Metals and valuable metal compounds are important parts of our everyday lives with applications ranging from aluminum foil over circuit boards to high-performance alloys for engineering and buildings construction. Large-scale metal production processes provide access to metals contained in numerous naturally occurring ores, earths and minerals and should be considered one of the major drivers of industrialization, leading to a continuous increase in living standards. Thereby, metals are often present in the form of oxides or other compounds of low reactivity and high stability. This makes metal extraction an often energy-intensive, environmentally problematic endeavor, relying on high reaction temperatures around 1000 °C or aggressive, corrosive and toxic chemicals. A disruptive, new approach for more sustainable metal production could be ionometallurgy, i.e., metal extraction by means of ionic liquids (ILs) and deep eutectic solvents (DESs). ILs, per definition, are salts with a melting point below 100 °C, while DESs are eutectic mixtures of two or more reagents with a melting point below that of the individual components. Both classes of materials feature favorable properties, such as a good solubility for many inorganic salts. Ionometallurgy is a seemingly simple approach, dissolving metal oxides at moderate temperature in an IL or DES and subsequently either electrodepositing the respective metal or producing valuable metal compounds by downstream chemistry. This thesis elucidated the general feasibility of the direct ionometallurgical metal production from metal oxides in two betaine-based solvents, namely the IL betainium bis(trifluoromethylsulfonyl)imide ([Hbet][NTf2]) and a DES consisting of betaine hydrochloride, urea and glycerol in the molar ratio 1 : 4 : 2.5 ([Hbet]Cl/4U/2.5GLY). Initial solubility studies involved a broad screening of the reaction behavior of numerous metal oxides with different properties regarding the position of the metal in the periodic table, its oxidation state as well as the basicity of the oxide. Exploiting the Brønsted-acidic functional group of the betainium cation, metal oxide dissolution in this case follows the principle of an acid-base reaction. Correspondingly, [Hbet][NTf2] favors the dissolution of basic or amphoteric metal oxides, while acidic metal oxides remain unaffected. In-depth investigations were performed for the examples of copper, cobalt and aluminum and identified the metal oxide lattice energy, the crystal structure and the reaction temperature as well as complex stabilities of the metal ions as additional factors to influence the solubility. How additives can affect the reaction outcome in multiple ways was shown for the example of chloride. In the copper system, small amounts of chloride act catalytically, while larger concentrations not only decrease the reaction time but also exhibit a structure-directing effect. For cobalt oxides, chloride is assumed to be reaction-driving due to the high chloride affinity of cobalt(II). These results were supported by seven new crystal structures found in the course of these investigations. Thereby, for the first time, metal oxide dissolution in [Hbet][NTf2] was systematically investigated under water-poor conditions. Abstaining from aqueous IL solutions, although water was shown to promote metal oxide dissolution, enables access to several metals via electrodeposition. This is facilitated by the large electrochemical windows of [Hbet][NTf2] and [Hbet]Cl/4U/2.5GLY, amounting to −2.0–1.4 V and −2.3–0.9 V, respectively. Copper, cobalt, nickel, tin, lead, zinc, and small amounts of vanadium were shown to be electrochemically reducible, whereas manganese, molybdenum and aluminum could not be electrodeposited within the electrochemical stability range of the IL or DES. For the deposition of the noble metal copper, the chloride content, the deposition temperature and additional organic solvents were identified as crucial parameters for the deposition potential as well as the quality of the deposit. By copper-coating a steel plate, a potentially industrially relevant application was demonstrated. Compared to the conventional industrial process for copper production, this ionometallurgical approach could imply a significant simplification and proceed at much lower reaction temperatures. Starting from tenorite or oxidic copper waste, copper coatings could directly be producible avoiding multiple process steps. Furthermore, the cobalt system revealed, that the thorough understanding of the complex equilibria present in solution is crucial for the successful electrodeposition of the metal. Thus, no deposits were obtained when anionic [CoCl4]2– was the predominant cobalt complex species. The adjustment of the cobalt-to-chloride ratio is a suitable method to generate sufficient amounts of cationic cobalt complexes, allowing for the deposition of the metal. Overall, several metals were directly produced from their oxides by the ionometallurgical approach at temperatures below 175 ℃. This means a significant temperature reduction compared to the conventional processes. Encouragingly, [Hbet][NTf2] already showed first promising results when applied to industrially relevant starting materials, such as black mass for the recycling of lithium ion batteries or bauxite as a highly relevant, naturally occurring aluminum resource. While this qualifies ionometallurgy in principle as a considerable improvement regarding process sustainability, the impact of [Hbet][NTf2] and [Hbet]Cl/4U/2.5GLY was analyzed in more depth. Thereby, the recyclability of the solvents is considered a very important factor for the efficient implementation of ionometallurgy in larger scale. First experiments in a two-compartment electrochemical cell showed that metals can be electrodeposited cathodically with a tailorable anode reaction. The oxygen evolution reaction in an aqueous electrolyte proved as suitable benign oxidation reaction in the anode half cell. The intactness of [Hbet][NTf2] after metal electrodeposition in this set-up was evidenced by NMR spectroscopy, qualifying the IL for reuse in principle. As opposed to this, decomposition reactions were identified to take place in both the IL and the DES. At 175 °C, [Hbet][NTf2] undergoes the chloride-induced decomposition via a Hunsdieker and a Deacon reaction, which is avoidable by a lower reaction temperature of 150 °C. NMR studies suggest that [Hbet][NTf2] does not decompose during the ionometallurgical process at this temperature. However, in the case of [Hbet]Cl/4U/2.5GLY, NMR and mass spectrometric studies proved the degradation via several decomposition pathways at 60 °C already. These decomposition reactions change the composition of the DES, which also affects the solubility of metal oxides. The thermal and chemical stability of [Hbet][NTf2] and [Hbet]Cl/4U/2.5GLY, besides other factors, have direct implications for their consideration as green solvents. Thus, [Hbet][NTf2] should only be used at reaction temperatures below 150 °C. Furthermore, its industrial application might be impeded by the expensive and toxic [NTf2]– anion. While betaine-based solvents can be easily accessible due to the natural abundance of betaine, the synthesis effort of the [NTf2]– anion makes [Hbet][NTf2] a considerably expensive IL. [Hbet]Cl/4U/2.5GLY is cheaper and easier to be synthesized from naturally abundant substances, yet not a considerable option due to its decomposition at low temperature already. Its thermal and chemical instability pose hardly surmountable obstacles regarding the recycling and the toxicity of [Hbet]Cl/4U/2.5GLY. Thus, both [Hbet][NTf2] and [Hbet]Cl/4U/2.5GLY do not qualify as green solvents and more benign alternatives should be found in the future. Altogether, this thesis showed that the ionometallurgical production of metals from their oxides is possible and, moreover, could be a sustainable alternative to conventional processes. The presented investigations extend our understanding of metal oxide chemistry in ILs or DESs and provide proofs of concept, laying a foundation for further work that leaves numerous opportunities for ongoing exploration and optimization. Hence, ionometallurgy could be one step to face the urgent challenge of climate change.

Abstract Nanocellulose is a renewable, biodegradable, and easily available material that is considered as an attractive resource for many different value-added applications in the emerging bio-based economy. Its outstanding properties, such as strength, lightness, transparency, and good thermal insulation, have inspired research and product development around nanocellulose. The potential of nanocellulose to replace synthetic chemicals made from non-renewable sources, for example, is considered to be very promising. Chemical functionalization, that is, the modification of the cellulosic surface properties, is seen to be beneficial in applications such as those in which higher hydrophobicity is needed. In this thesis, the ability of cellulose nanoparticles to stabilize oil droplets in oil-in-water emulsions was studied. The aim of the study was to explore the possibility of developing a new type of "green" oil spill chemical from cellulose. Therefore, the cellulose was chemically modified in an aquatic environment with a sequential periodate oxidation and chlorite oxidation followed by reductive amination reaction, which increased the hydrophobicity of the produced nanocellulose. In addition, the use of deep-eutectic solvents in the preparation of modified (succinylated and carboxylated) and non-modified cellulose nanoparticles was studied. Chemical (kraft) pulp, dissolving pulp, and semi-chemical fine fibers were used as raw materials in this research. The results demonstrated that chemically modified cellulose nanoparticles work well as stabilizers for oil-water emulsions resulting in small, stable oil droplets and impeding creaming, which is a typical phenomenon for particle stabilized emulsions. The modification of cellulose nanoparticles improved their ability to partition at the oil-water interface, which enabled efficient and irreversible adsorption. It was found that because of their small size, the cellulose nanocrystals can be compressed more tightly onto the surface of the oil droplet, while longer and more flexible cellulose nanofibrils formed a web structure between the oil droplets. All cellulose nanoparticle-stabilized emulsions were stable against droplet coalescence, and even at low temperatures, they retained their droplet size and stability. Salinity, on the other hand, improved stability when CNCs from chemical pulp were used, but it negatively affected stability when nanocrystals from semichemical pulp were used. / Tiivistelmä Uusiutuva, biohajoava ja helposti saatavilla oleva nanoselluloosa on merkittävä tulevaisuuden raaka-aine useissa erilaisissa käyttökohteissa. Sen ylivertaiset ominaisuudet, kuten lujuus, keveys, läpinäkyvyys ja lämmöneristävyys ovat olleet innoittamassa nanoselluloosan tutkimusta ja tuotekehitystä. Nanoselluloosan mahdollisuuksia ja käyttöä eri sovelluksissa korvaamaan esimerkiksi uusiutumattomista luonnonvaroista valmistettuja kemikaaleja, pidetään erittäin lupaavina. Kemiallisesta funktionalisoinnista eli selluloosan pintaominaisuuksien muokkauksesta nähdään olevan hyötyä, kun tavoitellaan nanoselluloosan toiminnallisuutta esimerkiksi hydrofobista luonnetta vaativissa sovelluksissa pinta-aktiivisen aineen tavoin. Tässä työssä tutkittiin erityisesti nanoselluloosapartikkeleiden kykyä stabiloida öljypisaroita dieselöljy-vesiemulsioissa. Tutkimuksen päämääränä oli selvittää mahdollisuutta kehittää uudentyyppistä, ”vihreää” öljyntorjuntakemikaalia selluloosasta. Tämän vuoksi selluloosaa muokattiin kemiallisesti vesiympäristössä yhdistetyllä hapetus- ja aminointikäsittelyllä, mikä lisäsi valmistetun nanoselluloosan hydrofobisuutta. Toisena käsittelyvaihtoehtona tutkittiin syväeutektisten liuottimien käyttöä sekä muokattujen (sukkinyloidut ja karboksyloidut) että muokkaamattomien nanoselluloosapartikkeleiden  valmistuksessa. Raaka-aineina työssä käytettiin kemiallista sellumassaa, liukosellua sekä puolikemiallista hienokuitua. Työn tuloksena voidaan todeta, että nanoselluloosasta valmistetut kemiallisesti muokatut (funktionalisoidut) nanopartikkelit toimivat hyvin öljy-vesiemulsiossa estäen emulsion öljypisaroiden yhteensulautumista. Nanopartikkelit stabiloivat emulsiossa olevan öljyn hyvin pieniksi pisaroiksi hidastaen kermottumista eli emulsion yleistä faasierottumista. Nanoselluloosan funktionalisointi paransi sen kykyä hakeutua öljy-vesi rajapintaan, mahdollistaen tehokkaan ja palautumattoman adsorption. Havaittiin, että pienen kokonsa vuoksi selluloosananokiteet pystyivät pakkautumaan tiiviimmin öljyn pinnalle, kun taas selluloosananokuidut, jotka ovat pidempiä, muodostivat verkkomaisen rakenteen myös öljypisaroiden väliin. Suolan lisäys vaikutti emulsion stabiilisuuteen vaihtelevasti eri näytteiden välillä, kun taas kylmät olosuhteet poikkeuksetta paransivat stabiilisuutta.

Настоящая работа состоит из 3 глав и посвящена бесферментному количественному определению креатинина, глюкозы, мочевины с использованием медь(II)-имидазольных каркасов. В ходе работы проведено формирование электрокаталитически активного слоя на поверхности рабочего электрода. Таким образом, каталитически активный слой с наибольшей чувствительностью сформирован на печатном электроде 3-в-1 с использованием многостенных углеродных нанотрубок (cMWCNT), электроосаждённым золотом и медь(II)-имидазольного каркаса, состоящего из иона меди(II) и 2-меркаптоимидазола и 2-метилимидазола. Проведены исследования селективности полученного каталитически активного слоя. / This work consists of 3 chapters and is devoted to the enzyme-free quantitative determination of creatinine, glucose, urea using copper(II)-imidazole frameworks. In the course of the work, the formation of an electrocatalytically active layer on the surface of the working electrode was carried out. Thus, the catalytically active layer with the highest sensitivity is formed on a 3-in-1 printed electrode using multi-walled carbon nanotubes (cMWCNT) electrodeposited with gold and copper(II)-imidazole framework consisting of copper(II) ion and 2-mercaptoimidazole and 2-methylimidazole. The selectivity of the obtained catalytically active layer has been studied.

[ES] Esta Tesis Doctoral se centra en la recuperación mediante electrodeposición del Sb presente en un efluente residual proveniente de la metalurgia del cobre. El efluente en el que se basa este estudio se produce en el proceso de regeneración con HCl concentrado de las resinas de intercambio iónico de una de las subetapas del electro-refinado del cobre. Se trata de un electrolito ácido que contiene diversas impurezas, entre las que destacan, Sb y Bi, que son considerados materias primas críticas por la Unión Europea, debido al riesgo de suministro que presentan y a su importancia en la economía. El objetivo de esta Tesis es la recuperación del Sb y la reutilización del HCl. Para alcanzar ambos propósitos se ha estudiado el empleo de la electrodeposición como operación de separación para el tratamiento del efluente. Este proceso se ha investigado mediante técnicas electroquímicas, en particular, voltametría cíclica y de barrido lineal. En primer lugar, se ha realizado el estudio con disoluciones sintéticas que emulan el efluente generado en las metalurgias chilenas. La caracterización electroquímica de la disolución de Sb en medio HCl ha evidenciado que la reducción del Sb(III) a Sb metálico está limitada por la transferencia de materia y que una concentración elevada de HCl favorece la recuperación del Sb. Los ensayos de electrodeposición han destacado la relevancia de las reacciones secundarias, la reacción de evolución del hidrógeno (HER) y la generación de cloro, y su influencia negativa sobre la deposición de Sb. La HER tiene lugar en el cátodo y conlleva la generación de burbujas de hidrógeno a elevadas densidades de corriente, que reducen la superficie útil del electrodo de trabajo e incluso causan el desprendimiento del depósito de Sb. Por su parte, la generación de cloro gas en el ánodo provoca la redisolución de los depósitos de Sb desprendidos a causa de la HER. Tras la realización de estos ensayos se ha concluido que se puede aumentar la tasa de recuperación de Sb si se tienen mayores concentraciones del elemento en la disolución o si se mejoran las condiciones hidrodinámicas. Se ha analizado también cómo influye la presencia de Bi en la disolución sintética durante la electrodeposición del Sb. El potencial de reducción de ambos elementos es similar, lo que implica que la recuperación individual de Sb sea compleja. No obstante, si se trabaja bajo condiciones en las que no se supere la densidad de corriente límite del sistema, se logra una elevada selectividad hacia el Sb. Si la concentración de Bi en la disolución es superior a la de Sb, se electrodepositan ambos elementos, pero se logra un elevado valor de eficiencia de corriente debido a que la influencia de la HER sobre el Bi no es tan fuerte. A continuación, se ha estudiado la aplicación de las técnicas previamente analizadas con un efluente real, facilitado por una empresa española. Se ha verificado que las conclusiones obtenidas con las disoluciones sintéticas son aplicables al efluente real. En particular, se ha confirmado que, al aumentar la densidad de corriente aplicada, la deposición de Sb se ve mermada debido a la relevancia del resto de reacciones: la reducción de los demás elementos y la evolución del medio. Los depósitos obtenidos contienen algunos de los elementos presentes en el efluente real: Sb, Bi, As y Cu, siendo mayoritario el primero. Como resultado, se ha concluido que es posible purificar el HCl mediante la electrodeposición de los elementos contenidos en el electrolito. Finalmente, se ha planteado la posibilidad de sustituir el HCl empleado como regenerante por un disolvente eutéctico profundo, debido a la alta solubilidad de metales y su procedencia de fuentes renovables. En particular, la investigación se ha llevado a cabo con la oxalina, la cual presenta una elevada capacidad de disolución para el Sb y una amplia ventana de potencial que beneficiaría la aplicación de la técnica de electrodeposición para la recuperación del Sb. / [CA] Esta Tesi Doctoral se centra en la recuperació mitjançant electrodeposició del Sb present en un efluent residual provinent de la metal·lúrgia del coure. L'efluent en què es basa este estudi es produïx en el procés de regeneració amb HCl concentrat de les resines d'intercanvi iònic d'una de les subetapes de l'electro-refinat del coure. Es tracta d'un electròlit àcid que conté diverses impureses, entre les quals destaquen, Sb i Bi, que són considerats matèries primeres crítiques per la Unió Europea, a causa del risc de subministrament que presenten i a la seua importància en l'economia. L'objectiu d'esta Tesi és la recuperació del Sb i la reutilització de l'HCl. Per assolir aquests dos propòsits s'ha estudiat l'ús de l'electrodeposició com a operació de separació per al tractament de l'efluent. Este procés s'ha investigat mitjançant tècniques electroquímiques, en particular, voltametria cíclica i de rastreig lineal. En primer lloc, s'ha realitzat l'estudi amb dissolucions sintètiques que emulen l'efluent generat a les metal·lúrgies xilenes. La caracterització electroquímica de la dissolució de Sb en medi HCl ha evidenciat que la reducció del Sb(III) a Sb metàl·lic està limitada per la transferència de matèria i que una concentració elevada de HCl afavorix la recuperació del Sb. Els assajos d'electrodeposició han destacat la rellevància de les reaccions secundàries, la reacció d'evolució de l'hidrogen (HER) i la generació de clor, i la seua influència negativa sobre la deposició de Sb. La HER té lloc al càtode i comporta la generació de bambolles d'hidrogen a elevades densitats de corrent, la qual cosa reduïx la superfície útil de l'elèctrode de treball i fins i tot causa el despreniment del depòsit de Sb. Per la seua banda, la generació de clor gas a l'ànode provoca la redissolució dels depòsits de Sb despresos a causa de la HER. Després de la realització d'estos assajos s'ha conclòs que es pot augmentar la taxa de recuperació de Sb si es tenen majors concentracions de l'element en la dissolució o si es milloren les condicions hidrodinàmiques. S'ha analitzat també com influïx la presència de Bi en la dissolució sintètica durant l'electrodeposició del Sb. El potencial de reducció dels dos elements és similar, la qual cosa implica que la recuperació individual de Sb siga complexa. No obstant això, si es treballa sota condicions en què no se supere la densitat de corrent límit del sistema, s'aconseguix una elevada selectivitat cap al Sb. Si la concentració de Bi en la dissolució és superior a la de Sb, s'electrodepositen ambdós elements, però s'aconseguix un elevat valor d'eficiència de corrent pel fet que la influència de la HER sobre el Bi no és tan forta. A continuació, s'ha estudiat l'aplicació de les tècniques prèviament analitzades amb un efluent real, facilitat per una empresa espanyola. S'ha verificat que les conclusions obtingudes amb les dissolucions sintètiques són aplicables al efluent real. En particular, s'ha confirmat que, en augmentar la densitat de corrent aplicada, la deposició de Sb es veu minvada a causa de la rellevància de la resta de reaccions: la reducció dels altres elements i l'evolució del medi. Els depòsits obtinguts contenen alguns dels elements presents en el efluent real: Sb, Bi, As i Cu, sent majoritari el primer. Com a resultat, s'ha conclòs que és possible purificar l'HCl mitjançant l'electrodeposició dels elements continguts en l'electròlit. Finalment, s'ha plantejat la possibilitat de substituir l'HCl emprat com regenerant per un dissolvent eutèctic profund, a causa de l'alta solubilitat de metalls i la seua procedència de fonts renovables. En particular, la investigació s'ha dut a terme amb l'oxalina, la qual presenta una elevada capacitat de dissolució per al Sb i una àmplia finestra de potencial que beneficiaria l'aplicació de la tècnica d'electrodeposició per a la recuperació del Sb captat durant el procés de regeneració de les resines. / [EN] This Doctoral Thesis focuses on the recovery by electrodeposition of Sb present in an effluent from the copper metallurgy. The effluent on which this study is based is generated during the regeneration with concentrated hydrochloric acid of the ion exchange resins used in one of the sub-stages of copper electro-refining. It is an acid electrolyte containing several impurities, among them, Sb and Bi, which are considered critical raw materials by the European Union due to their supply risk and economic relevance. The aim of this Thesis is the recovery of Sb and reuse of HCl. To achieve both objectives, electrodeposition has been studied as a separation operation for the treatment of the effluent. This operation has been investigated through electrochemical techniques, primarily, cyclic and linear sweep voltammetry. First, the study has been conducted with synthetic solutions emulating the effluent generated in the Chilean metallurgy industries. The electrochemical characterization of the Sb solution in the HCl medium has shown that, mass-transfer limits the reduction of Sb(III) to metallic Sb and a high HCl concentration favors the recovery of Sb. From the electrodeposition tests the relevance and negative influence on Sb deposition of the secondary reactions, the hydrogen evolution reaction (HER) and the chlorine generation, has been proven. The HER occurs at the cathode and involves the generation of hydrogen bubbles at high current densities, which decrease the effective surface area of the working electrode and even cause the detachment of the Sb deposits. The chlorine generation at the anode leads to the redissolution of the Sb deposits detached by the HER. After conducting these experiments, it has been concluded that it is possible to increase the Sb recovery rate, if higher concentrations of this element are present in the solution or the hydrodynamic conditions of the electrodeposition process are improved. The influence of the presence of Bi in the synthetic solution on the Sb electrodeposition has also been investigated. The reduction potential of both elements is similar, implying that the individual recovery of Sb by electrodeposition is challenging. However, if the operating conditions do not imply exceeding the limiting current density of the system, a high electrodeposition selectivity towards Sb is achieved. If the concentration of Bi in the solution is higher than that of Sb, the simultaneous electrodeposition of both elements takes place, but, on the contrary, a high value of current efficiency is obtained because the influence of the HER on Bi reduction is not as significant as that on Sb deposition. The application of the previously analyzed techniques has been studied with a real effluent, that was provided by a Spanish company. It has been proven that the conclusions obtained with the synthetic solutions can be applied to a real effluent. It has been confirmed that, as the applied current density increases, the Sb deposition worsens due to the relevance of the other reactions that take place during the process: the reduction of the other elements and the evolution of the medium. The deposits obtained contain some elements present in the real effluent: Sb, Bi, As and Cu, the most significant being the first. From this study, it has been concluded that purifying the HCl by removing the elements contained in the electrolyte via electrodeposition is possible. Finally, the possibility of replacing the HCl used as a regenerant with a deep eutectic solvent has been considered based on their properties, among which are a high solubility of metals and their synthesis from renewable sources. In particular, the research has been carried out with oxaline, which presents a high dissolution capacity for Sb and a wide potential window that would benefit the application of the electrodeposition technique to recover Sb captured during the resins regeneration process. / Me gustaría agradecer la financiación a la Agencia Estatal de Investigación (AEI/10.13039/501100011033) (España) bajo el proyecto PCI2019-103535, gracias al cual he podido desarrollar la presente Tesis Doctoral, y a FEDER Una manera de hacer Europa / Hernández Pérez, L. (2024). Estudio electroquímico para la recuperación de antimonio de efluentes del electro-refinado de cobre por electrodeposición [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/203892