Browsing by Author "Alves, Luís"
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- Acacia wood fractionation using deep eutectic solvents: extraction, recovery, and characterization of the different fractionsPublication . Magalhães, Solange; Moreira, Adriana; Almeida, Ricardo; Cruz, Pedro Fernandes; Alves, Luís; Costa, Carolina; Mendes, Cátia; Medronho, Bruno; Romano, Anabela; Carvalho, Maria da Graça; Gamelas, José A. F.; Rasteiro, Maria da GraçaThe selective extraction and recovery of different lignocellulosic molecules of interest from forestry residues is increasing every day not only to satisfy the needs of driving a society toward more sustainable approaches and materials (rethinking waste as a valuable resource) but also because lignocellulosic molecules have several applications. For this purpose, the development of new sustainable and ecologically benign extraction approaches has grown significantly. Deep eutectic solvents (DESs) appear as a promising alternative for the processing and manipulation of biomass. In the present study, a DES formed using choline chloride and levulinic acid (ChCl:LA) was studied to fractionate lignocellulosic residues of acacia wood (Acacia dealbata Link), an invasive species in Portugal. Different parameters, such as temperature and extraction time, were optimized to enhance the yield and purity of recovered cellulose and lignin fractions. DESs containing LA were found to be promising solvent systems, as the hydrogen bond donor was considered relevant in relation to lignin extraction and cellulose concentration. On the other hand, the increase in temperature and extraction time increases the amount of extracted material from biomass but affects the purity of lignin. The most promising DES system, ChCELA in a ratio of 1:3, was found to not significantly depolymerize the extracted lignin, which presented a similar molecular weight to a la-aft lignin. Additionally, the P-31 NMR results revealed that the extracted lignin has a high content of phenolic OH groups, which favor its reactivity. A mixture of ChCl:LA may be considered a fully renewable solvent, and the formed DES presents good potential to fractionate wood residues.
- Brief overview on bio-based adhesives and sealantsPublication . Magalhães, Solange; Alves, Luís; Medronho, Bruno; Fonseca, Ana C.; Romano, Anabela; Coelho, Jorge F.J.; Norgren, MagnusAdhesives and sealants (AS) are materials with excellent properties, versatility, and simple curing mechanisms, being widely used in different areas ranging from the construction to the medical sectors. Due to the fast-growing demand for petroleum-based products and the consequent negative environmental impact, there is an increasing need to develop novel and more sustainable sources to obtain raw materials (monomers). This reality is particularly relevant for AS industries, which are generally dependent on non-sustainable fossil raw materials. In this respect, biopolymers, such as cellulose, starch, lignin, or proteins, emerge as important alternatives. Nevertheless, substantial improvements and developments are still required in order to simplify the synthetic routes, as well as to improve the biopolymer stability and performance of these new bio-based AS formulations. This environmentally friendly strategy will hopefully lead to the future partial or even total replacement of non-renewable petroleum-based feedstock. In this brief overview, the general features of typical AS are reviewed and critically discussed regarding their drawbacks and advantages. Moreover, the challenges faced by novel and more ecological alternatives, in particular lignocellulose-based solutions, are highlighted.
- Eco-friendly methods for extraction and modification of cellulose: an overviewPublication . Magalhães, Solange; Fernandes, Catarina; Pedrosa, Jorge F. S.; Alves, Luís; Medronho, Bruno; Ferreira, Paulo J. T.; Rasteiro, Maria da GraçaCellulose is the most abundant renewable polymer on Earth and can be obtained from several different sources, such as trees, grass, or biomass residues. However, one of the issues is that not all the fractionation processes are eco-friendly and are essentially based on cooking the lignocellulose feedstock in a harsh chemical mixture, such as NaOH + Na2S, and water, to break loose fibers. In the last few years, new sustainable fractionation processes have been developed that enable the obtaining of cellulose fibers in a more eco-friendly way. As a raw material, cellulose’s use is widely known and established in many areas. Additionally, its products/derivatives are recognized to have a far better environmental impact than fossil-based materials. Examples are textiles and packaging, where forest-based fibers may contribute to renewable and biodegradable substitutes for common synthetic materials and plastics. In this review, some of the main structural characteristics and properties of cellulose, recent green extraction methods/strategies, chemical modification, and applications of cellulose derivatives are discussed.
- Effect of chitosan properties and dissolution state on solution rheology and film performance in triboelectric nanogeneratorsPublication . Araújo, Francisca; Magalhães, Solange; Medronho, Bruno; Eivazi, Alireza; Dahlström, Christina; Norgren, Magnus; Alves, LuísChitosan films with potential application in triboelectric nanogenerators (TENGs) represent a promising approach to replace non-biobased materials in these innovative devices. In the present work, chitosan with varying molecular weights (MW) and degrees of deacetylation was dissolved in aqueous acetic acid (AA) at different acid concentrations. It was observed that the MW had a greater influence on the viscosity of the solution compared to either the acid concentration or deacetylation degree. Gel formation occurred in high-MW chitosan solutions prepared with low AA concentration. Films prepared from chitosan solutions, through solvent-casting, were used to prepare TENGs. The power output of the TENGs increased with higher concentrations of AA used in the chitosan dissolution process. Similarly, the residual AA content in the dried films also increased with higher initial AA concentrations. Additionally, hot-pressing of the films significantly improves the TENG power output due to the decrease in morphological defects of the films. It was demonstrated that a good selection of the acid concentration not only facilitates the dissolution of chitosan but also plays a key role in defining the properties of the resulting solutions and films, thereby directly impacting the performance of the TENGs.
- Enhancing cellulose and lignin fractionation from acacia wood: optimized parameters using a deep eutectic solvent system and solvent recoveryPublication . Magalhães, Solange; Aliaño González, María José; Rodrigues, Mariana; Fernandes, Catarina; Mendes, Cátia V. T.; Carvalho, Maria Graça V. S.; Alves, Luís; Medronho, Bruno; Rasteiro, Maria da GraçaCellulose and lignin, sourced from biomass, hold potential for innovative bioprocesses and biomaterials. However, traditional fractionation and purification methods often rely on harmful chemicals and high temperatures, making these processes both hazardous and costly. This study introduces a sustainable approach for fractionating acacia wood, focusing on both cellulose and lignin extraction using a deep eutectic solvent (DES) composed of choline chloride (ChCl) and levulinic acid (LA). A design of experiment was employed for the optimization of the most relevant fractionation parameters: time and temperature. In the case of the lignin, both parameters were found to be significant variables in the fractionation process (p-values of 0.0128 and 0.0319 for time and temperature, respectively), with a positive influence. Likewise, in the cellulose case, time and temperature also demonstrated a positive effect, with p-values of 0.0103 and 0.028, respectively. An optimization study was finally conducted to determine the maximum fractionation yield of lignin and cellulose. The optimized conditions were found to be 15% (w/v) of the wood sample in 1:3 ChCl:LA under a treatment temperature of 160 degrees C for 8 h. The developed method was validated through repeatability and intermediate precision studies, which yielded a coefficient of variation lower than 5%. The recovery and reuse of DES were successfully evaluated, revealing remarkable fractionation yields even after five cycles. This work demonstrates the feasibility of selectively extracting lignin and cellulose from woody biomass using a sustainable solvent, thus paving the way for valorization of invasive species biomass.
- Extraction and characterization of microplastics from portuguese industrial effluentsPublication . Magalhães, Solange; Alves, Luís; Romano, Anabela; Medronho, Bruno; Rasteiro, Maria da GraçaMicroplastics (MPs) are contaminants present in the environment. The current study evaluates the contribution of different well-established industrial sectors in Portugal regarding their release of MPs and potential contamination of the aquifers. For each type of industry, samples were collected from wastewater treatment plants (WWTP), and different parameters were evaluated, such as the potential contamination sources, the concentration, and the composition of the MPs, in both the incoming and outcoming effluents. The procedures to extract and identify MPs in the streams entering or leaving the WWTPs were optimized. All industrial effluents analysed were found to contribute to the increase of MPs in the environment. However, the paint and pharmaceutical activities were the ones showing higher impact. Contrary to many reports, the textile industry contribution to aquifers contamination was not found to be particularly relevant. Its main impact is suggested to come from the numerous washing cycles that textiles suffer during their lifetime, which is expected to strongly contribute to a continuous release of MPs. The predominant chemical composition of the isolated MPs was found to be polyethylene terephthalate (PET). In 2020, the global need for PET was 27 million tons and by 2030, global PET demand is expected to be 42 million tons. Awareness campaigns are recommended to mitigate MPs release to the environment and its potential negative impact on ecosystems and biodiversity.
- Hydrophobic interactions control the self-assembly of DNA and cellulosePublication . Lindman, Björn; Medronho, Bruno; Alves, Luís; Norgren, Magnus; Nordenskiöld, LarsDesoxyribosenucleic acid, DNA, and cellulose molecules self-assemble in aqueous systems. This aggregation is the basis of the important functions of these biological macromolecules. Both DNA and cellulose have significant polar and nonpolar parts and there is a delicate balance between hydrophilic and hydrophobic interactions. The hydrophilic interactions related to net charges have been thoroughly studied and are well understood. On the other hand, the detailed roles of hydrogen bonding and hydrophobic interactions have remained controversial. It is found that the contributions of hydrophobic interactions in driving important processes, like the double-helix formation of DNA and the aqueous dissolution of cellulose, are dominating whereas the net contribution from hydrogen bonding is small. In reviewing the roles of different interactions for DNA and cellulose it is useful to compare with the self-assembly features of surfactants, the simplest case of amphiphilic molecules. Pertinent information on the amphiphilic character of cellulose and DNA can be obtained from the association with surfactants, as well as on modifying the hydrophobic interactions by additives.
- Insights on microplastic contamination from municipal and textile industry effluents and their removal using a cellulose-based approachPublication . Magalhães, Solange; Paciência, Daniel; Rodrigues, João M. M.; Lindman, Björn; Alves, Luís; Medronho, Bruno; Rasteiro, Maria da GraçaThe rampant use of plastics, with the potential to degrade into insidious microplastics (MPs), poses a significant threat by contaminating aquatic environments. In the present study, we delved into the analysis of effluents from textile industries, a recognized major source of MPs contamination. Data were further discussed and compared with a municipal wastewater treatment plant (WWTP) effluent. All effluent samples were collected at the final stage of treatment in their respective WWTP. Laser diffraction spectroscopy was used to evaluate MP dimensions, while optical and fluorescence microscopies were used for morphology analysis and the identification of predominant plastic types, respectively. Electrophoresis was employed to unravel the prevalence of negative surface charge on these plastic microparticles. The analysis revealed that polyethylene terephthalate (PET) and polyamide were the dominant compounds in textile effluents, with PET being predominant in municipal WWTP effluents. Surprisingly, despite the municipal WWTP exhibiting higher efficiency in MP removal (ca. 71% compared to ca. 55% in textile industries), it contributed more to overall pollution. A novel bio-based flocculant, a cationic cellulose derivative derived from wood wastes, was developed as a proof-of-concept for MP flocculation. The novel derivatives were found to efficiently flocculate PET MPs, thus allowing their facile removal from aqueous media, and reducing the threat of MP contamination from effluents discharged from WWTPs.
- Lignin extraction from acacia wood: crafting deep eutectic solvents with a systematic D-optimal mixture-process experimental designPublication . Fernandes, Catarina; Aliaño González, María José; Gomes, Leandro Cid; Bernin, Diana; Gaspar, Rita; Fardim, Pedro; Reis, Marco S.; Alves, Luís; Medronho, Bruno; Rasteiro, Maria Graça; Varela, CarlaLignin is a complex biopolymer whose efficient extraction from biomass is crucial for various applications. Deep eutectic solvents (DES), particularly natural-origin DES (NADES), have emerged as promising systems for lignin fractionation and separation from other biomass components. While ternary DES offer enhanced fractionation performance, the role of each component in these mixtures remains unclear. In this study, the effects of adding tartaric acid (Tart) or citric acid (Cit) to a common binary DES mixture composed of lactic acid (Lact) and choline chloride (ChCl) were investigated for lignin extraction from acacia wood. Ternary Cit-based DES showed superior performance compared to Tart-based DES. Using a combined mixture-process D-Optimal experimental design, the Lact:Cit:ChCl DES composition and extraction temperature were optimized targeting maximum lignin yield and purity. The optimal conditions (i.e., Lact:Cit:ChCl, 0.6:0.3:0.1 molar ratio, 140 degrees C) resulted in a lignin extraction yield of 99.63 +/- 1.24 % and a lignin purity of 91.45 +/- 1.03 %. Furthermore, this DES exhibited feasible recyclability and reusability without sacrificing efficiency.
- Lignin extraction from waste pine sawdust using a biomass derived binary solvent systemPublication . Magalhães, Solange; Filipe, Alexandra; Melro, Elodie; Fernandes, Catarina; Vitorino, Carla; Alves, Luís; Romano, Anabela; Rasteiro, Maria G.; Medronho, Bruno; MDPILignocellulosic biomass fractionation is typically performed using methods that are somehow harsh to the environment, such as in the case of kraft pulping. In recent years, the development of new sustainable and environmentally friendly alternatives has grown significantly. Among the developed systems, bio-based solvents emerge as promising alternatives for biomass processing. Therefore, in the present work, the bio-based and renewable chemicals, levulinic acid (LA) and formic acid (FA), were combined to fractionate lignocellulosic waste (i.e., maritime pine sawdust) and isolate lignin. Different parameters, such as LA:FA ratio, temperature, and extraction time, were optimized to boost the yield and purity of extracted lignin. The LA:FA ratio was found to be crucial regarding the superior lignin extraction from the waste biomass. Moreover, the increase in temperature and extraction time enhances the amount of extracted residue but compromises the lignin purity and reduces its molecular weight. The electron microscopy images revealed that biomass samples suffer significant structural and morphological changes, which further suggests the suitability of the newly developed bio-fractionation process. The same was concluded by the FTIR analysis, in which no remaining lignin was detected in the cellulose-rich fraction. Overall, the novel combination of bio-sourced FA and LA has shown to be a very promising system for lignin extraction with high purity from biomass waste, thus contributing to extend the opportunities of lignin manipulation and valorization into novel added-value biomaterials.