The emergence of nanocellulose aerogels in CO2 adsorption

Mitigating the effect of climate change toward a sustainable development is one of the main challenges of our century. The emission of greenhouse gases, especially carbon dioxide (CO2), is a leading cause of the global warming crisis. To address this issue, various sustainable strategies have been formulated for CO2 capture. Renewable nanocellulose aerogels have risen as a highly attractive candidate for CO2 capture thanks to their porous and surface-tunable nature. Nanocellulose offer distinctive characteristics, including significant aspect ratios, exceptional biodegradability, lightweight nature, and the ability for chemical modification due to the abundant presence of hydroxyl groups. In this review, recent research studies on nanocellulose-based aerogels designed for CO2 absorption have been highlighted. The state-of-the-art of nanocellulose-based aerogel has been thoroughly assessed, including their synthesis, drying methods, and characterization techniques. Additionally, discussions were held about the mechanisms of CO2 adsorption, the effects of the porous structure, surface functionalization, and experimental parameters. Ultimately, this synthesis review provides an overview of the achieved adsorption rates using nanocellulose-based aerogels and outlines potential improvements that could lead to optimal adsorption rates. Overall, this research holds significant promise for tackling the challenges of climate change and contributing to a more sustainable future.The authors would like to acknowledge the financial support of the Basque Government (project IT1498-22) and the University of the Basque Country (PIF21/52)

Acid Hydrolysis of Almond Shells in a Biphasic Reaction System: Obtaining of Purified Hemicellulosic Monosaccharides in a Single Step

The aim of this work is to comprehend the biphasic reaction systems through another perspective; the simultaneous purification and production of carbohydrates during the pretreatment of biomass. A dilute acid hydrolysis of almond shells in a 2-Methyltetrahydrofuran/H2O system was optimised to maximise the obtaining of hemicellulose-derived monosaccharides with the minimum formation of degradation products. The optimised conditions of the biphasic reaction system, which produced 205.3 g hemicellulose-derived monosaccharides/Kg almond shells, were replicated in a monophasic reaction system to assess the benefits of the biphasic reaction systems. The latest system allowed the removal of 85.3% of the furans generated during the dilute acid hydrolysis, creating antioxidant extract, together with the catalysis of the hydrolysis of the hemicelluloses in a 20%. Therefore, the proposed process could become a promising method to purify carbohydrates with an environmentally friendly procedure that allowed the obtaining of multiple added-value products in a single step.Dr. I. Dávila would like acknowledge to the University of the Basque Country (UPV/EHU) for the financial support (Grant reference No. DOCREC19/47

Electrochemical Activity of Lignin Based Composite Membranes

Our society’s most pressing challenges, like high CO2 emission and the constant battle against energy poverty, require a clean and easier solution to store and utilize the renewable energy resources. However, recent electrochemical components are expensive and harmful to the environment, which restricts their widespread deployment. This study proposes an easy method to synthesize and fabricate composite membranes with abundantly found biomass lignin polymer to replace conventional costly and toxic electrode materials. Easier manipulation of lignin within the polymeric matrix could provide the improved composite to enhance its electrochemical activity. Our major focus is to activate the quinone moiety via oxidation in the polymeric mixture using a strong ionic acid. The physico-chemical and electrochemical characterizations of two different lignins within varied polymeric mixture compositions have been carried out to confirm that the redox properties of pure unmodified lignin could be achieved via intrinsic mutual sharing of the structural properties and intercross linkage leading to improved integrity and redox activity/conductivity.This research was funded by the Basque Government (project IT1008-16)

Nanocellulose-based sensors in medical/clinical applications: The state-of-the-art review

In recent years, the considerable importance of healthcare and the indispensable appeal of curative issues, particularly the diagnosis of diseases, have propelled the invention of sensing platforms. With the development of nanotechnology, the integration of nanomaterials in such platforms has been much focused on, boosting their functionality in many fields. In this direction, there has been rapid growth in the utilisation of nanocellulose in sensors with medical applications. Indeed, this natural nanomaterial benefits from striking features, such as biocompatibility, cytocompatibility and low toxicity, as well as unprecedented physical and chemical properties. In this review, different classifications of nanocellulose-based sensors (biosensors, chemical and physical sensors), alongside some subcategories manufactured for health monitoring, stand out. Moreover, the types of nanocellulose and their roles in such sensors are discussed.This work was supported by the University of the Basque Country (Training of Researcher Staff, PIF 20/197)

Influence of lignin modifications on physically crosslinked lignin hydrogels for drug delivery applications

So far, the possibility of synthesizing hydrogels based on multiple biopolymers has been investigated, and among them lignin has proven to be one of the potentials for this purpose due to the multiple advantages it offers. However, because of its high molecular weight, steric hindrance and few reactive sites on its structure, it is sometimes necessary to improve its reactivity though chemical modifications. On the basis of previous results, two chemical modifications were selected in order to enhance almond, walnut and commercial alkaline and organosolv lignins' reactivity: a peroxidation reaction for alkaline ones and a hydroxymethylation for organosolv ones. Both reactions were confirmed by multiple techniques (i.e. FTIR, GPC and TGA). Hydrogels were syn-thesized from these lignins according to previous works. The high lignin waste of the synthesized hydrogels suggested that despite the modification of the lignins, just the highest molecular weight fractions reacted with the matrix polymer. Moreover, the swelling capacity of modified alkaline lignin-based hydrogels was negatively affected, whereas the one for organosolv lignin-based samples improved. The SEM micrographs explained the aforementioned, and the results from the DSC and compression tests were in accordance with them. Self -extracted quercetin loading and release studies suggested that these samples could be used for controlled drug delivery.The authors would like to acknowledge the financial support of the Department of Education of the Basque Government (IT1498-22) . A. Morales would like to thank the University of the Basque Country (Training of Researcher Staff, PIF17/207) . P. Gullón would like to acknowledge the Grants for the recruitment of technical support staff (PTA2019-017850-I) under the Spanish State Plan for Scientific and Technical Research and Innovation 2017-2020. The authors thank SGIker (UPV/EHU/ERDF, EU) for their technical and human support

Microwave-assisted esterification of bleached and unbleached cellulose nanofibers

Microwave-assisted synthetic pathway was explored for the sustainable esterification of cellulose nanofibers (CNFs) using an aromatic amine compound. For this purpose, nanofibers were isolated from unbleached and bleached eucalyptus pulp through the homogenization process. The chemical composition, the structural properties, the morphology, and the thermal properties of the extracted nanofibers were investigated. para-aminobenzoic acid (PABA) was employed to esterify CNFs's aliphatic hydroxyl groups. FTIR and 13C NMR spectroscopy confirmed the success of the chemical modification. The structural characterization of the cellulose nanofibers and lignocellulose nanofibrils esterified (CNF-E and LCNF-E) confirmed the grafting of the aromatic amine counterparts onto CNFs's surface. The thermogravimetric technique assessed the thermal stability of the nanofibrils. The thermal properties were affected by the esterification resulting in a significant improvement of the char yield (CR) compared to the original CNFs (from CR≈ 10% to > 20%). Finally, this sustainable chemical pathway increases CNFs's functionality by introducing ester and aromatic amine functionalities, making LCNF-E and CNF-E sustainable platforms for further smart applications.The authors wish to acknowledge financial support of the Basque Government (IT1498-22) and the University of the Basque Country (PIF21/52 and COLAB20/04). E.R. wants to acknowledge the tenure track position "Bois: Biobased materials" part of E2S UPPA supported by the "Investissements d'Avenir" French program managed by ANR [ANR-16-IDEX-0002]. The authors would like to acknowledge the technical and human assistance received from SGIker [UPV/ EHU/ERDF, EU], Spain. The authors would also like to thank Antoine Adjaoud for the scientific discussion

Nanocellulose-based sensing platforms for heavy metal ions detection: A comprehensive review.

Increase in industrial activities has been arising a severe concern about water pollution caused by heavy metal ions (HMIs), such us lead (Pb2+), cadmium (Cd2+) or mercury (Hg2+). The presence of substantial amounts of these ions in the human body is harmful and can cause serious diseases. Hence, the detection of HMIs in water is of great importance. As technological advances have developed, some conventional methods have become obsolete due to some methodological disadvantages, giving way to a second generation that uses novel sensors. Recently, nanocellulose, as a biocompatible material, has drawn a remarkable attraction for developing sensors owing to its extraordinary physical and chemical properties. This review pays a special attention to the different dimensional nanocellulose-based sensors devised for HMIs recognition. What is more, different sensing techniques (optical and electrochemical), sensing mechanisms and the roles of nanocellulose in such sensors are discussed.The authors would like to thank the University of the Basque Country (Training of Researcher Staff, PIF 20/197)

Impact of the lignin type and source on the characteristics of physical lignin hydrogels

[EN] Multiple natural polymers have been investigated for the synthesis of hydrogels to the present date, but lignin has demonstrated to be a promising one for this purpose for the multiple advantages it offers. Lignin can be isolated from lignocellulosic material such as nut shells, which are usually undervalued wastes, and would be a great step forward on circular economy. Thus, in the present work, lignin was extracted from almond and walnut shells following a single-step (delignification) and double-step (autohydrolysis and delignification) biorefinery scheme. After the chemical composition and structures of these lignins were determined, hydrogels were synthesized combining them with poly (vinyl alcohol) by the means of freeze-thawing cycles so as to study the influence of the different lignins on their final properties. Additionally, the last thawing cycle of the synthesis process was lengthened in order to confirm previous assumptions about its effect on the characteristics of the synthesized materials. The obtained results showed significant variation between the 8 lignin samples, especially in their purity, molecular weights and total phenolic contents. The variation on the lignins leaded to several hydrogel morphologies, which directly affected their properties, primarily their swelling capacity, glass transition temperatures and compression strengths. It was also demonstrated the great effect that the duration of the last thawing had on the morphology and, hence, on the characteristics of the obtained materials. The synthesized samples were successfully employed as dye adsorbents and the evaluation of their antifungal activity showed positive results in some of the samples, which could be applied for food packaging.The authors would like to acknowledge the financial support of the Department of Education of the Basque Government (IT1008-16). A. Morales would like to thank the University of the Basque Country (Training of Researcher Staff, PIF17/207). P. Gull ' on would like to acknowledge the Grants for the recruitment of technical support staff (PTA2019-017850-I) under the State Plan for Scientific and Technical Research and Innovation 2017-2020. The authors thank SGIker (UPV/EHU/ERDF, EU) for their technical and human support

Formation of Palygorskite Clay from Treated Diatomite and its Application for the Removal of Heavy Metals from Aqueous Solution

Environmental contamination by toxic heavy metals is a serious worldwide phenomenon. Thus, their removal is a crucial issue. In this study, we found an efficient adsorbent to remove Cu2+ and Ni2+ from aqueous solution using two materials. Chemical modification was used to obtain palygorskite clay from diatomite. The adsorbents were characterized using X-ray florescence, Fourier transform infrared spectroscopy and X-ray diffraction. The effects of contact time, initial concentration, temperature and pH on the adsorption process were investigated. Our results showed that the (%) of maximum adsorption capacity of diatomite was 78.44% for Cu2+ at pH 4 and 77.3% for Ni2+ at pH 7, while the (%) of the maximum adsorption on palygorskite reached 91% for Cu2+ and 87.05% for Ni2+, in the same condition. The results indicate that the pseudo-second-order model can describe the adsorption process. Furthermore, the adsorption isotherms could be adopted by the Langmuir and the Freundlich models with good correlation coefficient (R-2). Thus, our results showed that palygorskite prepared from Tunisian diatomite is a good adsorbent for the removal of heavy metals from water.This research was funded by Department of Education of the Basque Government grant number [IT1008-16]" and "The APC was funded by Department of Education of the Basque Government

Integral valorisation of walnut shells based on a three-step sequential delignification

[EN] Walnut kernels represent no more than 50-60% of the total weight of the fruit, so the sum of walnut shells generated every year is immense. Nonetheless, these shells could be further valorised for the extraction of their main constituents following a biorefinery scheme. Hence, the objective of this work was an integral valorisation of walnut shells, which involved a sequential organosolv delignification (200 ?, 90 min, 70/30 v/v EtOH/H2O, LSR 6:1) and several posterior non-isothermal hydrothermal treatments (180, 195 and 210 ?, LSR 8:1). Moreover, the spent solids after the aforementioned treatments were evaluated as possible sources of cellulose nanocrystals. The results showed that the sequential organosolv delignifications presented relative lignin yields up to 60%, which leaded to lignins that just differed on their molecular weight distributions. The hydrothermal treatments were efficient for the removal of still present hemicelluloses (14.7-71.8%), and permitted a successful cellulose nanocrystal obtaining whereas the spent solid from the delignification stages did not. Thus, this study presented an innovative strategy for the integral valorisation of walnut shells.The authors would like to thank the Department of Education of the Basque Government (IT1008-16) for the financial support. A. Morales would like to thank the University of the Basque Country (Training of Researcher Staff, PIF17/207). The authors would like to thank SGIker for the provided technical and human support (UPV/EHU/ERDF, EU)