Percorrer por autor "Bernin, Diana"
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- Levulinic acid-based “green” solvents for lignocellulose fractionation: on the superior extraction yield and selectivity toward ligninPublication . Melro, Elodie; Riddell, Alexander; Bernin, Diana; Rosa Da Costa, Ana; Valente, Artur J. M.; Antunes, Filipe E.; Romano, Anabela; Norgren, Magnus; Medronho, BrunoThe high potential use of lignin in novel biomaterialsand chemicalsrepresents an important opportunity for the valorization of the mostabundant natural resource of aromatic molecules. From an environmentalperspective, it is highly desirable replacing the hazardous methodscurrently used to extract lignin from lignocellulosic biomass anddevelop more sustainable and environmentally friendly approaches.Therefore, in this work, levulinic acid (a "green" solventobtained from biomass) was successfully used, for the first time,to selectively extract high-quality lignin from pine wood sawdustresidues at 200 degrees C for 6 h (at atmospheric pressure). Moreover,the addition of catalytic concentrations of inorganic acids (i.e.,H2SO4 or HCl) was found to substantially reducethe temperature and reaction times needed (i.e., 140 degrees C, 2 h)for complete lignin extraction without compromising its purity. NMRdata suggests that condensed OH structures and acidic groups are presentin the lignin following extraction. Levulinic acid can be easily recycledand efficiently reused several times without affecting its performance.Furthermore, excellent solvent reusability and performance of extractionof other wood residues has been successfully demonstrated, thus makingthe developed levulinic acid-based procedure highly appealing andpromising to replace the traditional less sustainable methodologies.
- 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.
- Optimizing lignin cationization: unveiling the impact of reaction conditions through multi-response analysisPublication . Fernandes, Catarina; Gomes, Leandro Cid; Bernin, Diana; Alves, Luís; Rasteiro, Maria Graça; Medronho, Bruno; Varela, CarlaLignin, a natural and abundant biopolymer, holds great potential for cosmetic applications. However, its limited solubility and inherently negative charge restrict its use in certain formulations. This is particularly relevant for hair conditioning, where a positively charged polymer is preferred to effectively treat negatively charged damaged hair. To overcome this limitation, lignin extracted from acacia wood residues was chemically cationized, through an etherification reaction, using 3-chloro-2-hydroxypropyltrimethylammonium chloride (CHPTAC) as cationization agent. The cationization process was optimized through a full factorial design of experiments aiming to maximize both the degree of substitution (DS) and ζ-potential of the lignin derivatives, thereby obtaining more positively charged derivatives. The reaction parameters temperature and CHPTAC-tolignin molar ratio were selected as independent variables to be optimized. Results revealed that the reaction temperature is the most relevant parameter for lignin cationization, showing a significant positive influence on lignin modification, while the CHPTAC-to-lignin ratio has no significant impact. Under optimal conditions, soluble derivatives with a DS of 0.61 ± 0.03 and a ζ-potential of 18.79 ± 0.30 mV were obtained, confirming the success of the reaction. This straightforward and efficient approach enhances acacia's lignin solubility and charge properties, broadening its application potential. In particular, it offers a promising alternative for hair conditioning, thus contributing to the sustainable development of bio-based cosmetic ingredients.