120 research outputs found
Optimización del proceso TEMPO para la producción sostenible de nanocelulosa
No full textTesis inédita de la Universidad Complutense de Madrid, Facultad de Ciencias Químicas, leída el 26/02/2025. Tesis formato europeo (compendio de artículos)Los nanomateriales de celulosa, o nanocelulosas (NCs), descubiertos en el siglo XX, han experimentado un crecimiento muy significativo en el siglo XXI debido a su origen renovable y a sus excepcionales propiedades mecánicas, ópticas y térmicas, así como su biocompatibilidad y biodegradabilidad. Estas características les confieren un enorme potencial para numerosas aplicaciones en diversos sectores industriales. Las propieda des de las NCs dependen en gran medida del tipo específico de NC, el cual está determinado tanto por el método de obtención como por la materia prima utilizada. Además, las propiedades de las NCs también están fuertemente ligadas a su comportamiento coloidal, lo cual influye e n s u capacidad de autoensamblaje, estabilidad e interacción con otras partículas. Por ello, en la Publicación I se revisa el estado del arte de las NCs desde una perspectiva coloidal, dado que este enfoque resulta crucial para comprender y optimizar su comportamiento y sus aplicaciones...
Cellulose nanomaterials, or nanocelluloses (NCs), discovered in the 20th century, have experienced significant growth in the 21st century due to their renewable origin and exceptional mechanical, optical, and thermal properties, as well as their biocompatibility and biodegradability. These characteristics give them a great potential for numerous applications in various industrial sectors. The properties of NCs fundamentally depend onthe type of NC, which is related to the production method and the raw material used. Additionally, NC properties are strongly linked to their colloidal behavior, which influences their self-assembly capabilities, stability mechanisms, and interactions with other particles. Therefore, Publication I reviews the state of the art of NCs from a colloidal perspective, as this approach is essential for understanding and optimizing their behavior and applications...Fac. de Ciencias QuímicasTRUEpu
Recycled Fibers for Sustainable Hybrid Fiber Cement Based Material: A Review
No full textReinforcing fibers have been widely used to improve physical and mechanical properties of cement-based materials. Most fiber reinforced composites (FRC) involve the use of a single type of fiber to improve cement properties, such as strength or ductility. To additionally improve other parameters, hybridization is required. Another key challenge, in the construction industry, is the implementation of green and sustainable strategies based on reducing raw materials consumption, designing novel structures with enhanced properties and low weight, and developing low environmental impact processes. Different recycled fibers have been used as raw materials to promote circular economy processes and new business opportunities in the cement-based sector. The valuable use of recycled fibers in hybrid FRC has already been proven and they improve both product quality and sustainability, but the generated knowledge is fragmented. This is the first review analyzing the use of recycled fibers in hybrid FRC and the hybridization effect on mechanical properties and workability of FRC. The paper compiles the best results and the optimal combinations of recycled fibers for hybrid FRC to identify key insights and gaps that may define future research to open new application fields for recycled hybrid FRC.Comunidad de MadridDepto. de Ingeniería Química y de MaterialesFac. de Ciencias QuímicasTRUEpu
Celulosa nanofibrilada y su aplicación en la industria papelera para la mejora de productos reciclados
No full textTesis de la Universidad Complutense de Madrid, Facultad de Ciencias Químicas, Departamento de Ingeniería Química, leída el 08/05/2017. Tesis formato europeo (compendio de artículos)La fabricación de papel es un sector industrial sostenible donde el reciclaje constituye uno de los pilares fundamentales. En Europa, el 54% de la materia prima que utiliza la industria papelera proviene del papel recuperado siendo la tasa de reciclaje del 72% (CEPI 2015). Sin embargo, uno de los principales problemas de las fibras recuperadas es mantener el nivel de calidad de los productos papeleros que aumenta continuamente por las exigencias del mercado. Además, la demanda de papel ha disminuido debido a la recesión económica y al uso de otros soportes de información, lo cual exige una continua reducción de costes dentro del sector para mantener la competitividad de las empresas. Aunque la industria papelera trata de compensar la pérdida de calidad de las fibras secundarias con la aplicación de procesos de refino y el uso de aditivos de resistencia, la baja resistencia mecánica de los productos papeleros sigue siendo la principal fuente de reclamaciones a los fabricantes de papel reciclado. Por este motivo, es necesario la búsqueda de nuevas estrategias que permitan mejorar el enlace entre las fibras, y la celulosa nanofibrilada (CNF) abre nuevos horizontes como agente de resistencia alternativo...Papermaking is a sustainable industrial sector in which paper recycling has been recognized as being of great importance. In Europe, 54% of the paper industry’s feedstock comes from recovered paper, which corresponds to a paper recycling rate of 72% (CEPI 2015). However, one of the main problems in the utilization of secondary fibers is to maintain the quality levels of the paper products which is continuously increasing following customer demands. On the other hand, paper demand has decreased due to both economic recession and replacement of paper by other information supports, what results in a need to continuously reduce production costs in the sector to maintain competitiveness. Although the paper industry has tried to counterbalance the low quality of secondary fibers with the application of refining processes and the use of strengthening additives, the low mechanical strength of the papers remains the main source of customer complaints to paper manufacturers. It thus becomes necessary to explore new strategies to improve interfiber bonding. Inthis context cellulose nanofibers (CNF) have potential as alternative strengthening agent...Depto. de Ingeniería Química y de MaterialesFac. de Ciencias QuímicasTRUEunpu
Influence of swelling on the efficiency of TEMPO reaction, nanofibril production and characterization
No full textThis paper studies the effect of three swelling pretreatment processes (glycerol, alkaline, and molten salt hydrate) to improve the efficiency of 2,2,6,6-tetramethylpiperidine-N-oxyl (TEMPO)-mediated oxidation (TMO) to produce cellulose nanofibrils (CNFs). The novelty of this research lies in the presentation of a new approach that increases the process`s sustainability. The new pretreatment results in the reduction of both chemical reagents and energy consumption. Results demonstrate that pulps pretreated with molten salt hydrate exhibit a crystallinity index up to 50 % lower than the original fibers, while the carboxyl groups obtained during oxidation increase up to 30 %. The increase in oxidation efficiency allows us to obtain a highly fibrillated CNF with a 50 % dose reduction of TEMPO and NaBr at the same time that the energy consumption (kWh/kg) is reduced by 15%.Ministerio de Ciencia e Innovación (España)Depto. de Ingeniería Química y de MaterialesFac. de Ciencias QuímicasTRUEpu
Recycling of TEMPO-mediated oxidation medium and its effect on nanocellulose properties
No full textThe potential of TEMPO (2,2,6,6-tetramethyl-1-piperidinyloxy)-mediated oxidation (TMO) to produce cellulose nanofibrils (CNFs) is hindered using costly and environmentally harmful catalysts, limiting its large-scale implementation. To promote sustainability, the TMO medium should be reused but there is a lack of knowledge on this process. The novelty of this research is the identification of the key parameters that affect the recirculation of the TMO medium, and their impact on the quality of the oxidized pulps and CNF products. Contrary to previous hypothesis, results show that the accumulation of salts is not a key parameter; instead, the pulp consistency during oxidation plays a vital role since concentrations higher than 10 g/L led to better CNF quality. Thus, reusing 75 % of the reaction medium, when high pulp consistency is used, does not alter the CNF properties. By reusing the reaction medium up to six times, the catalyst dose is dramatically reduced by >90 % for TEMPO and 80 % for NaBr, compared to the conventional process (0.1 mmol of TEMPO/g and 1 mmol of NaBr/g without medium reuse). Additionally, the high consistency oxidation enables a reduction of >80 % in the reaction time and effluent, and thus a threefold increase in CNF production.Ministry of Science and Innovation of SpainCommunity of MadridDepto. de Ingeniería Química y de MaterialesFac. de Ciencias QuímicasTRUEpu
Critical comparison of the properties of cellulose nanofibers produced from softwood and hardwood through enzymatic, chemical and mechanical processes
No full text10 p.-10 fig.Current knowledge on the properties of different types of cellulose nanofibers (CNFs) is fragmented. Properties variation is very extensive, depending on raw materials, effectiveness of the treatments to extract the cellulose fraction from the lignocellulosic biomass, pretreatments to facilitate cellulose fibrillation and final mechanical process to separate the microfibrils. Literature offers multiple parameters to characterize the CNFs prepared by different routes. However, there is a lack of an extensive guide to compare the CNFs. In this study, we perform a critical comparison of rheological, compositional, and morphological features of CNFs, produced from the most representative types of woody plants, hardwood and softwood, using different types and intensities of pretreatments, including enzymatic, chemical and mechanical ones, and varying the severity of mechanical treatment focusing on the relationship between macroscopic and microscopic parameters. This structured information will be exceedingly useful to select the most appropriate CNF for a certain application based on the most relevant parameters in each case.Authors want to acknowledge the Spanish Ministry of Economy and Competitiveness for the funding of the projects CTQ2017-85654-C2-1-R and CTQ2017-85654-C2-2-R, the Spanish Ministry of Science and Innovation (PDC2021-120964-C21 and PDC2021-120964-C22), the Community of Madrid for funding the RETO-PROSOST-2-CM (P2018/EMT4459), as well as the support of Universidad Complutense de Madrid and Banco de Santander for the grant of J.L. Sanchez-Salvador (CT17/17). Thanks also to Spanish Ministry of Science and Innovation for the Juan de la Cierva aid of Cristina Campano (Ref. FJC2019-040298-I).Peer reviewe
Enhancement of the production of TEMPO-mediated oxidation cellulose nanofibrils by kneading
No full textThe industrial use of TEMPO -mediated oxidation (TMO) reaction to produce highly fibrillated cellulose nanofibrils has been hindered by high catalyst costs, long reaction times and high reaction volumes. The hypothesis that cellulose concentration during TMO process is key to increase the process of efficiency has been confirmed. The novelty of this research is the proof -of -concept for a significant enhancement of the TMO reaction by kneading the cellulose to work in concentrations above 120 g/L. Results show that the increase of the cellulose concentration in the TMO reaction, from the traditional 10 g/L to 120 g/L, increase not only the production for the same reaction volume (1200 %) but also the pulp recovery (up to 94 %). Moreover, the oxidation time can be reduced from 42 min to only 4 min while properties of both the oxidized pulps and the final nanocellulose are similar. On the other hand, the use of buffers in the TMO reaction allows us to keep the pH constant without using NaOH, and to improve the selectivity of the carboxyl groups production. The proposed process also minimizes the final environmental impact.Ministerio de Ciencia e Innovación (España)Depto. de Ingeniería Química y de MaterialesFac. de Ciencias QuímicasTRUEpu
Nanocellulose from a colloidal material perspective
No full textCellulose nanomaterials present unique properties of interest for their many applications. Their behavior is mainly related to the colloidal properties that determine their self-assembly and stability mechanisms as well as their interaction with the particles present in different matrices. This review shows the state of the art of nanocellulose from a colloidal material perspective, from the approach of how to control these properties and their influence on the final products, such as drug delivery, coatings, nanocomposites, or tissue engineering, emphasizing the role of colloidal behavior in determining their performance.Science and Innovation Ministry of SpainCommunity of MadridDepto. de Ingeniería Química y de MaterialesFac. de Ciencias QuímicasTRUEpu
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