Study of The Reaction Mechanism to Produce Nanocellulose-Graft-Chitosan Polymer

Cellulose and chitin are the most abundant polymeric materials in nature, capable of replacing conventional synthetic polymers. From them, cellulose nano/microfibers (CNFs/CMFs) and chitosan are obtained. Both polymers have been used separately in graft copolymerization but there are not many studies on the use of cellulose and chitosan together as copolymers and the reaction mechanism is unknown. In this work, the reaction mechanism to produce nano/microcellulose-graft-chitosan polymer has been studied. Recycled cellulose pulp was used, with and without a 2,2,6,6-tetramethylpiperidin-1-oxyl-radical (TEMPO)-mediated oxidation pretreatment, to produce CNFs and CMFs, respectively. For chitosan, a low-molecular weight product dissolved in an acetic acid solution was prepared. Grafted polymers were synthesized using a microwave digester. Results showed that TEMPO-mediated oxidation as the cellulose pretreatment is a key factor to obtain the grafted polymer CNF-g-CH. A reaction mechanism has been proposed where the amino group of chitosan attacks the carboxylic group of oxidized cellulose, since non-oxidized CMFs do not achieve the desired grafting. 13C NMR spectra, elemental analysis and SEM images validated the proposed mechanism. Finally, CNF-g-CH was used as a promising material to remove water-based inks and dyes from wastewater

Gel Point as Measurement of Dispersion Degree of Nano-Cellulose Suspensions and Its Application in Papermaking

The dispersion degree of cellulose micro and nanofibrils (CMFs/CNFs) in water suspensions is key to understand and optimize their effectiveness in several applications. In this study, we proposed a method, based on gel point (Øg), to calculate both aspect ratio and dispersion degree. This methodology was validated through the morphological characterization of CMFs/CNFs by Transmission Electronic Microscopy. The influence of dispersion degree on the reinforcement of recycled cardboard has also been evaluated by stirring CMF/CNF suspensions at different speeds. Results show that as stirring speed increases, Øg decreased to a minimum value, in which the aspect ratio is maximum. Then, Øg increased again. Suspensions with lower Øg, in the intermediate region of agitation present very good dispersion behavior with an open and spongy network structure, in which nanofibril clusters are totally dispersed. Higher stirring speeds shorten the nanofibrils and the networks collapse. Results show that the dispersion of the nanocellulose at the minimum Øg before their addition to the pulp, produces higher mechanical properties, even higher than when CNFs and pulp are agitated together. This method allows for the determination of the CMF/CNF dispersion, to maximize their behavior as strength agents. This knowledge would be crucial to understand why some industrial trials did not give satisfactory results

Industrial Application of Nanocelluloses in Papermaking: A Review of Challenges, Technical Solutions, and Market Perspectives

Nanocelluloses (NC) increase mechanical and barrier paper properties allowing the use of paper in applications actually covered by other materials. Despite the exponential increase of information, NC have not been fully implemented in papermaking yet, due to the challenges of using NC. This paper provides a review of the main new findings and emerging possibilities in this field by focusing mainly on: (i) Decoupling the effects of NC on wet-end and paper properties by using synergies with retention aids, chemical modification, or filler preflocculation; (ii) challenges and solutions related to the incorporation of NC in the pulp suspension and its effects on barrier properties; and (iii) characterization needs of NC at an industrial scale. The paper also includes the market perspectives. It is concluded that to solve these challenges specific solutions are required for each paper product and process, being the wet-end optimization the key to decouple NC effects on drainage and paper properties. Furthermore, the effect of NC on recyclability must also be taken into account to reach a compromise solution. This review helps readers find upscale options for using NC in papermaking and identify further research needs within this field

Desarrollo y aplicación de una metodología innovadora para realizar visitas técnicas virtuales a empresas y centros de investigación

El objetivo del proyecto es desarrollar una metodología innovadora para realizar visitas técnicas virtuales a plantas industriales y/o centros de investigación con alumnos que podrán utilizarse en 8 asignaturas de 4 grados y 2 másteres de la UCM.FALSEVicerrectorado de Calidad Proyectos de Innovación (2021-2022) Innova-Docenciasubmitte

Clonal chromosomal mosaicism and loss of chromosome Y in elderly men increase vulnerability for SARS-CoV-2

The pandemic caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2, COVID-19) had an estimated overall case fatality ratio of 1.38% (pre-vaccination), being 53% higher in males and increasing exponentially with age. Among 9578 individuals diagnosed with COVID-19 in the SCOURGE study, we found 133 cases (1.42%) with detectable clonal mosaicism for chromosome alterations (mCA) and 226 males (5.08%) with acquired loss of chromosome Y (LOY). Individuals with clonal mosaic events (mCA and/or LOY) showed a 54% increase in the risk of COVID-19 lethality. LOY is associated with transcriptomic biomarkers of immune dysfunction, pro-coagulation activity and cardiovascular risk. Interferon-induced genes involved in the initial immune response to SARS-CoV-2 are also down-regulated in LOY. Thus, mCA and LOY underlie at least part of the sex-biased severity and mortality of COVID-19 in aging patients. Given its potential therapeutic and prognostic relevance, evaluation of clonal mosaicism should be implemented as biomarker of COVID-19 severity in elderly people. Among 9578 individuals diagnosed with COVID-19 in the SCOURGE study, individuals with clonal mosaic events (clonal mosaicism for chromosome alterations and/or loss of chromosome Y) showed an increased risk of COVID-19 lethality

Depósitos adherentes en el proceso de fabricación de papel reciclado

La utilización de papel de recuperación como materia prima para la fabricación de papel reciclado presenta numerosas ventajas medioambientales y económicas. Sin embargo, también tien graves inconvenientes, debido a la cantidad de contaminantes que se introducen en el sistema. Los contaminantes que se encuentran en forma de materia disuelta y coloidal no pueden ser eliminados por los procesos mecánicos convencionales y cuando se desestabilizan, por un cambio brusco de las condiciones del sistema, son responsables directos de la formación de manchas y agujeros en el producto final. El objetivo de esta Tesis es el desarrollo de un procedimiento para determinar la tendencia de la materia disuelta y coloidal presente en un agua papelera a la formación de depósitos adherentes, de manera práctica y precisa. El método desarrollado consta de las etapas necesarias para la obtención de las aguas blancas, en condiciones similares a las que se obtienen en el proceso de fabricación de papel reciclado. Las aguas caracterizadas se desestabilizan con un polímero catiónico para favorecer la formación de depósitos utilizando un equipo de deposición diseñado para tal fin, denominado "Rotor de Deposición", que permite llevar a cabo la determinación cuantitativa de los depósitos mediante un sistema de análisis de imagen. Con el método desarrollado, una vez validado y determinada su reproducibilidad, se lleva a cabo un estudio en aguas blancas obtenidas a partir de suspensiones de pasta que contienen los contaminantes propios del proceso de reciclado de papel: adhesivos, compuestos de estucado y jabones de destintado. Se estudia el efecto que jercen distintas variables, como la naturaleza del contaminante, la presencia de aditivos de destintado, la naturaleza de los agentes de desestabilización, la dosis empleada y las características del medio (pH, conductividad y durez de las aguas), sobre la tendencia a la formación de depósitos adherentes. Así mismo, se lleva a cabo un estudio de la depositabilidad de la materia disuelta y coloidal contenida en muestras de dos fábricas que utilizan papel de recuperación como materia prima, con el fin de comparar los resultados de las muestras de laboratorio con los que se obtienen de muestras reale

Analysis of the quality of the recovered paper from commingled collection systems

The need to increase the recovery rates of recyclables from households, reducing at the same time the collection costs, has favored the spreading of commingled collection systems. This study presents a thorough analysis of the quality of a secondary source of recovered paper of a Spanish newsprint mill, imported from the United Kingdom, where these systems are widely practiced. The results show that the quality of recovered paper from commingled systems is very far from the quality obtained with selective systems: the unusable material content vary from 1% to 29% (11.9% on average) compared to less than 1%. Larger materials recovery facilities (MRF), less oversaturated and with advanced sorting techniques, have demonstrated to be able to render better qualities, the unusable material content varying from 0.3% to 16.6% (8.1% on average). However, the quality is still far from contamination levels typically found with selective systems, especially in terms of non-paper components. This fact limits significantly the use of this recovered paper for graphic paper production where the major potential for an extended use of recovered paper in papermaking lies. Furthermore, there is a discussion on the cost efficiency of these systems and how the legislation and private or public initiatives are affecting the spreading of these systems, especially in the United States and the United Kingdom

Corn stalk from agricultural residue used as reinforcement fiber in fibercement production

In the last few years an increasing high interest has been drawn to the potential use of agricultural waste as raw material to produce structural reinforcement fibers for building materials, due to environmental and economical aspects. Corn is the world's most produced cereal in terms of quantity, what entails the generation of large quantities of waste. Despite this fact, only a few research works concerned with the use of fibers from waste corn stalks in the production of fiber-cement have been published and there is a complete lack of data on the characterization of these fibers. The objective of this research is to study the feasibility of using fibers obtained from corn stalk as reinforcement fibers in the production of fiber-cement through new environmentally friendly cooking methods. This study encompasses the morphological characterization of the fibers and the study of the effects that the use of these fibers has on the flocculation, retention and drainage of the fiber-cement suspensions and on the mechanical and physical properties of the final product. The results obtained in the tests confirmed the high potential of the corn stalk as a source of fibers for the manufacture of a fiber-cement capable of meeting the requirements of demanding applications