RESUMEN

Cellulose 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 °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.

Asunto(s)

RESUMEN

Cellulose 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.

RESUMEN

In sugar production, polyacrylamide-based anionic flocculants are added for juice treatment, the main objective being to remove impurities that affect the quality of the sugar. However, if they remain in the final product, those polymers can present carcinogenic and neurotoxic actions besides contaminating the soils where the waste is discharged. To overcome this problem, the present study proposes, for the first time, natural flocculants based on cellulose obtained from sugarcane bagasse (residue from sugarcane processing) as substitutes for the flocculants based on polyacrylamide, normally used in sugar cane juice purification. Additionally, cellulose-based flocculants obtained from Acacia wood, developed in a previous study, have also been tested for sugar juice treatment. Acacia wood and sugarcane bagasse were first treated with a choline chloride/levulinic acid solution in a molar ratio of 1:2, at 160 °C, for 4 h. Subsequently, the cellulose-rich samples were modified by a two-stage process (oxidation with sodium periodate followed by reaction with sodium metabisulfite), and polyelectrolytes with different characteristics were produced. The final products obtained were characterized, and their performance in the treatment of sugarcane juice, at different concentrations (10, 50, 100, 250, and 500 mg kg-1), was evaluated and compared to the synthetic commercial flocculant (Flonex, based on polyacrylamide) usually used by the sugarcane industry in Brazil. The substitution of petrol-based flocculants by natural-based ones, obtained from sugarcane residues, is presented for the first time in this study, with very relevant performance of the new flocculants. Overall, it was possible to produce anionic flocculants, modifying the cellulose obtained from different raw materials, which showed good results in the purification of sucrose, when compared with the commercial polyacrylamide normally used. It is also important to stress that, for the first time, a residue from sugarcane industry could be used with success in the purification of the sugar juice itself, which constitutes a major novelty.

RESUMEN

The 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, ChCl:LA in a ratio of 1:3, was found to not significantly depolymerize the extracted lignin, which presented a similar molecular weight to a kraft lignin. Additionally, the 31P 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.

RESUMEN

Microplastics (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.

RESUMEN

Plastics are widely used due to their excellent properties, inexpensiveness and versatility leading to an exponential consumption growth during the last decades. However, most plastic does not biodegrade in any meaningful sense; it can exist for hundreds of years. Only a small percentage of plastic waste is recycled, the rest being dumped in landfills, incinerated or simply not collected. Waste-water treatment plants can only minimize the problem by trapping plastic particles of larger size and some smaller ones remain within oxidation ponds or sewage sludge, but a large amount of microplastics still contaminate water streams and marine systems. Thus, it is clear that in order to tackle this potential ecological disaster, new strategies are necessary. This review aims at briefly introducing the microplastics threat and critically discusses emerging technologies, which are capable to efficiently clean aqueous media. Special focus is given to novel greener approaches based on lignocellulose flocculants and other biomaterials. In the final part of the present review, it was given a proof of concept, using a bioflocculant to remove micronized plastic from aqueous medium. The obtained results demonstrate the huge potential of these biopolymers to clean waters from the microplastics threat, using flocculants with appropriate structure.

Asunto(s)

RESUMEN

The huge evolution of nanotechnology and the commercialization of nanomaterials (NMs) positively contributed for innovation in several industrial sectors. Facing this rapid development and the emergence of NMs in the market, the release of this nanometric sized materials in the environment and the possible impact on different ecosystem components attracted the attention of researchers in the last few years. In our study we aimed to assess the impact of titanium silicon oxide nanomaterial (nano-TiSiO4) on soil biota to estimate a risk limit for this material. In the present research a battery of standardized ecotoxicological assays aimed at evaluating a wide range of endpoints (avoidance and reproduction of earthworms and collembolans, emergence/growth of four selected terrestrial plants) were carried out, using OECD artificial soil as test substrate spiked with aqueous suspension of different concentrations of nano-TiSiO4. The results showed a maximum avoidance percentage of 40% for earthworms (Esenia andrei) at the highest concentration tested (1000mgkg(-1) soildw of nano-TiSiO4). No significant effect on the reproductive function of both invertebrate species was recorded. Nevertheless, significant phytotoxic data was registered at least for the growth of dicotyledonous plant species (Lactuca sativa and Lycopersicon lycopersicum) with EC20 values ranging between 236 and 414 mg kg(-1) soildw of nano-TiSiO4 for L. sativa dry mass and fresh mass, respectively. Further, the characterization of nano-TiSiO4 in suspensions used to spike the soil, performed by Dynamic Light Scattering, showed the formation of aggregates with important average size diameter, thus demonstrating that the toxic effects observed were likely not size dependent. A deterministic PNEC (predicted no effect concentration) for this NM of 10.02mg kg(-1) soildw of nano-TiSiO4, is suggested, while no more ecotoxicological information exists.

Asunto(s)