfer of PFAS / Les zones costaneres són unes àrees molt sensibles a la contaminació degut a la interacció entre els processos marins i antropogènics. Els emissaris submarins, les desembocadures dels rius, les activitats portuàries, l’abocament de residus, l’aqüicultura, etc. Són algunes de les activitats que poden produir la contaminació de les zones costaneres. Entre d’altres tipus de contaminants, es troben els contaminants orgànics persistents (COPs), aquells compostos orgànics que, en diferent grau, presenten resistència a la fotòlisis, la degradació química i la biològica. Degut a les seves característiques fisico-químiques, els COPs estan distribuïts per tot el món, podent trobar-se fins i tot en zones prístines molt allunyades de la seva font d’emissió original. Aquests contaminants tendeixen a bioacumular-se al llarg de les cadenes tròfiques, de manera que els grans depredadors són més sensibles a aquesta contaminació. Les aus marines estan molt exposades als contaminants orgànics degut als seus hàbits alimentaris i a la seva esperança de vida relativament llarga. En aquesta tesi s’ha estudiat l’acumulació de vàries famílies de contaminants orgànics en dues espècies de gavina de la Península Ibèrica, el gavià argentat (Larus michahellis) i la gavina corsa (L. audouinii). El gavià argentat és una gavina de grans dimensions molt comuna a la Península Ibèrica. És una espècie omnívora i oportunista. S’alimenta tant de recursos marins, com terrestres, com depredant sobre altres aus i també freqüenta abocadors i descarts pesquers. La gavina corsa és una gavina de dimensions mitjanes, endèmica de la regió mediterrània. Fa uns anys estava en situació de risc però el fort creixement poblacional de les últimes dècades l’ha deixat fora de perill sent considerada actualment a nivell internacional com a “quasi amenaçada”. És una espècie piscívora però cada vegada explota més descarts pesquers. En el primer estudi s’analitzen 6 famílies de contaminants orgànics inclosos o sota consideració pel Conveni d’Estocolm (els PCDD/Fs, PBDEs, PCBs, OCs, PFASs i SCCPs) en els ous de les dues espècies de gavina de les respectives colònies del Parc Natural del Delta de l’Ebre. A partir d’aquí els següents treballs es basen en l’estudi de la família dels PFASs en sang i ous d’ambdues espècies i pertanyents a diferents colònies de la Península Ibèrica (Delta de l’Ebre, Illes Medes, Illes Columbretes, Illa de Sa Dragonera, Illa Grosa, Illes Chafarinas, Illes Atlàntiques de Galicia i Ilhas Berlengas), totes en zones d’alt interès ecològic i sota alguna protecció ambiental (parcs naturals, nacionals, reserves marines, reserva de la biosfera, etc.). A partir dels nivells de PFASs trobats en les diferents matrius (primers ous de la posta, clara i rovell d’ou dels 3 ous de la posta i sang d’exemplars adults) s’estudia l’efecte d’aquests contaminants a nivell físic (paràmetres biomètrics de l’ou, gruix de la closca i índex de dessecació) i hormonal (via l’anàlisi de les hormones esteroidees 17β-estadiol i testosterona). S’estudia també l’acumulació d’aquests contaminants a partir de la dieta (analitzant el seu propi aliment i a partir de l’estudi dels isòtops estables de carboni i nitrogen (δ13C i δ15N), indicadors del règim alimentari) i es fa una estima de la depuració dels PFASs en sang i de la seva transferència de femelles a ous. Els resultats indiquen que els contaminants orgànics són presents en les poblacions de gavià argentat i gavina corsa de la Península Ibèrica, sent els OCs i els PCBs les famílies de compostos amb concentracions més elevades. Entre els PFASs, el compost majoritari és el PFOS. La transferència de contaminants orgànics de mares a cries queda demostrada amb els nivells trobats en els ous d’ambdues espècies. De l’anàlisi de PFASs en sang de mascles i femelles de les dues espècies de gavina s’observa que les femelles descarreguen part dels compostos acumulats als ous presentant així nivells en sang inferior que els mascles. No es troba cap relació entre els nivells de PFASs i els paràmetres biomètrics, com tampoc amb els nivells d’esteroides. Tanmateix, l’estudi de les hormones permet comparar els nivells en ambdues espècies amb altres estudis i discutir la influència de la dieta. L’anàlisi de PFASs en clara i rovell d’ou per separat dels 3 ous de les postes de gavina corsa demostren que aquests compostos tenen més afinitat pels lípids del rovell ja que no es detecten en les clares. La concentració decreixent de PFOS al llarg de la seqüència de posta demostra que les femelles descarreguen la majoria de contaminant en el primer ou però que existeix una bona correlació dels nivells de PFOS entre els 3 ous d’un mateix niu. L’augment de les concentracions d’alguns PFASs en el 3r ou i les diferències en els valors de δ13C entre el 1r-3r i 2n-3r ou s’atribueixen a l’anomenat “efecte mare” (possible ús de reserves endògenes per a la formació de l’últim ou enlloc de l’energia aportada per la dieta prèvia a la posta). Aquesta tesi permet augmentar el coneixement sobre l’acumulació de COPs en el gavià argentat i la gavina corsa de la Península Ibèrica, avaluar les diferències entre ambdues espècies i associar-ho a la seva biologia, determinar la distribució geogràfica de COPs utilitzant els ous com a bioindicador de contaminació ambiental i estudiar els processos d’acumulació i transferència de PFASs.

En el presente trabajo se han diseñado, sintetizado y caracterizado catalizadores heterogéneos. Se ha estudiado la actividad y selectividad, de estos materiales, en el tratamiento de compuestos que comportan problemas medioambientales. Para la preparación de los catalizadores se han utilizado diferentes técnicas tales como impregnación, proceso redox y combustión. A su vez, se han sintetizado nanopartículas metálicas, depositándolas en diferentes materiales y testado su actividad catalítica. La actividad de estos catalizadores se ha comparado con catalizadores comunes en diferentes procesos. Por otro lado, se han utilizado diferentes materiales, alumina, carbón activo, ceria e hidrotalcitas, con el propósito de estudiar el efecto del soporte.La contaminación por nitratos en las aguas subterráneas es un problema importante en determinadas regiones. Esta problemática ha impulsado el estudio de la eliminación catalítica de los nitratos, en la que se enfoca la primera parte de la tesis. Este estudio se realizó en un reactor en continuo de lecho fijo. Se sintetizaron, caracterizaron y ensayaron, varios catalizadores monometálicos, bimetálicos y de nanopartículas soportadas. Una vez determinada la actividad y la estabilidad de los catalizadores se procedió a optimizar los materiales con el fin de mejorar la selectividad de éstos hacia nitrógeno. El presente trabajo ha sido el punto de partida para la puesta en marcha de una planta piloto para el tratamiento de aguas subterráneas reales contaminadas con nitratos. Próximamente será inaugurada una planta de eliminación catalítica de nitratos de aguas subterráneas con capacidad 500m3/día en las proximidades de El Morell (Tarragona).La segunda parte de la tesis se enfoca en el proceso de hidrodecloración catalítica de compuestos orgánicos clorados como el tricloroetileno. Los experimentos se llevaron a cabo en fase gas utilizando diferentes tipos de catalizadores, los cuales fueron sintetizados y caracterizados. Se emplearon diferentes catalizadores, mono y bimetálicos, para la transformación del tricloroetileno a un producto de valor añadido, como es el etileno.El presente trabajo, además de aportar conocimientos fundamentales en la catálisis heterogénea, contribuye a forjar soluciones a problemas medioambientales reales que afectan a la salud humana. / In the present study have been designed, synthesised and characterised heterogeneous catalysts. Their activities and selectivity have been studied in the treatment of compounds that present environmental problems. For the catalysts preparation different protocols such as incipient-wetness impregnation, co-impregnation, redox and combustion have been followed. In addition, metal nanoparticles were synthesized and deposited on several materials as well as tested their catalytic behaviour. The activity and the selectivity of nanoparticle catalysts with that of other catalysts in different processes were compared. On the other hand, different materials such as alumina, active carbon, ceria and hydrotalcites were used to study the role of them as catalyst supports.In the light of the current demand for drinking water, the first part of this thesis studies the catalytic hydrogenation of nitrates. The study is carried out in a fixed bed continuous reactor. Several bimetallic, monometallic and supported nanoparticle catalysts have been synthesised, characterized and tested in order to improve their activity and stability and to optimise their selectivity to nitrogen. The present study was further extended and some of the catalysts have been used as a starting point for a Pilot Plant investigation into eliminating nitrate in real ground water. At this moment, a plant is being constructed in the vicinity of El Morell, Tarragona, which can use catalysis to reduce nitrates in 500 m3/day of groundwater.The second part of the thesis deals with the catalytic hydrodechlorination of chlorinated organic compounds such as TCE. The experiments were done in gas phase. Different types of catalysts have been synthesised, characterized and tested and the final objective is to obtain an active and stable catalyst that is selective toward valuable products such as ethylene. This research aims to use catalytic technologies to contribute to solving real environmental problems that affect human life.

Tesi realitzada al Centre de Projecció Tèrmica - Universitat de Barcelona / The main subject of this Thesis is the production of hard, wear and corrosion resistant cermets tungsten carbide and cobalt cermets (WC-Co) with different contents in cobalt matrix, onto low carbon steels and aluminum alloy Al7075-T6 substrates, by means of Cold Gas Spray (CGS). The current state of the art for the deposition of WC-Co uses High Velocity Oxy-Fuel (HVOF) as the main technique. Understanding both techniques was also one of the keys points in this work. A deep theoretical approach about the CGS process, in which no melting of the particles occurs, was made at first to gain a better comprehension about the behaviour of the powder particles when sprayed onto different substrates and therefore being able to produce good quality coatings. The starting purpose of this doctoral Thesis was to produce WC-25, 17 and 12%Co coatings onto low carbon steel and Al7075-T6 substrates. Until the day, using nitrogen as the process gas, such coatings could not be produced with enough adhesion, thickness and wear and corrosion properties. These are the main characteristics sought by the industry in these coatings. In the end of this doctorate WC-Co coatings were obtained with excellent mechanical and electrochemical properties, adhesion to both low carbon steel and Al7075-T6 substrates. Besides, these properties were increased and improved when compared to the same WC-Co coatings obtained by HVOF conventional deposition technique. Initial problems such as flowability of the powders, bad adherence to the substrate, poor coating quality and extremely low deposition efficiencies were resolved during the period of the Thesis. Also, and taking advantage of the novel coatings and excellent properties obtained using the referred feedstock powders and substrates, the knowledge was transferred to the industry as a trade secret. / En primer lugar, el objetivo principal de este trabajo de investigación fue proporcionar un nuevo método de deposición para depositar cermets de WC-Co. Esta nueva tecnología proporcionó nuevos recubrimientos sin ninguna descomposición de la microestructura del polvo inicial y por lo tanto la mejora de las presentes aplicaciones de WC-Co en la gran industria. La deposición de cermets de WC-Co resistentes al desgaste ha sido siempre una de las principales aplicaciones de las técnicas de proyección térmica convencionales como por ejemplo High Velocity Oxy-Fuel (HVOF). Las demandas de la industria en términos de producción y la necesidad y constante búsqueda de mejores propiedades mecánicas y electroquímicas conducen al objetivo principal y la motivación de esta tesis: la producción de nuevos y mejores recubrimientos de WC-Co sobre varios sustratos utilizando una técnica de deposición nueva, Cold Gas Spraying (CGS). El hecho de que antes de la publicación del primer artículo que nació de este trabajo de investigación no se había depositado previamente con éxito este tipo de materiales por CGS fue también uno de los principales puntos de motivación. Por esta razón, el lector encontrará, en la integridad del documento, los trabajos de investigación que fueron publicados durante estos años de programa de doctorado y cumplen los objetivos principales de esta tesis titulada "Deposición de cermets de WC-Co por Proyección Fría".

The presence of volatile fragrant molecules is generally associated with a feeling of pleasantness or cleanness in consumer products. Because of their high volatilities, the perception of fragrances is limited over time. Therefore, various delivery systems have been developed by the industry to control and extend the release of volatile ingredients by diffusion and also to protect active molecules against degradation. A promising encapsulation technique is the formation of capsules with tunable permeability, so-called colloidosomes. These are generally formed by locking the nanoparticles at the interface of a Pickering emulsion. However, there are very few articles concerning colloidosomes stabilized by covalent cross-linking. In addition, although Pickering emulsions have been known for over a century, the range of nanoparticles used to stabilize emulsions has been limited to silica, clays, polystyrene, polyacrylate latexes or metallic nanoparticles. Within the aim to apply colloidosomes or Pickering emulsions as delivery systems, the use of biodegradable and biocompatible polymeric nanoparticles such as polyester nanoparticles is of major interest. Polyester nanoparticles are solid colloidal particles with sizes generally between 20 and 500 nm that can be prepared in colloidal systems by polymerization of monomers in nano-emulsions which act as template for the nanoparticle formation. Nano-emulsions are emulsions with extremely small droplet size, typically in the range of 20-500 nm. Due to their small droplet size, nano-emulsions are transparent and present a better stability against gravitational separation than conventional emulsions. Nano-emulsions can be prepared by low-energy methods taking advantage of the internal energy of the system components which is released during the emulsification process. Despite the large number of articles describing the polymerization of monomers in nano-emulsions, only few articles refer to this process in nano-emulsions obtained by low-energy methods (Spernath, 2007). Therefore, studies on the preparation of polymeric nanoparticles from nano-emulsion droplets obtained by low-energy methods are of great interest. Concerning in-situ polymerization of monomers in nano-emulsions, many types of reactions have been reported generally requiring harsh conditions (low pH, toxic initiator, high temperature) to obtain polymers with acceptable yield and molecular weight. A research effort is needed to obtain polyester nanoparticles by polymerization under mild conditions. The global objective of this research work was the design, characterization and applications of polyester nanoparticles obtained by polymerization in mild conditions of monomer-in-water nano-emulsions obtained by low-energy methods. In a first step, bluish transparent lactone-in-water nano-emulsions are formed using either the PIT or the PIC methods at various O/S ratios and high water content. Nano-emulsions presented a good stability at room temperature and at 45ºC to carry out the polymerization in the droplet of the nano-emulsions. The formation of polyester nanoparticles was achieved by ring-opening polymerization of a lactone at 45ºC in nano-emulsions obtained by low-energy methods. The properties of the obtained nanoparticles such as size or crystallinity were optimized by varying the composition of the nano-emulsions template and/or the reaction parameters. Furthermore, the functionalization of the nanoparticles was confirmed by synthesizing nanoparticles by ring-opening polymerization of a hydroxy functionalized monomer or by copolymerization of two lactone monomers thereby controlling the degree of functionalization. The stabilization of emulsions of perfume-in-water by polyesters nanoparticles was investigated. Parameters such as the wettability of the nanoparticles, the concentration of nanoparticles, the ratio of each phase as well as the addition of electrolytes were studied These emulsions have been used as controlled release systems for model fragrance, but could not effectively control the release. Furthermore, in order to avoid the rapid evaporation of the perfume, the nanoparticles at the oil/water Pickering emulsions interface were covalently cross-linked leading to the formation of core-shell microcapsules, allowing the controlled release of perfume. / En la presente tesis, se ha estudiado la formación de nanopartículas de poliésteres por polimerización por apertura de anillo de una lactona (catalizada por enzima y baja temperatura) usando nano-emulsiones obtenidas por métodos de baja energía. Se han optimizado las propiedades de las nanopartículas obtenidas tales como el tamaño o la cristalinidad mediante la variación de la composición de las nano-emulsiones plantilla y/o de los parámetros de reacción. Además, se ha confirmado la posibilidad de funcionalizar las nanopartículas mediante la adición de un grupo hidroxilo en su estructura o mediante la copolimerización de monómeros cíclicos controlando así el grado de funcionalización. Se ha estudiado también la estabilización de emulsiones de Pickering de un perfume-en-agua por las nanopartículas de poliésteres. Se han utilizado estas emulsiones como sistemas de liberación controlada de una fragancia modelo, pero no se pudo controlar eficientemente su liberación. Asimismo, con el objetivo de evitar la rápida evaporación del perfume, se han reticulado covalentemente las nanopartículas en la interfase aceite/agua de las emulsiones de Pickering conduciendo a la formación de microcápsulas con estructura núcleo-coraza, permitiendo un mayor control de la liberación de perfume.

Tesi realitzada a l'Institut de Diagnosi Ambiental i Estudis de l'Aigua (IDAEA-CSIC) / This Thesis deals with the resolution of hyperspectral imaging data by using chemometric methods, in particular by using appropriate data pretreatment methods and by using Multivariate Curve Resolution (MCR) methods. The main contribution of the present Thesis is the study and implementation of the MCR-ALS (Multivariate Curve Resolution Alternating Least Squares) method for the resolution of hyperspectral images, collected by remote sensing (airborne or space borne Earth observation instrument) and by micro-spectroscopy imaging. Specifically, in this Thesis work, we explore the combination of chemometric and hyperspectral imaging methods for the resolution of spectra (signatures) and spatial distribution maps of the chemical constituents of a sample. The ultimate goal of this study is to improve the analysis and interpretation of hyperspectral imaging data by taking advantage of different chemometric powerful tools. Local rank/selectivity properties describing the spatial information of spectroscopic images can be used as a constraint to increase the performance of MCR methods significantly, decreasing rotation ambiguity uncertainties. Different multivariate resolution methods were compared, such as MCR-ALS, Principal Component Analysis (PCA), and Minimum Volume Simplex Analysis (MVSA), Multivariate Curve Resolution-Function Minimization (MCR-FMIN), MCR-BANDS and FAC-PACK. All these approaches have been used for the evaluation of the extension of rotation ambiguities remaining in the results after their application. Several hyperspectral images provided by standard and widely used instruments such as NASA’s Airborne Visible Infra-Red Imaging Spectrometer (AVIRIS), Raman hyperspectral imaging Spectrometer, and Infrared hyperspectral imaging Spectrometer have been used as example of data sets to test the different methods, in particular to test the MCR-ALS method. The results obtained in this Thesis show that MCR-ALS method can be successfully used for hyperspectral image resolution purposes. The spectra signatures of the pure constituents present in hyperspectral images and their concentration distribution at a pixel level can be estimated. Constituents identification can be performed using the resolved pure spectra signatures and comparing them to reference spectra from spectral libraries or from experimental spectra of reference samples. Application of image data pretreatment methods reduce significantly the presence of strong fluorescence background in Raman hyperspectral images. In contrast, infrared hyperspectral imaging is not affected by fluorescence. Kramers-Kronig transform enables to calculate absorption spectra in case only reflectance spectra can be measured for infrared spectra. The extent of rotation ambiguity associated to MCR-ALS and other resolution methods can be rather high when they are applied for hyperspectral image resolution with high noise. The correct resolution of hyperspectral images can only be guaranteed if additional constraints are applied, such as those providing information about the local rank properties of the image, i.e. about the presence or absence of the different constituents (components) in the image pixels. Only in this way it is possible to increase the reliability of the solutions provided by MCR methods and decrease the uncertainties associated to them. Appropriate use of local rank and selectivity constraints can improve significantly the quality of the pure spectra (signatures) and of the constituent distribution maps resolved by MCR-ALS analysis of hyperspectral images in remote sensing studies. Use of correlation coefficients between selected spectra and image pixel spectra is shown to provide an alternative way for the application of the selectivity constraint in hyperspectral images for the first time. This alternative method resulted to be satisfactory when pure pixels exist. MCR-BANDS method can be used to get estimations of the extension of rotation ambiguities in MCR resolved results. The Area of Feasible Solutions represents feasible solutions geometrically. The range of rotation ambiguity calculated by MCR-BANDS and AFS are in agreement. MCR-ALS with the trilinearity constraint is an effective way to characterize and resolve Excitation-Emission Matrix fluorescence spectra (EEM). / Esta Tesis trata de la resolución de datos de imágenes hiperespectrales utilizando métodos quimiométricos, en particular mediante el uso de métodos de pretratamiento de datos y utilizando métodos de resolución multivariante de curvas (MCR). La principal contribución de la presente Tesis es el estudio y la aplicación del método MCR-ALS (resolución multivariante de curvas mediante mínimos cuadrados alternados) para la resolución de imágenes hiperespectrales, adquiridas mediante técnicas de teledetección y mediante técnicas de micro-espectroscopia. Específicamente, en el trabajo de esta Tesis, se explora la combinación de los métodos quimiométricos y de los métodos de análisis de imágenes hiperespectrales, para la resolución de los espectros (firmas) y de los mapas de distribución de los componentes químicos de la muestra. El objetivo final de este estudio es mejorar el análisis y la interpretación de los datos de imágenes hiperespectrales mediante el aprovechamiento de diferentes herramientas quimiométricas poderosas. La detección del rango local y las propiedades de selectividad que describen la información espacial de los componentes presentes en las imágenes espectroscópicas. Se han comparado diferentes métodos de resolución, tales como MCR-ALS, MVSA (Mínimo Volumen Simplex Análisis), PCA (Análisis de Componentes Principales), y MCR-FMIN. Los métodos MCR-BANDS y FAC-PACK se han utilizado para la evaluación de la extensión de las ambigüedades rotacionales existentes en los resultados después de la aplicación de estos métodos de resolución multivariante. En esta Tesis se han analizado diversos conjuntos de datos compuestos por varias imágenes hiperespectrales proporcionadas por instrumentos estándar tales como el espectrómetro de imágenes hiperespectrales en el visible y en el infrarrojo AVIRIS de la NASA, y diversos espectrómetros de imágenes hiperespectrales Raman y infrarrojo de laboratorio. La eficacia del procedimiento MCR-ALS se ilustra proporcionando comparaciones exhaustivas con otros métodos de resolución de mezclas espectrales a partir de conjuntos de datos hiperespectrales simulados y reales.

En esta tesis doctoral se combinan técnicas estadísticas y el uso de sistemas de información geográfica para modelizar y representar algunas propiedades de la capa arable de los suelos de la Región de Murcia que tienen relación con su capacidad de almacenamiento de humedad. El primer objetivo es elaborar modelos a escala regional que permitan predecir el contenido de diversos constituyentes del suelo (carbono orgánico, carbonato cálcico total o equivalente, y fracciones granulométricas), representando cartográficamente el resultado de los modelos obtenidos. El segundo objetivo es la obtención de modelos que permitan predecir las mismas variables a escala local, para compararlos con los modelos obtenidos anteriormente a escala regional y analizar las diferencias entre ellos. El tercer objetivo es validar funciones de transferencia obtenidas en una revisión bibliográfica para la estimación de las propiedades hídricas de los suelos (densidad aparente, contenido de agua a capacidad de campo y en el punto de marchitamiento), y comparar su desempeño con nuevas funciones de edafotransferencia calibradas con los datos disponibles para los suelos de la región de Murcia. Las fuentes de información utilizadas para la predicción de las propiedades físico-químicas fueron tres bases de datos de suelos; el Modelo digital de elevaciones (MDE) con una resolución de 25 m; datos climáticos procedentes de 625 estaciones climáticas; el mapa de usos y coberturas de suelo de CORINE Land Cover de 1990, y el mapa digitalizado de suelos elaborado por la CARM. Estos datos fueron analizados con el programa estadístico R y los sistemas de información geográfica GRASS y SAGA, obteniendo un total de 181 variables, posteriormente estandarizadas. De ellas, se han eliminado las que presentaban un alto grado de colinealidad usando el método del Factor de Inflación de la Varianza. Para la obtención de los modelos, se ha utilizado un método de regresión-krigeado, en el cual la tendencia fue ajustada utilizando diferentes técnicas paramétricas y no paramétricas, y los residuos mediante técnicas de krigeado. Se elaboraron 11 modelos con el programa estadístico R para cada una de las variables estudiadas, utilizando un sistema de validación cruzada con 5 bloques: los cuatro primeros se utilizaron para la calibración y el último para la validación. El ajuste a los datos observados se expresó a través de la correlación y el valor de RMSE. Los modelos a escala regional elaborados, a pesar de no ser capaces de reflejar toda la variabilidad espacial mostrada por las propiedades seleccionadas, sirven para estimar sus valores medios. En todos los modelos a escala regional, el método de Random Forest con validación cruzada en bloques fue el que mejor resultado proporcionó, incluyendo mayoritariamente variables climáticas, los tipos de suelos y coberturas y algunas variables geomorfométricas. El contenido de carbono orgánico y carbonato cálcico los que obtienen un mejor resultado y una mejor estructura espacial de los residuos, que pudieron interpolarse con Krigeado ordinario, mientras que las fracciones granulométricas obtuvieron modelos con mayores valores de error y menores correlaciones y la estructura espacial de los residuos es peor. En el caso de los modelos a escala local, no se produce un aumento de la capacidad predictiva. De las funciones de edafotransferencia obtenidas en la revisión bibliográfica, la que mejor resultado proporciona para las tres variables hídricas estudiadas fue la de Barahona y Santos (1981). El uso de los datos disponibles para calibrar nuevas funciones no mejora el resultado. A pesar de la propagacion de errores en los mapas de variables físicoquímicas, se considera que los mapas de variables hídricas ofrecen una estimación satisfactoria de estas propiedades edáficas. / This PhD Thesis combines statistical techniques and the use of Geographic Information Systems to model and map some water storage capacity features of the soil arable layer in the Region of Murcia. The first objective involves regional scale models to predict and map the amount of several soil components (organic carbon, total or equivalent calcium carbonate and texture fractions). The second objective is to obtain models to predict the same soil properties at a local scale, in order to compare them with the models obtained at the regional scale and to analyse the differences between them. The third objective is to validate pedotransfer functions from the literature for the estimation of hydrological properties of the soil (bulk density, soil water content at field capacity and permanent wilting point), and to compare their accuracy with new pedotransfer functions calibrated with the soil data available for the Region of Murcia. The information sources used for the prediction of the physical-chemical soil properties were three soil data surveys; the Digital Terrain Model (DTM) at a 25m resolution; climatic data from 625 weather stations; the CORINE Land Cover map from 1990, and the map of soil classes digitalized by the Region of Murcia Autonomous Community (CARM). These data were analysed using the statistical software R and the geographic information systems GRASS and SAGA, obtaining 181 variables that were subsequently standarized. Afterward, those showing a higher collinearity were removed using the Variance Inflation Factor method. In order to obtain the predictive models, a regression-kriging method was selected, in which the trend was adjusted using different parametric and non-parametric techniques, and the residuals were interpolated using ordinary kriging. For each selected soil component, 11 models were tested using different packages of R. A 5-Fold-Cross-Validation method was used, in which the first 4 blocks worked as calibration set, and the last fifth block worked as validation set. The goodness of fit of each model was measured through the correlation between measured and predicted values and the value of RMSE. The models performed at the regional scale are useful to estimate the mean values of the selected soil properties, although they are not able to explain all the spatial variability of the selected properties. In all of them, the Random Forest method with 5-Fold-Cross-Validation was the technique that obtained better results, including mainly climatic predictors, soil classes and covers, and some morphometric features. The highest goodness of fit and the best spatial structure of the residuals were obtained for Soil Organic Carbon and total calcium carbonate contents. On the other hand, The models for the texture fractions obtained lower correlations, higher error values and also a worst spatial structure of the residuals. The accuracy of the models at the local scale was no better than at the regional scale. Regarding the pedotransfer functions obtained from the literature, the best results for the three hydrological properties were obtained with the Barahona and Santos (1981) equation. The use of the available data to calibrate new pedotransfer functions did not improve these results. Notwithstanding the error propagated from the maps of physical-chemical soil parameters, it can be considered that the maps of the hydrological soil properties provide a good estimation of these edaphic attributes.

Di-n-butyl ether (DNBE) is considered a very attractive oxygenate compound to reformulate diesel fuel. The research work performed along this thesis has clearly proven that sulfonic P(S-DVB) ion exchange resins are suitable catalysts for the synthesis of DNBE from the liquid phase dehydration of 1-butanol at the temperature range of 140-190 °C. A catalyst screening of acidic P(S-DVB) ion exchange resins showed that resins activity is enhanced with high acid capacities and with polymer matrices that are able to swell moderately allowing 1-butanol ready access to the active sites but without resulting in very large distance between the active centers. The resin Amberlyst 36 (oversulfonated, medium values of %DVB) proved to be the most active catalysts tested. However, in an industrial process a high selectivity to DNBE is extremely desirable from an environmental and economic standpoint, and resins that present a more elastic polymer matrix and higher ability to swell (gel type resins and Amberlyst 70) are the ones that present higher selectivities. Among all the tested resins, Amberlyst 70 was selected as the most suitable catalyst for industrial use given its excellent property balance: satisfactory activity, high selectivity to DNBE and thermal stability up to 463 K. The relatively large value found for the thermodynamic equilibrium constant of DNBE formation and the fact that the formation of the secondary product 1-butene was extremely slow assure high conversion levels in an industrial etherification process. DNBE formation proved to be a slightly exothermic reaction, almost athermic, whereas 1-butene formation was found to be an endothermic reaction. A comprehensive kinetic analysis enlightened that the reaction rate to form DNBE on Amberlyst 70 is highly influenced by the temperature and the presence of water. Two kinetic models that are able to predict the reaction rates of DNBE formation were identified. One of them stems from a Langmuir-Hinshelwood-Hougen-Watson (LHHW) formalism in which two adsorbed molecules of 1-butanol react to yield ether and water, being the reversible surface reaction the rate limiting step. The other one stems from a mechanism in which the rate limiting step is the desorption of water and where the adsorption of DNBE is negligible. Both models present several characteristics in common: in both water inhibition effect is correctly represented by a correction factor derived from a Freundlich adsorption isotherm; the number of free active sites is found to be negligible compared to the occupied ones; both present similar values of apparent activation energies (122 ± 2 kJ/mol). The study of the influence of typical 1-butanol impurities (isobutanol or ethanol and acetone, depending on the production process) demonstrated that isobutanol enhances the formation of branched ethers whereas ethanol leads to the formation of ethyl butyl ether and di- ethyl ether and acetone hardly reacts. In the second part of this thesis, it was demonstrated the suitability of molecular dynamics simulations in the understanding of the microscopic structure of P(S-DVB) ion-exchange resins and the prediction of their properties. Atomistic simulations of the structure of sulfonated P(S-DVB) resins reveled the decisive role that internal loops (closed polymer chains) play in defining the properties (i.e. density, porosity and structures) of highly cross-linked resins. Thus, although crosslinks ensure the local backbone structure, internal loops confer rigidity and loop architecture. It was also demonstrated that the developed atomistic model is able to predict the swelling behavior of ion-exchange resins in 1-butanol. From the swelling study performed by means of molecular dynamic simulation it was possible to characterize and quantify the structure of the swollen polymeric network at molecular level and to conclude that alcohol molecules tend to interact with the sulfonic groups of the resin.